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Sustainable Agriculture Research and Education in the Field: A Proceedings (1991)

Chapter:PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION

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Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

PART THREE

Research and Education in the Southern Region

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×
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Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

10

Southeastern Apple Integrated Pest Management

Dan L. Horton, Douglas G. Pfeiffer, and Floyd F. Hendrix, Jr.

Integrated pest management (IPM), in its commercially usable forms, is a synthesis of discrete management concepts. Sustainability is an inherent theme of pest management. Fruit crops, because of their high unit value and the demand for blemish-free products, are an especially challenging area for IPM research and implementation (National Research Council, 1989). Compromises between scientists from several disciplines focusing on growers' needs to manage pest populations in an optimum cropping system lead to good pest management. Successful pest management is also regionally adapted. It attempts to exploit any regional advantages while adopting and modifying the successful IPM practices of other regions as they are needed.

Low-input sustainable agriculture (LISA) funding in 1988 linked complementary apple pest management programs in Virginia and Georgia. Funding enabled both states to broaden and accelerate their long-standing commitments to pest management. Virginia is an important apple-producing state, while Georgia is not a major apple producer. The two are, however, on either end of the primary southeastern apple belt, which follows the Appalachian Mountains and includes production areas in North Carolina, South Carolina, Tennessee, and Alabama. Pest management programs in both Virginia and Georgia have sought to provide good regionally adapted control (Taylor and Dobson, 1974). The authors of this chapter have tried to provide growers with dependable, low-risk, preventative spray guidelines and to emphasize regional pest biology and selective, well-timed pesticide use. Through the years, significant effort has been made to encourage growers to adopt a pest management mentality. This chapter provides an

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

overview of pest pressures and phenology with particular emphasis given to the differences between Georgia and Virginia.

OVERVIEW OF SOUTHEASTERN ARTHROPOD PESTS AND DISEASES

Pests and beneficial arthropod complexes do not differ greatly from the mountains of north Georgia through North Carolina and on into much of Virginia. The abundance and severity of certain arthropod pests do vary within the region, however. Southeastern arthropod seasonality and pest severity were thoroughly evaluated and summarized in a 5-year study by Shaffer and Rock (1983). Management programs in Virginia and Georgia attempt to control primary pests (those that incur high economic cost if uncontrolled) early in the growing season.

Control of primary pests commonly begins with the use of dormant oil. Sampling to estimate the size of successful overwintering populations of these pests is not feasible. Control of mites and aphids becomes more challenging, more disruptive to predators and parasites, and more expensive as the crop progresses beyond the 0.5-inch green-tip stage of development. Use of superior oil treatment gives nondisruptive suppression of scales, primarily San Jose scale (Quadraspidiotus perniciosus Comstock), European red mite (Panonychus ulmi Koch), and a complex of aphids, with the rosy apple aphid (Dysaphis plantaginea Passerini) being of primary concern. The delayed dormant period around the 0.25-inch green-tip stage presents a second and somewhat more effective control window for the use of oil. The addition of an organophosphate insecticide such as chlorpyriphos (Lorsban) in this oil spray for the green-tip stage improves the control of rosy apple aphid, which is not controlled by oil alone (Hull and Starner, 1983b).

Tarnished plant bugs (Lygus lineolaris Palisot de Beauvois), spotted tentiform leafminers (Phyllonorycter blancardella F.), and green fruitworms (Lithophane antennata W. spp.) are injurious between the tight cluster and pink stages. Spotted tentiform leafminers are relatively new apple pests in the southeastern United States. Walgenbach et al. (1990) found that vigorous, prebloom control of overwintered leafminers generally provides acceptable season-long suppression. This minimizes the need for postbloom control, which often encourages mite outbreaks. Plant bugs are erratic, very mobile, and potentially damaging. The need for leafminer sprays at this stage makes integration of plant bug thresholds (Michaud et al., 1989) impractical for Georgia and Virginia growers since leafminer sprays provide plant bug control. Green fruitworms also are controlled at the pink and petal fall stages with sprays made for other pests. Prolonged cool springs with longer than normal periods between sprayings for the pink and petal fall stages

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

make a scheduled spraying at the pink stage very worthwhile in current IPM practices.

The most important postbloom pests are codling moth (Cydia pomonella L.) and plum curculio (Conotrachelus nenuphar Herbst). Both of these primary pests attack the fruit. They are joined by tufted apple budmoth (Platynota idaeusalis Walker) and, in Virginia, variegated leafroller (Platynota flavendana Clemens) as pests that must be controlled for the production of a successful crop.

San Jose scale crawlers, white apple leafhoppers (Typhlocyba pomaria McAtee), Japanese beetles (Popillia japonica Newman), green June beetles (Cotinis nitida L.), and European red mites must also be monitored and controlled as necessary. San Jose scale crawlers remain in the susceptible crawler stage of development for a very brief period. Emergence normally occurs at about the time of the second cover spray; however, more precise timing can be had by using the earliest pheromone trap catches as a biological fix to better predict crawler emergence (Pfeiffer, 1985). Japanese beetles and green June beetles may be injurious, and caution should be exercised. Spraying for foliage feeding by these pests is sometimes warranted, but control of these pests carries the risk of inducing mite problems. White apple leafhopper infestations also raise concerns over mite infestations. They carry a greater risk of inducing mite outbreaks because the carbamate insecticides (carbaryl, Sevin; formetanate hydrochloride, Carzol) needed to control them are especially toxic to mite predators (Rajotte, 1988).

European red mites are challenging pernicious pests (Prokopy et al., 1980) whose leaf-feeding injury accumulates through a growing season. Mite management includes suppression with oil treatments early in the season. Conservation of natural enemies, primarily Stethorus punctum LeConte lady beetles and the predator mite Amblyseius fallacis Garman in the southeast (Farrier et al., 1980), is fostered by making every effort to avoid unnecessary pesticide use. Careful pest management minimizes all unwarranted pesticide use (Croft and Brown, 1975). This preserves mite predators and normally lowers pesticide inputs. Mite control decisions are based on regular monitoring and the use of thresholds.

Apple diseases in Georgia are unique compared with those in much of the rest of the United States. Scab is a minor problem, while the summer rots are of major importance. The opposite is true from the mountains of North Carolina through the northeastern United States. A thorough investigation and understanding of the epidemiology of Georgia apple diseases was a necessary prerequisite to beginning a LISA program for the crop in Georgia.

Black rot of apples in Georgia, caused by Botryosphaeria obtusa (Schw.) Shoemake, differs from the disease of northern areas in that conidia are the

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

primary source of inoculum. Infestation of buds occurs in the winter, infection occurs in the early spring, and the disease can cause losses in excess of 50 percent. Conidia of B. obtusa are produced on dead wood in the trees and on the orchard floor throughout the year (Beisel et al., 1984). Conidia are found on and in buds from December through March. Even though conidia of the fungus are present in the buds for several months, infection does not occur until the silver-tip stage of bud phenology. Thus, a single spray at the silver-tip stage instead of the five sprays suggested previously (Smith and Hendrix, 1984) can be used to control this fungus. The fungus does not rot fruit until about 6 weeks before harvest, even though infection occurs in March and April.

Apple scab, which is caused by Venturia inequalis (Cke.) Wint., is a minor problem in Georgia because high temperatures frequently preclude secondary disease cycles. In most years, there is a primary cycle early in the spring. In some years, there is one secondary cycle in the fall (Hendrix et al., 1978). If an orchard had scab in the previous year, it is suggested that three scab sprayings be applied. In the absence of scab the previous year, no sprays are needed.

Cedar apple rust (Gymnosporangium junipera-virginianae Schw.) and quince rust (Gymnosporangium clavipes Cke. & Pk.) occur to some extent in Georgia orchards (Hendrix et al., 1978). Two prebloom sprays are suggested for orchards where there is a history of a problem with these diseases, but no sprays are suggested in other orchards.

Fire blight of apples (Erwinia amylovora [Burr.] Winslow et al.) occurs sporadically in Georgia apple orchards (Hendrix, 1990). Temperatures between 70° and 80°F and rainy, humid weather are necessary for epidemic outbreaks (Van Der Zwet and Keil, 1979). Avoidance of excessive vegetative growth also aids in disease reduction. Fire blight control by spraying is suggested only in those years when the weather favors major outbreaks.

Brooks spot of apple (Mycosphaerella pomi [Pass.] Lindau) is a minor disease in Georgia. Light infection may not be noticed at the time of harvest because of the small lesion size. Infection occurs from late April to mid-June in North Carolina, but it is slightly earlier in Georgia because of warmer temperatures. Sprayings from the time of petal fall until the second cover appears to provide adequate control (Sutton et al., 1987). No sprays are suggested for use in orchards with no history of the disease.

Black pox of apple (Helminthosporium papulosum Berg) can cause severe losses. The fungus reproduces in old bark lesions and spreads to new leaves, fruit, and bark. Infections occur throughout the growing season (Taylor, 1970). Because of the length of the period when infection can occur, orchards with a history of this disease require season-long preventative spraying and are not candidates for inclusion in a LISA-type program.

Bitter rot of apple (Glomerella cingulata [Stonem.] Spauld. & Schrenk.)

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

does not reach damaging levels every year in Georgia orchards. When it does occur, it can cause losses of up to 80 percent (Noe and Starkey, 1980, 1982; Taylor, 1971). While infection can occur anytime after bloom, it is considered a midsummer disease. Most infections occur after the fruit reaches full size (Hendrix et al., 1978). Temperatures of greater than 21°C and free moisture are necessary for disease development. The fungus over-winters primarily on dead wood in the tree and on the orchard floor. It also survives on a small percentage of mummified Georgia fruit. The Georgia spray guide suggests five to eight sprays for pest control from the time of bloom to harvest.

White rot on fruit and Bot canker on trees are caused by Botryosphaeria dothidea (Moug. ex. Fr.) Ces. & de Not. The fungus survives on dead wood in the tree and on the orchard floor. Conidia are produced throughout the summer, but fruit is susceptible to infection only after the soluble solids reach 10.5 percent (Kohn and Hendrix, 1982, 1983). This is usually about 6 weeks before harvest. Prior to the work of Kohn and Hendrix (1982, 1983), sprays were applied from the time of bloom to harvest.

Botryosphaeria dothidea infects apple stems primarily through improperly made pruning cuts (Brown and Hendrix, 1981). Stub cuts on which the bark dies are the most common point of infection. This disease can be controlled by making proper pruning cuts and maintaining proper sanitation.

Sooty blotch, which is caused by Gloeodes pomigena (Schw.) Copby, and flyspeck, which is caused by Zygophiala jamaicensis Mason, are fungi which grow on the surface of apples. They do not cause decay but do cause cosmetic blemishes. Efforts were made in 1986 and 1987 to monitor the development of these diseases and to control them with prescription-type sprays. None of the currently registered fungicides, however, is capable of arresting development of these diseases once they start. Control of sooty blotch and flyspeck in the orchard does not fit into any current IPM techniques for apple production. Data are not available for predicting these diseases.

PATHOLOGY RESEARCH

University of Georgia LISA fruit research centered on the development of IPM-compatible controls for sooty blotch and fly speck. The heavy preventative spraying required to control these diseases was not conducive to further pest management implementation. This study is examining the efficacy of chlorine dips for postharvest removal of sooty blotch and flyspeck from apples. The removal of pesticide residues and effects on shelf life were also examined.

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

TABLE 10-1 Chlorine Removal of Sooty Blotch and Flyspeck from Apples with a 5-Minute Postharvest Chlorine Dip

Chlorine (ppm)

Percentage Posttreatment

 
 

Sooty Blotch

Flyspeck

0

100a

100a

100

97a

96a

300

16b

70b

500

6b

56c

NOTE: Fruits were not brushed. Values with the same symbol are not significantly different.

Postharvest Removal of Sooty Blotch and Flyspeck

Initial testing of postharvest chlorine dips in 1988 showed that these treatments removed sooty blotch and reduced flyspeck. Several postharvest chlorine rinses are labeled for use on a variety of fruits and vegetables. Sodium hypochlorite, the active ingredient, volatilzes rapidly, eliminating chlorine residues. The U.S. Environmental Protection Agency (EPA) has exempted sodium hypochlorite from food tolerances, indicating its low risk. The rates found to be effective are above those currently listed by the EPA.

High levels of chlorine (940, 1,270, and 1,670 ppm) were found to remove completely sooty blotch from fruit at all concentrations tested. Flyspeck was reduced but not eliminated. This experiment was repeated with lower concentrations of chlorine (Table 10-1). At 300 and 500 ppm of chlorine, sooty blotch was reduced from 100 percent to 16 and 6 percent, respectively. Flyspeck was reduced from 100 percent to 70 and 56 percent, respectively. Fruit tested in both experiments showed no symptoms of phytotoxicity or damage to their finishes. This test was repeated five times, with similar results obtained each time.

In subsequent tests, fruit was treated in the dump tank of a commercial packing plant. Fruit was exposed to 0, 50, 100, 300, 400, or 500 ppm of chlorine for 5 to 7 minutes. It was then passed over a series of wet brushes and rinsed with nonchlorinated water. The addition of brushes improved the process. Sooty blotch removal by treatment with 200 ppm of chlorine (Table 10-2) was equivalent to that at 500 ppm without brushing (Table 10-1). Flyspeck removal by treatment with 300 ppm of chlorine with brushing was equivalent to that with 500 ppm without brushes. With 500 ppm of chlorine and brushes, flyspeck was reduced from 100 to 27 percent. At

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

TABLE 10-2 Chlorine Removal of Sooty Blotch and Flyspeck from Apples in a Commercial Packing Plant

Chlorine (ppm)

Percentage Posttreatment

 
 

Sooty Blotch

Flyspeck

0

100a

100a

50

92b

95a

100

26c

45c

200

6d

52b

300

4d

58b

400

2d

36c

500

0d

27d

NOTE: Fruits were dipped postharvest in chlorine-treated, dump tank water for 5 minutes, brushed, and then rinsed with nonchlorinated water. Values with the same symbol are not statistically significant.

this level of chlorine, sooty blotch was reduced to 0 percent. This test was repeated in 1989 with similar results.

Chlorine Treatment Effects on Pesticide Residues

Sample apples that were treated with 500 ppm of chlorine, brushed, and rinsed in nonchlorinated water were tested for pesticide residue in an EPA-approved laboratory at the University of Georgia. Pesticide residues were reduced by the postharvest chlorine treatment (Table 10-3). Captan resi

TABLE 10-3 Effects of a 5-Minute Dip of 500 ppm of Chlorine Followed by Brushing and Rinsing with Non-chlorinated Water on Residues of Captan, Phosmet, and Maneb on Harvested Apples

 

Residues (ppm)

   

Phosmet

Treatment

Captan

Sample 1

Sample 2

Maneb

Water dip

0.42

0.30

0.16

5.84

Chlorine dip

0.00

0.20

0.00

1.63

NOTE: Values are averages of 21 residue analyses.

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

TABLE 10-4 Effect of Postharvest Chlorine Treatment and Fruit Waxing on Weight Loss of Red and Golden Delicious Apples after 12 Weeks of Storage at 1° to 3°C

     

Date 1

Date 6

Weight Loss (g)

 

Treatment

Weight (g)

Standard Deviation (g)

Weight (g)

Standard Deviation (g)

 

Cultivar

Wax

Chlorine

Golden

+

105.9

10.4

101.2

10.3

4.7

Delicious

+

+

102.1

11.1

97.8

10.8

4.2

 

97.4

7.6

92.6

7.5

4.8

 

+

102.4

10.8

98.3

10.4

4.1

Red

+

154.9

16.5

150.7

16.0

4.2

Delicious

+

+

142.1

27.2

138.5

24.4

3.6

 

156.1

15.7

152.0

15.3

4.1

 

+

164.9

14.1

156.5

14.2

8.4

dues were reduced to less than detectable levels, phosmet levels were reduced by 33 percent or more, and Maneb levels were reduced by 73 percent.

Shelf Life of Chlorine-Treated Apples

Red Delicious and Golden Delicious apples were harvested and treated with chlorine in a commercial packing plant, and half of the fruit was waxed. The fruit was stored in boxes with dividers at 34° to 37°F for 12 weeks. Weight loss was determined by weighing individual fruit at 2-week intervals. Weight loss averaged about 4.5 percent for Golden Delicious and 3.6 percent for Red Delicious apples over the 12-week period (Table 10-4). Neither chlorine nor wax treatment affected weight loss.

Phytotoxicity and Fruit Finish Trial

Fruit was treated with chlorine at levels of up to 4,100 ppm, with and without buffer, to determine phytotoxic levels. Fruit finish was not affected at 4,100 ppm of chlorine, with or without buffer, even when fruit was stored for 30 days in plastic bags in the presence of chlorine solution.

