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ARS Home » Plains Area » El Reno, Oklahoma » Grazinglands Research Laboratory » Forage and Livestock Production Research » Research » Research Project #424179

Research Project: Integrated Forage Systems for Food and Energy Production in the Southern Great Plains

Location: Forage and Livestock Production Research

2018 Annual Report

The long-term objectives of this project are to develop improved techniques that will enhance ecological function and efficiency of resource use in prairie and pastureland, increase forage productivity, and promote sustainability of livestock production systems in the Southern Great Plains. Specifically, during the next five years we will focus on the following: Objective 1: Enhance productivity and ecological function of native tall-grass prairies by development of management practices, including management-intensive grazing, and restoration strategies to follow invasive brush and tree species removal. Sub-objective 1A: Compare the effects of different systems of intensive grazing on plant communities and soil properties of over-utilized tallgrass ecological sites, and define shifts in responses to applied management regimes. Sub-objective 1B: Determine greenhouse gas emissions from soil, plant, and animal components of diverse grazing systems. Sub-objective 1C: Define the influence of eastern redcedar trees on local soil conditions of abandoned cropland (old fields), and identify restoration practices that enhance conversion of retrogressed old fields to native prairie. Objective 2: Increase sustainability in grazing systems and improve year-round availability of forages for grazing through: improved pasture establishment and persistence, use of multipurpose legume crops, reduced need for purchased inputs in crop and forage production systems, and increased efficiency of water and nitrogen use. Sub-objective 2A: Assess effect of tissue damage on grass growth, development, and persistence characteristics. Sub-objective 2B: Identify forage species and management practices, including use of legume crops for green manure, that promote efficiency of resource use, especially N and water use, to increase year-round availability of forage for grazing. Objective 3: Increase marketing options, including providing high-quality farm-finished beef, through development of management systems that optimize on-farm feed resources and minimize the need for external inputs. Sub-objective 3A: Identify and evaluate forage resources for efficacy at critical times in the production cycle for farm-finished beef of different genetic types. Objective 4: Provide decision-support tools to aid land managers in evaluating climatic risks and ecologic and economic outcomes in selecting production and conservation practices and strategies for grazingland ecosystems. Objective 5: Develop improved cool-season grasses and legumes to improve productivity and sustainability of grazing and crop lands in the Southern Great Plains. Sub-objective 5A: Develop tools to support selection of improved cultivars. Sub-objective 5B: Identify germplasm of perennial cool-season grass forages adapted to heat, drought, and nutrient stresses of the Southern Great Plains.

Livestock production systems in the Southern Great Plains are confronted with problems of limited and uncertain forage supply, increased climatic variability, and environmental degradation that threaten economic viability and system sustainability. This project will develop management practices and identify forage genotypes that are resilient under variable climate and will increase forage productivity and input use-efficiency on livestock farms at a range of scales. Commensurate with the scope of the location as a Long-Term Agroecosystem Research network site, we will initiate assessments of greenhouse gas (GHG) emissions and agricultural production under different livestock systems of the Southern Great Plains, including both native prairie and wheat pasture. Data from this study will be pooled with results from similar flux studies in the region to evaluate climate and environmental impacts on system response. To evaluate system resilience, over-utilized prairie ecological sites with a mix of native and introduced species indicative of good and poor condition mixed grass prairie will be used to evaluate the use of infrequent, high-intensity grazing on succession and diversity of forage species at the sites. The impact of prior encroachment of redcedar on old-field nutrient and seedbank reserves and consequent recovery of understory and grass species following removal of redcedar will be assessed. The use of legumes and grasses as green manure sources will be researched for summer (sorghum) and winter (wheat) grain crops to promote efficiency of N and water use. Nitrogen turnover and utilization by the subsequent crop will be assessed. Also, N-uptake and efficiency of utilization of cool-season annual and perennial species will be measured in greenhouse experiments to develop screening methods for plant germplasm. Improved management methods will be developed to fully utilize the genetic potential of new cultivars by enhancing establishment, yields, and utilization by livestock. To increase marketing options of livestock producers, we will determine appropriate forage resources for production of farm-finished beef, either on all forage or with limited grain inputs. Interactions of animal genetic type (frame score) and finishing system (forage or grain) will be assessed. Time-series data from ryegrass trials in four southern states in the last decade will serve as the basis for examining the possible importance of 5-day and 7-day summary weather statistics of the near-surface environment, and the variations of those statistics around decade-long averages, as a predictor for seasonal production. Plant breeding technologies will be used to develop improved cultivars of perennial C3 grasses, particularly fescue, that are more persistent under the regional climatic conditions, and are more water-use efficient. Basic molecular biology and biochemistry/physiology information will be developed that will improve plant breeding techniques and products.

