Grassland agriculture is the largest land use in the United States. Publicly and privately owned range, pasture and forage lands cover about 55% of the nation’s total land area. In addition to being the foundation of an $80 billion livestock sector, these lands also provide recreational opportunities, heritage values, critical water and air sheds, and habitat for a vast array of plants and animals. Turf production, establishment, maintenance, and use is a multi-billion dollar industry that touches every American’s life. There is growing interest in using grasses and legumes as feedstock for bio-energy production to protect the environment and increase national security. The Agricultural Research Service (ARS) has a long history of conducting basic and applied research to provide the knowledge, plant materials and technology needed to manage lands for these activities in a sustainable manner.
The rangelands, pasture and forages national program includes research at over 30 ARS locations to address a broad range of national issues including profitability in a global economy, assessing and managing risk, conserving natural resources, and providing sound science for environmental protection. In addition, ARS scientists develop decision-support tools such as models, expert systems, and monitoring systems to aid the public in applying research findings to resolve real world problems. The following presents a list of significant accomplishments by national program components for Fiscal Year 2003:
Ecosystems and their Sustainable Management
Economic and environmental advantages of using dredged materials to aid in establishing grass ecosystems. Bahiagrass is particularly important pasture grass in much of the Gulf Coast region. Successful establishment of an excellent, uniform stand of bahiagrass increases the returns on pasture investment costs while protecting the soil and water resources from erosion. However, poor nutrient availability in the sandy soils in the region often adversely affects pasture establishment. Researchers at Brooksville, Florida, demonstrated the feasibility of using dredge materials from lake bottoms on bahiagrass pastures to enhance pasture establishment and reduce the need for its disposal in landfills. Lake-dredged materials’ concentrations of heavy metals and human pathogens are well below levels approved by the Environmental Protection Agency (EPA), and the dredged materials increased both plant height and dry matter production. The average biomass increase of bahiagrass in plots treated with dredged materials was about 173% compared to plots not treated with dredged materials. Using dredged materials for pasture establishment creates both economical and environmental benefits, including a use for dredged materials that would otherwise be a disposal burden.
Monitoring and assessing rangeland health with ultra-light aircraft. Bare ground where soil is exposed to erosion is a common measure of ecological integrity. Measuring bare ground with traditional on-the-ground methods over thousands of acres of rangelands is expensive and often inaccurate because sampling size is limited. ARS scientists at Cheyenne, Wyoming, working with the Bureau of Land Management used an ultra-light aircraft fitted with a high-speed digital color camera and GIS system to survey 200,000 acres of rangelands at six locations and 50 miles of associated riparian zones. They were able to obtain high-resolution photographs suitable for assessing several important ecological indicators. The electronic photographs are available in the field to assess flight effectiveness, and following ecological evaluation; the photos can become part of a permanent record for long-term monitoring. This reliable, low-cost system will enable public and private land managers to gather critical data for rangeland monitoring in a timely and affordable manner.
Impacts of wildfires. ARS scientists at Tucson, Arizona, in collaboration with scientists from the University of Arizona and the U.S. Forest Service have studied the effects of wildfire on hydrology and soil sediment yield on semi-arid grasslands. Using a rainfall simulator on different sites, they found that runoff immediately after a fire increased by 20 to 80% and sediment yields by 400 to 2200%. This information can be used by Burned Area Emergency Rehabilitation Teams to target the areas with the highest risk of runoff and help land managers plan prescribed burns to minimize adverse impacts on soil and water resources.
Global change. Many questions remain on the impact of increasing carbon dioxide levels on rangeland ecosystems. ARS scientists at Temple, Texas, found that increased CO2 levels may indirectly promote woody invasion of grasslands by reducing the depletion of soil water by grasses. They studied how three different CO2 levels affected water levels in grassland soils and the establishment and survival of seedlings of shrub honey mesquite. By adjusting soil water levels to reflect going from pre-industrial CO2 to current levels, seedling survival increased from 1.5% to 15%, and at future projected levels, survival increased to 28%. Rising CO2 level appear to contribute to the loss of native grasslands by favoring the invasion of woody species.
Evaluating long-term impacts. Arid areas frequently respond slowly to ecosystem remediation management practices so there is a need for long-term experiments that can be monitor efficiently over many years. ARS scientists at Las Cruces, New Mexico, used aerial photography to reevaluated remediation practices that were installed in the 1930’s at the Jornada Experimental Range. When the experimental water management practices were installed over 60 years ago, they appeared to be ineffective, but recent reevaluation has shown that over time they were much more effective than originally thought.
