Location: Sustainable Agricultural Systems Laboratory
2019 Annual Report
Objectives
OBJECTIVE 1: Identify and elucidate agroecological principles that drive the function of grain and forage 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. Evaluate soil function and ecosystem services in long-term 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 and overall system performance.
OBJECTIVE 2: Develop technologies and management strategies to improve productivity, enhance soil and water conservation, improve efficiency of nutrient cycling and support food safety and nutritional security goals for grain-based and horticultural cropping systems.
' Sub-objective 2.A. Screen and breed cover crop germplasm to improve winter hardiness, biomass production and early vigor in legumes, grasses, and brassicas, and disease resistance and nitrogen fixation in legumes.
' Sub-objective 2.B. Develop optimal cover crop-based agronomic practices for improving nutrient and water availability and use efficiency, soil health, system resilience, production and economics in reduced-tillage field corn production.
' Sub-objective 2.C. Develop strategies to improve beneficial and safe use of organic amendments in horticultural crop production.
OBJECTIVE 3: Collaborate with the Hydrology and Remote Sensing Laboratory to operate and maintain the Lower Chesapeake Bay LTAR network site using technologies and practices agreed upon by LTAR leadership. Contribute to LTAR working groups and common experiments. Submit relevant data with appropriate metadata to the LTAR Information Ecosystem.
Approach
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.
Progress Report
Under objective 1, the 23rd and 5th years of research at the long-term Farming Systems Project (FSP) and Cover Crop Systems Project (CCSP), respectively, were completed, testing hypotheses about factors controlling crop yields and crop yield variability. Archived FSP soil and plant samples collected every five years are being analyzed to address questions about soil C sequestration and N retention. Poultry litter reduction and soybean microplots within FSP are contributing data to test questions related to N and P balance and use efficiency and N fixation. Phosphorus and K balances for FSP have been conducted while C and N balance data are being compiled. Nine years of FSP data have been published comparing the economic performance of the five FSP cropping systems. Questions related to cropping systems impacts on soil microbial communities are beginning to be addressed through a data base of information from archived nucleic acid samples extracted from FSP and CCSP soils during the period from 2008 to 2019.
To address questions under objective 2, cover crop breeding trial accessions have been evaluated for biological N fixation efficiency. A subset of promising accessions was evaluated directly for root-associated symbiotic bacteria. Nodule metagenomes were analyzed for 15 accessions of crimson clover. Research was also conducted on-farm to quantify the effects of intrinsic factors, management and their interactions on cover crop performance, corn grain yield, and N and water use efficiency. These data are being compiled for input into regionally specific data decision tools. To develop strategies to improve beneficial and safe use of organic amendments in horticultural crop production, a Professor of Plant Physiology on sabbatical worked with a Sustainable Agricultural Systems Lab (SASL) scientist to develop a novel technique for genotyping and pathotyping important plant pathogens in a high-throughput manner using new long read sequencing technology. To improve suppression of root diseases and foodborne illness pathogens, SASL scientists developed techniques for sequencing the genomes of biological control agents, which are very closely related to foodborne illness pathogens. The use of comparative genomics techniques will greatly facilitate identification of foodborne illness pathogens in soil.
Under Objective 3, SASL scientists are conducting research that contributes to objectives for the Lower Chesapeake Bay Long-Term Agroecosystem Research (LTAR). ARS scientists provide leadership on the LCB LTAR Executive Committee, one SASL scientist provides leadership of the Non-CO2 Gas Working Group and another SASL scientist is contributing to the Soils Working group “soil water sensing” subgroup. A third SASL scientist provides leadership of a nationwide Soil Biology Network (SBGx), which contributed to the Soil Health Institute’s recently published protocols and procedures “North American Project to Evaluate Soil Health Measurements” and the National Resources Conservation Service (NRCS)’ Soil Health Technical Note “Notice of Recommended Standard Methods for Use as Soil Health Indicator Measurements.” The SBGx is working with the LTAR Network to facilitate implementation of a unified set of standardized techniques and protocols across the LTAR network at all sites.
Accomplishments
1. A diverse organic crop rotation outperforms simpler organic and conventional crop rotations. While demand for organic grain is increasing, sound information about the economic performance of organic production is needed to help guide farmers’ decisions. An analysis of input costs, yields and net returns from the two conventional and three organic cropping systems at the long-term USDA-ARS Farming Systems Project in Beltsville, Maryland, for the period 2006 to 2014 shows that organic system returns, despite lower yields, exceeded those of conventional systems due to premium prices for organic grains. A crop rotation that included both grain and forage crops was the least risky organic system, despite having greater input costs than simpler grain crop rotations. These results will be of interest to organic farmers, organic farming educators, and policy makers.
