Alternative Agriculture (1989) / Chapter Skim
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3 Research and Science
3 Research and Science
Pages 135-194
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From page 135... ...
These practices include: Crop rotations that mitigate weed, disease, and insect problems; increase available soil nitrogen and reduce the need for synthetic fertilizers; and, in conjunction with conservation tillage practices, reduce soil erosion. Integrated pest management (IPM)
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From page 136... ...
These farmers have modified their farming practices, often in innovative ways, to reduce production costs. Examples include a wide variety of conservation tillage systems; the use of legume-fixed nitrogen through rotations; interplanting; the substitution of manures, sewage sludges, or other organic waste materials for purchased inorganic fertilizers; and the use of IPM systems and biological pest control.
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From page 137... ...
This interdisciplinary problem-solving team approach is essential to understanding alternative farming practices. Agricultural research has not been organized to address this need except in a few areas, such as IPM, the use of organic residues as an alternative nutrient source, and the use of leguminous green manure crops and rotations for erosion control and as a nitrogen source.
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From page 138... ...
Only a limited amount of research has taken this comprehensive approach. Nevertheless, the scientific literature about specific farm practices and the empirical evidence from individual operators illustrate the efficacy and potential of alternative farming methods and provide the foundation on which to build a program of alternative farming research.
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From page 139... ...
In fact, yields of grains following legumes are often 10 to 20 percent greater than continuous grain regardless of the amount of fertilizer applied. Many factors are thought to contribute to the rotational effect, including increased soil moisture, pest control, and the availability of nutrients.
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From page 140... ...
This pest control is achieved primarily through the seasonal change in food source (the crop) , which usually prevents the establishment of destructive levels of pests.
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From page 141... ...
Hay and forage crops and closely sown field grain crops, such as wheat, barley, and oats, can provide some soil erosion control benefits in rotations. In some eroding areas with steep terrains, the practice of strip cropping corn (a row crop)
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From page 142... ...
In SOI ,. Soil Properties anti Plant Nutrients Soil Texture The mineral particles that make up the soil are classified on the basis of their size.
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From page 143... ...
The greatest benefits of organic matter in soil are its water-holding capacity; the manner in which it alters soil structure to improve soil filth; its high exchange capacity for binding and releasing some mineral nutrients; its presence as a food source for soil microbiota that recycle soil nutrients; and its mineralization to nitrogen, phosphorus, and sulfur. The cycling of mineral nutrients between living organisms and dead organic components of the soil system provides an important reservoir of the elements needed in plant growth.
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From page 144... ...
In mixed crop and livestock operations, for example, many of the nutrients contained in the grain and residue from crops grown on the farm can be returned to the soil if the manure and crop residues are incorporated into the soil. Crop rotations that include legumes can also play an essential role in nutrient cycling, particularly for replenishing the nitrogen supply.
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From page 145... ...
For alternative farming, legumes are an effective and often profitable way to supply nitrogen. Leguminous nitrogen is consistently released throughout the growing season when temperatures are high enough to permit microbial decomposition.
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From page 146... ...
For example, nitrogen budget analyses on midwestern soybeans show that 40 percent of nitrogen in the crop is derived from nitrogen fixation and 60 percent is from residual nitrogen in the soil. Typically, the nitrogen removed in the soybeans at harvest exceeds the amount of nitrogen fixed, leading to a net nitrogen loss of about 70 pounds per acre.
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From page 147... ...
But at 30°C the nitrogen fixation of the fava beans declined by 86 percent. Using legumes in a rotation, or as winter cover crops in the South, can reduce and, in some cases, eliminate the need for nitrogen fertilizers (Dabney et al., 1987; Goldstein and Young, 1987; Neely et al., 1987~.
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From page 148... ...
42 Days 63 Days 84 Days 105 Days Hairy vetch 10 100 108 147 223 20 46 88 67 122 30 14 8 12 30 S we e t clover 10 21 46 67 66 20 52 86 128 122 30 42 46 50 104 Fava bean 10 154 131 135 122 20 136 124 122 134 30 22 12 11 4 Lespedeza 10 0 4 3 0 20 9 29 93 145 30 16 22 60 176 Field pea 10 36 48 29 51 20 38 21 12 8 30 12 10 6 0 White clover 10 20 54 88 162 20 39 78 108 153 30 2 0 40 38 Nodulated soybeans 10 31 33 37 34 20 116 215 315 415 30 94 163 260 291 Crimson clover 10 43 43 72 107 20 54 79 86 56 30 9 2 14 5 ~ aValues are expressed as a percentage of the nitrogen fixation found in hairy vetch at 10°C for 42 days, which was arbitrarily selected as the basis for comparisons. To translate these percentages to the originally reported data (in milligrams/pot)
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From page 149... ...
Department of Agriculture's (USDA) Agricultural Research Service and the University of Minnesota Agricultural Experiment Station, fixed 94 pounds of nitrogen per acre between the last harvest in early September and the death of the plant at the first frost in October (Barnes et al., 1986~.
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From page 150... ...
