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. FY 2010 Program Increase Funding Objective: Develop new management practices and systems for integrating forage-livestock and crop producation practices into efficient farming systems that can reduce the farming carbon footprint whle improving economic returns for farmers. This research will contribute to GRACEnet cross-location project. The standardized procedures for measurements of GRACEnet will be adapted and used and experimental data will be submitted to the GRACEnet database.
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
Progress by subobjective: 1.A.1. Software to calculate 11 functional diversity indices identified in a detailed literature has been written and tested using field mixture trial results. Modifications to adapt this mathematical ecological theory for use in managed ecosystems are being considered. Development and testing will be completed by the end of FY2010. 1.A.2. Data from 2009 (first year of the study) indicate that increasing species evenness of grass-legume mixtures did not affect forage yields at four locations in Pennsylvania and Wisconsin. Legume composition of the mixtures appeared to be the controlling factor. Analysis of forage nutritive value is underway at the Dairy Forage Research Center in Madison, WI. The study will be continued for two more years to obtain adequate environmental replication. 1.A.3. Optimization methods for use with functional trait data from pasture species are being developed in collaboration with Dr. T. Veith and tested using species trait and field plot data from previous years. Development and preliminary testing will be completed by the end of FY2010. 1.B.1. Research was conducted in collaboration with NRCS to quantify milk production and other animal performance measures on an organic dairy farm in New York that is currently feeding molasses to cows on pasture. Cows supplemented with molasses had lower milk production, milk persistency, and body condition score than predicted with Cornell Net Carbohydrate and Protein System model, whereas milk urea nitrogen was greater than predicted, suggesting opportunity to improve this ration to feed more energy and achieve greater production. Data analysis is underway. 1.B.2. Four grass species were fermented in continuous culture to evaluate their effect on ruminal fermentation. Forage species did not have a significant impact on nutrient digestibility, however, differences observed in nitrogen metabolism and bacterial protein synthesis may impact intake and behavior decisions via post-ingestive feedback mechanisms. 2.A.1. Analysis of soils sampled through 2008 showed greater accumulation of organic C and N in upper 20 cm of the profile under pasture and reed canarygrass compared to switchgrass or the corn/soybean/alfalfa rotation. Nitrous oxide emissions have generally been low with no large differences among land uses. The biggest control over emissions has been soil moisture with the only substantial emissions after rainfall. 2.A.2. Seasonal monitoring of autotrophic and heterotrophic respiration has been completed and manuscript preparation begun. Mixed orchardgrass-white clover plots have been established and instrumented to monitor respiration partitioning during a mid-summer regrowth cycle. 2.B.1. Annual and perennial crops were established at the Penn State Hawbecker farm. Other management practices were completed 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.
1. Native grasses from Northeastern CRP lands for biofuel production. Concerns about finding sufficient land for biofuel production has experts eyeing marginal croplands that have been placed in the Conservation Reserve Program (CRP). An extensive study by ARS scientists (at University Park, PA) of grassland sites across major Northeastern ecoregions determined the effects plant species composition, diversity, above ground biomass, and chemical composition had on potential biofuel yield. This study showed that CRP lands with a high proportion of native warm-season prairie grasses have the potential to produce more than 600 gallons of ethanol per acre, while still maintaining the ecological benefits of grasslands.
2. Surrounding land use strongly affects pasture plant communities. The soils, climate and topography of a site determine what plant species can thrive there, but surrounding land uses may also influence the plant community by providing seeds or hosting predators or pathogens. ARS scientists at University Park analyzed pastures across the northeastern United States and discovered that forage species were little affected by surrounding land use or landscape pattern, but composition of nonforage species was strongly related to local land use and landscape pattern, as well as to soils and climate. Local and regional biodiversity depends not only on site characteristics and management, but on the structure of the entire landscape.
3. No long-term changes due to pasture fallowing. Some grazers in the northeastern U.S. have adopted fallowing, the practice of leaving pastures ungrazed for a period to encourage reseeding and rejuvenation. The lack of mowing or grazing may increase grass seed production, but also decrease legume populations and increase weed abundances. ARS scientists at University Park conducted research on a farm in Maryland that had pastures fallowed from 0-6 years ago and documented only temporary changes in the seed bank and the above-ground vegetation. More grass and weed seeds were produced, but they did not persist in the seed bank or lead to longer-term differences in pasture composition. Fallowing does not appear to be a viable strategy for pasture regeneration in the northeastern United States.