Conclusions of Fruit IPM Research

Postharvest chlorine dips have been found to be an effective technique for the removal of sooty blotch and the reduction of flyspeck. Chlorine treatments allow growers to ignore sooty blotch and flyspeck. Postharvest use of chlorine complements existing IPM techniques, including sanitation;

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

scouting for insects, mites, and bitter rot; and prescription use of white rot control measures, as dictated by fruit-soluble solids and weather. A state label granting Georgia growers the right to elevate their chloride concentrations to 500 ppm has been obtained. Postharvest chlorine treatment has allowed Georgia growers to eliminate up to eight sprays that, in preventative programs, are dedicated, at least in part, to the control of sooty blotch and flyspeck. No chlorine treatment-induced phytotoxicity was observed, even when eight times the necessary concentrations or two times the necessary exposure durations were used. Apples can be stored for up to 3 months after treatment with minimal but acceptable weight loss. Postharvest chlorine treatment also reduces pesticide residues. This may be important, because many consumers feel that even minimal pesticide residues compromise food safety.

ENTOMOLOGY RESEARCH

Virginia Polytechnic Institute and State University (VPI&SU) has provided the research lead in entomology. Objectives are (1) pheromone mating disruption to control codling moth and variegated leafroller, (2) inventory of orchard ground cover management practices and evaluation of the impacts of these practices on mites, (3) determination of the toxicity of herbicides to the predaceous mite A. fallacis, and (4) assessment of grower IPM expertise.

Mating Disruption

Mating pheromones are chemical cues that many insects use to help them find mates. Pheromone mating disruption provides insect control without the use of conventional toxic insecticides. Saturation of an orchard with pheromone confuses the mate-finding process, which prevents mating and eliminates the damaging larval stages of these pests. The elimination or drastic reduction of reliance on conventional disruptive, toxic sprays to control these pests does a great deal to conserve natural enemies. This use of nondisruptive, behavior-altering chemicals may well usher in what has been called “second-stage IPM ” (Prokopy, 1987).

Codling moth, a primary pest of apples, must be controlled each year. This entails considerable pesticide use. Rothschild (1982) reviewed codling moth biology and ecology and noted the characteristics of this moth that make it a good candidate for disruption of the mating process. The codling moth's narrow host range and relatively low fecundity, the females' limited dispersal capabilities, the low number of generations, and the apparent lack of nonolfactory mate-finding mechanisms were noted as factors that lend themselves to pheromonal control. Charmillot and Bloesch (1987) reported

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

on an 11-year Swiss study that had considerable success. They also offered possible reasons for control failures by this approach. Variegated leafroller and tufted apple budmoth are also important fruit-feeding pests that are candidates for mating disruption.

Pheromone mating disruption of codling moth and leafrollers was performed very successfully in a 4.7-acre commercial block at Daleville, Virginia. The pheromone-treated block was isolated, but there was a small abandoned block nearby. The block in which pests were controlled by following VPI&SU's spray guide method was about 1 mile away, and was surrounded by additional commercial apple orchards. Leafroller pheromone dispensers were put into place on May 5; those for codling moth were put into place on May 8. Four hundred dispensers for each species were placed in per acre. The original target for leafroller disruption was variegated leafroller. The pheromone blend used was: E,Z-11-tetradecenyl acetate, 96 percent (ratio of E:Z isomers, 70:30); E,Z-11-tetradecenol, 2 percent (ratio of E:Z isomers, 70:30); and Z-9-dodecenyl acetate, 2 percent. It was hoped that this would provide disruption for several species with pheromones that are mainly of the E isomer.

Pheromone traps for variegated leafroller, tufted apple budmoth, and redbanded leafroller were monitored weekly. Three traps for each species were placed in each block. Damage was also assessed weekly by examining at least 200 peices of fruit in each of the blocks (pheromone-treated, control by the Georgia spray guide method, and abandoned).

Male Orientation to Traps

Codling moth traps were placed in the blocks before the arrival of dispensers; pretreatment trap counts demonstrated the presence of codling moth in the blocks. Placement of pheromone dispensers was followed by a 100 percent shutdown of codling moth attraction to traps. Trap captures were reduced for each of the leafroller species, but not by 100 percent. There was a working assumption that limited mating was taking place. Leafrollers usually feed by tying leaves together; occasionally, a leaf is tied to a fruit, causing damage. Because these leafrollers are not direct fruit feeders, control of fruit damage may be attained without complete mating disruption. Variegated leafroller capture has been suppressed to a greater degree than has tufted apple budmoth capture. An unexpected development involved another leafroller species. On August 9, obliquebanded leafrollers were caught in the redbanded leafroller traps in the control block (8.7 per trap). Only a single obliquebanded leafroller was detected in the pheromone block (0.3 per trap). Although this species has not been important in Virginia, it has been an important pest in New York State and New England.

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×
Damage Assessment

Control of damage by mating disruption for both groups of pests appeared to be similar to pesticide control, with certain restrictions. Mating disruption of first generation codling moths did not result in detectable injury to the fruit. In the periphery of the block, codling moth damage at the time of harvest was about 0.6 percent in Red Delicious apples, and 5.0 percent in Golden Delicious apples. When injuries to fruit caused by first-generation codling moth were seen, the grower was asked to begin spraying the outer two rows in the pheromone-treated block. Injuries to fruit by second generation codling moth were higher in the interior of the disruption block (2 percent) than they were on the periphery (0.7 percent). This came about because of spraying of the outermost rows. Leafroller damage in the interior of the pheromone-treated block was 1 percent for Red Delicious apples and 3 percent for Golden Delicious apples. Leafroller damage to Red Delicious apples at the time of harvest was 2.7 percent on the periphery and 5 percent inside the orchard. Golden Delicious apples sustained more injuries, but injury counts were not taken at time of harvest. Damage from both codling moths and the leafroller on the periphery of the orchard resulted from immigration of mated females into this relatively small block. This has been found to be a common problem in mating disruption research. Spraying of the outer two rows of the pheromone-treated block effectively dealt with the immigration of mated females.

Damage in the abandoned block reached 39 percent for codling moth, 17.5 percent for leafroller, and 35.5 percent for plum curculio. Peak damage from two generations of codling moths could be discerned. Damage in the conventional control block was 0 percent for codling moth, 6.5 percent for leafroller, and 0 percent for plum curculio. Plum curculio is not controlled by mating disruption, but it is significant to note that a single, well-timed late petal-fall spray controlled this key pest in the pheromone disruption block.

Ground Cover Management Inventory

A survey of the ground cover management practices of Virginia growers was expanded to all pesticides and plant growth regulators that are applied to fresh-market apple orchards. About 45 conventional growers responded. These growers accounted for about 76 percent of fresh-market apple producers in the state. Surveys were also mailed to organic growers, but this clientele was more diffuse and there was no single mailing list of growers. Even without complete survey information, it appeared that organic growers perceived a greater threat from direct pests, which attack the harvest product, like codling moth and plum curculio than did conventional growers; the reverse was true for indirect pests, which attack other plant parts.

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

European red mite was consistently rated as the most severe pest in conventional orchards. European red mite is a classic example of a secondary pest, which may be defined as one that is induced by the application of pesticides for primary pests.

Azinphosmethyl (Guthion) is the most widely used insecticide in Virginia. This organophosphate is not very disruptive to predatory populations. However, there are increasing problems with resistance in leafrollers, white apple leafhopper, and spotted tentiform leafminer. Methomyl, a carbamate, is the second most frequently applied insecticide and is often targeted against leafrollers, leafhoppers, and leafminers. Carbamates, particularly methomyl, are disruptive to predators. Propargite (Omite) is the most frequently applied acaricide; dicofol (Kelthane) follows.

Mancozeb (Manzate) is the most widely used fungicide in Virginia. Paraquat (Gramoxone) is the most widely used herbicide in Virginia, with an average of 1.5 applications per season. It is highly toxic to predatory mites while they are in the ground cover (Pfeiffer, 1986). In Virginia, chlorphacinone is the most frequently applied rodenticide for the control of voles (Microtus spp.). Rodenticides are frequently applied in bait stations and likely do not affect predatory populations.

Pesticide Applications Toxic to Beneficial Predators

Some data are available from the literature on the toxicity of pesticides to Amblyseius fallacis (Hislop and Prokopy, 1981). Materials considered highly toxic are permethrin (Ambush, Pounce), formetanate hydrochloride, methomyl, oxythioquinox (Morestan), fenvalerate (Asana, Pydrin), carbaryl, oxamyl (Vydate), phosalone (Zolone), diazinon, dimethoate (Cygon), ammonium sulfamate (AMS), paraquat, glyphosate (Roundup), and benomyl (Benlate).

Insecticides considered highly toxic to Stethorus punctum are carbaryl, fenvalerate, and permethrin; moderately toxic insecticides are formetanate hydrochloride, dimethoate, diazinon, methomyl, parathion, phosphamidon (Dimecron), and endosulfan (Thiodan) (Colburn and Asquith, 1973; Hull and Starner, 1983a).

Pesticides that are highly toxic to Amblyseius fallacis are frequently applied to the majority of Virginia's apple acreage. This probably accounts for the low densities of this predator that have been observed.

Assessment of Grower Expertise for IPM

Evaluations have revealed that most growers in Virginia are lacking in critical pest management skills. Similar weaknesses are thought to predominate in Georgia and may well exist in other southeastern states. Grow-

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

ers were unable to identify such important predators as predatory mites and the larvae of Stethorus punctum, lacewings, syrphid flies, and predatory midges. Most growers (80 percent) responded that they consider which predatory populations are present before selecting pesticides. There would surely be greater benefits if growers' predator identification skills were enhanced. Only 51 percent of growers responded that action thresholds are used when they decide whether sprays are needed.

GEORGIA GROWER IPM TRIALS

Georgia grower IPM trials relied on the judicious use of currently labeled, readily available chemicals and cultural controls. Thorough control of overwintering populations was emphasized. This protected the crop from injury and suppressed the magnitude of pest pressure experienced from subsequent generations.

Insect control strategies in the Georgia trails were a regional adaptation of successful programs and research in Massachusetts, New York, Pennsylvania, North Carolina, and Virginia. Control of the primary pests in Georgia, codling moth and plum curculio were emphasized. Early-season suppression of other pests was sought. Historical data on pheromone catches from orchards in North Carolina (Rock and Yeargan, 1974), South Carolina (C. S. Gorsuch, personal communication), and Georgia (D. L. Horton, unpublished data) provided a framework for formulating the expected seasonal abundance of each species. Pheromone monitoring for codling moth, redbanded leafroller, tufted apple budmoth, and variegated leafroller was used to follow the population trends of each pest. Pheromone trap-based codling moth thresholds were adhered to (Rock et al., 1978). Rather than applying pheromones to the entire orchard, varieties were sprayed individually.

Dormant oil sprays were used. This standard practice provided for nondisruptive control of mites, scale, and aphids. Phosmet (Imidan) was the insecticide for all of the sprayings that followed. Sprayings that were solely for insect control were made to alternate row middles to hold down costs and conserve predators. Prepink and pink sprays were applied to the alternate row middles for spotted tentiform leafminer, tarnished plant bug, and green fruitworms in a scheduled preventative fashion. After bloom, sprayings were made for plum curculio, codling moth, and leafroller to the middles of alternate rows. Orchards were scouted once a week. Examination of fruit was emphasized, and at least 200 fruit were examined during each visit to check for insect injury or disease lesions.

Disease control in apples is based on sanitation and fungicides. In the spray guide approach, fungicides are applied on a weekly or biweekly schedule without regard for weather or disease activity. In a low-input pest

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

TABLE 10-5 Comparison of Sprayings in Four Orchards in 1988 Treated by Georgia Spray Guide and Low-Input Sustainable Agriculture (LISA) Methods

   

Number of Sprays Applied Under

Spray

Material

Georgia Spray Guide

LISA

Dormant

Superior oil

1

1

Silver tip

Captan

1

1

Prepink

Captan, Carzol Imidan

1

1

Pink

Captan, Thiodan

1

0

Bloom

Captan

2

0

 

Agrimycin

4

0

Petal Fall

Captan, Guthion

1

 
 

Imidan, alternate row middle (ARM)

 

0.5

Cover 1

Captan, Guthion

1

 
 

Imidan, ARM

 

0.5

Cover 2

Captan, Guthion

1

 
 

Imidan, ARM

 

0.5

Cover 3

Captan, Guthion

1

 
 

Imidan, ARM

 

0.5

Cover 4

Captan, Guthion

 

1

 

Imidan, ARM

 

0.5

Cover 5

Captan, Guthion

1

 
 

Dikar (Early Blaze only)

 

1

Cover 6

Captan, Guthion

1

0

Cover 7

Captan, Guthion

1

 
 

Benlate, Maneb (Early Blaze, Prima only)

 

1

 

Dikar (Red Delicious only)

 

1

Cover 8

Captan, Guthion

1

 
 

Maneb (Red Delicious only)

 

1

Cover 9

Captan, Benlate, Imidan

1

0

NOTE: The common or chemical names of the brand names cited are as follows: Agrimycin, streptomycin; Benlate, benomyl; Captan, captan; Carzol, formetanate hydrochloride; Dikar,dinocap; Guthion, azinphosmethyl; Imidan, phosmet; Maneb, manganese ethylenebisdithiocarbamate; Thiodan, endosulfan.

management program, scouting, weather, and disease activity are considered. Fungicides are applied on a prescription basis.

Sanitation is practiced by pruning out and removing as much dead wood from the trees as possible and by either removing dead wood from the orchard and destroying it or mowing the wood on the orchard floor with a

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

flail mower (Starkey and Hendrix, 1980). The flail mower chops the wood finely and removes the bark. The bark decays rapidly and no longer supports saprophytic growth of the fungi that cause black rot, bitter rot, white rot, and Bot canker. Each orchard participating in the Georgia IPM program is inspected for sanitation; those without superior sanitation are excluded from low-input management.

Using the low-input system under the conditions found in Georgia, a spray is applied at the silver-tip stage for black rot control. Only one spray is needed if it is properly timed. If scab, rust, and Brooks spot have not been a problem in the orchard in the past, it is not necessary to apply sprays for these diseases. If they have been a problem, the sprays suggested in the Georgia apple spray guide should be applied. Fire blight sprays should be applied only if the weather conditions are favorable for fire blight epidemics. Orchards with a history of black pox are not included in this system, since infection occurs throughout the summer.

Trees in the lowest, wettest part of the orchard are marked and scouted for bitter rot. This disease occurs in these areas first. No sprays are applied for bitter rot control until it occurs. One spray is then applied, diseased fruit is removed from the tree, and additional sprayings are used after 2 weeks if the disease becomes active again. Soluble solids are measured each week after the fruit is about half grown. When readings reach 10.5 percent, a spray is applied for white rot if the forecast calls for rain. In dry weather, no sprays should be applied.

Sooty blotch and flyspeck are not controlled in the orchard, which saves up to eight sprayings. These blemishes are removed by using chlorine as a postharvest treatment.

In 1989, three grower orchards and the Georgia Mountain Branch Experiment Station orchards were managed under the LISA system. Approximately 65 acres were involved. All orchards were examined for sanitation, and a history of insect and disease problems was established. Even though 1989 was an extremely wet year, total pesticide applications were reduced from 29 to 9.5 in the LISA orchards (Table 10-5). Many of the sprays in these orchards were only insecticides, applied to alternate row middles, or fungicides. This further reduced the amount of pesticides that were used. Because several varieties were present in the orchards and the varieties were sprayed individually, the amount of pesticide needed was also reduced. For example, the fifth cover spray was applied only to the cultivar Early Blaze, which made up about 5 percent of the trees in the orchards. Twenty-nine pesticide applications at a cost for materials of $246.85 per acre were applied by using the spray guide, while 9.5 sprays, at a cost for materials of $98.87 per acre, were applied to the LISA orchards. There were additional savings and reduced inputs in the LISA orchard because of reduced machinery costs (Table 10-6).