Identifying superior stress-tolerant cultivars of turfgrass. The National Turfgrass Evaluation Program (NTEP) located at Beltsville, Maryland, in cooperation with 40 states and five Canadian provinces continued to evaluate grasses to provide information to turf managers and home owners to aid in selecting cultivars that will reduce input costs and maximize environmental benefits while meeting user objectives. The 2003 summary reports on six key grass species were mailed to 1400 users.
Improving alfalfa to remediate nitrate contamination at heterogeneous locations. Nitrate contamination of drinking water can occur from land where too much nitrogen is present in the soil, such as under fertilizer spills or abandoned barnyards. Nitrogen is not distributed uniformly at these sites. As a result, most crops grown to clean up these heterogeneous sites will grow unevenly, reducing overall yield and the levels of nitrogen removal. Legumes, like alfalfa, have a remarkable ability to convert (fix) atmospheric nitrogen into a useful form. Legumes like other plants can also take up nitrogen from the soil. Therefore, legumes have the option to taking up nitrogen from the soil, or if soil supplies are inadequate, fixing nitrogen from the atmosphere. At an abandoned barnyard site, ARS researchers at St. Paul, Minnesota, compared normal alfalfa with an experimental nonfixing type they developed. Results showed that neither alfalfa type completely eliminated nitrate leaching to groundwater on sandy soil, since water moved the nitrate too quickly through the root zone, but both types removed large amounts of nitrogen, 60 to 250 kgN/ha, in the harvested hay. Both hay yield and nitrogen removal were better with the normal alfalfa than with the nonfixing type. The nonfixing alfalfa that could not get nitrogen from the air to make up soil deficiencies did not grow well where soil nitrogen supply was not high, so hay yield and quality were impaired. This research demonstrated how legumes with flexible strategies for nitrogen acquisition can help remove excess nitrogen at affordable costs and still produce a uniform, high quality crop on sites where excess nitrogen is heterogeneous in concentration.
Germplasm releases. To speed up the development of affordable and appropriate germplasm for rehabilitating and conserving rangelands, ARS scientists at Logan, Utah, have been using molecular techniques to identify genes associated with important characteristics including biodiversity in native and introduced species. This year they released Star Lake Indian ricegrass germplasm for rangeland rehabilitation and Cashe Meadow bromegrass for forage production under limited irrigation. They are completing work on adapting two important legumes, kura clover and sainfoin, for use on dry range sites. These legumes provide nitrogen for companion grasses while staying green through much of the dry season to provide high-quality forage and reducing fire hazard. ARS scientists at Lincoln, Nebraska, in cooperation with scientists at the Universities of Nebraska and Kansas State, USDA Natural Resources Conservation Service (NRCS) and other ARS locations released two new intermediate wheatgrass cultivars, Beefmaker and Haymaker, to help meet producers’ needs in the northern Great Plains for higher-quality forages for better animal performance. ARS scientists at College Station, Texas, in cooperation with other ARS locations and universities including Texas A&M, Arkansas, Mississippi State, and Auburn evaluated a new strain of dallisgrass for winter hardiness across the South. This new strain was found to be the more productive and persistent than other dallisgrasses evaluated in southern Texas and Louisiana, but without information on winter hardiness, recommendations could not be made to producers on how far north this strain could be established. Results indicate that it can be used as far north as central Arkansas and along the southern border of Tennessee.
Native grasses in the Northeast. The use of native grasses for ecosystem restoration and conserving biodiversity is an important national priority. ARS scientists at University Park, Pennsylvania, and Beaver, West Virginia, worked closely with the NRCS plant specialists to assess the potential for introduced pasture grasses with native grasses. They evaluated several collections of Virginia wildrye for yield and persistence in multiple locations in the Northeast. The wildrye produced less than half the dry matter of orchardgrass because the ryegrass had a lower capacity for tillering especially during re-growth. Virginia wildrye may have potential for conservation objectives but not those involving livestock grazing.
Protective enzymes. Quantification of superoxide dismutase (SOD) has proven difficult and this has made it difficult to understand the role this enzyme plays in protecting the plant following stress (drought, heat, cold). ARS researchers at Corvallis, Oregon, have developed a new approach that allows hundreds of samples to be analyzed per day. In developing the process they observed that in grasses subject to heat stress there is an accumulation of compounds that inhibit SOD. Being able to measure SOD efficiently is an important step in understanding plant processes that inhibit plant protection during times of stress and will ultimately help plant breeders to increase plant tolerance to stress.
