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
These activities fall under ARS National Program 215, and contribute to Problem Area G (Need for economically viable pasture-livestock systems for the Northeast and North Central states that enhance the environment) and Problem Area J (Need for economically viable, energy efficient and environmentally enhancing production systems for establishing, growing, maintaining, harvesting, treating, storing, and transporting forages for livestock, bioenergy, bioproducts, and conservation objectives). Under objective 1a, preliminary testing of functional diversity indices against earlier field trial data has been completed. A spatially -based version of the functional diversity index has been developed, and is being applied across a whole farm. Development of optimization methods has continued, and these methods are being applied to the whole-farm scale as well as to within-pasture variability. The Integrated Farm System Model (IFSM) does not yet have the capability to evaluate differences in pasture communities, but alternative strategies for using this simulation model will be completed by the end of FY2011. Under Objective 1b, research was conducted in collaboration with the University of New Hampshire’s Organic Research Dairy to evaluate the effects of molasses or corn meal supplementation on intake and productivity of grazing organic dairy cows. While pasture intake was slightly higher for cows fed molasses, there were no differences in milk yield. Compared to corn meal, molasses had no detrimental effect on animal performance and improved nitrogen utilization. Research was also conducted in collaboration with the ARS US-Dairy Forage Research Center to evaluate the effects of grass species and sward structure on herbage intake of grazing dairy heifers. Four grass species (orchardgrass, meadow fescue, quackgrass and reed canarygrass) were grazed by dairy heifers. Results of this study indicate that herbage intake was generally not influenced by grass species, but were more likely to be a function of sward leaf or stem bulk density, and their distribution in the sward. Under objective 2a, soil gas emission measurements for 3 years indicated little impact of crop type on nitrous oxide emissions, but showed a strong relationship between nitrous oxide emissions and soil aeration regardless of the crop type. Analysis of soils obtained in 2010 showed similar organic C and N concentrations among crop types (dairy forage rotation, switchgrass, reedcanary grass, and grazed pasture) except for significantly greater concentration in the upper 5 cm of soil in reedcanary grass plots. Plant and soil respiration were measured and 13C signature of respired CO2 collected for a second year during mid-summer regrowth cycle to quantify rhizosphere contribution to total soil respiration. Under Objective 2b, annual and perennial crops were established at the Penn State Hawbecker farm and other management practices were completed as appropriate during the growing season including biomass harvest. Data from Cycle 2 of summer, fall, and spring harvests, and from annual, biennial, and triennial harvest frequencies of switchgrass were summarized.
1. Improved remote sensing capabilities in grazinglands. Remote sensing is a key component of regional and national monitoring programs for grazinglands, and for meeting both rangeland and pastureland Conservation Effects Assessment Project (CEAP) objectives. To efficiently and accurately meet these goals, ARS scientists at University Park, PA, developed and published software to automate corrections for atmospheric and topographic conditions that are necessary before Landsat and other satellite imagery can be used. These analysis tools are being applied to pastures in the northeastern United States. The use of remotely -sensed information in grazinglands also requires an accurate classification of land use. National Land Cover Data estimates of agricultural use were compared with the more accurate but non-spatial National Agricultural Census data to determine whether county-level areas were correctly identified in the twelve Northeastern states. Total agricultural areas were similar for the two data sources, but the National Land Cover Data were poor at distinguishing between row crops and pasture or hayland. This research highlights the need for an improved method of classification to accurately identify grazing and forage areas in the diverse landscape of the northeastern United States.
Allen, V., Batello, C., Berretta, E., Hodgson, J., Kothmann, M., Li, X., Mclvor, J., Milne, J., Morris, C., Peeters, A., Sanderson, M.A. 2011. An international terminology for grazing lands and grazing animals. Grass and Forage Science. 66(1):2-28. DOI:10.1111/j.1365-2494.2010.00780.x.