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

TABLE 10-6 Comparison of Georgia Spray Guide and Low-Input Sustainable Agriculture (LISA) Spraying Costs

 

Spray Guide

LISA

Type of Pesticide

Number of Sprayings

Cost ($)

Number of Sprayings

Cost ($)

Bactericides

4

23.60

0.0

0.0

Fungicides

14

126.65

4.0

55.40

Insecticides

11

96.60

5.5

43.47

Total

29

246.85

9.5

98.87

The control of insect and disease injury in the LISA orchards was equal to or better than that in the Georgia spray guide blocks. It was not possible to make direct comparisons with spray guide treatments in adjacent orchards, because the cooperating growers began to adopt and mimic the IPM practices in their other orchards. Insect injury at the time of harvest in the IPM grower blocks is noted in Table 10-7. Grower 2 had heavy variegated leafroller pressure late in the season, which is an unusual occurrence in Georgia. Spray was applied to control this population. Despite the increased injury to the apples that was sustained, insect control was good. The IPM blocks were comparable to the control that could be expected with the Georgia apple spray guide. At the time of harvest, these growers had 1.75 percent bitter rot in Early Blaze apples and 2.4 percent bitter rot in Red Delicious apples. Injuries from tarnished plant bug, green fruit-worms, and the leafroller complex were 5 to 6.5 percent. The percentage of apples that could be packed, after chlorine treatment for sooty blotch and flyspeck was equivalent to that in the Georgia spray guide blocks.

TABLE 10-7 Insect Injury to Harvested Apples in 1989 Grower Trials in Georgia

 

Loss (%)

Pest

Grower 1

Grower 2

Tarnished plant bug

4.0

3.0

Green fruitworms

0.5

0.5

Leafrollers

0.5

3.0

Total

5.0

6.5

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

REFERENCES

Beisel, M., F. F. Hendrix, Jr., and T. E. Starkey. 1984. Natural inoculation of apple buds by Botryosphaeria obtusa. Phytopathology 74:335–338.

Brown, E. A., and F. F. Hendrix. 1981. Pathogenicity and histopathology of Botryosphaeria dothidea on apple stems. Phytopathology 71:375–379.

Charmillot, P. J., and B. Bloesch. 1987. La technique de confusion sexuelle: Un moyen specifique de lutte contre le carpocapse Cydia pomonella L. Rev. Suisse Vitio. Arboric. Hortic. 19:129–138.

Colburn, R., and D. Asquith. 1973. Tolerance of Stethorus punctum adults and larvae to various pesticides. Journal of Economic Entomology 66:961–962.

Croft, B. A., and A. W. A. Brown. 1975. Response of arthropod natural enemies to insecticides. Annual Review of Entomology 20:285–335.

Farrier, M. H., G. C. Rock, and R. Yeargan. 1980. Mite species in North Carolina apple orchards with notes on their abundance and distribution. Environmental Entomology 9:425–429.

Hendrix, F. F., Jr. 1990. Fire blight of apples in Georgia. Georgia Apple Grower 3(19):2–3.

Hendrix, F. F., W. M. Powell, and N. McGlohan. 1978. Apple diseases in Georgia and their control. Fruit of the South 2:112–116.

Hislop, R. G., and R. J. Prokopy. 1981. Integrated management of phytophagous mites in Massachusetts (U.S.A.) apple orchards. 2. Influence of pesticides on the predator Amblyseius fallacis (Acarina: Phytoseiidae) under laboratory and field conditions. Protection Ecology 3:157–172.

Hull, L. A., and V. Starner. 1983a. Impact of four synthetic pyrethroids on major natural enemies and pests of apple in Pennsylvania. Journal of Economic Entomology 76:122–130.

Hull, L. A., and V. R. Starner. 1983b. Effectiveness of insecticide applications timed to correspond with the development of rosy apple aphid (Homoptera: Aphididae) on apple. Journal of Economic Entomology 76:594–598.

Kohn, F. C., and F. F. Hendrix. 1982. Temperature, free moisture, and inoculum concentration effects on the influence and development of white rot of apple. Phytopathology 72:313–316.

Kohn, F. C., and F. F. Hendrix. 1983. Influence of sugar content and pH on development of white rot on apples. Plant Diseases 67:410–412.

Michaud, O. D., G. Boivin, and R. K. Stewart. 1989. Economic threshold for tarnished plant bug (Hemiptera: Miridae) in apple orchards. Journal of Economic Entomology 82:1722–1728.

National Research Council. 1989. Alternative Agriculture. Washington, D.C.: National Academy Press.

Noe, J. P., and T. E. Starkey. 1980. Effect of temperature on incidence and development of bitter rot lesions on apples. Plant Diseases 64:1084–1085.

Noe, J. P., and T. E. Starkey. 1982. Relationship of apple fruit maturity and inoculum concentration to infection by Glomerella cingulata. Plant Diseases 66:379–381.

Pfeiffer, D. G. 1985. Pheromone trapping of males and prediction of crawler emer-

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
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gence for San Jose scale (Homoptera: Diaspidiidae) in Virginia apple orchards. Journal of Entomological Sciences 20:351–353.

Pfeiffer, D. G. 1986. Effects of field applications of paraquat on densities of Panonychus ulmi (Koch) and Neoseiulus fallacis (Garman). Journal of Agricultural Entomology 3:322–325.

Prokopy, R. J. 1987. The second stage of IPM in Massachusetts. Fruit Notes (University of Massachusetts) 52(3):9–12.

Prokopy, R. J., W. M. Coli, R. G. Hislop, and K. L. Hauschild. 1980. Integrated management of insect and mite pests in commercial apple orchards in Massachusetts. Journal of Economic Entomology 73:529–543.

Rajotte, E. G., ed. 1988. Tree Fruit Production Guide 1988. University Park, Pa.: Cooperative Extension Service, The Pennsylvania State University.

Rock, G. C., and D. R. Yeargan. 1974. Flight activity and population estimates of four apple insect species as determined by pheromone traps. Environmental Entomology 3:508–510.

Rock, G. C., C. C. Childers, and H. J. Kirk. 1978. Insecticide applications based on Codlemone trap catchers vs. automatic schedule treatments for codling moth control in North Carolina apple orchard. Journal of Economic Entomology 71:650–653.

Rothschild, G. H. L. 1982. Suppression of mating in codling moths with synthetic sex pheromone and other compounds. Pp. 117–134 in Insect Suppression with Controlled Release Pheromone Systems, Vol. 2, A. F. Kydonieus and M. Beroza, eds. Boca Raton, Fla.: CRC Press.

Shaffer, P. L., and G. C. Rock. 1983. Arthropod abundance, distribution, and damage to fruit. In Integrated Pest and Orchard Management Systems for Apples in North Carolina, G. C. Rock and J. L. Apple, eds. Technical Bulletin 276. Raleigh: North Carolina Agricultural Research Service.

Smith, M. B., and F. F. Hendrix, Jr. 1984. Primary infection of apple buds by Botryosphaeria obtusa. Plant Diseases 68:707–709.

Starkey, T. E., and F. F. Hendrix, Jr. 1980. Reduction of substrate colonization by Botryosphaeria obtusa. Plant Diseases 64:292–294.

Sutton, T. B., E. M. Brown, and D. J. Hawthorne. 1987. Biology and epidemiology of Mycosphaerella pomi, cause of Brooks fruit spot of apple. Phytopathology 77:431–437.

Taylor, J. 1970. Incubation period of Helminthosporium papulosum on fruit and bark of apples. Photopathology 60:1704–1705.

Taylor, J. 1971. Epidemiology and symptomatology of apple bitter rot. Phytopathology 61:1028–1029.

Taylor, J., and J. W. Dobson. 1974. Minimum rates of pesticides on apples. Phytopathology 58:247–251.

Van Der Zwet, T., and H. L. Keil. 1979. Fire blight—a bacterial disease of rosaceous plants. USDA Agricultural Handbook No. 510. Washington, D.C.: U.S. Department of Agriculture.

Walgenbach, J. F., C. S. Gorsuch, and D. L. Horton. 1990. Adult phenology and management of the spotted tentiform leafminer (Lepidoptera: Gracillariidae) in the southeastern United States. Journal of Economic Entomology 83:985–994.

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
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11

Low-Input Crop and Livestock Systems in the Southeastern United States

John M. Luna, Vivien Gore Allen, W. Lee Daniels, Joseph P. Fontenot, Preston G. Sullivan, Curtis A. Laub, Nicholas D. Stone, David H. Vaughan, E. Scott Hagood, and Daniel B. Taylor

During the past decade, increasing concerns for the economic viability and ecological sustainability of agriculture have produced an accelerated search for alternative farming systems. The concept of low-input sustainable agriculture (LISA) has emerged that addresses multiple objectives: increasing agricultural profitability, conserving energy and natural resources, and reducing soil erosion and loss of plant nutrients (Harwood, 1990; Schaller, 1989). The term low-input implies a reduction of external production inputs (i.e., off-farm resources such as fertilizers, pesticides, and fuels) “wherever and whenever feasible and practical to lower production costs, to avoid pollution of surface and groundwater, to reduce pesticide residues in foods, to reduce a farmer's overall risk, and to increase both short- and long-term farm profitability” (Parr et al., 1990, p. 52). Low-input farming systems seek to optimize the management and use of internal production inputs (i.e., on-farm, renewable resources) to utilize beneficial ecological processes such as nitrogen fixation, nutrient cycling, and biological pest control more efficiently (Luna and House, 1990).

This change of production paradigm, from managing industrial inputs to managing ecological processes, is fundamental for the transition to a more environmentally sound sustainable agriculture. Expansion and documentation of the scientific basis of agroecology and translation of this knowledge into site-specific, usable information form the challenge for agricultural researchers and educators. Also important is the acquisition, evaluation, and horizontal distribution of the indigenous, local knowledge that exists among farmers (Berry, 1984; Ehrenfeld, 1987).

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×
LOW-INPUT CROP AND LIVESTOCK SYSTEMS

Livestock production is a major agricultural enterprise in the southeastern United States. In Virginia, for example, beef cattle is the leading agricultural commodity, averaging $360 million annually (Virginia Agricultural Statistics Services, 1988). Current livestock production systems in this region rely heavily on forage and grain crops produced on the farm. A major portion of the variable production costs for most farms in the region is for the purchase of synthetic fertilizers, insecticides, and herbicides. Various alternative production practices are available, however, that have the potential for reducing the quantity of these inputs while maintaining or increasing yield (National Research Council, 1989).

Forages play a unique role in creating sustainable and profitable agricultural systems (Parker, 1990). Their dense canopy and extensive root systems stabilize soils, largely preventing soil erosion and fertilizer chemical movement into groundwater and surface waters. Nitrogen can be supplied to the soil-plant-animal system through legumes, providing a high-quality diet to grazing animals and avoiding purchases of nitrogen fertilizers. Properly managed, grazed perennial pastures require fewer inputs of seed, fertilizers, and lime and have lower planting and harvesting costs compared with those of annual row crop systems. Forage provides the major feed for beef cattle throughout the South, particularly for cow-calf and stocker cattle operations. Because of its favorable soil and climate, the South has a comparative advantage for forage production over many other areas of the country, and high-quality forages can, through proper management, be utilized in grazing systems nearly year-round.

The recent availability of economical and practical fencing materials has renewed interest in intensified grazing systems that allow for increased animal numbers per unit of land area. Grazing management systems can promote efficient recycling of nutrients for optimum plant and animal production, and can avoid contamination of surface water and groundwater. Controlled grazing can also promote vigorous growth of desirable forage species and reduce growth and encroachment of weedy species, thus reducing or eliminating the need for herbicides. These systems, however, must be compatible with the management capabilities of farmers who are often employed in off-farm enterprises.

Economically viable all-forage systems have been developed for cow-calf and stocker production (Allen et al., 1987, 1989c; Blaser, 1986). Recent research has demonstrated that stocker cattle grazed on tall fescue-alfalfa (Festuca arrundinacea-Medicago sativa) during fall and winter made higher daily gains both during the growing phase and again 1 year later when these cattle were finished on corn silage (Allen et al., 1989b). These pastures were maintained during 6 years with no nitrogen fertilizer. Yields

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

were similar to all fescue pastures where nitrogen was applied twice yearly at 143 pounds/acre (lbs/acre) each year. Soil nitrate and ammonium levels were similar between pastures where nitrogen was applied and those where alfalfa was grown, but nitrogen utilization by sheep was improved by inclusion of the legume compared with that of the nitrogen-fertilized grass (Absher et al., 1989). Systems for rotational or continuous grazing for cows, calves, and 1stockers have also been developed (Allen et al., 1989a). Recently, research has been initiated to develop systems for taking stocker steers to a finished weight and grade to meet present market demands (Fontenot et al., 1985).

In addition to forages, corn (Zea mays) production plays a central role in southeastern livestock systems. This crop was chosen as a major focus for the study described in this chapter to evaluate low-input practices because of (1) the large acreage in the southeast; (2) the high-input requirements of fertilizers, herbicides, and insecticides in corn production; and (3) the high rates of soil erosion commonly associated with corn production, particularly where conventional tillage is used.

Growing winter-annual legumes is an important alternative practice for reducing nitrogen (N) fertilizer use in corn production in the southeast and for improving soil conservation and productivity (Hargrove and Frye, 1987). Legume cover crops can contribute more than 80 lbs of N per acre to the succeeding crop (Corak et al., 1987; Ebelhar et al., 1984; Hargrove, 1986; Mitchell and Teel, 1977; Neely et al., 1987). Extensive work on the use of legumes in conservation tillage systems has been summarized by Power (1987). However, very few farmers in the mid-Atlantic region and other areas of the South utilize these legumes in their production systems.

No-till planting of corn into cover crops or previous crop residue without primary tillage has been widely used by farmers in an effort to reduce soil erosion as well as production costs. A common practice in the mid-Atlantic region is to plant rye (Secale cereale) in the fall as a winter cover crop and then desiccate the rye in the spring with a herbicide prior to corn planting. The rye protects the soil during winter, recycles some soil nitrogen, and contributes a moisture-conserving mulch for the corn crop.

Insect pest problems, however, can be increased by using a rye cover crop. No-till corn planted into a rye cover crop has a higher incidence of damage from the common armyworm (Pseudaletia unipuncta Haworth), however, than do conventionally tilled fields or fields without a rye cover crop. Adult armyworm moths lay eggs in the rye, which serves as host for the developing larvae. When the rye is desiccated with the herbicide, the army-worm larvae move onto the corn seedlings, frequently causing severe defoliation and economic damage. To control this pest, growers commonly use a prophylactic application of an insecticide mixed with the herbicide when the cover crop is killed.

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

One conservation tillage alternative to no-till planting is that of ridge-till planting. Ridge-till systems have been used quite successfully for corn and soybean production in the Midwest (Behn, 1982; Little, 1987; National Research Council, 1989), but little work with ridge-till systems has been reported under southeastern conditions. While functioning as effective conservation tillage systems, ridge-till systems permit mechanical cultivation, reducing or eliminating the need for weed control with herbicides. In the low-input corn research project reported here, the central focus is the integration of winter-annual cover crops into ridge-till systems for corn production. Particular emphasis is placed on weed management, evaluation of mechanical cultivation, the role of the cover crop mulch in weed suppression, and banded herbicide applications.

RESEARCH PROJECT ORGANIZATION

The research and education project described here comprises four distinct yet closely interrelated components: (1) establishment of a long-term crop and livestock farming systems comparison study, (2) development of a low-input corn production system, (3) development of a prototype expert system for whole-farm crop rotation planning, and (4) implementation of an extension education program.

An interdisciplinary research group involving faculty and graduate students from six academic departments at Virginia Polytechnic Institute and State University (VPI&SU) was involved in the design and operation of these projects. Two farmers and several extension faculty members participated in discussions of project design and field implementation. This degree of interdisciplinary cooperation is essential for this type of project to be successful and is a unique attribute of this effort. Some components of this project were initiated in 1987; however, major work began in 1988 with funding from the U.S. Department of Agriculture (USDA) low-input sustainable agriculture program.

CROP-LIVESTOCK SYSTEMS COMPARISON STUDY

In order to examine the long-term productivity and ecological interactions associated with whole farming systems, a replicated crop-livestock farming systems comparison study was established. This interdisciplinary project compares a conventional crop-livestock system typical of the mid-Appalachian region with an experimental, low-input system. The conventional system utilizes the best management production practices most commonly used by growers within the region. The low-input system involves a different integration of farming practices, with specific emphasis on the minimization of soil erosion and the use of agricultural chemical

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

inputs while maintaining or improving economic viability. Both conventional and low-input systems consist of four replicates of 10 acres of land and 6 steers each, for a total of 80 acres and 48 steers. Although the land area and total animal stocking rate remain the same in both systems, the crop mix, rotation plan, and production methods differ between the systems. Grazing is also used more extensively in the low-input system in an effort to reduce harvest costs, optimize forage utilization, and recycle animal manures.