2. Legume cover crops reduce poultry litter requirements by half in organic production systems. Soil phosphorus (P) levels in agricultural fields with a history of animal manure application may be excessive because manures provide more P than nitrogen (N) relative to plant needs. Excessive soil P can result in negative effects on the quality of surface and ground water supplies. Organic farmers may be able to draw down soil P levels by decreasing manure application rates along with using a legume cover crop to supply adequate N to corn. In a two-year study at three organic sites in Maryland, ARS scientists found that poultry litter application rate can be reduced by half and still achieve the same corn grain yield when used in conjunction with a legume cover crop. These results will be of interest to farmers, environmentalists, policy experts and others concerned with the health of the Chesapeake Bay and other estuaries impacted by agricultural losses of N and P.
3. Nitrous oxide emissions increase exponentially with increasing rate of organic nitrogen sources. Agricultural soils are the primary source of nitrous oxide, a greenhouse gas and the leading cause of stratospheric ozone decay. The relationship between application rates of organic nitrogen sources and nitrous oxide emissions has not been well established. Using a diverse combination of legume-grass cover crop mixes and poultry litter application rates ARS researchers in Beltsville, Maryland, showed that nitrous oxide emissions increase exponentially with increasing rate of organic nitrogen inputs. These results will be of interest to scientific colleagues including modelers, to the agricultural community at large that is interested in reducing the greenhouse gas footprint of agriculture, and to policy makers.
4. Improved method for locating old drain tile fields with ground penetrating radar. Finding old agricultural drainage pipe systems on farm and research fields is important to better interpret spatial variability in data collected using precision agriculture sensors, such as GPS-connected yield monitors. Ground penetrating radar is often capable of detecting buried drainage pipes; however, efficient methods for employing this technique in larger fields have not been adequately identified. ARS scientists in Beltsville, Maryland, along with colleagues found that a ground penetrating radar with 250 MHz antennas integrated with a real-time kinematic global navigation satellite system improved the ability to identify diverse drainage pipe configurations. These results show that this new combination of tools can be valuable for farmers and drainage contractors needing maps of subsurface drainage systems.
5. Farming practices impact gene abundance of soil bacteria responsible for nitrous oxide emissions. Agricultural soils are the dominant source of nitrous oxide, a greenhouse gas and catalyst of stratospheric ozone decay. The dominant source of nitrous oxide in many agricultural soils is denitrification, a process carried out by soil microbes. In a long-term study in Beltsville, Maryland, ARS scientists showed that the abundance of denitrification genes was affected by the specific crop in a crop rotation, time of year, a farming system (no-till, conventional till or organic). However, gene quantities did not correspond to nitrous oxide emissions patterns. This information is important in the on-going search for reliable indicators of microbially mediated soil greenhouse gas emissions and will be important for scientists to improve models predicting soil microbial community dynamics and greenhouse gas emissions.
Review Publications
White, K.E., Cavigelli, M.A., Conklin, A.E., Rasmann, C. 2019. Economic performance of long-term organic and conventional crop rotations in the Mid-Atlantic. Agronomy Journal. 111:1-13.
Thapa, R., Mirsky, S.B., Tully, K. 2018. Cover crops reduce nitrate leaching in agroecosystems: A global meta-analysis. Journal of Environmental Quality. 47:1400-1411.
Youngerman, C.Z., Ditommaso, A., Curran, W.S., Mirsky, S.B., Ryan, M.R. 2018. Crop density effect on interseeded cover crops, weeds, and grain yield. Agronomy Journal. 110:2478-2487.
Allred, B.J., Wishart, D., Martinez, L.R., Schomberg, H.H., Mirsky, S.B., Meyers, G.E., Elliott, J., Charyton, C. 2018. Delineation of agricultural drainage pipe patterns using ground penetrating radar integrated with a real-time kinematic global navigation satellite system. Agriculture. 8(11):167. https://doi.org/10.3390/agriculture8110167.
Williams, A., Wells, M.S., Dickey, D.A., Hu, S., Maul, J.E., Raskin, D.T., Reberg-Horton, S.C., Mirsky, S.B. 2019. Establishing the relationship of soil nitrogen immobilization to cereal rye residues in a mulched system. Plant and Soil. 426:95-107.
Vann, R., Reberg-Horton, C., Castillo, M., Mirsky, S.B., Mcgee, R.J. 2019. Winter pea, crimson clover, and hairy vetch planted in mixture with small grains in the Southeast USA. Agronomy Journal. 111:805-815.
Reddy, K.N., Cizdziel, J.V., Williams, M., Maul, J.E., Rimando, A.M., Duke, S.O. 2018. Glyphosate resistance technology has minimal or no effect on maize mineral content and yield. Journal of Agricultural and Food Chemistry. 66:10139-10146. https://doi.org/10.1021/acs/jafc.8b01655.
Buyer, J.S., Vinyard, B.T., Maul, J.E., Selmer, K.J., Lupitskyy, R., Rice, C., Roberts, D.P. 2019. Combined extraction method for metabolomic and PLFA analysis of soil. Applied Soil Ecology. 135:129-136.
