Toward Sustainable Agricultural Systems in the 21st Century (2010) / Chapter Skim
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3 Improving Productivity and Environmental Sustainability in U.S. Farming Systems
Pages 83-188

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From page 83...
... Research aimed at understanding how these management practices and engineering approaches work continue to provide additional tools for progress toward the sustainability goals outlined in Chapter 1. This chapter briefly discusses some of the management approaches and practices that are relevant to productivity and environmental sustainability and have an impact on agriculture's natural resource base (goals 1 and 2 in Chapter 1)
From page 84...
... Maintain and enhance environmental quality and resource base a. Maintain or • Soil nutrient levels, • Soil-fertility • Fertilizer and organic improve soil quality nutrient use efficiency management amendment application, use of soil and tissue tests, nutrient budget calculations • Soil organic matter • Organic- • Conservation tillage, organic content, microbial and matter amendments, composts, green macrofaunal populations management manure and communities • Soil physical structure such • Organic- • Conservation tillage, organic as bulk density, water- matter amendments, compost, green holding capacity, aggregate management manure stability, porosity, water infiltration rate b.
From page 85...
... Proper soil management is a key component of sustainable agricultural production practices as it produces crops and animals that are healthier and less susceptible to pests and diseases. It provides a number of important ecosystem services, such as reduced nitrogen runoff and better water-holding capacity (NRC, 1993)
From page 86...
... Conservation tillage, including ridge-till, mulch-till, and no-till practices, is any tillage and planting system that leaves 30 percent or more of the soil surface covered by crop residues after planting to reduce soil erosion by water. No-till leaves 50 to 100 percent of the soil surface covered from harvest to planting, depending on the crop residue, because it uses specifically designed seed planters or drills to penetrate all remaining surface residues (Huggins and Reganold, 2008)
From page 87...
... . Soil Organic Matter The amount of organic matter in soil subject to conventional tillage has been compared to soil subject to conservation tillage or no-till in different locations.
From page 88...
... agricultural systems and found an average net soil loss of 3.9 mm/yr under conventional agriculture and 0.12 under conservation agriculture that included conservation tillage, no-till methods, and terracing. Montgomery further examined 39 studies involving direct comparisons of soil erosion under conventional and no-till methods representing a wide variety of settings with different erosion rates and showed that no-till practices reduce soil erosion up to 1,000 times, enough to bring agricultural erosion rates into line with rates of soil production.
From page 89...
... Zero-till can also reduce emissions of particulate matter, especially if the practice is used with mulching or cover cropping. For example, in the dryland areas of wheat production on the eastern side of the Cascades and in portions of the Great Plains, clean fallow for moisture conservation has long been practiced.
From page 90...
... That estimate did not include the additional efficiencies gained from increased productivity as a result of increased soil quality as described above for enhancement of ecosystem services. When calculated for a 2100-acre Michigan corn–oats–soybean–wheat rotation farm, diesel fuel savings over conventional tillage would have been 28 percent for mulch-till, 27 percent for ridge-till, and 52 percent for no-till (USDA-NRCS, 2008a)
From page 91...
... The accounting of long-term effects, including impact of increased surface organic matter and changed fertilizer requirements during the transition period, complicates total energy balance considerably.
From page 92...
... They observed a significant reduction in soluble phosphorus accumulation in runoff with no negative effects on soil quality or crop yield. Further research is needed on management of no-till systems to reduce negative water quality effects.
From page 93...
... . Among the conservation tillage practices, no-till has been used on an increasing proportion of land (from 17 million acres in 1990 to 61 million acres in 2004; Figure 3-2)
From page 94...
... Such practices as mulching, cover cropping, and crimping or rolling crop residues also can be used with conservation tillage to suppress weeds. Cover Cropping Cover cropping is the practice of using vegetative crops, such as clover or vetch, to prevent soil erosion, control weeds, and provide nitrogen to a subsequent crop.
From page 95...
... . Nutrient Management Cover crops help support soil microbial communities, which break down organic matter and make nutrients available to subsequent crops.
From page 96...
... The precise effect of cover crops on beneficial insect and pest complexes and on soil-borne diseases is likely to depend on several factors, including the composition of cover crops, the prevalence and types of pests and pathogens at the location, temperature, irrigation management, and tillage. Adoption of Cover Cropping Despite their benefits on soil and water quality, cover crops are not widely planted.
From page 97...
... . Although 96 percent of the farmers surveyed believe that cover crops are effective in controlling soil erosion and increasing soil organic matter, only 18 percent of the farmers surveyed have used cover crops.
From page 98...