More information is needed on nitrogen cycling in agricultural systems; the yield-boosting effects of rotations; the effects of tiliage practices; and how fixed nitrogen is affected by other sources of nitrogen, soil organic matter, compost, and crop residues. Manure as a Source of Nutrients Animal wastes can make a substantial contribution to nitrogen, phosphorus, potassium, and other nutrient needs.
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From page 151... ...
Anaerobic fermentation of manure to produce the biogas methane is not economical compared to the cost for other fuels. In addition, TABLE 3-4 Nitrogen Losses in Manure Affected by Handling and Storage Method N loss (percent)
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From page 152... ...
Department of Agriculture, 1987~. Similar data are not available for trace nutrients and organic matter supplied by , ~ manure.
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From page 153... ...
(P2Os) Swine Solid NB 10 6 9 8 Solid B 8 5 7 7 Liquid P 36 26 27 22 Liquid L 4 3 2 4 Beef cattle Solid NB 21 7 14 23 Solid B 21 8 18 26 Liquid P 40 24 27 34 Liquid L 4 2 9 5 Dairy cattle Solid NB 9 4 4 10 Solid B 9 5 4 10 Liquid P 24 12 18 29 Liquid L 4 2.5 4 5 Turkeys Solid NB 27 17 20 17 Solid B 20 13 16 13 Horses Solid B 14 4 4 14 aNB = No bedding; B = bedding; P = pit; L = lagoon.
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From page 154... ...
Potassium fertilizer applications, however, are especially required in humid regions and highly organic soils. Potassium has a net positive charge, so ~ Is nounu to tne soil's cation exchange complex.
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From page 155... ...
o ~ ~~9~_e ~ ~ 1 ._ ~ =~_ I ' or 1i i j jlj jl j~l~l4~ 155 FIGURE 3-1 The relative availability of 12 essential plant nutrients in well-drained mineral soils in temperate regions in relation to soil pH. (Aluminum is not an essential nutrient for plants, but it is shown because it may be toxic below a soil pH of 5.2.)
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From page 156... ...
Department of Agriculture, 1987~. While these practices may advance some of the goals of alternative farming, such as increasing organic matter in soil and reducing soil erosion, some conservation tillage practices may increase the need for pesticides, particularly herbicides (Gebhardt et al., 19851.
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From page 157... ...
Ridge tillage is an effective alternative tillage system that can reduce erosion and costs and help control weeds without herbicides. Here, seeds are planted in a field with the residue of last year's corn crop, which protects the soil surface from erosion.
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From page 158... ...
Some plant diseases overwinter in crop residues left on the soil, above and below ground insects survive, and perennial weeds may establish a foothold. The effects of these pest populations are more severe if the same crop is planted the next year but may be inconsequential or minimized in a rotation.
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From page 159... ...
Credit: Soil Conservation Service, U.S.
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From page 160... ...
Legumes are an effective source of nitrogen in some conservation tillage systems, although different tillage methods can influence the amount of nitrogen available to subsequent crops (Heichel, 1987~. Conservation tiliage can reduce water runoff from fields.
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From page 161... ...
These conventional tillage operations work the soil into fine particles and leave almost no crop residue on the soil surface. This field could experience high soil losses if hard spring rains occur before the growing crop begins to protect the soil surface.
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From page 162... ...
The use of reduced tilIage is expected to increase primarily as a means to meet conservation compliance provisions of the Food Security Act of 1985. As its use increases, farmers and researchers will need to better understand its effects on soil structure, soil biota, plant growth, and pest populations.
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From page 163... ...
Warm soil facilitates crop germination, which slows weed emergence. Crop residue between the ridges also reduces soil erosion and increases moisture retention.
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From page 164... ...
The relationships among soil microorganisms, nutrient cycling, pest pressure, plant growth, yield, and many other factors of crop production need further study. LIVESTOCK Livestock play an important role in many alternative farming systems in terms of nutrient cycling and their ability to make crop rotations economically feasible through the consumption of forage crops (see the Spray, BreDahl, Sabot Hill, Kutztown, and Thompson case studies)
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From page 165... ...
Consequently, many livestock producers choose to maximize use of grains and silage and to minimize the area devoted to pastures and forages. Because pastures and forages have some advantages over row crops, such as reduced soil erosion and the potential to supply nitrogen, they are an important element in many alternative farming systems.
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From page 166... ...
Research is needed to improve the bioavailability of lignocellulose. This would include plant breeding to improve the digestibility of pastures and forages and the vegetative portions of crop residues.
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From page 167... ...
For example, porcine growth hormone increases growth rate feed efficiency, and ratio of muscle to fat. Animal Health Systems Disease prevention through management has become an increasingly important research objective throughout the last decade.
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From page 168... ...
use of antibiotics in feed and to treat disease has reinforced a trend not to manage for disease prevention and to accept the costs of antibiotic feeding and use as a routine production expense. Feeds that contain antibiotics are widely used because, on the typical farm, they help animals use feed more efficiently.
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From page 169... ...
