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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Sustainable Agricultural Systems Laboratory » Research » Research Project #424914

Research Project: Defining Agroecological Principles and Developing Sustainable Practices in Mid-Atlantic Cropping Systems

Location: Sustainable Agricultural Systems Laboratory

2017 Annual Report

The long-term goal is to develop and translate fundamental agroecological knowledge into products and recommendations that help organic farmers meet consumer demand and improve their economic returns. Strategies developed for organic systems will also help increase sustainability of conventional farms. To reach the long-term goals focus will be on the following objectives over the next five years. Objective 1: Identify and elucidate agroecological principles that drive the function of organic and conventional cropping systems and quantify ecosystem services. Sub-objective 1.A. Compare factors controlling crop performance in long-term organic and conventional cropping systems. Sub-objective 1.B. Determine mechanisms controlling soil carbon sequestration and greenhouse gas flux in organic and conventional cropping systems. Sub-objective 1.C. Identify factors controlling soil biological community structure and its relationship to soil functions and the provision of ecosystem services in organic and conventional cropping systems. Sub-objective 1.D. Conduct integrated analyses to assess the impacts of organic and conventional cropping systems on the provision of ecosystem services. Objective 2: Develop technologies and management strategies to improve productivity, enhance soil and water conservation, and improve the efficiency of nutrient cycling on organic and conventional farms. Sub-objective 2.A. Develop new strategies for incorporating legumes (e.g., alfalfa, hairy vetch, clovers) into organic and conventional crop rotations to maximize nitrogen fixation within these systems. Sub-objective 2.B. Develop strategies for beneficial and safe use of animal manures and composts for organic and conventional agriculture. Sub-objective 2.C. Develop optimal agronomic practices for managing nutrients, weeds, and production on organic farms.

Approaches to identifying and elucidating agroecological principles include investigating the following variables within the Beltsville long-term Farming Systems Project that compares two conventional and three organic rotations, and associated projects: crop performance, soil carbon sequestration and greenhouse gas fluxes, soil microbiological community structure, and integrated analyses that evaluate overall systems performance. Approaches to developing component strategies include: incorporating legumes into organic crop rotations to maximize nitrogen fixation, composting that provides a productive and safe amendment for organic agriculture, integrating cover crop and manure management practices, reducing tillage in organic systems, and evaluating perennial wheat varieties.

Progress Report
Under objective 1, the 21st year of research at the long-term Farming Systems Project (FSP) was completed with crop yield, crop and cover crop biomass, soil fertility, soil moisture and other data collected. Microplots to study the impacts of crop varieties, weed competition, and soybean nitrogen fixation were established, sampled and harvested. The first year of projects to assess impacts of subsoiling and reduced poultry litter application rates on crop performance was initiated. Research focused on understanding plant and soil controls on microbial community composition continued with analysis of the soil and root associated microbial community in conventional and organic farming systems with and without exposure to glyphosate. Plant associated microbial communities differed significantly by location (Beltsville, Maryland; Urbana, Illinois; Stoneville, Mississippi). Also, the historic legacy of farming system practices was more influential on the structure of the root and soil microbial communities than the application of glyphosate to the above ground portion of the crop. We also found that there were acceptable levels of the active herbicide (glyphosate) or its breakdown product aminomethylphosphonic acid (AMPA) in the leaves and seed. For objective 2, legume germplasm screening and selection of hairy vetch, crimson clover, and winter pea continued. Partnerships with additional universities and Plant Material Centers permitted broader regional development of cultivars. Protocols were developed to use variation in symbiotic biological nitrogen fixation as a selectable trait among leguminous winter annual cover crops. From the same breeding study, roots and nodules were collected from each breeding accession to determine the composition and potential function of the plant root microbiome. The germplasm screening effort was expanded to include screening and selection of cereal cover crops. Results of a pilot-study supported the concept and technical feasibility of using gas-permeable membrane systems to capture NH3 from poultry houses. The membrane systems resulted in a 35% reduction in ammonia emissions. The potential benefits of this technology include: improved bird productivity and health (4% less mortality), reduced ammonia emissions and energy requirements for heating, cleaner air and emissions, and production of a concentrated ammonium salt as a valuable plant nutrient product. Additional modifications of the membrane configurations to improve performance are underway.

1. Roundup Ready gene has minimal effects on crop attributes. A multi-location experiment was designed to test the effects of the Roundup Ready gene and glyphosate on crops and on the soil microbial community. Field experiments were carried out in Stoneville, Mississippi, Urbana, Illinois, and Beltsville, Maryland, in which corn and soybean were grown in rotation with and without the application of glyphosate and in which the soybean did or did not have the Roundup Ready gene. The first results from the experiments in Stoneville show that there were EPA acceptable levels of the active herbicide (glyphosate) and its breakdown product aminomethylphosphonic acid (AMPA) in the leaves and seed of soybean plants. Lack of the Roundup Ready gene and glyphosate application had minimal effects on yield and mineral and amino acid content of glyphosate-resistant soybean. The results of this study will impact the perception and policy related to the on-going debate about GMO (genetically modified organism) crops. Information from this report can help guide herbicide recommendations for Roundup Ready corn and soybean producers.

