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Introduction
Publicly and privately owned range, pasture and forage lands cover about 55 percent of the nation’s total land area. In addition to being the foundation of a $70 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. The ARS has a long history of conducting basic and applied research to provide the knowledge, plant materials and technology needed to manage these lands in a sustainable manner.
In accordance with the Action Plan for the rangelands, pasture and forages national program, research at 38 ARS locations is organized into five components 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. The five program components are: (1) Ecosystems and their sustainable management; (2) Plant resources; (3) Forage management; (4) Grazing management: livestock production and the environment; and, (5) Integrated management of weeds and other pests. In addition, ARS national programs 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 2002:
Ecosystems and their Sustainable Management
Environmental impacts on rangeland ecosystems: ARS researchers at Miles City, Montana, found that climatic variation can have a more significant impact on rangelands than livestock grazing. They evaluated seven livestock grazing systems based on light and moderate stocking rates and found that none of them had a major near-term (less than 10 years) impact on local rangeland health and productivity. Compared grazed and ungrazed sites indicated that annual climatic variation was much more significant. They found that grazing during the year of a severe late-spring to early-fall drought and during the following year does not significantly alter herbage production, plant species composition, water yields, quality of runoff, sediment production, root growth dynamics, seedbank dynamics, or tiller growth dynamics. These results, plus those resulting from a long-term continuation of this research, will provide information critical to developing economically and environmentally sustainable grazing management strategies.
Toxic plants, disease and animal health: Timely response to animal poisoning and disease depends upon accurate diagnoses. Differentiating between Chronic Wasting Disease (CWD) and locoweed poisoning can be critical. Deer and elk have developed CWD (an infectious spongiform disease) in areas in Wyoming and Colorado where locoweed is endemic. Elk can also be poisoned by locoweed. However, the effects of locoweed on deer were not known until studied by ARS scientists at Logan, Utah. After a 12-week feeding trial that included locoweed components, the deer appeared normal. Other classes of animals in similar trials showed severe symptoms of chronic locoweed poisoning. However, after an additional 6 weeks, the deer developed rough hair coats, prominent intention tremors, and lost weight. There were also numerous internal symptoms of poisoning. The researchers used these results to document the differences in clinical and histological symptoms between CWD and locoweed poisoning to aid in correctly diagnosing the causes of poor health. Additional research is required to determine if locoweed poisoning affects the progression of CWD.
Improving carbon sequestration in pastures: Long-term carbon sequestration is influenced by the ability of pasture and range plants to fix carbon. ARS scientists at University Park, Pennsylvania, studied the effects of species diversity on carbon sequestration in cool-season pastures by measuring sequestration at pastures with 2, 3, or 11 forage-species mixtures. Among their findings are during dry years, the 3 and 11 species pastures had greater photosynthesis at mid-day and a greater total root biomass with more of the root mass at lower depths than the 2-species planting.
Improving carbon sequestration on rangelands: At Woodward, Oklahoma, researchers studied carbon flux in properly managed and overgrazed rangelands. Properly managed grasslands sequestered carbon on a sustainable basis while overgrazed rangelands released carbon into the atmosphere. For many years in the Northern Great Plains, yellow-flowered alfalfa (Medicago sativa ssp. falcata) has been interseeded on native rangelands to increase herbage production by an average of 1000 kg/ha. Researchers at Cheyenne, Wyoming, measured the impact of such interseedings on carbon sequestration by evaluating sites that had been interseeded 4, 14, and 36 years ago. The longer the site had been interseeded the higher the level of carbon storage when compared to untreated areas. In the site interseeded 4 years ago, there was a 4 percent increase; at 14 years, 8 percent; and at 36 years, 17 percent. Interseeding with yellow-flowered alfalfa that will improve forage production for grazing while increasing the storage of carbon in the soil, thus helping to reduce carbon dioxide in the atmosphere. To help capture the benefits of alfalfa on rangelands, ARS scientists at Mandan, North Dakota, evaluated 16 alfalfa entries for persistence in local grasslands under heavy grazing pressure. For varieties developed for colder climates, grazing reduced their survival between 2.8 and 4.1 percent. In contrast, warmer-climate varieties were reduced by 43 to 49 percent indicating that climate had more of an impact than grazing pressure on survival.
