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.
Under objective 1, the 19th year of research at the long-term Farming Systems Project (FSP) was completed with crop yield, crop and cover crop biomass, soil quality and other data collected. Microplots to study the impacts of crop varieties, weed competition, soybean nitrogen fixation, glyphosate, and Roundup-Ready soybeans were established, sampled and harvested. A new project was established at FSP to assess impacts of management and crop varieties on corn metabolomics and gene expression. For objective 2, germplasm assessments of hairy vetch and crimson clover were continued. A manuscript describing weed seed indicators of time-temperature target thresholds for pathogen kill in composting manures is being completed. The Cover Crop Mixture Injection Trial, which assessed cover crop biomass, corn yield and nitrogen uptake, soil nitrogen availability around subsurface bands of poultry litter, greenhouse gas emissions, and litter bag studies was completed.
1. Mechanical scarification—abrasion of the seed coat — can eliminate the potential of hairy vetch becoming a weed in winter annual cereal grain crops. Hairy vetch is an important cover crop for temperate regions: it grows rapidly, produces tremendous levels of biomass rich in nitrogen, forms a dense weed-suppressive mulch, reduces erosion and can inhibit soil-borne diseases. However, adoption of hairy vetch has been greatly impeded by farmer concerns about it becoming a weed since hairy vetch seeds can last a long time in the soil due to having a hard seed coat. ARS scientists in Beltsville, Maryland, conducted multi-site and -year field trials evaluating how variety, seed burial depth, and seed scarification influence hairy vetch emergence and seedbank persistence. Across all sites, varieties, burial depths, and year replications, scarification of hairy vetch seed resulted in no viability of hairy vetch in the soil after six months. These results have tremendous implications for the use of hairy vetch as a cover crop by farmers. Removing hairy vetch hard seed will greatly change farmers reluctance to use this cover crop. Furthermore, our results will inform seed companies on strategies to improve both their products and their sales.
2. Management and nutrient source alter stratification of phosphorus forms in soil. Loss of phosphorus (P) in runoff from agricultural fields negatively impacts water quality of streams and lakes. Therefore, it is important to understand how management and nutrient source can help control P losses from agricultural soils. USDA, Agriculture and Agri-Food Canada, and Stanford University scientists investigated the stratification of P forms in soils from a long-term study at the USDA ARS location in Watkinsville, Georgia. Results suggested P fertilizers should be placed below the soil surface and thus reduce potential P loss in surface runoff. Care should be taken to avoid applying excess P when fertilizing with animal manures such as poultry litter. These results are of interest to farmers, agricultural consultants, policymakers and others interested in reducing nutrient losses from agricultural production practices.
3. Runoff curve numbers for no-till cropping systems should be smaller than currently accepted. The runoff curve number (CN) method is a simple, widely used and efficient method for estimating the amount of runoff for water quantity and quality modeling. It was empirically developed using runoff data collected from small catchments and hillslope plots prior to widespread adoption of no-tillage (NT). Little work has gone into validating CNs for NT cropping. Using rainfall-runoff data gathered from 1972 to 2010 from a watershed near Athens, Georgia, USDA ARS scientists derived CNs for conventional tillage (CT) and NT management periods. Results supported the hypothesis that CNs for NT cropping systems should be smaller than currently used for comparable tilled watersheds in the region. These results have implications for hydrologic modeling for water quantity and quality, where the use of the CN method is ubiquitous. These results will be of interest to NRCS, EPA, and state and local agencies that use runoff estimates to evaluate water quantity and quality from agricultural systems.
4. Development of tools to improve legume cover crops. Legume cover crops in rotation with cash crops reduce the environmental impact of agricultural systems, but there has been little effort in improving the cover crop varieties available to farmers in the U.S. A successful breeding program for cover crop improvement requires in-depth understanding of the biology, ecology and genetics of cover crop germplasm. The genome of hairy vetch (Vicia villosa) cultivar Purple Prosperity® was sequenced by ARS scientists in Beltsville, Maryland, and the draft sequence was deposited on the iPlant Collaborative cloud platform. An ARS scientist in Beltsville, Maryland, previously described the phylogenetic relationships among 64 accessions of hairy vetch maintained in the USDA National Plant Germplasm System. These efforts represent a major step forward in developing tools that plant breeders can use to quickly identify the underlying genetics controlling hairy vetch traits that farmers desire, such as nitrogen fixation, weed suppression, and improved soil quality. Results will be of interest to plant breeders and eventually farmers.
5. Gas-permeable membrane technology can be an effective method to capture and recover ammonia from poultry facilities. Volatilization of ammonia (NH3) gas from poultry manure is one of the major environmental and human health concerns associated with confined poultry production, adversely affecting the health of workers and birds. Technologies to remove and recover NH3 from poultry houses could lead to improved interior and exterior air quality, reduced ventilation costs, and a concentrated liquid ammonium salt useful as fertilizer. ARS scientists in Beltsville, Maryland, conducted a study in collaboration with the University of Maryland Eastern Shore and ARS-Coastal Plains Soil, Water, and Plant Conservation Research Unit, to test the capture of NH3 from the interior of a research poultry room housing 400 broiler birds from chick to maturity using novel gas-permeable flat (gutter) and tubular membrane modules. Acid solution pH 2 pumped through each module captured free NH3 from the room air, and was stabilized as a concentrated ammonium salt. These positive NH3 capture results are being used in additional trials and other applications of the technology such as with in-vessel composting systems where substantial amounts of NH3 are typically volatilized during the thermophilic stages of the process. Results will be of interest to poultry house operators and workers.
6. The composition of soil organic matter is impacted by tillage, poultry litter, crop types and their interactions. Our understanding of how agricultural management practices impact soil organic carbon levels—important for soil fertility, soil quality and mitigation of excessive atmospheric carbon dioxide—is limited because of our limited understanding of the composition of soil organic matter. In collaboration with Brazilian scientists, ARS researchers in Beltsville, Maryland, evaluated the impact of agricultural management on soil carbon composition using infrared spectroscopy (IR) and pyrolysis—gas chromatography—mass spectrometry (PY-GC-MS). Results show that soils receiving poultry litter have more recalcitrant forms of soil carbon, that soil organic carbon sequestration at 20 to 30 cm depth may be facilitated by tilling organic materials to that depth, and that crop types influence the forms of carbon in soils. Results indicate that combined use of IR and PY-GC-MS improves our understanding of how agricultural management practices impact soil organic carbon. These results will be of interest to farmers, policymakers and others interested in improving agricultural soils and mitigating climate change induced by elevated levels of atmospheric carbon dioxide.
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