Each 10-acre replicate of the conventional system consists of 4 acres of N-fertilized fescue (for winter stockpiling), 3 acres of a fescue-clover mixture for grazing and hay, 1.5 acres of alfalfa, and 1.5 acres of corn. All crops are grown in the same fields for 5 years, and then the corn and alfalfa fields are rotated. In the low-input system, each 10-acre replicate is divided into a 4-acre field of fescue-alfalfa mixture for stockpiling, grazing, or hay, and four 1.5-acre fields are rotated among the following crops in a 4-year rotation: corn, wheat (Triticum aestivum) and foxtail millet (Setaria italica) (double-cropped), and alfalfa (2 years). Insect pest management practices in the low-input system rely on rotational effects, and insecticides are applied based on pest population sampling and economic thresholds. Use of preemergent herbicides is minimal, with postemergent herbicides and rates based on the weed species present and their densities and stages of growth.

It is hypothesized that the low-input crop rotation and grazing system will reduce need for insecticides, herbicides, and fertilizers. Specifically, (1) spring and fall grazing of alfalfa will reduce the need for insecticides for control of alfalfa weevil, (2) planting of alfalfa following millet will reduce the need for herbicides and insecticides during establishment, (3) first-year corn following alfalfa will not require insecticides for corn root-worm or armyworm control and will have reduced N fertilizer needs, (4) inclusion of alfalfa in the fescue pasture will eliminate N fertilizer needs for the grass, (5) grazing of all land areas will aid in recycling nutrients and reducing fertilizer needs, and (6) scouting for weeds and insect pests and using pesticides based on economic thresholds should also reduce pesticide inputs.

Plot Location and Sampling

This experiment was established at the VPI&SU Whitethorne Research Farm, near Blacksburg, Virginia, during 1988 and 1989. Each crop or pasture block was located on a uniform soil landscape with a uniform cropping and cover history. A survey of the dominant soil types was made to ensure uniformity within experimental blocks. Large bulk soil samples were taken in the early spring of 1989 before the addition of fertilizers and pesticides. An additional sampling was made in the late summer of 1989,

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

and the soil within each plot will be sampled annually. Soil samples have been analyzed for pH and nutrient levels and are undergoing analysis for organic matter, aggregate stability, and several other parameters. Changes in important soil parameters will be carefully documented in each plot over time, as will all nutrient additions and removals.

Pasture Establishment

Four replications of pastures for the LISA and conventional systems were established during the summer and fall of 1989. Pastures for the LISA system are tall fescue-alfalfa (Festuca arundinacea-Medicago sativa). Pastures for the conventional system are (1) tall fescue and (2) tall fescuered clover (Trifolium pratense). To prepare the land for pasture establishment, the entire area was seeded in millet (Seteria italica) in June 1989. Millet was harvested for hay in August, and the entire area was sprayed with paraquat. Pastures were established by drilling seed into the residual sod. Lime was applied as indicated by soil analyses in the early spring of 1989. Pastures were fertilized at the time of crop establishment with N, phosphorus, and potassium according to soil test recommendations from the VPI&SU Soil Testing Laboratory.

Establishing the Crop Rotation Sequence
LISA System

In order to initiate the crop rotation sequence required in this experiment, Cimmaron alfalfa was seeded into three blocks and corn was seeded into the fourth block in the spring of 1989. Pioneer 3192 corn was no-till drilled into herbicide-killed sod in 1.5-acre blocks with four replications. Alfalfa was drilled into herbicide-suppressed sod with four replications of each of the three blocks. Fertilizer and lime were applied at the time of establishment of the respective crops based on soil test recommendations. Acceptable stands were achieved. Abruzzi rye was drilled into one alfalfa block in the fall of 1989. This rye was killed by mowing in the spring of 1990 for no-till seeding of corn. Corn was harvested as silage in September 1989, and the plots were overseeded with Massey wheat. Wheat was harvested in 1990 and was followed by millet preparatory to the planting of alfalfa. This completed the establishment of the rotation sequence for the LISA system of corn, wheat, millet-alfalfa, and alfalfa.

Conventional System

Pioneer 3192 corn and Cimmaron alfalfa were established by the no-till method into herbicide-killed sods in the spring of 1989 in blocks of 1.5

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

acres each with four replications. Alfalfa establishment was successful, beginning the 5-year stand life for this crop. Corn was harvested for silage in September 1989, and Wheeler rye was drilled into the stubble. Rye was killed with paraquat in the spring of 1990, preparatory to no-till establishment of the second-year corn crop. Lime and fertilizer were applied following soil test recommendations, as described above for LISA systems.

Establishment of all crops was successful; thus, no delays are anticipated in the progress of this project. Cattle began grazing the systems in November 1990, and fencing and water systems were completed by the time the cattle entered the project.

Sampled Variables

System productivity will be compared by measuring animal gains (both per animal and per area) and carcass quality, and excess forage will be harvested for hay. All systems will provide maximum grazing and minimum hay harvesting and feeding. The required inputs of labor, fertilizer, seeds, fencing, water, and shade will be compared among the systems. The influence of the grazing system on uniformity of nutrient recycling will be determined. Changes in soil physical and chemical properties will be monitored over time. Shifts in botanical composition within pastures will be measured to determine weed percentages and types and the dominance of desirable forage species. Percentage ground cover will be measured, and erosion potential will be monitored. The effects of animal impacts on soils will be determined by measurements of bulk density and characterization of traffic patterns and camping sites. The distribution of manure within pastures as influenced by the grazing system and the presence of shade will be evaluated.

An economic analysis of inputs, fixed costs, labor, and profitability will be conducted for each system. The potential of systems to provide economically viable forage and beef cattle systems for farmers in the region will be determined. The potential impact of the new systems (if adopted) on local employment and income profiles will be estimated.

LOW-INPUT CORN PRODUCTION SYSTEMS

Three separate research subprojects have been conducted under the objectives of this project: (1) evaluation of the contribution of various winter-annual legume and small grain combinations to silage corn production, (2) evaluation of alternative cover crop management practices for winter-annual cover crops in no-till corn (comparing the effects of rotary mowing with those of conventional herbicide desiccation), and (3) evaluation of a ridge-till production system which uses winter-annual cover crops.

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×
Contribution of Winter-Annual Legume and Small Grain Cover Crop Combinations to Silage Corn Production

This experiment was conducted near Blacksburg, Virginia, in 1987 to 1989 on a Hayter cobbley loam soil. A 2-by-6 factorial experimental design with four replications was used to examine contributions of several winter-annual cover crops to corn production. Fall-seeded cover crops included rye, hairy vetch (Vicia villosa), bigflower vetch (Vicia grandiflora), rye-hairy vetch, and a hairy vetch-bigflower vetch mixture.

Two tillage practices were used: (1) no-till, with corn slot-planted directly into the herbicide-killed cover crops, and (2) minimum-till, in which the cover crops were disked prior to corn planting. For each tillage practice, crops were grown in control plots by standard practices. This consisted of a fallow plot with 125 lbs of N per acre for the minimum-till plots and a rye cover crop with 125 lbs of N per acre for the no-till plots. The individual plot size was 12 feet in width (four corn rows, 36 inches apart) and 50 feet in length.

Cover crops in the minimum-till plots were incorporated about 2 weeks before the corn was planted. Cover crops in the no-till treatments were desiccated with paraquat herbicide immediately before the corn was planted. All plots were treated with a residual herbicide mixture of metolachlor and cyanazine. Pioneer 3233 corn was planted on May 19, 1988, and on May 22, 1989, following cover crop kill and harvested as for silage (35 to 42 percent dry matter).

Cover crop yields, total nitrogen, and carbon:nitrogen (C:N) ratios were determined prior to disk incorporation or desiccation. The effects of cover crops and tillage practices on weed densities, water infiltration rates and soil moisture, seasonal N uptake, and corn silage yields were determined. Only the effects on corn silage yields and soil moisture are reported here.

Results

The results reported here are summarized from the work of Sullivan (1990). Soil moisture during the corn growing season was correlated (p < 0.05) to the biomass of the cover crop on the soil surface, confirming the importance of soil mulches in reducing moisture stress to crops. In late summer, soil moisture was highest under the rye cover crop mulch. This was possibly due to the high C:N ratio of the rye (58:1) compared with the much lower C:N ratio of the vetch cover crops (11:1), which reduced the rate of microbial decomposition of the rye cover crop. In addition, reduced water uptake by nitrogen-deficient corn plants growing in the rye-only plots could have influenced the soil water content.

In both years in both tillage systems, corn that was grown following a

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

mixture of hairy and bigflower vetch cover crops produced yields similar (p > 0.05) to those of corn that was grown without cover crops plus 125 lbs of N per acre or with a rye cover crop plus 125 lbs of N per acre (Figure 11-1). Pure stands of either bigflower or hairy vetch produced corn silage yields comparable to those in 1988, but produced less corn (p < 0.05) in 1989 than did the vetch mixtures or the controls (Table 11-1). Pure stands of rye cover crop without any nitrogen fertilizer produced the lowest corn yields in the no-till treatments in both years. Mixtures of rye and vetch produced corn yields similar to those of the control in 1988, but they yielded significantly less in 1989.

A rye-vetch mixture may be a more effective cover crop, however, since the rye produces a ground cover more quickly in the fall. However, additional N fertilizer will be needed for the rye-vetch cover crop mixture to provide economically optimum yields (Frye et al., 1985; Ott and Hargrove, 1989). Although the purpose of this experiment was not to evaluate cover crops as possible forage crops, the rye-hairy vetch mixture produced significantly more biomass than any of the other cover crops did in both years under both tillage systems ( Table 11-2). The total N in the rye-vetch mixture was significantly higher than that in the rye alone. Since many farmers in the mid-Atlantic region grow rye as a silage double crop followed by no-till corn, the addition of hairy vetch to the rye could increase the yields and protein content of the forage. The delayed growth of the vetch in the spring, however, may reduce this benefit.

Corn establishment problems were encountered when no-till planting into the cover crops was used. The rolling coulter in front of the no-till corn planter tended to push the cover crop into the planted slot, reducing seed-to-soil contact. The cover crop residue also impeded seedling emergence in places.

All cover crop treatments were analyzed under the two tillage regimes for economic feasibility; however, only the hairy vetch and control crops grown by standard practices are discussed here. Variable costs for labor, machinery, seeds, pesticides, lime, and fertilizer were based on 1989 prices (Maxey et al., 1989). Differences in net returns occurred among treatments and among years (Table 11-3). Averaged across both years and cover crops, the no-till system produced a $44 greater net return per acre than that of the disk tillage system. Within the no-till system, the hairy vetch cover crop produced net returns of about $22/acre greater than that of the rye cover crop with 125 lbs of N per acre. Under disk tillage, net returns were similar, with fallow plus fertilizer producing an average of $4/acre more net return than that of the vetch cover crops.

These data augment a growing body of published literature confirming the economic advantages of using winter legume cover crops in corn and other cropping systems (Frye et al., 1985; Ott and Hargrove, 1989). How-

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

FIGURE 11-1 Influence of cover crops and tillage on corn silage yields near Blacksburg, Virginia, 1988–1989. Vertical bars within a cluster followed by different letters are statistically different (F-protected LSD; alpha = 0.05).

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

TABLE 11-1 Corn Silage Yields Following Various Winter Annual Crops and Fallow Plus N Fertilizer, Blacksburg, Virginia, 1988 and 1989

Cover Crop

Corn Silage Yields* (tons/acre)

 

1988

1989

Fallow + 125 lbs of N/acre

19.4ab

22.2a

Hairy + bigflower vetch

20.8a

20.9ab

Hairy vetch

20.7a

19.5bc

Bigflower vetch

16.9b

17.7c

Rye + hairy vetch

17.3b

14.9d

Rye

16.3b

11.3e

NOTE: N, nitrogen. Means within a column followed by different letters are different (F-protected LSD; alpha= 0.05).

* Tons of silage per acre at 35 percent dry matter.

No additional N fertilizer was used to grow the corn following the cover crops.

ever, a critical underestimation of the value of cover crops has occurred in virtually all economic analyses of cover crops, including the net benefit analysis of this project described above. Net benefit analyses, even though multiyear in scope, are generally based on single-year crop yield responses. The potential long-term, cumulative beneficial effects resulting from soil conservation, improvement in soil organic matter content and soil tilth, and delayed nutrient release from the mineralized cover crops are not factored into the analyses because the published studies have been short term in nature (Allison and Ott, 1987). Additional long-term research is needed to incorporate these variables into economic analyses of cover crops.

Evaluation of Alternative Cover Crop Management Practices for Winter-Annual Cover Crops in No-Till Corn

The second subproject for developing a low-input corn system involved the evaluation of alternative cover crop management practices for rye cover crops in no-till corn, comparing the effects of mowing with those of conventional herbicide desiccation. Demonstration experiments were conducted on five farms in two Virginia counties in 1988 and 1989. Rye cover crops were planted in September and October 1988. In early May, two experimental treatments were established in a randomized block design: (1) conventional herbicide desiccation with paraquat and (2) mowing with a tractor-mounted rotary mower. Plots were 60 by 50 feet, and

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

TABLE 11-2 Cover Crop Biomass and Total N Production Averaged Across Two Tillage Methods

 

Cover Crop

Year

Rye

Hairy Vetch

Bigflower Vetch

Hairy Bigflower Vetch

Rye-Vetch

Biomass tons/acre

1988

3.1a

1.6a

1.3a

2.0a

4.3a

1989

2.1b

1.9a

1.6a

1.8a

2.6b

Total lbs of N/acre

1988

60a

85b

45b

124a

133a

1989

36b

147a

112a

133a

109b

NOTE: N, nitrogen. Means within a half column followed by the same letter are not significantly different (F-protected LSD: alpha = 0.05).

each treatment was replicated four times. Corn was planted with the various no-till corn planters used by the cooperating farmers. Residual herbicides and fertilizers were applied based on the cooperating farmers' practices.

Densities of armyworm larvae were estimated from the time of corn seedling emergence until armyworm larvae were no longer found. Sampling was conducted every 4 to 5 days. The sampling unit was a 2-by-5-foot quadrat placed lengthwise over a corn row. Other variables examined included armyworm parasitoids, ground-dwelling predator populations, cover crop regrowth, and corn silage yields.

TABLE 11-3 Estimated Net Return to Management from Corn Silage Following Two Cover Crop Treatments and Two Tillage Methods

 

Estimated Net Return (S/acre)*

 

Vetch

Rye + 125 lbs N/acre

Year

No-Till

Disk

No-Till

Disk

1988

436

345

389

284

1989

373

350

376

421

Average

405

348

383

352

NOTE: N, nitrogen.

* Based on corn silage at $25.00/ton and N fertilizer at $0.24/lb.

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×
Results

The results reported here are summarized from the work of Laub (1990). In four of the five fields in both years, mowing significantly reduced armyworm population densities in the early stages of corn growth (Figure 11-2). In the fifth (Bishop) field in 1989, a very poor corn stand was produced in both treatments because of excessively wet conditions and feeding by the common garden slug. In the Bishop field, armyworm numbers were higher in the plots that were treated by mowing, although the densities in plots that were treated by both methods were very low. Increased numbers of certain species of predacious ground beetles and spiders were also higher early in the season in the mowed treatments in some of these fields, although it is not known whether these predators influenced armyworm abundance. Reduction in armyworm densities in the mowed plots could also be due to mechanical destruction during the mowing process.

Mowing also adequately suppressed rye cover crop regrowth in all fields, but it should be noted that the rye was mowed after the initiation of flowering. Mowing before this stage of growth does not kill the rye plant. Corn silage yields tended to be slightly higher in the mowed treatments than the herbicide-treated rye in all fields, although these differences were not statistically significant (p < 0.05) (Figure 11-3).

Costs of the cover crop management methods are calculated to be ca. $6.00/acre for mowing and $10.00/acre for paraquat spraying. Calculated costs include fuel, maintenance, labor at $5/hour, and depreciation on equip-ment. Herbicide cost was calculated at 2 pints of paraquat (Gramoxone Super) per acre, which cost $40.35/gallon in 1990. The recommended application rate for paraquat for contact killing of rye cover crops is 1.5 to 2.5 pints/acre (Webb et al., 1988). The net economic benefits of the two cover crop management practices were compared by using mean silage yields and calculated costs of the two treatments (Table 11-4). Averaged across both years and all fields, mowing of the cover crop produces an estimated net return of $40/acre more than the use of paraquat does.

Although mowing winter cover crops appears to have the potential both to reduce herbicide and insecticide use and to increase yields and profits, additional research is needed to determine proper timing of mowing in relation to cover crop phenology to ensure cover crop kill. Also, the requirements for labor during a critical time of year may restrict the adoption of this practice. Spraying of a herbicide could be accomplished at a rate of 15.3 acres/hour (using a 35-foot boom traveling at 6 miles/hour and with a 60 percent efficiency), whereas only 4.9 acres could be mowed per hour (using a 12-foot-wide mower traveling at 4 miles/hour and with an 85 percent efficiency).

