1a. Objectives (from AD-416)
The goal of this research will be to obtain knowledge and develop tools that will enable planners, decision makers, and producers to more effectively manage, conserve, and protect water resources. Specific objectives are as follows: 1)Develop cotton and peanut production systems for humid areas that are based on site-specific water and nutrient applications, 1a)Develop water management strategies in humid areas that optimize spatial and temporal water applications, 1b)Develop and explore spatial nutrient management for irrigated and non-irrigated crops in humid areas; 2)Develop practices that increase crop water use efficiency in rainfed/irrigated cropping systems in relation to tillage, irrigation, and crop management practices; and 3) Develop practices and technologies that enhance denitrification and expand the knowledge of microbial communities including their genetics and implication on geospecific disease in riparian buffers, wetlands, and streams for improving water quality.
1b. Approach (from AD-416)
This 5-year project utilizes a systems approach to identify and develop strategies for improved spatial management of water and nutrients. The project explores the spatial components of irrigation, tillage, and nutrient management. In spatial irrigation, the project will focus on identifying strategies for managing a site-specific irrigation system to conserve water and nutrients while maintaining cost effective production. In tillage management, the project will focus on efficiency of water use using tillage practices that will improve infiltration and soil water-holding capacities under site-specific irrigation to determine the spatial uptake and water use efficiency to improve spatial water management. In nutrient management, the project will focus on both in-field and off-site management. In-field nutrient management will focus on spatial nitrogen applications on cotton and Coastal bermudagrass to improve crop production and reduce the impact of off-site nitrogen movement. Off-site nitrogen management will focus on understanding the spatial variability of nitrous oxide emissions from riparian buffers and treatment wetlands.
3. Progress Report
1) Irrigation experiments on peanuts were conducted on the Center’s site-specific irrigation facility for a second year to assess three spatial irrigation scheduling methods. The three spatial irrigation treatments were a) individual soils within plots based on tensiometers, b) individual soils based on an expert system, and c) whole plot irrigation based on the expert system. This research contributes to National Program 211, Water Availability and Watershed Management, Problem Area 2.1, Product 3 Irrigation scheduling tools for humid and sub-humid regions. 2) An experiment was initiated under the site-specific center pivots to evaluate nitrogen and irrigation interactions on Coastal bermudagrass forage yield and quality. The study includes four irrigation amounts, three nitrogen rates, two cutting frequencies, and three replications (72 plots). Experimental design is a split-plot with cutting frequency as main plots and the irrigation by nitrogen levels as subplots. Canopy temperatures and vegetative indices were measured during the growing season and biomass samples collected for forage nitrogen concentration and forage ruminant nutritive quality. This research contributes to the goals of National Program 211, Water Availability and Watershed Management, Problem Area 2.4, Site Specific Technologies to Conserve Water, Nutrients, and Energy. 3) On-farm research on two local producers’ fields was completed; one field was monitored in 2006 and the other field monitored in 2007. We evaluated the relationship among cotton growth, plant water status, and soil electroconductivity (EC). In each year, 10 areas were selected and measures of plant height, leaf stomatal resistance, and soil water content were collected during the growing seasons. Normalized difference vegetative index images of the fields were collected from an aircraft twice each season. The field monitored in 2006 had more soil variability than the field monitored in 2007. Initial analyses indicate that there is potential for using soil EC to delineate irrigation management zones, but that remote sensing techniques are needed for optimizing in-season water applications. This research contributes to the goals of National Program 211, Water Availability and Watershed Management, Problem Area 2.4, Site Specific Technologies to Conserve Water, Nutrients, and Energy. 4) Using a photoacoustic gas analyzer and the mixed chamber method along with denitrification enzyme activity measurements, we measured nitrous oxide, methane, and carbon dioxide emissions from riparian buffers of a golf course and natural areas within a state park. The golf course caused no increase in greenhouse gases relative to natural riparian buffers. These data are being used to contrast other riparian buffers as part of the Natural Resources Conservation Service Conservation Effectiveness Assessment Program. This research contributes to the goals of National Program 211, Water Availability and Watershed Management, Problem Area 5, Product 2, Management tools and decision support information for restoration of riparian buffers, wetlands, and streams, and improvement of aquatic ecology.