... . Practices such as rotating crops, preserving genetic variety, planting crops together, incorporating cover crops, and managing noncropped land properly could increase the robustness and resilience of farming systems against the unpredictability of pest problems and against varying market conditions.
From page 99...
... Crop rotations can enhance accumulation of soil organic carbon. Including legumes in a rotation supplies symbiotically fixed nitrogen to the soil (Havlin et al., 1990)
From page 100...
... Corn yields in the most diverse rotation (corn–soybean–winter wheat with two cover crops per main crop) were more than 60 percent higher than corn in the twoyear corn–soybean rotation that had no cover crops (R.G.
From page 101...
... The economic aspects of crop rotations and cover crop use in rotations are discussed in Chapter 4. Adoption of Crop Rotations Most major crop production involves rotational cropping of some form, with the exception of cotton (Figure 3-4)
From page 102...
... 0 TOWARD SUSTAINABLE AGRICULTURAL SYSTEMS IN THE 21ST CENTURY 3-4a.eps FIGURE - Cropping patterns on corn and soybean for 10 major producing states. SOURCE: USDA-ERS (Sandretto and Payne, 2006)
From page 103...
... between the crop components enhance biomass yield and provide key ecological services such as nutrient cycling, biological pest control, and water and soil conservation. The challenge in strip cropping is to identify the correct assemblages of species to maximize their biological synergisms, while having compatible use of agricultural equipment and conservation tillage practices (Altieri and Nicholls, 1999)
From page 104...
... has been shown to reduce nitrate leaching losses with subsurface drainage water (Kanwar et al., 2005)
From page 105...
... The range of services include a reduction in soil erosion, buffer strips along riparian areas, habitat for wildlife, and a general increase in plant and animal diversity. Vegetation diversity in agricultural landscapes may also improve biological control of certain pests.
From page 106...
... varieties of crops that were in cultivation prior to the introduction of hybrid varieties and synthetic agrochemicals in the 1950s may contain valuable traits for sustainable agricultural systems, such as sensory qualities related to taste and smell, enhanced nutritional value, resistance to pests and diseases, greater biomass and ability to compete with weeds, and greater nutrient and water-use efficiency. Their negative traits may include susceptibility to diseases and pests, low yields, lodging, longer maturity dates, and a more limited postharvest shelf life.
From page 107...
... As organic and other sustainable farming systems generally require more complex crop management practices, these factors (such as crop rotations and cover crops) also need to be taken into account (Van Bueren et al., 2002; Murphy et al., 2007; Wolfe et al., 2008)
From page 108...
... . Molecular Markers and Genetic Engineering in Cultivar Development Classical or conventional plant breeding, which involves sexual recombination and phenotypic selection of plants with superior traits, continues to be the primary mechanism to improve crops for both conventional and sustainable farming systems.
From page 109...
... . Impact Plant breeding has been improving yield through increased productivity, improved pest and weed resistance, and improved drought tolerance for decades.
From page 110...
... . WATER-USE MANAGEMENT To meet sustainability goals of conserving water resources, water management is critically important.
From page 111...
... In addition to managing water consumption, precipitation can be captured or water can be reused to improve the long-term sustainability of water use in agriculture. Irrigation Scheduling Quantitative irrigation scheduling methods rely on one of two approaches: soil or crop monitoring or a combination of both; or soil water balance computations.
From page 112...
... were able to reduce irrigation water additions to corn from 283 mm to 127 mm without significant yield reduction by precisely monitoring canopy temperature. An extension project in north central Nebraska also showed that irrigation scheduling reduced energy costs, applied less water, and led to higher harvested yields for center-pivot irrigated corn.
From page 113...
... Improved water management practices for gravity irrigation remains an area of significant growth potential, with many available technology or management improvements such as alternate row irrigation, furrow modification, tailwater reuse, or soil amendments not in widespread use (Schaible and Aillery, 2006)
From page 114...
... calculated, based on research reports for the costs of irrigation for orchards in the Michigan area, that the energy savings in a 100-acre orchard could be up to 20 percent by adding a flow meter, irrigation scheduling, and maintenance and upgrades to a basic diesel-powered sprinkler system. Use of a micro-irrigation system (after installation costs)
From page 115...
... subjects crops to moisture deficit during stress-tolerant growth stages to minimize negative effects of yield. Impact of Regulated Deficit Irrigation Regulated deficit irrigation could be applied to a variety of crops including grapes, pistachios, and stone fruits (Cooley et al., 2009)
From page 116...
... . Water quality impacts downstream of these small dams can be slight or significant, depending on sediment and nutrient inputs from upstream, water residence time in the impoundment, and whether surface (warmer)
From page 117...
