1a. Objectives (from AD-416):
1.A. Develop tools to facilitate the selection of species mixtures for pastures, the distribution of pasture types across a farm, and the assessment and monitoring of pastures at multiple scales to improve forage/grassland system function and reduce production risks. 1.B. Identify new grazing management and supplementation strategies that complement grazing preferences of dairy cattle to optimize the utilization of mixed-species cool-season pastures of the Northeast U.S. and to reduce inputs costs for pasture-based producers. 2.A. Identify management systems that minimize net greenhouse emissions in forage, grassland, and energy crop systems in humid-temperate climates. 2.B. Determine optimal management and environmental benefits of perennial and annual bioenergy cropping systems in the Northeast U.S. to reduce production costs and increase yields.
1b. Approach (from AD-416):
1.A. A trait-based index will be developed to relate pasture plant community composition (both species presence and abundance) to ecosystem function in grasslands. A multi-site field-plot trial will be conducted to test the hypothesis that mixed plant communities with greater species evenness produce more herbage and are more resistant to weed invasion than mixtures with lower evenness or monocultures. Science-based decision support tools will be developed for forage species selection within pastures and across farms to meet producer goals for ecosystem functions given the climate, landscape and soils. 1.B. Observational research will be conducted on pasture-based dairy farms feeding a range of supplementation strategies with varying pasture composition to characterize the effects of supplementation on grazing behavior and diet selection. Ingestive behavior will be quantified on during spring, summer, and fall grazing. Detailed feeding and milk production information will be collected from farm records and personal interviews. Continuous culture fermenters will be used to identify ruminal fermentation products that influence grazing patterns via post-ingestive feedback mechanisms. Sward-box studies will be used to evaluate cattle grazing behavior responses to monocultures and mixtures of selected grasses and legumes. 2A. Multi-location field plot and farm-scale trials will be conducted to determine the greenhouse gas emissions and economics of perennial and annual crops grown for bioenergy. Differences in C isotope discrimination (d13C) of C3 and C4 species will be exploited to partition respiration between new C respired from C3 plants such as orchardgrass and white clover and old C respired from the active pool of soil organic matter that has formed under the C4 species, big bluestem. 2B. Biomass yield, feedstock quality, and greenhouse gas emissions of current annual and proposed perennial bioenergy crops under the same climate and soil will be measured, and the resulting data will be used to validate the DAYCENT biogeochemical model at a site in the northeastern U.S.
3. Progress Report:
Under objective 1.A.1, trait- and process-based indices have been developed and tested against field data from other pasture studies, but validation of the trait-based index against evenness studies conducted under 1.A.2 has been delayed somewhat by departure of the scientist responsible for this sub-objective. Validation against the data from 1.A.2 will be completed by the end of the fiscal year. Under objective 1.A.2, use of the data collected in 1.A.2 for validating mathematical indices has been delayed somewhat by departure of the scientist responsible for 1.A.2. This validation process will be completed by the end of the fiscal year. Under objective 1.A.3, optimization methods have been used to create preliminary trait- and process-based planting recommendations for pasture mixtures to provide particular ecosystem services. Because these recommendations have not yet been validated against independent data as intended, they cannot be distributed to producer groups. A manuscript on the research component is in progress, and will be completed by the end of the fiscal year. For objective 1.B.1, results were presented to farmers, researchers, and industry personnel at 4 pasture walks/field days, 2 webinar presentations and 1 invited trade journal article. For objective 1.B.2, results were presented to farmers, researchers, and industry personnel at 3 pasture walks/field days, 2 farmer-oriented conferences, and 1 webinar presentation. Under objective 2.A.1 monitoring of crop productivity and soil C continued. We determined that data collection needs to continue for several additional years before cropping system C sequestration potential can be properly assessed. Manuscript preparation will be delayed until additional data are available. Under objective 2.A.2, all soil respiration data have been collected and are being summarized. Under objective 2.B.1, annual and perennial crops were established at the Penn State Hawbecker farm and other management practices were completed as appropriate during growing season including biomass harvest. Under objective 2.B.2, switchgrass yield, feedstock quality, and ancillary data from different seasons and harvest frequency were measured as scheduled.
Wilson, T., Mcneal, F.M., Spatari, S., Abler, D.G., Adler, P.R. 2011. Densified biomass can cost-effectively mitigate greenhouse gas emissions and address energy security in thermal applications. Environmental Science and Technology. 46(2):1270-1277.