Making the long, hot summer profitable for livestock grazing. Cattle profitability increases when low-cost, high-quality forages can be grazed on the farm. Researches at El Reno, Okalahoma, are developing forage production and grazing strategies to make optimal use of pastures when high-quality forages are traditionally available and to fill in the seasonal gaps when forage quality is not adequate for profitable grazing. In the southern Great Plains, warm-season grasses are of high quality in early summer but are inadequate in late summer. They found that doubling stocking rates of stocker cattle in the early summer produces 28% more gain per acre than traditional grazing of the same area throughout the summer with lower stocking rates. However, the early summer intensive stocking results in the problem of what to do with the cattle the rest of the year. One option is to sell the cattle in mid-summer but more profits could be made if the producers had a low-cost, high-quality forage for the cattle in the late summer and early fall. The scientists have identified a non-traditional forage that may fill this seasonal gap. Early results indicate that pigeonpeas can provide high-quality grazing in the late summer plus they can be grown on cropland also used for winter wheat. This farming-system combination of early intensive grazing of warm-season grass pastures followed by grazing on pigeonpeas grown on cropland during the winter-wheat summer fallow provides opportunities for increased profits through better resource utilization for livestock production and the ability to double crop the wheat land.
Increasing profit opportunities for Appalachian small farms. When compared to wool sheep, hair sheep breeds have advantages in adapting to a variety of climates, utilizing low quality forages, reproducing prolifically and not requiring shearing. However, information is lacking on the performance of different hair sheep breeds on low-cost finishing diets based on forages. ARS and university researchers in Beaver, West Virginia, and Petersburg, Virginia, evaluated three hair breeds (Barbados Blackbelly, Katahdin, St. Croix) finished on low-cost hay diets supplemented with corn. They found that Katahdin had a 25% higher average daily gain and utilized dietary protein 13% better than St. Croix and Barbados Blackbelly lambs. The increased protein use and weight gains when feeding Katahdin hair sheep allow producers to reduce feeding costs and optimize profitability so they can take advantage of a fast growing ethnic niche market. To identify appropriate sheep breeds for the hot, humid South, ARS scientists at Booneville, Arkansas, and the University of Arkansas compared the growth and carcass traits of three hair sheep breeds (Dorper, St, Croix and Katahdin) and one traditional wool breed (Suffork). The best results in terms of animal performance, carcass muscularity and quality for lambs weaned at 60 days and managed on a finishing ration till harvest at 180 days of age came from Dorper x St. Croix cross.
Reestablishing alfalfa. Failure to reestablish alfalfa after severe winters is a common problem and thought to be due to autotoxicity caused by chemicals released from alfalfa plants of the previous stand that restrict the growth of new seedlings. ARS scientists from St. Paul, Minnesota, and the University of Minnesota conducted six field experiments and found that alfalfa seedlings were 15% smaller following alfalfa than other crops, and the age and cultivar of the alfalfa in the previous crop had no apparent impact. However, the later the reseeding took place in the growing system the more significant the adverse impact on the seedlings. Reseeding success can be increased by moldboard plowing in the spring and planting as soon as possible.
Extending the grazing season. The length of the forage-producing season is determined by the frost-free interval. ARS scientists at Beaver, West Virginia, developed an inexpensive sensor that measures forage-canopy temperature at night. They found that conifer silvopasture systems can provide a forage canopy temperature increase of up to 10-degrees C during a radiation frost event. The higher temperature can reduce the damage to the forage crop and extend the grazing season in the spring and fall. The temperature increase was linearly correlated with the amount of longwave radiation emitted by the area of tree foliage obscuring the sky field-of-view of the forage canopy. This information can be used to design agroforestry systems to balance the tradeoffs between lengthening the growing season and lowering overall forage production.
Self-seeding annual grasses. Limited-resource farmers often cannot use highly productive annual forage grasses because the annual reseeding costs. ARS scientists at Langston, Oklahoma, evaluated alternative harvest practices for annual ryegrass to determine the harvesting dates for optimizing forage yields while leaving sufficient grass to mature and produce adequate seed for self-seeding next year’s stand. They found that the greatest seed deposition resulted in July following mid-April harvest while the maximum forage yield resulted from mid-May harvesting but inadequate seed was produced for reseeding. Farmers need to evaluate the tradeoffs between seed production and forage yield in deciding when to harvest.
Grazing Management: Livestock Production and the Environment
Promoting sustainable livestock grazing in riparian zones. Conflicts over the sustainability of livestock grazing along streams are difficult to resolve because of major gaps in the scientific information on how herbaceous riparian vegetation responds to the timing and intensity of grazing. Researchers at Burns, Oregon, found that with proper grazing management, riparian plants could have time to re-grow and meet riparian ecological standards. Previous research had shown that too much forage removal or grazing late into the summer tended to limit re-growth excessively. This 3-year study demonstrated that adequate re-growth occurs if grazing ceases in June when a plant height of two inches is left. If grazing continues into July more than two inches may be desirable. This information will help public and private grazing managers develop grazing management plans that will provide forage for livestock while maintaining riparian ecological health.
