Location: Sustainable Agricultural Systems Laboratory
2019 Annual Report
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.
