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United States Department of Agriculture

Agricultural Research Service


Location: Pasture Systems & Watershed Management Research

2008 Annual Report

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
The project was approved in December 2007. Thus, research is in the start-up phase. Progress by subobjective: 1.A.1. Trait values for dominant pasture species of the northeastern U.S. have been collected from the literature and European databases. Prior and current field and greenhouse data are being used to assess European data for use in the Northeast. 1.A.2. Five research sites have been selected and maps of soil spatial variability have been developed to aid experimental design and provide baseline data. Field plots will be established in August 2008. 1.A.3. Soils, topographic, and climatic data have been collected and spatially cross-referenced with land use data to characterize the landscape types occupied by pasture in the Northeast. Forage mixture information was obtained from field surveys, seed catalogs, and producers. 1.B.1. Research on appetite level affects and grazing was completed. Rumen fill affected rate of pasture consumption, bite mass, and bite dimensions. As rumen fill increased (and appetite decreased), cows took bites that were deeper with smaller surface area, resulting in lower bite mass. Appetite-regulating hormones ghrelin and insulin decreased while glucose increased. Research on how protein supplementation affected digestion and ruminal fermentation of a pasture-based diet was completed. Increasing supplemental protein may reduce pasture intake due to reductions in daily grazing time and meal sizes, which may be due to nutritional imbalances such as an excess of ruminal ammonia. 1.B.2. Research on changes in herbage toughness in relation to diurnal changes in herbage chemical composition was completed. Herbage toughness decreased as the day progressed, corresponding with a decrease in herbage fiber and protein, and an increase in sugar. Research on diurnal changes in fatty acid composition of herbage was completed. Concentrations of fatty acids in grass pasture remained stable during the day. Time of day of grazing may not affect beneficial fatty acid composition of pasture-based meat and milk products. 2.A.1. Gas emissions have been sampled weekly from pasture, forage crop rotations, and biofuel crops beginning in April 2008. Nitrous oxide emissions have been low and similar between land uses. Soil samples were obtained from each land use in April 2008 and are being processed for total C and N analysis. 2.A.2. Soil respiration was measured on tilled ground and on adjacent non-tilled borders during site preparation following herbicide treatment of the existing grass stand. No increase in respiration rate due to tillage was observed. Forage and fallow plots were established and soil respiration measurements begun. 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. 2.B.2. Biomass samples were analyzed for feedstock quality and data summarized from Cycle 1 of summer, fall, and spring harvest seasons and annual, biennial, and triennial harvests of switchgrass. Cycle 2 switchgrass harvest occurred as appropriate as well as collection of ancillary data.NP215 Component3,Problem J.

4. Accomplishments

5. Significant Activities that Support Special Target Populations
Pasture is "easier" to chew in the evening: Organic dairies must rely on pasture as a feed source, thus increasing herbage intake on pasture is important. We designed a study to evaluate changes in pasture toughness in relation to pasture chemical composition throughout the day. Pasture samples were collected four times during the day and analyzed for dry matter, protein, sugar, fiber, and toughness. Toughness decreased as the day progressed, corresponding with a decrease in fiber and protein, and an increase in sugar. The results of this study suggest that herbage is less tough and easier to chew in the evening, and may partly explain why cattle prefer to graze longer and more intensely in the evening. Fatty acid composition of pasture stable throughout the day: Fatty acids in herbage influence the level of "healthy" fats in milk and meat from grazing cattle. We designed a study to evaluate fatty acid composition of herbage throughout the day. Pasture samples were collected four times during the day and analyzed for fatty acid concentration. Concentrations of fatty acids in grass pasture remained stable during the day. This would suggest that time of day of grazing may not impact beneficial fatty acid composition of pasture-based meat and milk products as a result of changes in pasture fatty acid composition.

Review Publications
Goslee, S.C., Richardson, C.J. 2008. Establishment of seedling growth of sawgrass and cattail from the everglades. In: Richardson, C. editor. The Everglades Experiments: Lesson for Restoration. Springer Verlag. p. 547-564.

Sanderson, M.A., Adler, P.R. 2008. Perennial forages as second generation bioenergy crops. International Journal of Molecular Sciences. 9:768-788.

Gregorini, P., Gunter, S.A., Beck, P.A., Soder, K.J., Tamminga, S. 2008. The interaction of diurnal grazing pattern, ruminal metabolism, nutrient supply and management in cattle. Professional Animal Scientist. 24:308-318.

Last Modified: 06/21/2017
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