4. Renovating chicory pastures. Chicory is a high yielding, drought resistance, nutritious forage, but its’ usefulness in permanent pasture is limited by poor persistence. ARS scientists at University Park evaluated the ability of three seeding methods, 1) frost seeding in February 2) no-till seeding in March, or 3) broadcast seeding combined with hoof incorporation of the seed in May, to reestablish chicory into productive cool-season pastures. Seedling emergence was adequate and did not differ among methods, but seedling mortality was high so that chicory only contributed 5% of total biomass by the fall of the establishment year. This research provides important information to producers interested in maintaining chicory as a component of their cool-season grazing system.
4. Best warm-season grasses for riparian buffers. The importance of grass buffers for protecting stream and wetland water quality is well recognized, but information is lacking on the appropriateness of specific warm-season species for inclusion in riparian buffers. ARS scientists at University Park in cooperation with USDA-NRCS plant materials specialists evaluated nine cultivars from five warm-season grass species for persistence and vigor under riparian conditions at four locations in the northeastern USA. Prairie cordgrass, eastern gamagrass and switchgrass cultivars were most suited for riparian zones, whereas, Indiangrass and big bluestem performed relatively poorly. Results from this study will provide much needed information to NRCS personnel for recommending suitable species and cultivars for riparian zones.
5. Switchgrass still productive after 20 years of management. Switchgrass, a warm-season perennial grass native to much of North America, has received extraordinary attention as a candidate cellulosic bioenergy crop. Despite being native, there is little information on its long-term (>10 years) persistence and performance. USDA-ARS scientists in University Park, PA measured the biomass yields and plant density of experimental switchgrass germplasm (experimental in 1989) and the standard cultivar Cave-in-Rock after 20 years of management. Biomass yields of all switchgrasses were stable and stand density was relative high after 20 years demonstrating the long-term sustainability of switchgrass as a bioenergy crop. These are the first long-term data on the experimental germplasm (since released as the cultivars BoMaster and Peformer by ARS in Raleigh, NC) and indicate that southerly adapted lowland cultivars can provide diversity in cultivar choices for switchgrass bioenergy production in the northeastern U.S.
6. Forage mixtures reduce risk and improve grazing economics. Using forage mixtures in pasture management can increase forage yields. Because mixtures may be more difficult to manage than moncultures, farmers will only adopt them if there is a greater net profit. USDA-ARS scientists at University Park, PA in cooperation with Penn State University used a computer model capable of simulating an entire farm along with 100 years of weather data to evaluate the short-term (2 years) and long-term (25 years) economics of altering forage mixtures and grazing strategies on a typical dairy farm. Results demonstrated that grazing management based on forage height rather than plant morphology criteria (e.g., first bloom in alfalfa) increased net economic returns by 8% in the short-term to 18% in the long-term. Using complex mixtures of up to 7 grasses and legumes increased net return by 15% in the short-term and 32% over the long-term compared with nitrogen-fertilized grass. Furthermore, forage mixtures had 30% smaller production risk. For dairy pastures, managing complex mixtures of forages is a valuable way to reduce production variability and increase profitability.
7. Species-rich pastures maintain nutritive value. Limited-resource farmers who manage pastures with complex mixtures of forage species are concerned that large changes in the botanical composition of these species-rich pastures may cause unstable and lower herbage nutritive value and compromise livestock production. USDA-ARS scientists at University Park, PA, measured the variability in nutritive value of pastures planted to complex (6 or 9 species) mixtures of forage species or a simple grass-legume mixture. The results showed that the number of forage species in the mixture did not control herbage nutritive value. Rather, functional group proportions (i.e., grasses, legumes, and forbs) controlled the nutritive value of mixed-species pastures. Legume proportion controlled crude protein in forage, whereas the grass component controlled fiber levels. Farmers who manage highly diverse pastures can realize greater yields with lower inputs without compromising forage nutritive value.
8. Native grass persistence and performance in riparian areas. Federal conservation programs such as Conservation Reserve Enhancement Program (CREP) have created a need for more information on the suitability of locally adapted native grasses for the northeastern USA. Native plants used in CREP plantings in riparian areas must be able to withstand seasonally wet soils. USDA-ARS scientists at University Park, PA in cooperation with USDA-NRCS plant materials specialists evaluated locally collected accessions of Virginia wildrye, a grass native to New England. The accessions were planted in Pennsylvania, Maryland, and New York on sites that would qualify for inclusion in the CREP program. Virginia wildrye tolerated wet soils at all sites and seasonal flooding at some sites during three years. The locally adapted accessions performed as well as commercially available sources. Populations from these wildrye accessions could be used as locally adapted plant material and provide diversity for site-specific conservation uses in the Northeastern USA.