Future on-farm research will continue to evaluate the potential of rotary

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

FIGURE 11-2 Influence of cover crop kill practices on mean number of total armyworm larvae in no-till corn in southwest Virginia, 1988 –1989.

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

FIGURE 11-3 Influence of cover crop kill practices on corn silage yield (35 percent dry matter) in southwest Virginia, 1988–1989. T-bars above the solid bars represent standard errors.

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

TABLE 11-4 Estimated Net Benefit of Mowing a Winter Cover Crop Compared with Spraying with Paraquat for No-Till Silage Production, 1988 and 1989

 

Fields

 

1988

1989

Cover Crop Kill Treatment*

Bishop

Childress

Bishop

VPI&SU

Allison

Average Value ($) of Silage/Acre

Mow

255

267

77

376

293

Spray

213

231

44

342

258

Silage benefit/acre of mowing

42

36

33

34

35

Savings/acre from mowing the cover crop

4

4

4

4

4

Total benefit from mowing

46

40

37

38

39

NOTE: VPI/SU, Virginia Polytechnic Institute and State University.

* Mow indicates mowing with a rotary mower (bushog); spray indicates spraying with paraquat at 2 pints/acre.

Calculated for corn silage at 35 percent dry matter, valued at $25.00/ton.

Costs of cover crop kill treatments: spraying, $10.00/acre: mowing, $6.00/acre.

mowing as an alternative to herbicide desiccation of the cover crop. Since no insecticides were applied to any of the treatments in 1988 or 1989, an additional treatment variable, with and without insecticide, will be included to determine whether mowing alone will replace the need for insecticide to control armyworm populations. Difficulty in planting into the mowed cover crop residue was also encountered in a few fields in this study. Corn planters will need to be equipped with residue-clearing attachments, although these are readily available for most modern conservation-tillage planters. Flail mowers will also be evaluated as an alternative to rotary mowers to improve the uniformity of distribution of the cover crop residue on the soil surface after mowing.

Evaluation of Ridge-Till Corn Production Systems Using Winter-Annual Cover Crops

Weed management practices were evaluated in a ridge-till corn production system using winter-annual cover crops. The experiment was conducted at the VPI&SU Whitethorne Research Farm, near Blacksburg, Virginia. Ridges were established in September 1988 by using a Buffalo cultivator (Fleischer Manufacturing, Inc., Columbus, Nebraska). Ridges were on 36-inch centers

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

and were approximately 7 inches tall. A cover crop of rye (90 lbs/acre) and hairy vetch (20 lbs/acre) was planted with a spin spreader on September 29, 1988. Very little hairy vetch cover crop was produced; thus, the cover crop consisted primarily of rye. The cover crop was killed with a tractor-drawn rotary mower (bushog) on May 24, 1989. Pioneer 3295 corn was planted on June 2, 1989, by using a Buffalo ridge-till planter (Fleischer Manufacturing, Inc.). Seventy pounds of actual N fertilizer was broadcast per acre on June 26, 1989, with an additional 30 lbs of N per acre broadcast on July 28.

A 2-by-4 factorial experiment was used to evaluate various combinations of mechanical and banded herbicide weed management practices. Ridges and furrows were treated separately, with four weed control treatments used on the ridges: preemergence herbicide, postemergence herbicide, cultivation, and control (no weed control). Two furrow treatments were used: preemergence herbicide and control (no weed control). A third weed control variable for the furrow, cultivation, was planned for the experiment, but excessively rainy weather delayed cultivation until the corn was too tall to avoid plant damage by the cultivator tool bar. This treatment will be included in the 1990 second-year replication of this experiment.

Weed biomass was sampled on August 8 and 9, 1989, by using 18-by-60-inch quadrats. Twelve randomly selected samples were taken in each treatment plot, six samples each in the furrow and on the ridges. Weeds were sorted into four categories: broadleaves, grasses, yellow nutsedge (Cyperus esculentus L.), and Pennsylvania smartweed (Polygonum pennsylvanicum L.). Samples were oven dried at 130° F for 48 hours, and estimates of total weed biomass per acre were calculated. Grain yields were estimated by removing ears within two 30-foot rows of corn within each plot. Corn was shelled in the field, and subsamples were oven dried to determine dry weight.

Results

Preemergence herbicides provided the best overall weed control in both ridges and furrows, although because of fairly high coefficients of variation in the data, no statistically significant differences (p < 0.05) were detected between the control (no weed control) and the preemergence herbicide treatment for total weed biomass (Table 11-5). Cultivation apparently stimulated germination of smartweed, with significantly more smartweed biomass than when no weed control treatment was used. Weed biomass in the furrows, where there was a thick mulch of cover crop residue, was considerably less than that on the ridges, where the soil was disturbed and no mulch existed.

Although weed control varied among treatments, all treatments produced

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

TABLE 11-5 Effects of Weed Control Practices on Weed Biomass in a Ridge-Till Corn Production System, 1989*

 

Pounds of Weeds/Acre

Weed Control Practice

BL

PSW

GR

YNS

Total

Ridge

None

149b

19b

224ab

1,648

2,040ab

Cultivation

163b

1,784a

117b

994

3,056a

Preemergence herbicide

110b

38b

22b

474

645b

Postemergence herbicide

502a

17b

469a

484

1,472ab

Furrow

None

52

277

43a

203

574

Preemergence herbicide

53

3

2b

128

185

NOTE: Means within a half column followed by the same letter arenot significantly different (Duncan multiple range test; alpha = 0.05).

* Samples were taken on August 8 and 9, 1989. Calculated on an oven-dried (135° F) basis.

BL, broadleaves; PSW, Pennsylvania smartweed; GR, grasses; YNS, yellow nutsedge.

statistically similar (p > 0.05) corn yields (Table 11-6). Areas surrounding the experimental plots were covered with a rank growth of Pennsylvania smartweed; however, within the ridge-till experiment, smartweed levels were relatively low. Although these first-year results are preliminary, they indicate that the ridge-till system, in which a mowed cover crop was used for mulch and a very shallow skimming of the ridge was used during planting, may provide significant levels of weed control, reducing the need for both mechanical and chemical weed controls. A second-year replication of this experiment is in progress, with rye-hairy vetch cover crops established in the fall of 1989. Economic analysis of both years' results will be conducted at the end of the 1990 season.

EXPERT SYSTEM DEVELOPMENT

Over the last decade, expert systems have been used extensively in industries from medicine to defense to solve complex problems that normally require human expertise. They are particularly well suited to problems in which the solution requires judgment, dealing with uncertainty, qualitative assessments, and rules of thumb rather than solutions to mathematical equations. When expert systems are integrated with conventional computer decision-making aids like simulation models and data bases, they become even more powerful, acting like a cadre of experts with access to sophisticated prediction tools and data.

Development of a low-input farming plan for a specific farm is an ideal

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

TABLE 11-6 Effects of Weed Management Practices on Corn Grain Yield in a Ridge-Till System Using a Winter Rye Cover Crop, Blacksburg, Virginia, 1989

Weed Control Treatment

Mean Corn Yield (bushels/acre)

Ridge

Furrow

None

None

99.5

None

Preemergence herbicide*

93.2

Preemergence herbicide

None

99.8

Preemergence herbicide

Preemergence herbicide

84.8

Cultivate

None

94.2

Cultivate

Preemergence herbicide

89.1

Postemergence herbicide

None

94.7

Postemergence herbicide

Preemergence herbicide

100.1

* Atrazine (AAtrex) was used at 3 pints/acre with metolachlor (Dual) at 2 pints/acre.

One cultivation with a modified V-sweep cultivator (set 5 inches from the centerline of the corn row) on June 30, 1989. Corn was approximately 12 inches tall and was at the six- to seven-leaf stage.

Bentazone (Basagran) was used at 2 pints/acre with crop oil (Dash) at 2 pints/acre.

problem for expert system techniques. There is an extensive qualitative knowledge base concerning the effects of crop rotations, tillage practices, legume N, and other practices on soil properties and crop productivity. Much of this knowledge cannot be put into mathematical equations because it is imprecise or qualitative. It is not possible or useful in a mathematical simulation, for example, to say that the incorporation of manure into soil increases the soil's tilth. Unless it can be transcribed to a rate function, the model cannot use this information. An expert system, on the other hand, like the one described here, is constructed from sets of statements. These statements make up an expert system's knowledge base, the knowledge that lets the computer solve a problem.

A prototype computer-aided decision-making system called CROPS (crop rotation planning system) has been developed for farm-level planning. This program uses artificial intelligence techniques to generate crop rotation plans for individual farms, implementing low-input sustainable practices and comparing these plans with conventional alternatives. It answers a fundamental need in the pursuit of a sustainable agriculture because it is impossible to implement low-input sustainable practices without addressing the whole-farm planning problem. Planning crop rotations involves or influences (1) the entire acreage of the farm, (2) tillage and soil conservation plans, (3) pest management, (4) use and purchase of fertilizers and lime, (5) farm economics, (6) farm diversification, and (7) livestock requirements and operation.

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

CROPS is now under further development, having received additional financial support from the 1990 USDA LISA program. The final version will not only generate crop rotation plans that implement low-input practices, it will also analyze the plans generated and allow the farmer-user to compare the generated plans with alternatives. The system will include simulation models for estimating soil erosion and for analyzing the financial status of the farm under various alternative combinations of crop mixes, farm program participation, and machinery complement.

EXTENSION EDUCATIONAL PROGRAMS

Several educational programs for farmers and extension personnel were conducted through the Virginia Cooperative Extension Service to provide practical information of low-input sustainable farming practices and systems. These included the following:

  1. A 1-day training session on low-input farming systems was held for extension agents as part of their annual in-service training. Extension agents learned new low-input practices that can be used across a wide array of cropping systems, as well as additional sources of information to serve interested clientele.

  2. The statewide Virginia Conference on Sustainable Agricultural Systems, March 13–14, 1989, in Charlottesville, was cosponsored by the Virginia Cooperative Extension Service, the Virginia State Horticultural Society, and the Virginia Division of Soil and Water Conservation.

  3. A multicounty farmer educational meeting on sustainable agriculture in Amelia County was cosponsored by the Virginia Cooperative Extension Service and the Virginia Farm Bureau Federation. Multicounty grower meetings on sustainable agriculture were also conducted at two other locations in 1989.

  4. A research update in-service training session on LISA projects for extension agents of the Virginia Cooperative Extension Service West-Central District was conducted by LISA project personnel.

  5. A low-input sustainable agriculture field day was held in August 1989 at the Whitethorne Research Farm, Blacksburg, Virginia.

  6. A conference entitled “Farming for Profit and Stewardship” was held on March 15–16, 1990; it was cosponsored by the Virginia Cooperative Extension Service, the Virginia Department of Agriculture and Consumer Services, the Soil Conservation Service, and other groups.

CURRENT PROJECT STATUS AND FUTURE PLANS

The long-term crop and livestock systems comparison study is now established, with all rotational sequences in place. Cattle will be introduced

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

into the experiment in the fall of 1990. Additional funding is currently being sought to continue operation of this study. As a long-term study, results of this work are not anticipated before completion of the first rotational cycle in 1995. In the interim, the project will serve as a demonstration model to teach farmers, extension personnel, and other agricultural professionals the concepts of farming systems design to maximize beneficial agroecological processes and to reduce off-farm inputs.

On-farm research on the use of mowing as an alternative to herbicides for cover crop desiccation and insecticides for armyworm control is continuing. The Tennessee Valley Authority is providing additional funding for this work. Research on the integration of cover crops into low-input ridge-tillage systems will also continue. Development of the computer-aided crop rotation farm planning system will be continued, with on-farm testing of the system anticipated in 1991.

Funding from the USDA LISA program has provided for a significant level of research and extension education programs that would have been impossible otherwise. Establishment of the long-term crop and livestock systems study will provide a catalyst to obtain additional funding to continue this work. In addition, the projects have stimulated a broad interest in the general area of sustainable agriculture within the university, extension field staff, and agricultural communities.

REFERENCES

Absher, K. L., V. G. Allen, and J. P. Fontenot. 1989. Effect of nitrogen fertilization of legumes on digestibility and nitrogen utilization of stockpiled fescue. Journal of Animal Science 67(Suppl. 1):270.

Allen, V. G., J. P. Fontenot, W. P. Green, R. C. Hammes, Jr.s, and H. T. Bryant. 1987. Year-round forage systems for beef cow-calf production. Journal of Animal Science 65(Suppl. 1):347.

Allen, V. G., J. P. Fontenot, and R. F. Kelly. 1989a. Performance and carcass characteristics of beef cattle on forage-based systems. Journal of Animal Science 67(Suppl. 1):270.

Allen, V. G., J. P. Fontenot, and W. H. McClure. 1989b. Intensive grazing systems for beef cattle. Pp. 160–164 in Proceedings of the 1989 American Forage and Grassland Conference. Belleville, Pa.: American Forage and Grassland Council.

Allen, V. G., J. P. Fontenot, W. P. Green, and R. C. Hammes, Jr. 1989c. Year-round grazing systems for beef production from conception to slaughter. Pp. 1197–1198 in Proceedings of the XVI International Grasslands Congress, Nice, France.

Allison, J. R., and S. L. Ott. 1987. Economics of using legumes as a nitrogen source in conservation tillage systems. Pp. 145–150 in The Role of Legumes in Conservation Tillage Systems, Proceedings of a National Conference, J. F. Power, ed. Ankeny, Iowa: Soil and Water Conservation Society.

Behn, E. E. 1982. More Profit with Less Tillage. Des Moines, Iowa: Wallace-Homestead Press.

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

Berry, W. 1984. Whose head is the farmer using? Whose head is using the farmer? Pp. 19–30 in Meeting the Expectations of the Land, W. Jackson, W. Berry, and B. Colman, eds. San Francisco: North Point Press.

Blaser, R. E. 1986. Forage-animal management systems. Virginia Agricultural Experiment Station Bulletin No. 86-7. Blacksburg, Va.: Virginia Polytechnic Institute & State University.

Corak, S. J., W. W. Frye, M. S. Smith, J. H. Grove, and C. T. MacKown. 1987. Fertilizer nitrogen recovery by no-till corn as influenced by a legume cover crop. Pp. 43–44 in The Role of Legumes in Conservation Tillage Systems, Proceedings of a National Conference, J. F. Power. ed. Ankeny, Iowa: Soil and Water Conservation Society.

Ebelhar, S. A., W. W. Frye, and R. L. Blevins. 1984. Nitrogen from legume cover crops for no-tillage corn. Agronomy Journal 76:51–55.

Ehrenfeld, D. 1987. Sustainable agriculture and the challenge of place. American Journal of Alternative Agriculture 2:184–187.

Fontenot, J. P., F. P. Horn, and V. G. Allen. 1985. Forages and slaughter cattle. Pp. 570–578 in Forages, the Science of Grassland Agriculture, 4th ed., M. E. Heath, R. F. Barnes, and D. S. Metcalfe, eds. Ames, Iowa: Iowa State University Press.

Frye, W. W., W. G. Smith, and R. J. Williams. 1985. Economics of winter cover crops as a source of nitrogen for no-till corn. Journal of Soil and Water Conservation 40:246–249.

Hargrove, W. L. 1986. Winter legumes as a nitrogen source for no-till grain sorghum. Agronomy Journal 78:70–74.

Hargrove, W. L., and W. W. Frye. 1987. The need for legume cover crops in conservation tillage production. Pp. 1–4 in The Role of Legumes in Conservation Tillage Systems, Proceedings of a National Conference, J. F. Power, ed. Ankeny, Iowa: Soil and Water Conservation Society.

Harwood, R. R. 1990. A history of sustainable agriculture. Pp. 3–19 in Sustainable Agricultural Systems, C. Edwards, R. Lal, P. Madden, R. Miller and G. House, eds. Ankeny, Iowa: Soil and Water Conservation Society.

Laub, C. A. 1990. Influence of Cover Crop Management on Armyworm, Pseudaletia unipuncta (Haworth) Seasonal Abundance, Natural Enemies, and Yield in No-Till Corn, and Diurnal Abundance and Spatial Distribution of Armyworm. M.S. thesis. Virginia Polytechnic Institute & State University, Blacksburg.

Little, C. E. 1987. Green Fields Forever; The Conservation Tillage Revolution in America. Washington, D.C.: Island Press.

Luna, J. M., and G. J. House. 1990. Pest management in sustainable agricultural systems. Pp. 157–173 in Sustainable Agricultural Systems, C. Edwards, R. Lal, P. Madden, R. Miller, and G. House, eds. Ankeny, Iowa: Soil and Water Conservation Society.