1. Denitrification of Agricultural Drainage Line Water via Immobilized Denitrification Sludge: Nonpoint source nitrogen is recognized as a significant pollutant worldwide. This nitrogen pollution is often exacerbated by subsurface drainage lines that bypass the active riparian zones of agricultural streams. Constructed wetlands and bioreactors have been used to remove some of this drainage water nitrogen. However, removal of nitrogen from drainage waters in sensitive water locations and under land-limited conditions may require smaller reactors with even higher removal rates. In these conditions, reaction chambers with immobilized denitrifying sludge (IDS) may be very useful. In this study we used bioreactors containing IDS. In a field test with drainage water, 50% of the nitrate-nitrogen was removed with a 1 hour hydraulic retention time. Expressed as a cubically-shaped bioreactor, the nitrogen removal rate would be 94 grams of nitrate-nitrogen per square meter per day, which is dramatically higher than treatment wetlands or passive carbonaceous bioreactors. The IDS bioreactors offer potential for reducing nitrogen discharge from agricultural drainage lines. They also offer a direction for future research on emerging bioreactors technology as a component of improved water quality on both watershed and basin scales. This research contributes to the goals of the National Program 211, Water Availability and Watershed Management, Problem Area 5, Watershed Management, Water Availability, and Ecosystem Restoration, Product 2, Management tools and decision support information for restoration of riparian buffers, wetlands, and streams, and improvement of aquatic ecology.
2. Subsurface Drip Irrigation on Forage: Land application of animal waste from livestock treatment systems is an environmental and social concern in the eastern US. To address these concerns, we installed a subsurface drip irrigation (SDI) system to evaluate the potential of using SDI for effluent application to bermudagrass hay. The SDI system was installed at 0.3 m below the soil surface with two lateral spacings (0.6 and 1.2 m). Both effluent (from swine wastewater treatment plant using Agricultural Research Service patented technology) and commercial fertilizers were used to supply nutrients to the bermudagrass. No significant differences in hay yields were found between the irrigation lateral spacings. The plots receiving treated effluent had significantly greater hay yields. Moreover, they had significantly greater nutrient biomass removal than the commercial fertilizer plots. The plant nutrient removal was, without a doubt, significant in preventing adverse impacts on soil or water quality. This research contributes to the goals of National Program 211, Water Availability and Watershed Management, Problem Area 2.1, Irrigation Scheduling for Water Use Efficiency, Product 3, Irrigation scheduling tools for humid and sub-humid regions, including crop coefficients, plant stress indicators, soil water sensing, and automation/feedback irrigation systems.
3. Variable Rate Irrigation Management: Variable rate irrigation provides farmers with a tool to spatially allocate limited water resources along with potentially increasing profits. Yet, management of these irrigation systems requires rapid and reliable management decision data. We conducted variable rate irrigation experiments on the variable rate, center pivot irrigation system developed by the Agricultural Research Service in Florence, SC, to evaluate methods of obtaining this irrigation management data using sensors to measure crop vegetation and canopy temperatures. Two types of sensors were employed: 1) Vegetative-index sensors mounted on both tractor and aircraft were used to estimate plant biomass; and 2) Infra-red thermometers mounted on a tractor were used to measure crop canopy temperatures. Preliminary results indicate that vegetative index sensors adequately determined spatial canopy biomass. They were also effective in determining site specific plant water needs. The infra-red thermometers identified field areas with water stress, indicating the thermometers could be used to control site specific irrigations. Results from this study can help farmers develop variable rate irrigation management systems -- saving water and money. This research contributes to the goals of National Program 211, Water Availability and Watershed Management, Problem Area 2.4, Site Specific Technologies to Conserve Water, Nutrients, and Energy, Product 7, Systems for spatially and temporally variable water, nutrient, and pesticide application based on soil-crop sensing and feedback.
4. Soil Electrical Conductivity May Be Useful In Developing Prescription Irrigation Maps on Coastal Plain Soil: Site-specific irrigation, or applying water at variable rates throughout a field, is technologically feasible, but information is needed to determine how best to use this technology. We found that a relationship exists between the timing of the onset of cotton plant water stress and electrical conductivity of the soil on a Coastal Plain field. This information will be useful in developing prescription irrigation plans for the Southeast USA that will provide a more efficient use of irrigation water. This research contributes to the goals of National Program 211, Water Availability and Watershed Management, Problem Area 2.4, Site Specific Technologies to Conserve Water, Nutrients, and Energy, Product 7, Systems for spatially and temporally variable water, nutrient, and pesticide application based on soil-crop sensing and feedback.
Stone, K.C., Hunt, P.G., Millen, J.A., Johnson, M.H., Matheny, T.A., Vanotti, M.B., Burns, J.C. 2008. Forage subsurface drip irrigation using treated swine wastewater. Transactions of the ASABE 51(2):433-440.