1a. Objectives (from AD-416)
The long-term research objective of this project is to develop and translate fundamental agroecological knowledge into recommendations and products to improve the economic position of organic farmers and to improve their ability to meet consumer demand for organic products. Objective 1 is to develop component technologies and management strategies that lead to improved productivity, enhanced soil and water conservation, and efficient nutrient cycling on organic farms. Objective 2 is to understand agroecological principles that drive the function of organic cropping systems and quantify ecosystem services.
1b. Approach (from AD-416)
Approaches to developing component strategies include A) incorporating legumes into organic crop rotations to maximize nitrogen fixation, B) composting that provides a productive and safe amendment for organic agriculture, and C) optimal agronomic practices for managing nutrients and production on organic farms. Approaches to determining agroecological principles include investigating the following variables within the Beltsville long-term Farming Systems Project that compares two conventional and three organic rotations, A) crop performance, B) soil nitrogen dynamics in relation to nitrogen inputs, C) soil carbon sequestration and greenhouse gas flux, D) soil biological community structure in relation to soil quality and production performance, and E) soil erosion and nutrient loss potential.
3. Progress Report
Field experiments to evaluate animal manures and OMRI-approved fertilizers as sources of K and P in organic forage production are in their second year at BARC and fourth year on-farm. Seed increases of Purple Bounty and/or Purple Prosperity hairy vetch varieties facilitated the first field scale trial using these varieties in an organic no-till corn production system. Field trials of eight representative hairy vetch gentotypes from around the world have been initiated on station and on farms. The capacity of biofiltration using wood chips to capture ammonia and odors from force-aerated piles, in-vessel composting, and poultry litter drying process was tested. Biofiltration effectively reduced odorous emissions and significantly increased nitrogen content of the wood chip media in the biofilters from 0.3 to 1.7 percent. Analysis of two years of field data indicate that sidedress, compared to pre-plant, application of organic N fertility sources (i.e., feathermeal, poultry litter, or blended materials) can substantially increase N use efficiency. The fourth year of a field trial evaluating the agronomic performance of organic field corn following a hairy vetch cover crop in tilled vs. no-tilled systems is complete. Results suggest delaying hairy vetch termination to optimize N availability can directly impact growing season duration, weed suppressive potential of surface mulches, and subsequent crop performance. Data are being collected for a second year in permanent weed-free and weedy check plots in organic and conventional systems in the FSP. We are monitoring weed population and community dynamics and weed-crop competition. A germinable assay is being conducted to determine long-term persistence of weed seedbanks. A University of Maryland Master’s student found that the DayCent model was better able to predict annual emissions of N2O, an important greenhouse gas, from the two conventional FSP systems than from an organic system, suggesting that the manure and cover crop modules in DayCent need to be improved to better predict N2O emissions from organic and other systems relying on organic sources of nitrogen. Another University of Maryland Master’s student is compiling 16 years of data collected at FSP to compare nutrient budgets (P, K, N, C) among cropping systems and evaluate nutrient management and soil carbon sequestration. A visiting scientist from Brazil (EMBRAPA) is comparing output from the DNDC model with five years of soil N2O emissions data from FSP and is helping collect a sixth year of N2O and supporting ancillary data. An undergraduate student is helping to conduct research on soil N2O emissions at FSP, supported by the FAR-B Summer Internship Program. A visiting PhD student from Brazil is measuring occluded and free particulate organic matter fractions in FSP soils, as part of our effort to evaluate mechanisms of soil carbon sequestration. We have developed and optimized qPCR and tRFLP methods for FSP soils and are using these methods to quantify and characterize denitrification genes. These data are being compared to measured soil N2O fluxes and other measures of soil microbial community structure.
Spargo, J.T., Cavigelli, M.A., Mirsky, S.B., Maul, J.E., Meisinger, J.J. 2011. Mineralizable soil nitrogen and labile soil organic matter in diverse long-term cropping systems. Nutrient Cycling in Agroecosystems. 90:253-266.