Maxey, H., T. Covey, B. McKinnon, and A. Allen. 1989. West Central District Crop Budgets. Special Publication. Blacksburg, Va.: Department of Agricultural Economics, Virginia Polytechnic Institute & State University.

Mitchell, W. H., and M. R. Teel. 1977. Winter annual cover crops for no-tillage corn production. Agronomy Journal 69:569–573.

National Research Council. 1989. Alternative Agriculture. Washington, D.C.: National Academy Press.

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

Neely, C. L., K. A. McVay, and W. L. Hargrove. 1987. Nitrogen contribution of winter legumes to no-till corn and grain sorghum. Pp. 48–49 in The Role of Legumes in Conservation Tillage Systems, Proceedings of a National Conference, J. F. Power, ed. Ankeny, Iowa: Soil and Water Conservation Society.

Ott, S. L., and W. L. Hargrove. 1989. Profits and risks of using crimson clover and hairy vetch cover crops in no-till corn production. American Journal of Alternative Agriculture 4:65–70.

Parker, C. F. 1990. Role of animals in sustainable agriculture. Pp. 238–248 in Sustainable Agricultural Systems, C. Edwards, R. Lal, P. Madden, R. Miller, and G. House, eds. Ankeny, Iowa: Soil and Water Conservation Society.

Parr, J. F., R. I. Papendick, I. G. Youngberg, and R. E. Meyer. 1990. Sustainable agriculture in the United States. Pp. 50–67 in Sustainable Agricultural Systems, C. Edwards, R. Lal, P. Madden, R. Miller, and G. House, eds. Ankeny, Iowa: Soil and Water Conservation Society.

Power, J. F., ed. 1987. The Role of Legumes in Conservation Tillage Systems. Proceedings of a National Conference. Ankeny, Iowa: Soil and Water Conservation Society.

Schaller, N. 1989. Low input sustainable agriculture. Pp. 216–219 in 1989 Yearbook of Agriculture. Washington, D.C.: U.S. Department of Agriculture.

Sullivan, P. 1990. Rye and Vetch Intercrops for Reducing Corn Nitrogen Fertilizer Requirements and Providing Ground Cover in the Mid-Atlantic Region. Ph.D. dissertation. Virginia Polytechnic Institute & State University, Blacksburg.

Virginia Agricultural Statistics Service. 1988. Virginia Agricultural Statistics. Richmond, Va.: Virginia Agricultural Statistics Service.

Webb, F. J., R. L. Ritter, E. S. Hagood, J. W. Wilcut, and H. P. Wilson. 1988. Weed control in field crops. Pp. 39–90 in 1988–89 Pest Management Recommendations for Field Crops. Publication No. 456-015. Blacksburg, Va.: Virginia Cooperative Extension Service.

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

12

Solarization and Living Mulch to Optimize Low-Input Production System for Small Fruits

Kim Patten, Jeff B. Hillard, Gary Nimr, Elizabeth Neuendorff, David A. Bender, James L. Starr, Gerard W. Krewer, Randall A. Culpepper, Mike Bruorton, and Barbara J. Smith

In the South, production of most horticultural crops is chemical and labor intensive. Disease, insect, and weed pressures can be major factors that limit successful fruit production. However, some fruit crops, such as blueberries and strawberries, lend themselves to low-input farming systems.

Blueberries can be grown with reduced or no chemical inputs if suitable management alternatives for soil fertility and weed control are available, because disease and insect pressures are minimal. One alternative is the use of living mulches. Under this scenario, a series of cover crops are grown in an all-year rotation between blueberry rows. The cover crops are mowed and windrowed under the blueberry plants for use as a mulch. Through proper selection of living mulch cover crops, weed competition may be eliminated because of allelopathic or smothering effects from the mulch barrier (Putnam, 1988), and nutrient inputs could be supplied by the decomposing mulch (Wagger, 1989). An improved edaphic environment (Patten et al., 1989) and reduced erosion would be additional benefits to the blueberry grower from this agroecosystem.

Chemical fumigation for the control of weeds and soil pathogens is routinely practiced for strawberry production. Fumigants, like methyl bromide, are effective in controlling many soil pests, but they are also expensive, require special licenses and equipment for application, are hazardous to agricultural workers, and may damage the environment. For these reasons a need exists to develop safe and economical alternatives to chemical fumigation.

Soil solarization is a nonchemical pest management practice that can be used to control a plethora of soil pests (Katan, 1981; Pullman et al., 1984;

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

Stapleton and Devay, 1986). This technique relies on increased soil temperatures, using a cover of clear polyethylene film to trap solar energy, to thermally deactivate soil pests. Solarization, however, is not a panacea and is not a widely used farming practice in the South. This lack of adoption partly results from the expense and difficulty of integrating solarization into routine cultural practices.

The cost of integrating solarization into a routine cultural practice for bedded row crops may be reduced by solarizing individual beds. After solarization, the clear plastic is pigmented with a latex paint to cool the soil and to allow planting directly through the plastic (Hartz et al., 1985). This method has been reported to be more cost-effective and require less specialized machinery than the conventional wide-tarp solarization method.

Annual strawberry production is ideally suited for bedded row solarization for several reasons. The strawberry off-season occurs during the hottest time of year (July and August), when solarization is most effective; and soil bedding, fumigation, and plastic mulch are standard practices that are used in the annual production system. This low-input system may be further optimized when it is used in combination with legume cover crops or manure application that enhance soil fertility.

Management-intensive, but chemically input-free, production systems for small fruit in the South not only provide for an opportunity to capitalize on a new market niche but also foster long-term soil productivity and reduce environmental hazards.

The low-input sustainable agriculture (LISA) project that is the subject of this chapter has two objectives:

  • to investigate the feasibility of eliminating fertilizer and herbicide inputs on blueberries grown in the South by using legumes and annual forage rotations for living mulches, and

  • to evaluate solarization and cover crops or manures as replacements for fumigation and fertilizers in annual strawberry production in the South.

OBJECTIVE ONE: BLUEBERRY LIVING MULCHES
General Farm Background

Experimental plots were established at seven growers and one experiment station to demonstrate the efficacy of living mulch systems for blueberries. The planting locations ranged from northeast Texas (Winnsboro, Tyler, and Overton), central east Texas (Nacogdoches), and southeast Texas (Huntsville) to southeast Georgia (Homerville, Chula, and Fargo).

Farm sizes varied from 5 to 50 acres of blueberries. Soils at all locations were typical of those used for blueberry planting, with a sandy loam texture, very low native fertility, and a strongly acidic soil pH (4.1 to 5.5).

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

Nitrogen (N) is readily leached, and frequent N fertilization is needed to ensure production. Average annual rainfall averaged 45 inches in Texas to 50 inches in Georgia, but rainfall patterns were erratic. A rainfall of only 0.5 to 2 inches per month was common during the east Texas summers.

The establishment of living mulch plots was frequently hampered by unseasonably wet or dry weather and severe winter freezes. Inadequate weed control was the only significant pest problem. Growers used conventional orchard floor management practices by applying combinations of preemergent (oryzalin [Surflan] and simazine [Princep]) and postemergent (glyphosate [Round-up] or paraquat) herbicides for control of weeds around the plants.

Experimental Protocols

In Georgia, the following experimental protocol was followed. Living mulch crops were grown in the winter at three blueberry farms (Homerville, Fargo, and Chula). The Chula site had a moderate soil pH (5.5) and fertility, whereas the other sites were strongly acidic and less fertile. The crops that were evaluated are listed in Table 12-1. Seeding methods varied at each site, ranging from harrowing plus grain drill, grain drill into existing orchard floor vegetation, or broadcasting with or without harrowing, depending on the site. Plots were split, with one section receiving no fertilizer, and the other receiving up to 100 pounds of N per acre (lbs of N/ acre). There were two to four replications per treatment, depending on the site.

A somewhat different experimental protocol was followed in Texas. During the winter and summer, cover crops were planted at five grower locations and at the Overton experiment station farm. The crops that were evaluated are listed in Table 12-1. Plots were seeded with a small plot drill with six double-disk openers, spaced 9 inches apart in the middle of the blueberry rows. There were four replications of each crop per site. Plots were reseeded if the initial stands failed in response to environmental stresses. In general, nonlegume plots received 100 lbs of N/acre at planting, and all crops received phosphorus (P) and potassium (K) applications of 20 lbs/acre.

The effects of N on summer living mulches in Texas were evaluated on Tifleaf pearl millet, Headless Wonder sorghum, and Green Graze sorghum sudan. These crops were sown in May at 90 lbs/acre by using a broadcast seeder in the middle of the blueberry rows at the Nacogdoches site. Plots were fertilized with 0, 100, or 200 lbs of N/acre in mid-June. All plots received 36 lbs of K/acre and 22 lbs of magnesium (Mg)/acre. There were three plots per treatment, each of which was 300 feet long.

The capacity of winter legume to supply N for a succeeding summer grain cover crop was evaluated at the Overton site. Sorghum was grown

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

TABLE 12-1 Evaluation of Forage Cultivars for Blueberry Living Mulch Production in Texas and Georgia in 1989 and 1990

Time Period and Forage

Location*

Overall Performance Rating

Winter 1988–1989

   

Tifton 86 ryegrass

HO

Very poor to fair

Gulf annual ryegrass

HO, FR, CH

Very poor to good

Marshall ryegrass

HO, FR, CH, OV

Very poor to good

GI-85 ryegrass

HO

Poor to fair

Wrens abruzzi rye

HO

Very poor to good

Elbon rye

OV, NC, HV, RU, TY

Poor to very good.

Coker 227 oats

HO

Very poor

Florida 302 wheat

HO, OV, NC, NC

Very poor

Atlas 66 wheat

HO

Very poor

Texas 182-85 wheat

OV

Very poor

Beagle triticale

HO

Very poor

B858 triticale

OV, NC

Very poor

T20 triticale

OV, NC

Very poor

Dixie crimson clover

CH, FR, OV, NC, HV, RU, TY

Poor to very good.

Mt. Barker subterranean clover

OV, NC

Very poor to fair.

Common hairy vetch

OV

Poor to good

Summer 1989

   

Tifleaf pearl millet

OV, NC, HV, TY, WB

Good to very good

Headless wonder sorghum

OV, NC, TY, WB

Poor to good

Green graze sorghum sudan

OV, NC, HV, WB

Fair to good

Iron and clay cowpeas

OV, NC, HU, TY, WB

Fair to very good..§

Sun hemp crotalaria

OV, NC, HV, TY, WB

Very poor to very good.§

Everglades 41 Kenaf

OV

Fair to good

Sericae lespedeza

OV

Fair

Winter 1989–1990

   

Gulf ryegrass

HO, OV, NC, HV, TY, WB

Poor to good..§

Elbon rye

OV, NC, HV, TY, WB

Poor to very good..§

Dixie crimson clover

HO, OV, NC, HV, TY, WB

Poor to fair..§.||

Common hairy vetch

OV, WB

Poor.§

Yucchi arrowleaf clover

OV, WB, TY

Very poor to poor.§

D-3 rose clover

OV

Poor to fair.§

* HO, Homerville, Georgia; FR, Fargo, Georgia; CH, Chula, Georgia: OV, Overton, Texas; NC, Nacogdoches, Texas; RU, Rusk, Texas; TY, Tyler, Texas; HV, Huntsville, Texas; WB, Winnsboro, Texas.

Poor stand at several locations.

Damaged by record cold temperatures in December 1989.

§Damaged by deer foraging.

|| Drought during germination and/or growth severely reduced growth.

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

between blueberry rows in 1989 on soil treated with 0 or 50 lbs of N/acre or following a winter cover crop of crimson clover. The clover was rototill incorporated into the soil in April, before seeding of the sorghum. Clover dry matter yield was 3,000 lbs/acre with a 1.2 percent leaf N concentration (36 lbs of N/acre in tops). The sorghum was sown in May with a precision seeder and was harvested in August.

An experiment was established at Overton in 1989 by using a split-plot design to evaluate the effects of irrigation and fertilization on mulch production of two cover crops. Whole plots had sprinkler irrigation or no irrigation, and subplots had factorial combinations of cover crops and fertilization. The cover crops were Sun Hemp crotalaria and Iron and Clay cowpeas. Subplots received 500 lbs of lime/acre, 50 lbs of P/acre, and 50 lbs of K/acre or were left unfertilized.

Weed suppression with cover crops was assessed by measuring weed densities in the field and allelopathic responses in the laboratory. Several crops were assessed for their allelopathic suppression of weed seed germination. Plant tops were air-dried (86°F), ground (40 mesh), and placed on the soil surface of a planting plug (2 by 2 inches) that was seeded with 25 seeds each of crabgrass, common bermudagrass, and pig weed. The percent germination was evaluated as a function of the cover crop and the amount of mulch applied.

Results

The living mulch crops that were evaluated, the locations where these crops were planted, and a summary of their general performance are listed in Table 12-1. Living mulch systems employing rye, ryegrass, or crimson clover (winter) and pearl millet (summer) were rated the highest based on overall production, stand consistency, weed control, cost, and resistance to deer foraging and winter cold temperatures.

Living mulch yield performance in Georgia for 1989 was dependent on soil pH and N fertilization (Table 12-2). Marshall ryegrass and Wrens abruzzi rye were the two best cover crops evaluated. Sites with low soil pH (less than 5.0), low fertility, or with no or a low level of applied N failed to produce cover crop stands. The low-pH locations also failed to produce a significant amount of mulch in 1990 compared with that produced by sites with a higher pH (5.5). Nutrient analysis of the cover crops indicated that the mulch contained sufficient N and K for blueberry production (greater than 70 lbs/acre) and that the nutrients were released from the mulch within 4 months after cutting (data not shown). Ryegrass grown with 100 lbs of N/acre resulted in good overall mulch production.

In Texas, Elbon rye provided the greatest amount of winter mulch (Table 12-3). Wheat, triticale, ryegrass, and subterranean clover were less suitable

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

TABLE 12-2 Yields of Blueberry Living Mulches in Georgia

   

Fresh Weight Yield (lbs/acre)

Cover Crop

Treatment

Homerville*

Fargo*

Chula

Gulf annual ryegrass

Fertilized

2,310

1,182

16,299

 

Unfertilized

1,448

0

4,152

Marshall ryegrass

Fertilized

3,933

2,321

8,080

 

Unfertilized

352

0

543

Wrens abruzzi rye

Fertilized

§

9,278

 

Unfertilized

586

Crimson clover

 

1,767

* Soil pH ≤ 4.4.

Soil pH = 5.5.

Fertilized in spring only.

§ — indicates that a crop was not planted.

TABLE 12-3 Yield of Blueberry Living Mulches for Different Locations in Texas

 

Dry Weight Yield (lbs/acre)

Time Period and Crop

Nacogdoches

Tyler

Huntsville

Winnsboro*

Overton

Winter 1988–1989

Elbon rye

2,948a

0

2,103a

5,642a

Triticale

3,799b

Marshall ryegrass

1,963c

Wheat

2,005a

3,038bc

Crimson clover

951b

0

2,394a

2,537bc

Subterranean clover

587b

0

0b

1,991c

Hairy vetch

4,224b

Summer 1989

Pearl millet

17,460a

11,563a

4,898a

26,550a

8,202b

Sorghum sudan

16,942a

1,410c

4,269a

21,895b

7,715b

Sorghum

20,803a

21,044b

7,056b

Cowpeas§

0b

5,009b

6,151a

12,901c

7,558b

Crotalaria§

0b

0d

1,251b

14,463c

17,910a

* Overhead irrigation was used at this location.

Different letters indicate separation of the means within columns by Duncan's test at the 0.05 percent level.

__ indicates that a crop was not planted.

§ Yields of cowpeas and crotalaria were very low at several locations because of deer foraging.

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

for a winter cover crop compared with rye. Several growers gave crimson clover high ratings as a cover crop. No applied N was required, yields were adequate, and it was visually attractive during bloom.

Establishment of good stands was hampered at several sites because of erosion and the subsequent washout of seeds or seedlings. Poor germination, soil infertility, or deer foraging also adversely affected the stands. The effects of an extremely dry fall and record low temperatures in the winter on stand establishment and growth of crimson clover during 1989–1990 were especially apparent. The weather also had an adverse effect on the other vegetations available for rabbit and deer populations in 1990. Consequently, mulch production at four of the five sites was markedly reduced by grazing from rabbits and deer. For the 1990 season, rye tolerated the adverse conditions better than did the other crops that were evaluated (data not shown).

Pearl millet was consistently the most productive living mulch crop in summer (Table 12-3). The other forage grains (sorghum and sorghum sudan) had similar levels of production, but they were not tolerant to frequent mowings to low heights. Yields of summer legumes (cowpeas and crotalaria) were erratic across all sites and were not tolerant to mowing. Legume mulches, if left unmowed, were undesirable because cowpeas grew into and up the blueberry plant and crotalaria grew too tall (greater than 12 feet).