Progress Report
This is the final report for the project 3070-21610-001-00D which terminated in December 2017 and was replaced by 3070-21610-002-00D that falls under NP215. Research scientist staffing through the reporting period was approximately 4.0 SY, or 68%, of the 5.85 SY required to execute the project plan, which hindered progress in many components of the project. In those areas where staffing and resources were adequate, implementation of the project proceeded as resources allowed. Substantial results were realized over the 5 years of the project. Enteric methane production was measured in a cow herd grazing native pasture for a 2-year period, as part of a broader study of greenhouse gas emissions from grazing systems (Sub-objective 1B). Greenhouse and field studies defined nitrogen use efficiency in cool-season grasses, and showed most cultivars of commercially available perennial cool-season grasses used in the Southern Plains produce useful amounts of high quality biomass for grazing during the March through May, despite short lifespans of pastures (Sub-objective 2B). Developed a novel approach for generating superior genotypes of tall fescue and its related species. This research resulted in the submission of three U.S., Australian, Canadian, New Zealand and European Union patent applications for the technology, and its adoption by a seed company. The patents and release of materials provide a new and efficient approach for the breeding of fescues that are adapted and tolerant of growing conditions in the Southern Great Plains (Sub-objective 5A). Scientists also produced and released new hybrid cool-season perennial and annual forage grasses during 2012 to 2017, including two cultivars of tall fescue, a drought-tolerant smooth bromegrass, a new wheatgrass hybrid that aggressively covers areas by vegetative reproduction with short rhizomes, and a new cultivar of annual forage rye. Seed companies have tested the perennials in a variety of environments of the U.S., in preparation of commercial seed production (Sub-objective 5B). Scientists undertook modelling studies of the function of different components of perennial grassland and croplands agroecosystems at the plant-soil-atmosphere interface. A series of remote sensing studies that defined leaf area of plant communities, its relationship with biomass production, and plant-water-energy relationships provided information on agroecosystem function at landscape scales in the SGP. Hand-held remote sensing techniques were developed to describe crude protein content and digestibility of Bermudagrass forage within pastures in real-time, and tested them on alfalfa. These tools will allow producers to quickly assess needs for dietary supplements for grazing cattle, or to efficiently determine the optimal timing for harvesting hay (Sub-objective 3A). Integrated eddy covariance systems, and other techniques were used to describe movement of carbon, water, and heat energy between plants, soils and the atmosphere of native tallgrass prairie, pastures of tame perennial warm-season grasses, soybeans and other crops (Objective 4). Studies examined how cool-season grasses responded to low-input approaches of seeding and fertilizer management to provide small and resource-limited producers in the SGP with tools to improve forage availability (Sub-objective 2B).

1. Development of integrated modeling framework for investigating water management practices in the Ogallala aquifer region. The Ogallala aquifer region (OAR) currently accounts for 30% of total crop and animal production in the U.S. More than 90% of the water pumped from the Ogallala aquifer is used for irrigated agriculture in this region. Consequently, groundwater levels in the Ogallala aquifer are rapidly declining. However, to date we have lacked an effective means of assessing possible water, land use, soil and agronomic scenarios that might extend the life of our shared groundwater resources. As a part of multi-institutional project, ARS scientists at El Reno, Oklahoma, undertook efforts to integrate scientific knowledge across disciplines to develop a comprehensive modeling framework that can be used to evaluate the effect of alternative crop, soil and water management strategies on groundwater demand and availability in the OAR under temporal and spatial climate variability, with an overarching goal of sustaining food production systems, rural communities, and ecosystem services in the region. It consists cropping system model, linked to watershed hydrology and groundwater hydrology models with an aim of retaining the strength of each model. This integrated modeling framework provides important guidance for groundwater management groups seeking to evaluate the potential water use and agricultural production impacts of management and policy options. In addition, this framework could be applied to other irrigated groundwater systems worldwide.

2. Remote sensing-based surface energy balance models to track water stress in rain-fed switchgrass under dry and wet conditions. Rain-fed biofuel production systems are more vulnerable to climate variability and extremes. The short-term, in-season dry spells that could reduce soil moisture and plant growth, particularly during the key growth period, are often ignored due to the level of complexity associated with characterizing such conditions. ARS researchers in El Reno, Oklahoma, evaluated the abilities of five widely-used surface energy balance models (SEBAL, METRIC, SEBS, S-SEBI, and SSEBop) to estimate crop water stress index (CWSI) and compared against CWSI derived from eddy covariance measured evapotranspiration (CWSIEC) for 32 Landsat images during dry and wet growing seasons. Their results showed that all models underestimated CWSI dry years. However, in the wet year, CWSI estimates from METRIC and SEBAL were within 4% and 8%, respectively. Overall, the SEBAL model performed the best under both dry and wet conditions followed by METRIC. Our results suggest that the integration of a soil moisture component into surface energy balance models could improve their performances under dry conditions. This modified approach to linking water stress to energy capture by biofuel crops provides important information that modelers can apply to improve efficiency in estimates of biomass (and forage) production, and impact management and policy options.