Restoring degraded rangeland ecosystems: At Dubois, Idaho, ARS and University of Idaho scientists continued a project to determine the optimum time after a fire to begin sheep grazing to promote the recovery of native plants over invasive weeds. Fall grazing 15 months after a wildfire has no negative impacts on the biomass and species composition of desirable plants. Results of spring grazing are still being studied. Because of declining sage grouse populations, ARS Scientists at Dubois, Idaho, and Mandan, North Dakota, in cooperation with Texas A&M and the Idaho Fish and Game have developed a model to simulate the effects of fire and grazing on sagebrush communities and sage-grouse population dynamics. Results indicate frequent, large scale fires may contribute to extinction of local populations. Sheep grazing may also result in declines in sage grouse numbers but does not appear to result in extinction. The model provides a useful tool in managing rangelands to benefit sage grouse populations. ARS and University scientists in Wyoming worked with the coal mining industry to develop strategies to re-establish sagebrush on disturbed lands. After a 5-year study, they found that seeding strategies had a much greater impact on revegetation success than topsoil management. They also found that sagebrush seed could remain viable in the soil beyond the first growing season. Therefore, land managers have more flexibility in soil management when establishing sagebrush and fourwing saltbush than previously thought. These scientists also studied the impact of wildlife grazing on shrub re-establishment and survival. Protected plants had five times the seed stocks as those grazed by wildlife. After 8 years, unprotected stands had a 59 percent stand survival rate when compared to the protected sites.
Plant Resources
Selecting the right legumes: New uses, including environmental rehabilitation, biofuels, and promoting carbon sequestration, are being found for alfalfa and other legumes traditionally used for livestock production. The challenge is to develop the best plant varieties for these new uses. Understanding nitrogen-uptake strategies helps in selecting the right alfalfa for the job. ARS and university scientists at St. Paul, Minnesota found that a plant relying mainly on absorbing nitrates from the soil for its nitrogen would be more useful in cleaning up soils with excess nitrogen. On the other hand, plants getting a majority of their nitrogen from the air would compete less with grasses in pastures. ARS scientists have developed the first field-based method for selecting between individual legume plants in terms of how they obtain nitrogen. Testing individual alfalfa plants during a stand-establishment year when nitrate levels were high in the soil, they found that the portion of plant nitrogen taken up as soil nitrate by the various plants ranged between 20 and 55 percent. With this information on each plant, alfalfa breeders can select plants that favor either air or soil nitrogen sources depending on the job to be done.
Birdsfoot trefoil persistence: A multi-location study on the expression of rhizomes in birdsfoot trefoil and their effect on persistence was completed by ARS scientists at Columbia, Missouri, in cooperation with other ARS scientists at Booneville, Arkansas, Corvallis, Oregon, Logan, Utah, and Madison, Wisconsin, plus university scientists at Iowa State and Cornell. While both lines being evaluated produced rhizomes at all locations, there were noticeable variations in the extent of rhizome expression and in plant persistence indicating the significant role of environment in birdsfoot trefoil performance.
Forage peanuts: Gulf-coast cattle producers depend heavily on tropical grasses for forage but the nutritional value of these grasses drops during the fall and winter. Researchers at Brooksville, Florida, have been evaluating a tropical forage legume, rhizoma peanut, for use in winter pastures. They found that this perennial peanut has good forage potential but there is a need for material better adapted to cold and wet conditions. In cooperation with ARS scientists at Griffin, Georgia, a plant collection trip was made to Paraguay and 65 accessions of the perennial peanut were selected for evaluation. Some accessions appear to have potential for low maintenance turf as well as pasture use.
