1a. Objectives (from AD-416):
Evaluate the physiological and morphological characteristics of annual and perennial forages as they relate to greenhouse gas and carbon sequestration in an organic farming context and scale up this information to a larger organic pasture-crop rotation effort.
1b. Approach (from AD-416):
Objective 1: Two varieties of two annual forage crops (teff and sorghum-sudangrass) will be established in replicated field plots at The Pennsylvania State University Organic Field Research Facility near State College. The annual forage crop main treatments will be subdivided to accommodate nitrogen input treatments of dairy manure or an annual legume intercrop. A perennial crop system consisting of a perennial legume and a perennial grass managed for organic hay production will be included also. The crops will be planted in spring 2011 and plantings repeated in spring 2012. Above ground biomass accumulation and morphological development will be measured weekly or biweekly in each treatment to construct growth curves. Forage harvests will be made at monthly intervals for teff and when the sorghum-sudangrass has reached a height of 1.5m. Forage samples will be processed and analyzed for nutritive value (crude protein, minerals, fiber components, and fiber digestibility). In addition, batch fermenter studies will be conducted on selected treatments to characterize ruminal fermentation patterns of teff and sorghum-sudangrass compared with the standard cool-season grass-legume mixture. Baseline soil data will be collected according to the standardized protocols of the GRACEnet national research plan (Greenhouse Gas Reduction through Agricultural Carbon Enhancement network; www.gracenet.usda.gov) to collect , process, and analyze soil, plant, and gas samples. Soil respiration and greenhouse gass emissions (nitrous oxide and methane) will be monitored following manure application and periodically tereafter during the growing season. Root carbon and nitrogen content will be measured to a depth of 1.0 m according to GRACEnet protocols. Root production, distribution, and turnover will be monitored using appropriate technologies including root cores and/or minirhizotrons. Objective 2: The data from Objective 1 will be used to design a larger scale treatment for inclusion in a research demonstration project at the Rodale Institute in Kutztown, PA. Currently, two systems are being compared: (1) two years of row crops (com 1 year, soybean 1 year) followed by two years of pasture and (2) a standard cash grain (corn-soybean) cropping system. Based on data collected in this proposed study, a third system will be designed that includes two years of row crops (com 1 year, soybean 1 year) followed by two years of pasture with annual forage crops as part of the pasture-grain crop rotation. Data on soil carbon sequestration and greenhouse gas emissions will be integrated into the USDA-ARS GRACEnet national project to enhance and expand the agricultural emissions database. The standard corn-soybean rotation represents business as usual for organic cropping systems, whereas, the corn-soybean-pasture, and corn-soybean-pasture-annual forage systems present opportunities to reduce net greenhouse gas emissions and maximize soil carbon (C) sequestration. These data will provide better information for targeting climate change mitigation and adaptation efforts.
3. Progress Report:
In 2012, three harvests were taken and forage nutritive value determined from the last harvest. Manure was applied between the second and third harvest to all plots except the red clover and perennial legume and grass plots. This year, manure was applied to all plots, except the perennial legume and grass plots, the plots were chisel plowed and silage corn planted. Annual pastures treatments similar to those in 2012 were planted and have been harvested once this year and species composition data were taken before the harvest. In addition to these two experiments, a third experiment was initiated in a field with no history of weeds. This was done to get a comparison of these forages in weedy and weed free conditions. A recently developed method utilizing ‘quantum dots’ to ‘label’ inorganic and organic N species, is being used to assess relative plant uptake in a greenhouse experiment. Characterizing organic N pools across a gradient of agricultural soil management was begun this summer. Results from this project were presented at the Penn State Ecology Colloquium series in February 2013 as well as in a poster presentation at the Penn State Sustainable Agriculture Systems Research Symposium in March 2013. Additionally, results will be presentation at the national Ecological Society of America conference in August 2013.