3. Carbon dioxide fluxes from winter wheat paddocks managed under different tillage and grazing practices. Understanding the variations in carbon dioxide fluxes in winter wheat paddocks managed under different tillage and grazing practices is crucial to evaluate the role of different management practices on carbon dynamics and to develop best management practices. ARS scientists at El Reno, Oklahoma, applied eddy covariance systems to measure carbon dioxide fluxes from grain only, graze-grain, and graze-out winter wheat paddocks managed under conventional till (CT) and no-till (NT) systems. Large variations in magnitudes and seasonal sums of carbon dioxide fluxes were observed among paddocks. Across-site analysis showed a strong linear relationship between percent of canopy cover and carbon dioxide fluxes. Differences in wheat canopies related to paddock management were major drivers for among-site variability in carbon dioxide fluxes. The results indicate that the effects of changing climate and management practices on vegetation properties or ecosystem structures will have huge implications on carbon dioxide fluxes in winter wheat cropping systems. This integrated, cross-site approach to defining how different forms of management impact the movement of carbon between the atmosphere, soil and plants provides important frameworks and guidance for management groups seeking to evaluate the potential impacts of agricultural production systems on the carbon balance of agroecosystems, their management and policy options.

4. Use of annual summer legumes in wheat-stocker cattle production systems. Traditional forage systems used to support grazing by yearling stocker cattle have periods when high quality biomass is in short supply. Further, the price of inorganic nitrogen (N) fertilizers has risen to levels that have generated producer interest in alternative, green sources of N. To address these similar issues, ARS scientists at El Reno, Oklahoma, tested the function of summer legumes grown as green sources of N and high quality forage, and their effects on crops of winter wheat grown following green N crops. While the tested legumes provided large amounts of green N in their biomass, they resulted in lower and more variable levels of production by winter wheat than treatments that included summer fallow, which indicates the capacity of green N crops to support winter wheat in short-term continuous rotations was limited. Experiments also showed short-duration pigeon pea cultivars produced high quality forage during August through September that supported acceptable gains by stocker cattle, and that water use by grazed and non-grazed pigeon pea was similar during the growing season, despite the removal of the majority of the leaves by cattle. These accomplishments provide producers and land management specialists with new information and tools that will aid in making decisions concerning modified wheat-stocker production systems to maximize profits while sustaining yields.

Review Publications
Bhattarai, N., Wagle, P., Gowda, P., Kakani, V. 2017. Utility of remote sensing-based surface energy balance models to track water stress in rain-fed switchgrass under dry and wet conditions. Journal of Photogrammetry and Remote Sensing. Available at:
Uddameri, V., Singaraju, S., Karim, A., Gowda, P., Bailey, R., Schipanski, M. 2018. Understanding climate-hydrologic-human interactions to guide groundwater model development for Southern High Plains. Journal of Contemporary Water Research and Education. 162: 79-99.
Lin, X., Harrington Jr., J., Ciampitti, I., Gowda, P., Brown, D.P., Kisekka, I. 2018. Kansas trends and changes in temperature, precipitation, drought, and frost-free days from the 1890s to 2015. Journal of Contemporary Water Research and Education. 162: 18-30.
Adhikari, P., Gowda, P., Marek, G.W., Brauer, D.K., Kisekka, I., Northup, B.K., Rocatelli, A. 2018. Calibration and validation of CSM-CROPGRO-cotton model using lysimeter data in the Texas High Plains. Journal of Contemporary Water Research and Education. 162: 61-78.
Baath, G.S., Northup, B.K., Gowda, P., Turner, K.E., Rocateli, A.S. 2018. Mothbean: A potential summer crop for the Southern Great Plains. American Journal of Plant Sciences. 9(7):1391-1402.
Anil, S.C., DuPont, J.I., Brady, J.A., McLawrence, J., Northup, B.K., Gowda, P. 2018. Microbial communities in soil profile are more responsive to legacy effects of wheat-cover crop rotations than tillage systems. Soil Biology and Biochemistry. 123:126-135.
Wagle, P., Gowda, P., Northup, B.K., Turner, K.E., Neel, J.P., Manjunatha, P., Zhou, Y. 2018. Variability in carbon dioxide fluxes among six winter wheat paddocks managed under different tillage and grazing practices. Atmospheric Environment. 185:100-108.