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:
Trait- and process-based indices based on both raw trait data and community-weighted process scores have been developed and tested against field data from other pasture studies, and validated on data collected in the field. Under sub-objective 1.A.2, the scientist responsible for this experiment has departed. Field data collection was completed regardless, and all data have been processed. These mixture trial field results have been used to validate index development conducted in 1.A.1. Under sub-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. Research results have been presented to producer groups and NRCS, and are being incorporated into a decision support tool developed by university collaborators. Under sub-objective 1.B.1 and 1.B.2, results have been transferred to end-users including peer-reviewed manuscripts, fact sheets, trade publication articles and numerous presentations at professional meetings, field days, pasture walks, conferences and stakeholder group meetings. Under sub-objective 2.A.1, which is a long-term project with about ten years of data so far, plot management operations including planting of annual crops, fertilization, weed control, harvests, and grazing of perennial forages were carried out as in previous years. Results will be evaluated at the end of the year to determine if the project should be terminated now or continued for another year. Under sub-objective 2.A.2, a manuscript titled “partitioning soil respiration during pasture regrowth” was published in the journal, Crop Science. Significant differences between years were found for respiration responses during regrowth which were possibly due to a combination of factors including resource limitation, soil moisture stress, and differences in soil temperature. Under sub-objective 2.B, 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. Switchgrass yield, feedstock quality, and ancillary data from different seasons and harvest frequency were measured as scheduled.
1. Flaxseed supplementation. ARS researchers at University Park, Pennsylvania compared the effects of supplementing a pasture-based diet with either a mix of stored feeds such as silage, dry hay, and grain or flaxseed, an energy-rich oilseed that is gaining popularity as a single energy source on ruminal digestion. Supplementing pasture with the stored feeds improved nutrient digestion compared with flaxseed, which could potentially translate into better animal performance. However, flaxseed still shows promise as an energy alternative for pasture-based diets and may provide additional benefits such as improved fatty acid profile in the milk which may have beneficial qualities for human health. Additionally, studies have shown that ruminant animals fed flaxseed produce less methane, a potent greenhouse gas.
2. When and how to cut the forage. Cutting forage in the evening and macerating (crushing) the forage are two management strategies that have independently improved forage quality and digestion in ruminants. ARS researchers at University Park, Pensylvania evaluated the combined effects of time of cutting (morning versus evening) and maceration of forage harvested as hay on nutrient digestion. These findings suggest that while these forage management techniques individually have the potential to increase nutrient utilization and environmental efficiency, there was no formal benefit to combining maceration with cutting forage in the evening to improve ruminal digestion. This suggests that there were only minimal benefits to maceration which must be balanced against the potential for leaf loss and added expense of operation.
3. Reducing the carbon footprint of cellulosic ethanol. After producing ethanol from crop residues such as corn stover and straw, a slowly decomposing byproduct remains which is typically burned for energy recovery, however harvesting crop residues can result in decreased crop yields and soil carbon levels. Agricultural Research Service (ARS) and Drexel University scientists compared the current practice of burning this residue at the biorefinery, to applying it back to the land to maintain soil carbon. They found that although most studies have recommended burning this material to generate electricity for the biorefinery, applying it to the land instead resulted in increased soil carbon and thereby reduced the greenhouse gas footprint of the ethanol and reduced costs for farmers and the biorefinery. This finding could help the industry evaluate the different markets for byproducts produced at the biorefinery, considering both the economic and environmental impacts.
Sanderson, M.A., Jolley, L., Dobrowolski, J.P. 2012. Pastureland and hayland in the U.S.: conservation practices and ecosystem services. In: Nelson, C.J., editor. Environmental Outcomes of Conservation Practices Applied to Pasture and Hayland in the U.S: The Pastureland Conservation Effects Assessment Project (CEAP). Lawrence, KS: Allen Press. p.25-40.