Living mulch crops were highly dependent on fertilization and irrigation, with N limiting the mulch production of nonlegumes. At Nacogdoches, mean dry weight yields of sorghum, sorghum sudan, and pearl millet supplied with 0, 100, and 200 lbs of N/acre were 6,000, 15,500, and 30,000 lbs/ acre, respectively. The Overton plot, where crimson clover was tilled into the row middles, produced a sorghum yield equivalent to that of plots supplied with 50 lbs of N/acre (data not shown). These plants, however, were still N deficient, with there being less than 0.7 percent leaf N. For summer legumes (cowpeas and crotalaria), fertilization with low levels of lime, P, K, and Mg increased the yield by 50 percent, while irrigation increased the yield by 150 percent (data not shown). The one site in Texas that used overhead irrigation—Winnsboro—had a significantly greater yield than other locations where the living mulch plots were not irrigated (Table 12-3).

The total cover crop yield multiplied by its N concentration indicated the theoretical amount of N available to the blueberry plants from the mulch system. In general, summer crops supplied three times the total N as that provided by winter crops (50 lbs of N/acre for rye and clover compared with 150 lbs of N/acre for pearl millet). This also showed the higher overall yield for summer cover crops and their greater demand on soil N. For example, when summer nonlegume cover crops were grown on a minimum N fertilizer program (50 lbs of N/acre), they exhibited severe N stress symptoms, and all had leaf N levels of less than 0.6 percent (data not

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

shown). On a typical unamended blueberry soil, it was also apparent that a winter/summer rotation of legume/legume or legume/nonlegume would be only marginally acceptable with respect to N recycling and weed control. This was concluded because winter clover supplied only enough N for the blueberry plants (45 lbs of N/acre), and summer legumes stands were too inconsistent.

Weed control results were also evaluated. Pearl millet was the most effective cover crop for suppressing weeds at all locations (Table 12-4). The allelopathic effects of several mulches were tested in a greenhouse. As in the field evaluations, pearl millet usually suppressed germination more than did the other crops that were tested (Table 12-5).

Discussion

Living mulches appear to be a practical and desirable cultural practice for controlling weeds and erosion and for reducing chemical fertilizer inputs for blueberries grown in the South. This system may also be appropriate for other perennial fruit crops. For this sustainable system to be viable, however, there are several criteria that must to be met.

Originally, the system was designed to operate with a winter legume/ summer legume rotation. No summer legume was identified that was consistent across a variety of sites, tolerant to mowing, and easy and inexpensive to establish and that had allelopathic properties. Crimson clover met several of the criteria for a winter legume, but it did not grow when the soil pH was less than 5.0 and did not tolerate the extremes of fall drought, cold weather, or deer foraging. The poor crop stands of crimson clover in 1990

TABLE 12-4 Weed Control Between Blueberry Rows as Affected by Living Mulch Cover Crops

 

Percentage of Ground Covered by Weeds*

Crop

Nacogdoches Plot 1

Nacogdoches Plot 2

Winnsboro

Overton

Pearl millet

15b

20c

1a

3a

Sorghum sudan

52b

31bc

21ab

26b

Sorghum

39b

36c

9ab

22ab

Cowpeas

100c

50b

45bc

Crotalaria

99c

66c

Control

100c

94a

* Weeds, mostly crabgrass.

Different letters indicate separation of the means within columns by Duncan's test at the 0.05 percent level.

— indicates that a crop was not planted.

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

TABLE 12-5 Allelopathic Suppression of Weed Seed Germination Through the Use of Mulches of Different Cover Crops*

 

Percent Germination

 

Crabgrass

Common Bermudagrass

Pig Weed

Cover Crop

20 Days

40 Days

20 Days

40 Days

20 Days

40 Days

Cowpeas

13b

48b

2a

52d

16b

40b

Crimson clover

15a

53c

1a

36c

10a

30ab

Pearl millet

13a

37y

1a

28ab

16b

25a

Elbon rye

22b

52c

2a

22a

21cc

34ab

* Stems and leaves of cover crops were air-dried at 25°C, ground to pass a 40-mesh screen, placed on top of soil that was planted with weed seeds, and misted with distilled water daily.

Different letters indicate separation of the means within columns by Duncan's test at the 0.05 percent level.

were not limited to the blueberry plots but were also apparent under normal pasture situations. In most years, crimson clover could be expected to do well if soils received significant inputs of lime, P, K, and Mg. When native soil fertility was higher, a good stand could be achieved with only minor nutrient inputs. The visual attractiveness of clover during bloom and its reseeding ability, if not mowed too early, were other advantages of using clover.

Overall, the highest mulch production and year-round weed control were achieved with a winter Elbon rye/summer pearl millet rotation. This rotation required significant N fertilizer or manure inputs, because soils on which blueberries were grown were too infertile to support good cover crop growth.

Manure has potential as a nutrient source for living mulches. In 1990, manuring resulted in a higher yield of Elbon rye than did N fertilization (data not shown). A single application of manure per year, however, may not provide sufficient N to grow both a winter and summer living mulch crop, and two applications may be necessary. The high levels of manure required to supply the nutrient inputs for the cover crops may have an adverse effect on seed germination or, over the long term, may increase soil pH or P levels above the range desired for blueberry plants. At some sites, reduced cover crop germination was observed for seeds that were sown directly after a manure application. Future research will evaluate some of these problems encountered with the application of manure.

Yields from several winter/summer living mulch systems were adequate to provide 3 to 10 inches of mulch around blueberry plants. The amount of mulch produced increased in direct proportion to the increased width of the cover crop strip. For example, crimson clover or ryegrass, when sown row

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

to row, resulted in a cutting area to mulched area ratio of 5:1, compared with a 2:1 ratio for a 5-foot band sown down the center of the row. Solid cover crop stands are more appropriate during the winter, when there is minimal competition between the cover crop and the blueberries. In the summer there should be at least an 8-to 20-inch buffer zone between the cover crop and the blueberry plant to avoid competition for water and nutrients.

The method of seeding determines the cover crop surface area and stand performance. The best stands were obtained with a grain drill that produced a 5-foot sward. For ryegrass and clover, good row-to-row stands at some sites were also obtained by broadcasting ryegrass or clover. Because many blueberry growers do not have access to a grain drill, an inexpensive hand broadcast seeder would be an appropriate low-cost alternative. Several growers in Georgia have adapted this technology and are broadcasting ryegrass in late fall. They report that this solid stand of ryegrass has suppressed winter and spring weeds, reduced erosion in the row middles, and helped to maintain the shape of the blueberry beds.

Cover crop harvesting was readily accomplished with a riding mower with a side-throw spout for crops with thin leaves (ryegrass and clover) and for crops that were not too tall. For thick-stemmed crops, like pearl millet, bush-hog mowers were necessary. Some summer crops, such as kenaf, cowpeas, and crotalaria, were not very tolerant of mowing and had little significant regrowth after they were mowed.

Living mulch systems may increase the potential for spring frost damage, as bare ground may provide increased temperatures (1° to 3°F) during a radiant frost over a vegetated orchard floor. Although this is a valid concern, earlier data on orchard floor management indicated that sodded row middles may reduce the radiant heat budget of the orchard floor, thereby delaying bloom and reducing the potential of frost damage (Patten et al., 1989).

The total cost of this system is a primary consideration for the blueberry grower. An enterprise budget detailing the cost of establishing and using a living mulch system is presented in Table 12-6. The estimated cost of growing and using cover crops for living mulch twice a year was $300/acre of blueberries. These costs represent approximately $80 more than those associated with fertilizers and herbicides in conventional blueberry production programs. Over time, soil fertility in the living mulch systems would increase and the cost of nutrient inputs would decrease. For blueberries cultivated on more fertile soils, a lower-cost living mulch system, such as hand broadcasting of crimson clover, could be cost-effective with respect to weed control and N inputs (less than $50/acre).

These small cost differences suggest that a living mulch agroecosystem could be advantageous to the grower in the long term. The sustainable

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

agriculture system, however, is unlikely to be cost-effective during the transition time between systems. During this period, weed control and nutrient input from living mulches may not be completely satisfactory. A detailed, long-term economic analysis of the living mulch system will not be available until all of the horticultural variables have been evaluated over an extended period of time.

TABLE 12-6 Farm Enterprise Budget for Blueberry Living Mulch Systems

System

Cost ($) per Acre of Blueberries*

Living mulch cost

 

Seeding (seed + planting cost, regardless of crop) Fertilizer

40

Option 1: Chicken manure, delivered and spread at 12 tons/acre

200

Option 2: 0.5 ton of NPK (13-13-13 fertilizer)/year + 5 N applications at 50 lbs/acre

200

Mowing four times per year

60

Total

300

Conventional cost§

 

Weed control

80

Fertilizer

140

Total

220

* Cost per acre of blueberries is 65 percent of the actual cost per acre, since the living mulch plot only covers approximately 60 to 70 percent of the land on an acre of blueberries.

Assumption included in this analysis are that the living mulch system has no effect on yield. Expenses are based on direct cost for supplies plus services as derived from the 1988 Texas Custom Rates Statistics Handbook.

The optimal rate and frequency of application for manure has yet to be determined.

§ Values are estimates based on a budget for a 15-acre blueberry farm in Georgia.

OBJECTIVE TWO: SOLARIZATION FOR STRAWBERRY PRODUCTION
General Farm Background

These experiments required closely monitored data collection that precluded the use of grower sites. Plots were established at experiment station farms at Lubbock, Texas; Overton, Texas; and Poplarville, Mississippi. Soils, planting methods, and pest control at all locations were typical of those usually recommended for strawberries. The soils were sandy loam to loamy sand, pHs were from 5.5 to 6.5, and native soil fertility was low. Nitrogen was the major limiting nutrient. All locations were watered by drip irriga-

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

tion, and protection against frost was done by sprinkler irrigation. Record low temperatures in February 1989 caused some plant damage at all locations. The planting at Lubbock was killed in 1988–1989 because of freeze damage. The type and severity of indigenous soilborne pests depended on the site. Weeds were the major limiting soilborne pest at all sites. Research plots at Overton contained a high density of yellow nutsedge (Cyperus esculentus L.) tubers. Extremely heavy rains during harvest in 1989 (greater than 16 inches) caused 10 to 15 percent cullage loss because of fruit rots. Plastic mulch helped to minimized fruit rot and reduce the need for cover sprays. One early fungicide spray was used to control decay. In general, the levels of decay were not significant enough to make fungicide applications a necessity.

Experimental Protocols

In the Overton experimental plots, the following experimental protocol was used. In 1987–1988, the soil treatments were 6 weeks of solarization, fumigation with 400 lbs of 98 percent methyl bromide and 2 percent chloropicrin per acre, or a control. Experimental units were 13-foot-long beds, 8 inches high and 28 inches wide, that were planted in double rows with 20 strawberry plants. Treatments were replicated 12 times. Solarization plots were covered with clear, 0.0015-inch-thick polyethylene for 6 weeks starting on August 10. Soil under the plastic was rewetted by drip irrigation three times during solarization. After 6 weeks, the plastic became too brittle for continued use. The old plastic was removed, and new clear 0.0015-inch-thick plastic was reapplied to provide plastic mulch for all plots. This plastic was then sprayed with a 7:1 ratio of water:white exterior latex paint to reduce soil heating and to allow strawberry planting without heat damage to the roots. Fumigation occurred 3 weeks before planting. Dormant Chandler strawberries were planted in double rows on September 22. Fertilizer was applied monthly with a trickle irrigation system in September, November, March, April, and May as N, P, and K at 36, 14, and 29 lbs/acre, respectively, in each application.

In 1988–1989, the experimental design was a split plot with six replications. Beds were varied at 8 or 13 inches in whole plots. Split plots (23 feet) were solarized, fumigated, or not treated. The solarization plastic (thickness, 0.0015 inch) was applied on July 29 and was removed October 14. All plots were drip irrigated three times during the solarization period. Fumigation of individual plots with 400 lbs of methyl bromide and chloropicrin per acre occurred on September 14. Beds were planted in double rows with 28 dormant Chandler strawberry plants on October 15. Pre-plant fertilizer (N, P, and K at 50, 65, and 75 lbs/acre, respectively) was tilled into the soil before bedding. Supplemental N was applied five times

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

through a drip line (every 21 days from February to May) at 15 lbs of N/ acre per application.

Weeds were controlled manually after ratings of weed density were taken. In the spring, soil samples were taken to evaluate nematode populations, and roots were examined for root-knot nematode infestations. Soil temperatures were monitored by placing thermocouples at soil depths of 4 and 8 inches.

For the 1989–1990 season, whole-plot soil treatments were expanded to include legume cover crops or manure combinations. Split plots were fumigated, solarized, or left untreated. Strawberries were planted in September. To date, only data on nematode populations and plant vigor ratings have been collected for these plots.

Because of differences in climate and growing conditions, a different experimental protocol was used in Lubbock. Plots were established in the fall of 1988 in west Texas by using a randomized complete block design with four replications. The experimental variables were factorial combinations of bed height (20 or 40 inches) and soil treatment (untreated, 1 month of solarization under clear plastic, metam sodium fumigation with water incorporation). Nematode populations were sampled before and after soil treatment. All plants were killed by cold temperatures in December.

In the Poplarville experiment, yet another protocol was required. Before the evaluation of solarization effects, Iron and Clay cowpeas were planted as a cover crop during the summer of 1988 and were tilled in the fall. Soil treatments were applied on September 1 and replicated six times. These treatments consisted of (1) clear plastic solarization for 2 months on raised beds, (2) clear plastic solarization on flat beds, (3) black plastic solarization on raised beds, (4) methyl bromide fumigation, or (5) an untreated control. On November 11, treatment plastic was removed, the plots were mulched with black plastic, and 12 Chandler strawberries were planted in each experimental unit. Strawberry yield and weed populations were evaluated in the spring.

The following protocol was used in Overton to study the impacts of various treatments on soil chemistry. To evaluate the effects of soil solarization and manures with variable carbon (C)/N ratios on nutrient availability, studies were initiated in the summer of 1989 on a fine sandy loam soil. The experimental design was a split plot, with whole-plot treatments being solarized or unsolarized soil. The split-plot treatments were factorial combinations of poultry manure applied at a rate to give 500 or 1,000 lbs of N/acre equivalents (5 or 10 tons/acre of manure) and fresh pine sawdust applied at 0, 40, or 80 tons/acre. Control plots that were either unamended or received fertilizer with N, P, and K (250, 40, and 75 lbs/acre, respectively) were included as split treatments. Split-plot treatments were applied in July and tilled into the top 10 inches of soil. A clear plastic tarp (thick-

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

ness, 0.0015-inch) was applied from July 18 to September 26. Following solarization, soil samples were collected to a 6-inch depth. Suction lysimeters were placed at a depth of 16 inches in four of the split-plot treatments. Elbon rye was seeded as an indicator crop. Soil leachate was collected after each rainfall of greater than 2 inches. Chemical analyses of soil samples were conducted according to the testing procedures of Texas A&M University (College Station, Texas). Weed populations were evaluated during December.

Results
Soil Temperatures

The mean maximum soil temperatures at the 4-inch depth in the center of the 8-inch-high bed were 113° and 105°F for solarized and nonsolarized soils, respectively. The total time above 104°F in 1988 at 4- and 8-inch depths for the 8-inch solarized bed was approximately 590 and 300 hours, respectively. For nonsolarized soil, these values were 74 and 0 hours at 4- and 8-inch depths, respectively.

Yield

At Overton, the total yield from solarized soil was greater than that from untreated soil in all years (Table 12-7). The yield was higher with fumigated soil than with solarized soil in 1988, but there was no difference between fumigated and solarized plots in 1989. Plants grown on 13-inch beds tended to have a greater total yield than did those grown on 8-inch

TABLE 12-7 Effect of Soil Treatment on Strawberry Yield and Weed Control

 

Total Strawberry Yield (lbs/acre)

Surface Area Covered by Weeds (%) 5/30/88

   

Treatment

1988

1989

Yellow Nutsedge

Annual Dicots*

Number of Annual Weeds/Plot 3/15/89

Yellow Nutsedge Plants/Plot 6/24/89

Fumigation

17,329a

21,991a

0.5a

0.8a

8a

4a

Solarization

15,526b

20,628a

10.5b

2.6a

11ab

17b

Bare soil

11,436c

18,428b

13.3b

8.3b

14b

13b

* Weeds included Lamium amplexicaule L., Oenothera laciniata Hill, and Vicia dasycarpa.

Different letters indicate separation of means within columns by Duncan's test at the 0.05 percent level.