National data indicate that approximately 50 percent of the dairy cattle in the country have mastitis (National Mastitis Council, 1987~. But other studies have identified large numbers of dairy herds that have very Tow levels of mastitis, as evidenced by the low numbers of white blood cells in the commercial milk produced (Bennett, 1987~.
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From page 170... ...
Credit: Grant Heilman. problem in swine production (National Research Council, 19881.
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From page 171... ...
The significant benefits of antibiotic feeding have revealed the extent of disease problems in modern swine production. Because of the complex etiology and the pervasiveness of disease in swine, the subtherapeutic feeding of antibiotics win likely remain a simple and effective method of reducing disease loss in lieu of changes in production practices with greater emphasis on other methods of disease prevention.
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From page 173... ...
Research on the integrated management of parasites associated with animals grazing on irrigated and nonirrigated pasture is needed in order to break the cycles of parasitic infection and reinfection. Genetic Resistance to Disease The genetic selection of animals has placed emphasis on productivity and efficiency and has potentially reduced natural disease resistance.
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From page 174... ...
Various stressors, such as close confinement, transportation, and temperature, have been shown to affect disease resistance. Although little scientific information is available that quantifies animal stress, observational research on the effects of stressors on animal health and behavior has fueled the debate on animal welfare and the significance of stress (Mickley and Fox, 1987~.
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From page 175... ...
Use of synthetic chemicals for pest control began in the 1940s, when the discovery of organic compounds such as dichioro diphenyl trichioroethane (DDT) , benzene hexachIoride (BHC)
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From page 176... ...
Ideally, the term IPM refers to control of all agricultural pests through the use of an integrated approach. IPM involves all aspects of crop production, including cultural practices such as cultivation, fertilization, postharvest management of fields, scouting for pests, tillage practices, the use of genetically improved pest-resistant varieties, rotations with other crops, and the use of biological controls (see the Florida, Pavich, Ferrari, and Kitamura case studies)
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From page 177... ...
Insects and disease are an ever-present threat in hot areas with a long growing season. Some plant diseases are more consistently a problem in hot areas with high humidity, such as the southeastern United States.
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From page 178... ...
Research shows, however, that significant progress has been made with other approaches. Incorporating pest control into the overall management of a farm by modifying cultural practices or rotating crops, for example, is essential to effective alternative pest control strategies.
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From page 179... ...
Natural biological controls, such as antagonists, predators, and self-clefense mechanisms, suppress most pests. Biological control of pests by natural enemies (parasites, predators, and insect pathogens)
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From page 180... ...
Department of Agriculture. is long-lasting if it is not disrupted by farming practices such as insecticide use, certain crop rotations, or unusual climatic conditions.
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From page 181... ...
infestation, rasher then on a routine schedule. Pesticide applications, as described in the Credit: Will Sargent.
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From page 182... ...
. Augmentation of indigenous natural enemies is an important biological control technique.
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From page 183... ...
Pheromones dispensed over fields to confuse males and prevent mating successfully control insect pests in a number of crops, including grape leafroller, oriental fruit moth on peaches, pink bollworm on cotton, and tomato pinworm. Commercial formulations are economically competitive with insecticides, even taking application costs into account.
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From page 184... ...
Cultural practices such as crop rotations, alteration of soil pH, sanitation, and adjustment of the timing of planting and harvest to avoid peak periods of the pathogens complement genetic resistance in many situations. For example, raising soil pH with lime from 6.5 to 7.5 reduces the severity of fusarium wilts on tomato and potato crops in Florida (Jones and Woltz, 1981~.
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From page 185... ...
better-targeted effects. The introduction or application of biological control agents has not been very successful with plant pathogens because of the great complexity in microbial communities.
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From page 186... ...
A less expensive, but also less effective, biological control option is the use of plants such as CrotaZaria spectabilis that prevent the nematode from reproducing. Coastal Bermuda grass (Cynodon daclylon)
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From page 187... ...
But a variety of other means, such as crop rotations, mechanical cultivations, competition with other plants, and biological control through natural enemies can control weeds (see Spray, BreDahI, Sabot Hill, Kutztown, Thompson, Pavich, and Lundberg case studies)
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From page 188... ...
In certain cases, this strategy could reduce weed control costs, improve weed control quality, and reduce human health hazards. SUMMARY Alternative farming encompasses a range of farming practices, including the use of crop rotations, IPM, biological and cultural pest control, use of organic materials to enhance soil quality, different tilIage methods, and animal rearing techniques that involve less reliance on antibiotics and confinement.
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From page 189... ...
The economics of these and other alternative farming practices and systems are discussed in the following chapter. REFERENCES Allen, W
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From page 190... ...
1983. The Nature and Practice of Biological Control of Plant Pathogens.
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From page 191... ...
-'95-~. the Economics of Crop Rotations and Land Use: A Fundamental Study in Efficiency with Emphasis on Economic Balance of Forage and Grain Crops.
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From page 192... ...
1985. Interactions of bacteria, fungi, and their nematode grazers: Effects on nutrient cycling and plant growth.
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From page 193... ...
1977. Biological Control by Augmentation of Natural Enemies.
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From page 194... ...
1986. Soil fertility guidelines for conservation tillage corn.
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