... . WATER QUALITY MANAGEMENT Reducing pollution of surface and ground water is a major goal for moving agriculture toward sustainability.
From page 118...
... Because DWM systems are typically managed during nongrowing season months or between crop rotations, there is little potential for yield loss.
From page 119...
... . Because wetlands can be an effective method for removing a wide variety of water quality contaminants, including sediments, nitrogen, and phosphorus (Howard-Williams, 1985; Nixon and Lee, 1986; Kadlec and Knight, 1996; Reddy et al., 2005)
From page 120...
... . Soil properties of wetlands, such as soil organic matter, exchangeable calcium, and oxalate extractable iron, are correlated to phosphorus sorption index.
From page 121...
... Riparian buffers can be designed to include trees, shrubs, native grasses and forbs, nonnative cool-season grasses, or some combinations of those to enhance ecosystem functions (for example, enhance surface and ground water quality, provide habitats for fish and wildlife, and reduce sediment transport) in specific habitats (Schultz et al., 2004)
From page 122...
... . Like wetlands, the effectiveness of buffers in improving water quality depends on a number of factors, including hydrology, buffer vegetation, width of buffer, and climatic events (Dukes et al., 2002; Herring et al., 2006)
From page 123...
... For example, the conversion of organic nitrogen in the soil to plant-available nitrate from fresh residue or existing soil organic matter is a two-step process mediated by soil microbes, first producing ammonium (mineralization) and then nitrate (nitrification)
From page 124...
... , in which case the remaining nitrogen that is unaccounted for is assumed to be lost via some combination of denitrification, volatilization, and, over the long term, as additions to soil organic matter. In California, eight years of budget calculations illustrated the effects of organic, low-input, and conventional management on net balances of different nutrients.
From page 125...
... . Soil tests have limitations, however, in that they do not take into account factors that affect the risk of actual loss from the field and of impacts on water quality.
From page 126...
... Crop rotations that include actively fixing legumes can reduce nitrogen fertilizer needs because some of the fixed nitrogen is returned to the soil with incorporation of crop residue, and by direct release into the soil via root exudation and root death. As discussed in the earlier section on cover crops, leguminous cover crops can be used as green manures to improve soil fertility.
From page 127...
... . Similarly, if legumes are used as a winter cover crop, nitrate released following incorporation in the spring can be vulnerable to leaching losses (Moller et al., 2008)
From page 128...
... . One solution is to adjust the manure rate to meet the phosphorus needs of the crop and to supply the additional nitrogen with fertilizer or a legume cover crop (Sullivan, 2004)
From page 129...
... Compost Compost is a mixture of decaying organic material and can be made from farm manure, sewage sludge, agricultural residues, or food wastes. Composting has been defined as "an aerobic process of decomposition of organic matter into humus-like substances and minerals by the action of microorganisms combined with chemical and physical reactions" (Peigne and Girardin, 2004, pp.
From page 130...
... Soil Quality Use of composts adds carbon to the soil, increases soil organic matter, can increase nutrient availability, and improve soil moisture retention and water infiltration. For example, in an 18-year study, compost additions increased soil carbon by 16 to 27 percent and soil nitrogen by 13 to 16 percent (Hepperly et al., 2009)
From page 131...
... . Precision Agriculture Precision agriculture can be broadly defined as "a management strategy that uses information technologies to bring data from multiple sources to bear on decisions associated with crop production" (NRC, 1997, p.
From page 132...
... . One goal of precision agriculture is to reduce the input of nitrogen and phosphorus fertilizer into agricultural fields.
From page 133...
... methods of applying nutrients reduce leaching and improve water quality when compared to uniform application methods (Wang et al., 2003)
From page 134...
... . Anaerobic Digestion with Biogas Recovery of Animal Manure Treatment of animal manure with anaerobic digestion coupled with biogas recovery and use is one method for animal operators to reduce odors and pathogens in manures and generate biogas for energy at the same time.
From page 135...
... . A few centralized combustion facilities also collect animal manure from nearby animal production facilities.
From page 136...
... To effectively manage the weed–disease–pest complex with reductions in, or elimination of, chemical use requires a suite of strategies (Shennan, 2008) that includes: breeding of crops that are pest and disease resistant and that are better able to compete with weeds in a given environment; use of different soil and crop management strategies; and diversification of crop rotations and noncrop vegetation.
From page 137...
... For example, changes in weed populations can provide new hosts for pests or pathogens increasing their severity; alternatively, they can provide refugia for beneficial arthropods and enhance soil suppressiveness to soil-borne pathogens, thus aiding biological control (Norris, 2005; Thomas et al., 2005; Wisler and Norris, 2005)
From page 138...
