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
A field experiment to evaluate animal manures and OMRI-approved fertilizers as sources of K and P in organic forage production was established at BARC; a similar on-farm experiment is in its third year. Data are being collected on forage yield and quality, and soil fertility. Sixty-four hairy vetch accessions from around the world are being evaluated for flowering date, biomass production, and nitrogen fixation in the field. Genomic marker analysis (AFLP) shows great diversity among accessions and biogeographical linkages among accessions from the same country of origin. Seed increases of Purple Bounty and/or Purple Prosperity through MTAs with private seed companies facilitated the first field scale trial using these varieties in an organic no-till corn production system. A postdoctoral associate is conducting a second year of field research to address nitrogen availability in organic grain crops. Initial results indicate that soil nitrogen mineralization is substantially greater in organic than conventional cropping systems, and that sidedressing organic materials provides a yield boost to corn compared to applying materials at planting. A four year field trial evaluating the agronomic performance of organic field corn following a hairy vetch cover crop in tilled vs. no-tilled systems is in its final year. Preliminary 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. Permanent weed-free and weedy check plots were established in organic and conventional systems in the FSP. We are monitoring population and community dynamics and weed-crop competition, and a germinable assay is being conducted to determine long-term persistence of weed seedbanks. Total soil carbon and nitrogen data to a depth of 1 m are being interpreted in light of carbon and nitrogen inputs to soil in the diverse FSP systems. Soils from FSP are also being evaluated for occluded and free particulate organic matter fractions, as part of our effort to evaluate mechanisms of soil carbon sequestration. A Master’s student at Hood College completed their thesis on the global warming potential of FSP cropping systems under the direction of the project’s lead scientist. We are using soil texture data collected at 748 spatially explicit locations at the FSP site to identify sampling locations to measure soil biological properties. 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.
1. Feather meal and feather meal-poultry litter blends show potential as side-dress fertilizers to improve nitrogen use efficiency in organic systems. Improving nitrogen use efficiency in corn production will provide economic benefits to farmers and environmental benefits to society. Researchers at ARS in Beltsville, Maryland showed that the N release characteristics of locally available sources of OMRI-approved N (raw poultry litter, pelletized poultry litter, feather meal, and a pelletized blend of feather meal and poultry litter) could serve as viable sources of supplemental N for organic and other grain production. The rate of N release of each material was relatively fast, suggesting that applying them to corn at the V5 growth stage (sidedress) could result in significant improvements in N use efficiency compared to pre-plant applications (the industry standard). Results showed that the feather meal and the feather meal-poultry litter blend were more nutrient dense than the raw and pelleted poultry litter and therefore less costly to transport per unit of available N. This information will benefit producers, extension educators, nutrient management plan writers, and others interested in improved soil fertility and nutrient management in organic and other grain cropping systems.
2. Weed seed persistence is similarly short for organic and conventional cropping systems. Crop yield loss from competition with weeds is particularly troublesome for organic farmers because of the inability to use herbicides for controlling weeds. It has been hypothesized that organic systems may be more resilient to spikes in weed seed production because weed seed in soil should be less persistent in high organic matter soils with high microbial activity that are characteristic of organic farms, compared to seed in conventionally managed soils. Comparison of weed seed persistence in organic and conventional soils in two long-term cropping systems experiments conducted by ARS, Beltsville, and Rodale Institute, Kutztown, Pennsylvania, showed that weed seed persistence was relatively short (half-life of approximately one year) and that there were only small differences (a couple of months) in half-life between organic and conventional systems. In addition, seed persistence half-life correlated poorly with various measures of soil microbial activity and organic matter content. Results suggest that more precise mechanistic hypotheses will be needed for defining factors responsible for weed seed longevity in soil.
5. Significant Activities that Support Special Target Populations
Members of this project’s research team participated in planning, organizing, and conducting the 11th Annual Future Harvest-CASA Conference, “Rebuilding the Real Economy: Nourishing Local Foods and Farmers” that was held in Shepherdstown, West Virginia, January 15-16, 2010. This conference targeted small farms, and female and organic producers in the mid-Atlantic area. Minority and disadvantaged farmers in Virginia and North Carolina were the target groups for the 7th Annual Small Farm Family Conference held in Richmond, Virginia, November 9-10, 2009. A project member was instrumental in organizing and planning this conference, and is serving in a similar capacity for the 8th annual “Small Farm Family Conference” to be held November 9-10, 2010 in Williamsburg, Virginia. Members of this project’s research team were instrumental in organizing a workshop on organic grain production in Queen Anne’s County, Maryland, March 9, 2010 and a workshop on organic vegetable production in Baltimore County, Maryland, June 16, 2010.
Teasdale, J.R., Cavigelli, M.A. 2010. Subplots facilitate assessment of corn yield losses from weed competition in a long-term systems experiment. Agronomy for Sustainable Development. 30:445-453.