2. Conservation tillage with cover crops reduces greenhouse gas emissions. Conservation soil management practices such as no-till (NT) and strip-till (ST) are effective ways to increase soil organic matter and sequester carbon in agricultural lands thereby diminishing carbon dioxide in the atmosphere. However, the impact of these practices on other greenhouse gases (GHG) such as nitrous oxide (N2O) varies depending on soil structure, climate, and duration of the practice. In a three-year study conducted in a field transitioning to organic vegetable production using winter cover crops in the Mid-Atlantic coastal plain of the USA, researchers found that using NT and ST practices reduced N2O emissions compared to the standard practice of using tillage and black plastic mulch. Crop yield-scaled N2O emissions were consistently greatest when using tillage and black plastic mulch and lower in NT. These results suggest that under coarse-textured soils in the coastal plain, conservation tillage with winter cover crops may be able to achieve net GHG emission reduction in upland soils. These results will be of interest to government agencies such as USDA-NRCS, other scientists, and policy makers.

3. Ability to predict soil nitrous oxide emissions is improved by considering soil bacterial diversity. Denitrification, a microbiological process, reduces the amount of nitrogen in soil and can therefore impact plant production. Denitrification is also the dominant source of nitrous oxide, which is both a greenhouse gas and the primary cause of stratospheric ozone decline. There are many different kinds of bacteria capable of denitrification such that understanding which bacteria are present in a given soil could help us understand the denitrification process and crop productivity. We found that the diversity of bacteria capable of denitrification does impact denitrification and nitrous oxide production rates. Thus, including information about bacterial diversity should improve denitrification models. This information will be of interest to scientific colleagues working to better understand the impacts of denitrification on crop production and environmental health.

4. A novel method of estimating nitrous oxide emissions from soils. Application of nitrogen fertilizer to soils as fertilizer accounts for 69% of U.S. emissions of nitrous oxide (N2O), a greenhouse gas that is also the dominant anthropogenic stratospheric ozone-depleting substance. Mitigating N2O production requires that we better understand the impacts of various agricultural management practices on emissions. However, a lack of uniformity in greenhouse gas sampling constrains our ability to compare results among studies. By sampling a field experiment intensively over time we developed a method of estimating N2O emissions for seven days following a soil wetting event by measuring emissions only once two days after the end of a wetting event. These results will help researchers develop standard methods for sampling frequency and extrapolating gas flux from select sampling events.

5. Nitrogen in surface applied crop residues is transferred to soil by fungi. When crop residues with high carbon to nitrogen ratios, such as cereal rye, are incorporated into soil the amount of plant available nitrogen in soil is reduced because soil microorganisms use the nitrogen during decomposition of the plant residues. When crop residues are left on the soil surface it is possible that soil fungi, which can grow into the residue from the soil, reduce soil nitrogen by translocating it into the crop residue during decomposition. Therefore, we conducted a field experiment to determine the extent to which nitrogen translocation into rye residue occurs in a rye cover crop-based no-till soybean production field. We observed a 36% increase in cereal rye residue nitrogen that appears to be due to fungal translocation. This work will form the basis for farmer recommendations on fertilizer use in high residue cropping systems.

6. Energy use is lower in organic than conventional systems and crop diversification reduces greenhouse gas emissions. Reducing energy use and greenhouse gas (GHG) emissions from agricultural systems are important aspects of sustainability. We quantified energy use and GHG emissions of two conventional and three organic long-term grain cropping systems using the Farm Energy Analysis Tool (FEAT) model. Energy use was greater in the conventional than the organic systems. Greenhouse gas emissions were higher in two- and three-year organic crop rotations than in the conventional systems and were lowest in a six-year organic crop rotation that featured a perennial crop. Results indicate that diversifying grain cropping systems to include perennials is a more important management strategy than organic management per se to reduce GHG emissions in agriculture. This analysis will be useful for educating researchers, policy makers, and agricultural professionals on the factors driving energy use and GHG emissions in diverse cropping systems.

Review Publications
Spargo, J.T., Cavigelli, M.A., Mirsky, S.B., Meisinger, J.J., Ackroyd, V. 2016. Organic supplemental nitrogen sources for field corn production after a hairy vetch cover crop. Agronomy Journal. 108:1992-2002.
Davis, B.W., Mirsky, S.B., Needelman, B.A., Cavigelli, M.A., Yarwood, S.A., Maul, J.E., Bagley, G.A. 2016. A novel approach to estimating nitrous oxide emissions during wetting events from single-timepoint flux measurements. Journal of Environmental Quality. 46:247-254.
Teasdale, J.R., Cavigelli, M.A. 2017. Meteorological fluctuations define long-term crop yield patterns in conventional and organic production systems. Scientific Reports. 7:688.
Duke, S.O., Rimando, A.M., Reddy, K.N., Cizdziel, J.V., Bellaloui, N., Shaw, D.R., Williams, M., Maul, J.E. 2017. Lack of transgene and glyphosate effects on yield, and mineral and amino acid content of glyphosate-resistant soybean. Pest Management Science. 74:1166-1173. https://doi.10.1002/ps.4625.
Kepler, R., Maul, J.E., Rehner, S.A. 2017. Managing the plant microbiome for biocontrol fungi: Examples from Hypocreales. Current Opinion in Microbiology. 37(1):48-53. doi:10.1016/j.mib.2017.03.006.
Zinati, G., Mirsky, S.B., Seidel, R., Grantham, A., Moyer, J., Ackroyd, V. 2017. High-residue cultivation timing impact on organic no-till soybean weed management. Weed Technology. 31:320-329.
Wells, M.S., Reberg-Horton, S.C., Mirsky, S.B., Maul, J.E., Hu, S. 2017. In situ validation of fungal N translocation to cereal rye mulches under no-till soybean production. Plant and Soil. 410:153-165.