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

TABLE 12-8 Solarization and Manure Effect on Weed Populations at Overton in 1989

 

Number of Weed Seedlings/8 inches2

Treatment

Purple Nut Sedge

Dandelion

Total Dicots

Total Monocots

Total Number of Weeds

Solarization + manure

3

1

3

4

7

Solarization + no manure

9

4

12

11

23

No solarization + manure

29

15

19

29

48

No solarization + no manure

42

29

39

42

81

ANOVA*

Solarization

0.01

0.05

0.05

0.05

0.02

Manure

0.05

0.003

0.002

0.05

0.004

Solarization by manure interaction

NS

0.09

NS

NS

NS

* ANOVA, analysis of variance.

Probablility of significance.

NS, not significant.

beds (data not shown). Because of record freezing temperatures in February 1989, the entire crop at Lubbock was lost. At Poplarville, soil treatments had no effect on the yields (data not shown). This lack of an effect may have been the result of solarizing too late in the fall or the cold temperatures in February that killed flower buds and plants.

Weed Control

Weed control in response to soil treatments varied by species. There was no difference in the number of annual dicots per plot between fumigation and solarization plots in 1988, and both treatments had fewer annual weeds than the control plots did (Table 12-7 and Table 12-8). In 1989, fumigated soil had fewer annual weeds than did untreated soil, and plots treated by solarization had intermediate weed populations. Fumigation was the only treatment that controlled yellow nutsedge (Cyperus esculentus) in both years. No attempt was made to distinguish between C. esculentus seedlings and regrowth from tubers, but most plants resulted from established tubers, not seeds. In other research plots, purple nutsedge (Cyperus rotundus L.) germinated from seeds and was controlled by solarization (Table 12-8). Chicken manure also reduced the annual weed populations. The combination of solarization and chicken manure resulted in the lowest weed density. At Poplarville, weeds were not affected by solarization (data not shown).

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×
Nematode Control

Root-knot nematodes were not observed on plant roots in 1988. Highly variable nematode populations, with no significant differences across treatments, occurred in the spring of 1989. Fewer nematodes were observed in solarized soil than in the control plot in the fall of 1989 (Table 12-9). Compared with fumigated soil, solarized soil had similar levels of ring nematodes but more free-living nematodes. Soil incorporated with the sorghum cover crop had increased ring nematode levels compared with the untreated soil, while chicken manure reduced the levels of ring nematodes and increased the levels of free-living nematodes. Nematode populations (primarily Pratyulenchus spp.) at Lubbock in 1989 were reduced by 85 to 90 percent and 90 to 95 percent by solarization and chemical fumigation, respectively (data not shown). In general, solarization provided a level of temporary control over nematodes in the field that was less efficacious than that provided by fumigation.

Soil Chemistry

Solarization increased soil pH and ammonium (NH4) levels, while soil electrical conductivity and calcium, magnesium, and nitrate (NO3) levels were reduced on solarized soil compared with those in untreated soil (Table 12-10). Manure applied before solarization markedly increased soil pH, electrical conductivity, potassium, calcium, magnesium, phosphorus, ammonium, zinc, manganese, and copper. The electrical conductivity and soil solution P, K, and calcium concentrations were also higher in leachate collected under soil treated with manure (data not shown).

TABLE 12-9 Solarization, Manure, and Cover Crop Effects on Ring and Free-Living Nematode Populations at Overton in 1989

 

Number of Nematodes/500 ml soil

Treatment

Ring

Free-Living

Solarization

38a*

569b*

Fumigation

0a

331a

Control

182b

790c

Manure

9a

737c

Manure + sorghum

174c

651b

Control

40b

300a

* Different letters indicate separation of the means within columns by Duncan's test at the 0.05 percent level.

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

TABLE 12-10 Effect of Solarization and Manure on Soil Fertility Parameters at Overton

     

Concentration (mg/kg)

Treatment

pH

EC (dS/m)

P

NO3

NH4

K

Ca

Mg

Control

4.8b*

0.6a

61

56a

16b

231

745a

59a

Solarization

5.3a

0.3b

49

42b

46a

182

559b

45b

NPK

4.8b

0.4b

35b

50ab

34b

153c

546b

34c

Manure (0 kg/ha)

4.0b

0.3c

28b

41b

14c

130c

533b

36c

Manure (550 kg/ha)

5.2a

0.4b

68a

51ab

21c

237b

734ab

61b

Manure (1,100 kg/ha)

5.4a

0.7a

87a

54a

53a

305a

794a

75a

NOTE: EC, electrical conductivity; P, phosphorous; NO3, nitrate nitrogen; NH4, ammonium nitrogen; K, potassium: Ca, calcium; Mg, magnesium.

* Different letters indicate separation of the means within columns by Duncan's test at the 0.05 percent level.

NPK, 250 lbs/acre of nitrogen, 40 lbs/acre phosphorus, and 75 lbs/acre potassium.

Application rates were based on the total nitrogen content of the chicken manure.

Discussion

Solarization resulted in strawberry yields comparable to those obtained with typical production systems located in areas with a hot summer climate. Solarization was not as effective as fumigation in certain areas, for example, in eradicating difficult to control perennial weeds (yellow nutsedge). The failure of solarization to eliminate perennials with an established deep root system, rhizomes, or tubers confirms results of previous studies (Pullman et al., 1984; Rubin and Benjamin, 1984). Poor control of perennial weeds was likely the result of a failure to achieve lethal heating below soil depths of 4 to 8 inches. Cyperus spp. can survive temperatures of greater than 140°F (Rubin and Benjamin, 1984). For most situations, however, control of annual weeds with solarization is sufficient to allow for production without herbicides or fumigation.

Obvious symptoms of plant diseases caused by soilborne pathogens were not indicated in these experiments. Pathogenic fungi or nematodes may not have limited yield. High populations of C. esculentus could account for the reduction in the yield with solarization compared with fumigation, but not for the increase in yield associated with solarization compared with the control. The reduction in annual weeds with solarization may explain some, but not all, of the increase in yield over that in untreated soil. In several other studies on solarization, increased plant growth response has also been reported in the absence of major soilborne pests (Katan, 1981; Stapleton and Devay, 1986). Modification of the soil pH or nutrient availability may also have been responsible for the increased plant growth re-

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

sponse. The effect of solarization on nutrient availability in these experiments likely would have been attenuated by the fertilization program. Much remains to be discovered about the complex biological interactions of the rhizosphere, as discussed by R. James Cook in Chapter 3.

A concern that growers may have with the use of solarization is the selection of an appropriate type of plastic (ultraviolet stabilized). In the solarization system described here, the plastic should last for at least 1 year under field conditions. This allows for the plastic to be in the field for 2 months for the solarization period, sprayed white, planted with strawberries, and then replanted with melons the following summer. Several earlier attempts at solarization were not completely successful because the plastic's integrity did not last for longer than 4 to 5 weeks. In an initial evaluation of the effects of different types of polyethylene on soil heating, no major differences in film types were detected. One method that did enhance solar heating by several degrees was to decrease the soil albedo (darken) by spreading manure on the soil surface prior to solarization.

Typically, soils in the South have insufficient soil N because organic matter is low and NO3 and NH4 are readily leached out of the topsoil. The goal has been to attempt to build a supply of slowly released N and other nutrients in the soil, under the plastic, that could supply several sequential crops with adequate fertilization. Direct manure applications have resulted in the most vigorous plants at the lowest cost in comparison with a combination of winter and summer legume cover crops and manuring followed by a nonlegume cover crop (data not shown). The application of 20 tons of chicken manure per acre increased the soil availability of P and K levels by 100 and 260 lbs/acre in eastern Texas. Based on fertilizer rate-soil analysis correlation data, the application of 1,000 and 900 lbs of P and K per acre, respectively, from commercial fertilizer sources produced an equivalent increase in the levels of P and K in soil. The application of 20 tons of poultry manure ($240 delivered cost within 50 miles of the source) per acre would provide the equivalent of approximately $300 of commercial fertilizer if only half of the N were available (500 lbs/acre).

An economic evaluation of strawberry production with solarization compared favorably with fumigation and was advantageous over no treatment of the soil. Comparative enterprise budgets for conventional and solarization and manure systems are presented in Table 12-11. This analysis assumed very conservative production costs and fruit prices ($0.55/lb), and a 10 percent greater yield by fumigation over that by solarization. The solarization and manure system would cost $275 less per acre than fumigation and conventional fertilization, and $150 more than black plastic, conventional fertilization, and hand weeding. Assuming a 10 percent yield differential between the fumigation and solarization systems and assuming that the price received for fruit is of equal value, the conventional system

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

TABLE 12-11 Farm Enterprise Budget for Strawberry Production Using Different Cropping Systems

System Analysis

Cost ($)/Acre of Strawberries

Nutrient inputs*

 

Option 1: Chicken manure delivered and spread at 15 tons/acre

240

Option 2: 600 pounds of 13-13-13 NPK fertilizer/year + 10 supplemental N applications at 20 lbs/acre through a drip line

165

Soilborne pest control

 

Option 1: Black plastic + hand weeding

375

Option 2: Solarization (cost of plastic laying, pigmenting, occasional hand weeding)

450

Option 3: Fumigation (custom application)

800

Yield comparison§

 

Average differential in total yield between conventional and low-input solarization systems (2 years of data) = 10 percent

 

Average differential in total yield between solarization system and black plastic without fumigation (2 years of data) = 18 percent

 
 

Cost ($)

Sample Budget Analysis||

Conventional

Solarization

Black Plastic

Nutrient inputs

165

240

165

Soilborne pest control

800

450

375

Other production costs

3,000

3,000

3,000

Total cost

3,965

3,690

3,540

Marketable yields (lbs/acre)#

12,000

10,800

8,856

Net returns at $0.55/lb

2,635

2,250

1,331

Net returns at $0.60/lb

3,235

2,790

1,774

* Costs are based on direct cost for supplies plus services cost as derived from the 1988 Texas Custom Rates Statistics Handbook.

Cost of manure is based on rates in eastern Texas, which depend on distance from source ($8/ton delivered within 20 miles, $12/ton for 20 to 50 miles).

Assumes that cost for control of fruit decay is the same for all systems.

§ Differentials are based on 2 years of data. Data comparing yield as a function of nutrient input sources is not yet available.

||The estimates for these costs, yields, and returns are conservative.

#Assumes a conservative total yield for conventionally grown fruit of 16,000 lbs/acre with 25 percent loss because of cullage. Yield differential between systems are estimates from 2 years of data.

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

is 15 percent more profitable than the low-input system. With only a $0.05/ lb price differential between low-input and conventional fruit, however, the solarization system has a 5 percent greater return. The solarization system was more profitable than the system in which just black plastic and hand weeding were used. Solarization would also enable the grower to capitalize on the organic market niche. Additional advantages of solarization would be the avoidance of restricted-use pesticides and elimination of specialized fumigation equipment. Alternatively, solarization in combination with fumigation may substantially decrease the level of fumigant used (Stapleton and Devay, 1986).

CONCLUSION

Results of this project have been presented at numerous growers meetings and field days. It is too early in the evaluation of these systems to estimate their potential significance and use by growers. Although these systems are effective replacements for conventional chemical input systems, the management intensity required for the successful use of the whole system may limit their use to only the most proficient growers. Individual components of these systems, however, could be adapted to other small fruit production and horticulture enterprises in the region or the nation.

REFERENCES

Hartz, T. K., C. R. Bogle, and B. Villalon. 1985. Response of pepper and muskmelon to row solarization. Horticultural Science 20:699–701.

Katan, J. 1981. Solar heating of soil for control of soilborne pests. Annual Review of Phytopathology 19:211–236.

Patten, K. D., E. W. Nuenedorff, G. Nimr, S. C. Peters, and D. C. Cawthon. 1989. Growth and yield of rabbiteye blueberry as affected by orchard floor management practices and irrigation geometry. Journal of the American Society for Horticultural Science 114:728–732.

Pullman, G. S., J. E. De Vay, C. L. Elmore, and W. H Har. 1984. Soil Solarization—a Nonchemical Method for Controlling Disease and Pests. Leaflet 21377. Oakland: Cooperative Extension of the University of California.

Putnam, A. R. 1988. Allelochemicals from plants as herbicides. Weed Technology 2:510–518.

Rubin, B., and A. Benjamin. 1984. Solar heating of the soil: Involvement of environmental factors in the weed control process. Weed Science 32:138–142.

Stapleton, J., and J. E. Devay. 1986. Soil solarization: A non-chemical approach for management of plant pathogens and pests. Crop Protection 5:190–198.

Wagger, M. G. 1989. Time of desiccation effects on plant composition and subsequent nitrogen release from several winter annual cover crops. Agronomy Journal 81:236–241.

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
×

13

Reactor's Comments

Research and Education in the South

Raymond E. Frisbie

This reaction is to three sustainable agriculture projects in the southern region described in the following chapters: “Southeastern Apple Integrated Pest Management” by Dan L. Horton and colleagues, “Low-Input Crop and Livestock Systems in the Southeastern United States” by John M. Luna and colleagues, and “Solarization and Living Mulch to Optimize Low-Input Production System for Small Fruits” by Kim Patten and colleagues.

In general, the three projects described in those chapters have made very good progress in organizing and beginning their respective research and education projects. The projects dealt at the whole-farm level and involved interactions with related cropping or habitat systems. There was a definite sense of a farming systems approach. Although limited success was reported or expected because of the newness of each project, it was clear that the funding period for these types of research and education projects is far too short. Whole or mixed farm systems that consider multiple variables require several years of study to achieve reliable results. In this reactor's opinion, 2 to 3 years of funding is not adequate. Funding for 4 to 6 years is more realistic. For example, the STEEP program in Washington and surrounding states has been ongoing for several years with a singular focus on erosion control. The benefits of this program are only now being fully realized.

The Georgia low-input sustainable agriculture (LISA) apple production program described by Dan Horton and colleagues was well designed to

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
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consider horticultural, pest management, and erosion control factors. Market considerations regarding the timing of supplying fruit of high quality were evident in the program's design. The authors indicated they were accomplishing improved integrated pest management (IPM) of codling moth, red-banded leafroller, other insect pests, and plant pathogens through an integrated approach of pheromone trapping, phytosanitation, and habitat management. Intensive field sampling for insect pests and plant pathogens was used to time pesticide applications. Although a fairly comprehensive IPM system was discussed, the authors narrowly defined IPM as a “scout and spray program.” This observation was pointed out.

The crop and livestock sustainable agriculture project at the Virginia Polytechnic Institute and State University described by John Luna and colleagues had, by far, the best system design in that it considered multiple production components and interactive linkages. It was clear that this interdisciplinary group had spent considerable time constructing a conceptual model on the operation of a fairly complex forage and livestock system. The group is to be complimented for using an innovative cover crop strategy that reduces erosion and provides supplemental nitrogen and for using a cultural management technique that controls armyworms and reduces insecticide use. Consideration of the impact of various forage production systems on calf weight gain and performance completes a very sophisticated system that should provide insight into the establishment of a sustainable system.

The project at Texas A&M University described by Kim Patten and colleagues that deals with strawberries and blueberries in eastern Texas is a good example of how to design a sustainable agriculture system in soils with extremely low levels of organic matter and that receive low levels of rainfall in summer. Although this research program has been under way for only a short time, it has shown that ground cover and other management strategies that may work in some areas of the country are not suitable everywhere. The group at Texas A&M University is to be congratulated for examining a series of innovative approaches, such as soil solarization for plant pathogen and nematode control. The fact that some of these techniques did not give positive results was not discouraging. It is as important to know what will not work in a sustainable agriculture system as to know what will work.

The research and extension faculty working on all three projects showed a very positive synergism in the development and conduct of their projects. They are to be congratulated.

Suggested Citation:"PART THREE: RESEARCH AND EDUCATION IN THE SOUTHERN REGION." National Research Council. 1991. Sustainable Agriculture Research and Education in the Field: A Proceedings. Washington, DC: The National Academies Press. doi: 10.17226/1854.
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Sustainable Agriculture Research and Education in the Field: A Proceedings Get This Book
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Interest is growing in sustainable agriculture, which involves the use of productive and profitable farming practices that take advantage of natural biological processes to conserve resources, reduce inputs, protect the environment, and enhance public health. Continuing research is helping to demonstrate the ways that many factors—economics, biology, policy, and tradition—interact in sustainable agriculture systems.

This book contains the proceedings of a workshop on the findings of a broad range of research projects funded by the U.S. Department of Agriculture. The areas of study, such as integrated pest management, alternative cropping and tillage systems, and comparisons with more conventional approaches, are essential to developing and adopting profitable and sustainable farming systems.

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