... The spectrum of definition is also reflected on the ground according to surveys of IPM practices among different farms in the United States and elsewhere. For some farmers, IPM means simply scheduling pesticide applications based on monitoring and established economic thresholds; others use more integrated IPM that combines a mix of cultural and biological control practices with or without pesticide use as a last resort (Shennan et al., 2001)
From page 139...
... Three types of biological control of arthropods are recognized: classical, which refers to the release of exotic organisms to control pests that are not effectively controlled by native natural enemies; augmentative, the periodic release of natural enemies to augment native populations; and conservation biological control, where habitat diversification is used to provide the resources necessary to support higher populations of natural enemies. Classical biological control has a long history, and numerous reviews of the successes and failures of classical biological control efforts can be found (Bale et al., 2008, and references therein)
From page 140...
... (2008) concluded that "Complex landscapes characterized by highly connected crop-noncrop mosaics may be best for long-term conservation biological control and sustainable crop production, but experimental evidence for detailed recommendations to design the composition and configuration of agricultural landscapes that maintain a diversity of generalist and specialist natural enemies is still needed."
From page 141...
... , and cultural and biological control practices. Cultural approaches include soil organic matter management, irrigation, fertility management, microclimate modification via planting arrangements, choice of irrigation methods and scheduling, crop rotation, and biofumigation methods (Shennan, 2008)
From page 142...
... Brassica species in particular have been widely studied for use as disease-suppressive cover crops (Snapp et al., 2005; Matthiessen and Kirkegaard, 2006) that can also help control plant parasitic nematodes (Zasada and Ferris, 2004)
From page 143...
... Compost additions and cover crop residues have been found to reduce fungal, bacterial, and nematode pathogens in a number of systems, although the effect can be highly variable depending on the specific crop–pathogen–amendment combination (Abawi and Widmer, 2000)
From page 144...
... . Crop rotations can be an effective nematode management tool when built around use of nematode-suppressive cover crops and residues, nonhost crops, or varieties, as well as appropriate tillage and organic matter to stimulate desired changes in soil communities (Caamal-Maldonado et al., 2001; Vargas-Ayala and Rodriguez-Kabana, 2001; Pyrowolakis et al., 2002; Zasada and Ferris, 2004; Snapp et al., 2005; Westphal, 2005)
From page 145...
... are being used. Allelopathic chemicals released by specific cash crop or green manure species has been shown to inhibit weed growth, although the effect is known to be highly specific to species and variety and is dependent upon the combination of microclimate, residue management, soil conditions, and target organism (Blackshaw et al., 2001; Caamal-Maldonado et al., 2001; Inderjit et al., 2001)
From page 146...
... Manipulation of crop rotations and inclusion of cover crops at key points can suppress weeds, and lifecycle models for weeds can be used to design appropriate sequences (Anderson, 2004)
From page 147...
... on disease suppressiveness appear to vary with crop rotations. It is possible that some crop rotations are better able than others to support populations of added beneficial organisms from amendments and enable more effective biological control (Larkin, 2008)
From page 148...
... , as has been argued for biological control tactics for plant diseases (Alabouvette et al., 2006; Matthiessen and Kirkegaard, 2006) and use of green manures (Cherr et al., 2006)
From page 149...
... Considerable progress has been made in development and commercialization of different kinds of augmentative biological control agents, yet sales of biocontrol products only account for 1 percent of total agricultural chemical sales (Fravel, 2005)
From page 150...
... • On-farm work to assess the ability of different kinds of vegetation diversification to increase indigenous biological control. If biological control advantages are well documented, growers will be more likely to diversify habitats within and around the farm, which will also provide other important ecological benefits.
From page 151...
... This section discusses genetics and nutrition as approaches to improving efficiency of animal production systems. Animal Breeding Efforts in animal breeding have focused on traits that influence output, such as weight gain, feed efficiency, reproductive efficiency (Grosshans et al., 1994; Kelm et al., 2000)
From page 152...
... , which is critical to future animal breeding efforts in the United States. Disadvantages of Animal Breeding Breeding animals for a specific trait could have unintended effects on animal health and welfare.
From page 153...
... For example, the improvements in dairy cattle feed conversion is summarized by Bull et al.
From page 154...
... This section has a different format than the others in this chapter because animal welfare research is relatively new compared to research discussed earlier. Moreover, the impact of different practices aimed to improve animal welfare depends on the criteria used to measure welfare.
From page 155...