9. Management of livestock concentration areas to reduce pasture degradation. Grazing livestock often congregate at waterers, feeding structures, or shaded places in pastures. Vegetation and soils in these livestock concentration areas is degraded by trampling causing soil compaction, reduced water infiltration, soil erosion, and nutrient runoff. USDA-ARS scientists at University Park, PA conducted research on five farms in Maryland, Pennsylvania, and New York and demonstrated that feeding areas (e.g., concentrate, hay, mineral feeders) accounted for the largest amount of pasture area (up to 3 acres on some farms) affected by livestock trampling and congregation. Most livestock concentration areas, however, were small (median area of 1100 square feet), isolated (median distance of 200 feet from a water body), and often surrounded by vegetation, which can buffer and filter surface water runoff. Mismanagement of these areas, however, would increase spatial variation in soil nutrients, provide sites for weed invasion, and encourage soil erosion. Farmers can avoid pasture degradation by rotational grazing, using movable feeders and waterers, and strategic placement of shade for livestock.
10. High supplemental protein impairs ruminal fermentation of pasture forage. High-quality pastures in the northeastern U.S. are high in crude protein. Despite this, many dairy graziers continue to feed high levels of supplemental protein. USDA-ARS scientists at University Park, PA evaluated the effects of increasing levels of protein supplementation in a pasture-based diet on ruminal fermentation. Supplementing a pasture-based diet with increasing levels of supplemental protein (and concurring decreases in carbohydrates) changed ruminal fermentation patterns and caused decreased nutrient digestibility, altered ruminal pH, and changes in volatile fatty acids and nitrogen metabolism. These nutritional imbalances cause greater nitrogen excretion (and greater chances of nitrogen loss to the environment) and reduce forage intake and milk production of grazing cattle by causing them to spend less time grazing. Reducing protein supplementation on pasture can save farmers money, increase milk production, and reduce environmental pollution.
11. Precise timing of corn silage supplementation improves grazing dairy cow performance. Corn silage is often used as a supplement in the diet of pastured dairy cows, however, little is known regarding how the timing of that supplement in relation to the grazing period affects ruminal fermentation. USDA-ARS scientists at University Park, PA investigated the effect of timing of corn silage supplementation (9 hours or 1 hour before a pasture meal) on ruminal nutrient digestibility and flows using continuous culture fermenters. Results showed that supplementing grazing cows 9 hours rather than 1 hour before a grazing period improves ruminal fermentation and digestibility and may reduce environmental impact of nitrogen losses in grazing cattle.
12. Molasses as a feeding supplement on organic dairy farms. Escalating organic grain prices and significant changes in milk contracts have forced organic dairy farmers to seek alternative energy sources for organic dairy cows. Sugar cane molasses, a rich source of sugars, may be a cheaper source of supplemental energy and minerals than organic grain; however, milk production responses to molasses supplements have been variable on organic dairy farms. USDA-ARS scientists at University Park, PA compared pasture supplementation with molasses or corn meal on ruminal fermentation in laboratory simulations of ruminal fermentation. Protein digestibility was increased with molasses supplementation; however, there was no effect on dry matter or fiber digestibility, ruminal pH, volatile fatty acids, or microbial protein production in the laboratory fermenters. At low levels of supplementation, molasses showed similar results to corn meal in improving ruminal fermentation and nitrogen utilization, with both supplements only showing minimal improvement compared with a pasture-only diet. Organic dairy farmers can use this information to fine-tune dairy rations for grazing dairy cattle.
5. Significant Activities that Support Special Target Populations
PSWMRU scientists have participated in activities targeting small farmers including: 1) education of organic farmers and women-farmer entrepreneurs on forage, grazing, and livestock management by participation in the Northeast Pasture Consortium, Pennsylvania Certified Organic workshops, and the Northeast Organic Farming Association; 2) on-farm research funded by the Organic Farming Research Foundation to evaluate inexpensive energy supplements for grazing dairy cattle on organic dairies; and 3) on-farm research funded by the Northeast Sustainable Agriculture Research and Education program demonstrating low-cost pasture management practices for limited-resource farmers including alternative forage species to reduce production costs and implementing ecological approaches to pasture management.
Skinner, R.H., Zobel, R.W., van der Grinten, M., Skaradek, W. 2009. Evaluation of native warm-season grass cultivars for riparian zones. Journal of Soil and Water Conservation. 64:413-422.