Improving grasses for forages, biofuels, turf and ecosystem restoration: Understanding the genetic and biological processes of plants provide important information in improving grasses for a variety of uses. ARS scientists at Corvallis, Oregon, demonstrated that drought tolerance in grasses is accompanied by the accumulation of a protein from the dehydrin family. Identifying plants that accumulate this dehydrin will help scientists select plants to use in breeding programs to increase drought tolerance in wheat and grasses. Scientists at Lincoln, Nebraska, released a new crested wheatgrass cultivar (NU-ARS AC2) for reseeding degraded crop and range lands on the shortgrass prairie. This grass was evaluated in five states of the Northern Great Plains and was highly productive in each. ARS and university scientists at College Station, Texas, released the buffelgrass cultivar “Frio.” This cultivar is more cold tolerant and will allow buffelgrass to be grown over a broader region. These scientists also identified a new cultivar of dallisgrass that is more persistent and productive than common dallisgrass while having similar forage quality and animal preference traits. At Logan, Utah, scientists released “RS-H hybrid wheatgrass germplasm” (Elymus hoffmanni) to improve forage quality on semi-arid pastures while being compatible with dryland legumes on semi-irrigated land.
Improved method for determining plant genotypes: The great majority of molecular markers are dominant, so they cannot be used to distinguish plants with one copy of a gene from plants with two copies of a gene. Expensive and time-consuming greenhouse tests are required to make this distinction. Scientists at Prosser, Washington, have developed a novel method based on PCR techniques that can rapidly and accurately (>98%) determine the number of copies of a gene of interest. This method will accelerate progress in plant breeding programs and is broadly applicable for genotyping all diploid plant species.
Forage Management
Improving forage establishment: Eastern gamagrass, a highly productive native grass, has not been widely used because of establishment problems. Scientists at Woodward, Oklahoma, studied the relationships between germination, seed weight, the role of the cupulate fruit case in dormancy, and the force required to open the fruit case. Based on their findings, eastern gamagrass should be planted in the late winter if soil moisture and favorable prechilling soil temperatures are present to stratify the seed prior to germination. If conditions are not favorable, pre-treated (cold stratified) seed should be planted in the early spring when temperatures are warm enough to sustain rapid germination. Scientists at St. Paul, Minnesota, showed that Kara clover is best established in soils with a pH that is nearly neutral (between 6 and 7). Using limestone to neutralize pH alleviated elemental toxicities and nutrient deficiencies typical of acid soils and this resulted in more root nodules increasing the supply of nitrogen to the plants.
Grazing management and supplementation: At Raleigh, North Carolina, ARS and university scientists examined the impact of the frequency and intensity of defoliation on seasonal growth rates and nutritional value of tall fescue. For a normal production year under intensive grazing, tall fescue should be grazed to a 2-inch stubble when it reaches a height of 6 inches to balance nutritive value and pasture production during the growing season. These and other results of this 3-year project will help producers optimize the timing and intensity of grazing. Researchers at El Reno, Oklahoma, are investigating options for improving stocker cattle production. Winter wheat pastures in the spring often provide inadequate energy. Feeding stockers a pound of corn a day increased daily gains by 60 percent and increased profitability. As an alternative to winter wheat fallow, use of summer-grown pigeon pea as a protein supplement was compared to traditional supplements such as cottonseed and alfalfa meal. Lambs supplemented with pigeon peas did as well as those on other supplements. By growing pigeon peas, winter-wheat producers can grow and harvest their own supplement for stockers during the summer while also fixing nitrogen in their fields for the winter wheat crop.
Grazing Management: Livestock Production and the Environment
Wildlife and livestock: Concerned about the impacts of livestock on wildlife habitat in the Great Basin, scientists at Burns, Oregon, in cooperation with the Bureau of Land Management and Oregon Department of Fish and Wildlife studied the impact of livestock grazing on antelope bitterbrush. This shrub is an important wildlife forage species because its nutritional value remains high throughout the late summer and winter when other forages are of low quality. Researchers compared excluding livestock grazing with the effects of light and heavy spring cattle grazing. They found that with light spring stocking rates, cattle focused on grazing the grasses intermixed with the bitterbrush. Under these conditions, reduced competition with the grasses stimulated bitterbrush growth. On average, the shrubs grew 11 percent taller and 27 percent wider than the shrubs in the ungrazed stands. This study demonstrates that livestock grazing can benefit wildlife habitat when science-based management strategies are developed and applied.