... . Improving animal health and welfare is an objective of the sustainability goal of enhancing environmental quality and the resource base (see Box 2-5 in Chapter 2)
From page 156...
... reported on changes in animal health associated with the implementation of the 1988 Swedish Animal Welfare Act, which mandated use of alternative housing systems in lieu of conventional battery cages. The study identified increases in submissions of animals for necropsy between 2001 and 2004 from litter-based systems and free-range production, compared to hens in cages.
From page 157...
... As with animal housing, the effect of dietary restriction on animal welfare requires further research to understand its impact on the animal's overall welfare. Environmental Enrichment Environmental enrichment is a term used to describe efforts to improve the living conditions of captive animals, including farm animals.
From page 158...
... . Challenges in animal welfare research include defining and assessing hunger in animals (D'Eath et al., 2009)
From page 159...
... Dietary enzymes can improve feed conversion and increase weight gain in pigs (Doyle, 2001)
From page 160...
... . Livestock owners have different motives for establishing an identification system for their animals including evaluating product quality and genetic improvements, protecting their livestocks from loss or theft, and evaluating animal health and tracing back diseases (Golan et al., 2004; USDA-APHIS, 2007)
From page 161...
... Research is needed to broaden crop coverage, solve problems in low-moisture areas, and increase the diversity of herbicides used while focusing on developing conservation tillage systems that would work with low-or-zero herbicide use, such as in organic agriculture. • Cover crop use has seen a resurgence of interest and use in the past two decades, adding to landscape-level diversity, more effective nutrient containment, and im proved soil quality, often in combination with conservation tillage.
From page 162...
... Precision agriculture is another tool for nutrient management.
From page 163...
... Weed management requires a suite of approaches to reduce annual seed production and the preexisting seed bank. Methods such as crop rotations, soil tillage, and organic matter management; use of cover crops and other crops with allelopathic properties; plant spacing; and water management all can affect weed populations.
From page 164...
... 2006. Biological control of plant diseases: the European situation.
From page 165...
... 2007. Impact of a cover crop on carbon and water balance of corn/soybean systems.
From page 166...
... 1994. Using cover crops to manage arthropod pests of orchards -- a review.
From page 167...
... 2004. A critical evaluation of augmentative biological control.
From page 168...
... 2001. Using winter cover crops to improve soil and water quality.
From page 169...
... 2008. Sustainable cover crop rotations with potential to improve yields, crop quality, and nutrient and water use efficiencies.
From page 170...
... 1990. Controlled Drainage Management Guidelines for Improving Water Quality.
From page 171...
... 1985. Conservation tillage.
From page 172...
... 2002. 50th anniversary invited article: cover crops and living mulches.
From page 173...
... 1990. Crop rotation and tillage effects on soil organic carbon and nitrogen.
From page 174...
... 2002. Infiltra tion and soil water storage under winter cover cropping in California's Sacramento Valley.
From page 175...
... 2008. Potential and limitations of cover crops, living mulches, and perennials to reduce nutrient losses to water sources from agricultural fields in the Upper Mississippi River Basin.
From page 176...
... 2008. Relative effects of biological amendments and crop rotations on soil microbial communities and soilborne diseases of potato.
From page 177...
... 1993. Conservation Tillage and Residue Management to Reduce Soil Erosion.
From page 178...
... 2008. Growth, composition, biological N-2 fixation and nutrient uptake of a leguminous cover crop mixture and the effect of their removal on field nitrogen balances and nitrate leaching risk.
From page 179...
... 2007. Conservation tillage, rotations, and cover crop affect ing soil quality in the Tennessee valley: particulate organic matter, organic matter, and microbial biomass.
From page 180...
... 2007. Is conservation tillage suitable for organic farming?
From page 181...
... 2003. Organic and other management strategies with two- and four-year crop rotations in Minnesota.
From page 182...
... 1995. The influence of winter legume cover crops on soilborne plant-pathogens and cotton seedling diseases.
From page 183...
... 1991. Effects of cover crops on surface water quality.
From page 184...
... 2008. Cover crops enhance soil organic matter, carbon dynamics and microbio logical function in a vineyard agroecosystem.
From page 185...
... 1998. Cover crop effects on soil water relationships.
From page 186...
... 2001. Bioremediative management of soybean nematode population densities in crop rotations with velvetbean, cowpea, and winter crops.
From page 187...
... 2006. Summer cover crops and soil amendments to improve growth and nutrient uptake of okra.
From page 188...
... 1996. Winter cover crops in a vegetable cropping system: impacts on nitrate leaching, soil water, crop yield, pests and management costs.


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