Locoweed and sheep reproduction. To assess mechanisms linking levels of locoweed consumption and livestock reproductive dysfunction, ARS scientist at Logan, Utah, fed open-cycling ewes the locoweed toxin, swainsonine, at one mg/kg body weight for 5 different time periods up to 28 days. Their results indicate that adverse impacts on embryo development are due to secondary maternal effects and not a direct effect of the locoweed toxin on the embryo.
Grazing and Evapotranspiration (ET). In the semi-arid areas of the northern Great Plains, water limits forage production. ARS scientists at Mandan, North Dakota, evaluated how alternative forage-management systems affect ET rates. For over 3 years, they compared the response of an ungrazed mixed-grass prairie, a grazed mixed-grass prairie, and a grazed western-wheatgrass pasture. Growing period ET for the grazed mixed prairie was 7% lower than for the non-grazed prairie and 8% lower than the western-wheatgrass pasture. Results indicate that a proper grazed prairie with considerable biodiversity uses water more efficiently than an ungrazed prairie and a grazed grass monoculture.
Impact of stocking rates. Stocking rates are considered the most important factor in determining the sustainability of rangeland grazing on the Great Plains. ARS scientists at Woodward, Oklahoma, over an 8-year period, analyzed the interrelationships between stocking rates and cattle (cow and calves) and economic performance on sand sagebrush range. They found that the interactions between these variables became increasing variable as stocking rates were increased. Stocking rates that maximized calf production per cow or acre did not maximized net economic returns. Results to date indicate that lower stocking rates can be both economically and environmentally sustainable.
Integrated Management of Weeds and Other Pests
Controlling invasive weeds in rangeland restoration. Restoring rangeland ecosystems degraded by wildfires, improper grazing and other disturbances is being hampered by invasive weeds. Lepidium latifolium (tall whitetop or perennial pepperweed) and other invasive weeds obstruct the establishment of desirable plants slowing the process ecosystem restoration. Researchers at Reno, Nevada, studied the geographic variation in the genetic structure of tall whitetop, a particularly pernicious weed, and found nearly as much genetic differences among plants found within a specific location as when comparing plants from widely separated locations. These findings that certain genetic lines occur all over the west are disturbing. Numerous genetic differences within a location suggest that control of tall whitetop will require a multifaceted approach instead of a single quick solution. The genetic differences also indicate that human activities such as using commercial grass and forb seeds contaminated with weeds may be a larger problem than realized. Such findings indicate that ecosystem restoration will require the development and implementation of highly coordinated strategies that integrated commercial seed production, integrated pest management, restoration ecology and rangeland management.
Cheatgrass mines nitrients. ARS scientists studying the effects of cheatgrass invasion of a winterfat shrub community near Reno, Nevada, found that the cheatgrass appears to be very effective in taking up nutrients. Through increased enzyme activities the cheatgrass takes up nitrogen and phosphorus more effectively than the native plants. The scientists are now evaluating the use of trace amounts of heavy metals such as copper, zinc, and nickel to control the cheatgrass by altering its biochemical processes.
Benefits of juniper control. Western juniper woodlands have spread across 8 million acres of the northern Great Basin and negatively impact multiple resource values. Over a 12-year period, ARS scientists at Burns, Oregon, in cooperation with the Bureau of Land Management and private landowners studied the response of herbaceous vegetation to the cutting of junipers. They found after cutting the herbaceous biomass increased by ten times, and during the last 6 years of the study, native perennial grass production doubled while noxious weed biomass decreased by 85%. They also found that on the drier sites, expensive reseeding was not required to restore the grass community when there was greater than two native bunch grass plants per square meter. With this information land mangers and ranchers can formulate affordable and practical juniper control programs.
Decision Support Tools
Models for beef and dairy cattle. Farmers are asked to manage increasingly complex agricultural systems to achieve economic and environmental sustainability. Scientists at University Park, Pennsylvania, are developing decision-support models that integrate at the farm level the knowledge being acquired from researching the various components of a farm. The researchers released a whole-farm simulation model to aid teachers and researchers in integrating the crop, dairy, and beef production systems more efficiently. This model is an improvement over their earlier model because a beef component with animal feed intake, growth and manure excretion was added. An improved phosphorus-loss component is also an important feature of the model. Such models can help managers and consultants assess the economic and environmental outcomes of incorporating new technologies and strategies prior to making substantial investments.