Pasture and animal waste: The livestock industry is faced with problems of animal waste polluting water resources. Applying waste to pasture and cropland can provide two benefits: providing nutrients to plants and providing a means for disposing of the waste. However, for this practice to be environmentally sustainable, farmers need good estimates of the nutrient availability from the waste so excessive amounts are not applied. Researchers at Madison, Wisconsin, for the past 5 years have been labeling nitrogen in dairy manure with a stable isotope (15N) and applying it to cornfields. They found that 13 to 22 percent of the nitrogen was taken up in the harvested corn silage while 50 to 65 percent of the nitrogen remained in the top three feet of the soil. They also found avoiding excessive phosphorus supplements in dairy diets resulted in a better balance of nitrogen and phosphorus in the manure so plant uptake of phosphorus was more complete. Of the experimental methods tested, using labeled nitrogen provided the most accurate measure of availability and plant uptake.
Integrated Management of Weeds and Other Pests
Cheatgrass control: Bromus tectorum (cheatgrass) is a highly invasive annual grass contributing to the degradation of millions of acres of western rangeland. Soil scientists at Reno, Nevada, found that calcium acetate accumulates in pots where cheatgrass is grown in greenhouse experiments for several years. As the calcium acetate increases in concentration, cheatgrass growth decreases. Preliminary experiments show that artificially increasing the level of this simple chemical in pots adversely affects cheatgrass growth. Scientists at Logan, Utah, investigated the perennial shrub forage kochia to determine why it is able to compete successfully with cheatgrass. They found that forage kochia takes up moisture at the same time as cheatgrass but can also access moisture at depths beyond the roots of the grass. This information will improve efficiency in selecting traits for shrubs that can compete successfully with cheatgrass.
Saltcedar control: The Eurasian shrub, saltcedar, has invaded many western waterways and streams causing economic and environmental damage. The ARS is pursuing an integrated strategy that includes developing tools both for controlling saltcedar and restoring riparian ecosystems. Scientists at Albany, California, continue to evaluate insects for the biological control of this invasive shrub while comparing seed germination and establishment of saltcedar with two native species, cottonwoods and willows. Saltcedar seeds were found to be short-lived but extremely viable and able to establish themselves throughout the summer following over-bank flooding. In contrast, the natives only produced seeds early in the season and cannot compete later in the year.
Annual weeds: In the Southern Great Plains, infestations of weedy annual cool-season grasses interfere with the establishment of perennial native and introduced cool-season grasses. ARS researchers at El Reno, Oklahoma, and Logan, Utah, examined how the availability of nitrogen in several forms affected the competition between the annual and perennial grasses. For both types, germination was unaffected by nitrogen availability but seedling growth was greater with nitrate than the ammonium form of nitrogen. When nitrogen availability was limited, root growth of the annual weedy grasses was more suppressed than for perennials. Management practices that reduce nitrogen levels prior to re-seeding pasture and rangelands could help reduce annual weed problems.
Decision Support Tools
Models for grass diseases: Stem rust is the most important disease limiting the production of seeds for cool-season grasses. ARS researchers at Corvallis, Oregon, have developed a model based on overnight and early morning temperatures and moisture to determine the probability of infection of perennial ryegrass. This model will aid producers to increase economic and environmental sustainability by making fungicide applications only when needed.
Models for beef and dairy cattle: For beef cattle, ARS scientists at Booneville, Arkansas, with scientists from Texas A&M University developed a model to assess how stocker cattle will perform in the feedlot in terms of percent retail product, marbling score, and carcass hot weight. Field tests of the model indicate that animal data gathered at the end of the grazing phase can aid in predicting the economic value of feedlot finishing. Such information will be helpful to stocker producers who are considering retaining ownership through the feedlot. For dairy producers, scientists at University Park, Pennsylvania, modified their dairy-farm model to evaluate the economic feasibility of using automatic or robotic milking systems on farms with 30 to 270 cows. Given current technology and costs, the automatic systems appear to provide long-term economic benefits only to farms with 50-60 cows.
Manuals: At Las Cruces, New Mexico, ARS scientists continue to develop knowledge and tools for improving rangeland monitoring and assessment. This past year they released a technical manual, Monitoring Manual for Grassland, Shrubland and Savanna Ecosystems. The manual will help producers and land managers monitor soil stability, hydrologic function and biotic integrity at the ecological site level. This information can then be used to help assess ecological responses to land management practices.
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