1a. Objectives (from AD-416):
1: Evaluate a new technique using mid-infrared spectroscopy to characterize soil organic matter (SOM) properties and its effects on soil water holding capacity and to characterize erodibility of agricultural landscapes. 1A: Identify management-induced changes in SOM characteristics affecting soil water availability in sandy soils using a new technique for characterization of chemical composition of SOM, Fourier-transform Mid-infrared Spectroscopy. 1B: Quantify the combined effects of wind and water erosion on subsequent erodibility of agricultural landscapes. Objective 2: Compare and contrast water use efficiency among deficit irrigation strategies, and develop decision support tools to determine optimal irrigation and crop rotation strategies. 2A: Compare three types of deficit irrigation scheduling methods (Stress Time, Stress Degree Hours, and Crop Water Stress Index) in terms of final irrigation amounts, irrigation timing and cotton crop water use efficiency. 2B: Develop decision support tools to determine optimal irrigation and crop rotation strategies. 2C: Quantify the effects of wind speed, tillage type, and surface irradiance on the surface evaporation component of water use efficiency. 3: Conduct climate analysis and integrate large-scale hydrology models with process level-plant growth models in order to simulate optimum water and energy use for crop production on the Southern High Plains. 3A: Develop informational web sites to inform producers of the Ogallala region and other agricultural regions of recent climate trends. 3B: Develop and test a simulation model that will calculate landscape-scale mass and energy balance in pivot irrigated cotton systems at a detailed spatial and temporal resolution. 4: Monitor and model water depth in temporary playa wetlands for potential agronomic uses and also to determine the potential for aquifer recharge. 4A: Design, fabricate, deploy, evaluate, and maintain climatologic and hydrologic instrumentation in playa wetlands. 4B: Determine effects of proximate land use on playa basin hydrologic characteristics.
1b. Approach (from AD-416):
Our goal is to develop and evaluate models and methods that use limited water resources efficiently to maintain economically viable deficit irrigated and dryland agricultural production systems. New approaches will identify land management effects on soil organic matter properties and resulting effects on soil water holding capacity. The combined effects of both wind and water on subsequent erodibility of agricultural landscapes will be quantified. Effects of irrigation timing and total application rate on water use efficiency will be compared among different deficit irrigation scheduling methods. New research will explore the interactive effects of tillage and environmental variables on the surface evaporation component of water use efficiency. Decision support tools will be developed to determine optimal irrigation and crop rotation strategies while other studies will develop simulation models of landscape-scale mass and energy balances at detailed spatial and temporal resolutions. These modeling studies will be used to simulate optimum water and energy use for crop production on the Southern High Plains. Climate analyses will be conducted to develop informational web sites to inform agricultural producers of recent climate trends and potential impacts on future agricultural productivity. Finally, temporary playa wet lands will be evaluated to determine the potential for aquifer recharge as well as for future agronomic uses. This multifaceted research program will provide the knowledge base for optimizing the use of scarce water resources in arid and semi-arid regions where ground water resources are being depleted.
3. Progress Report:
We found that the ratio of MidIR spectra peaks for aromatic CH/quartz absorbance was significantly higher in the Srf–Rye and Ct–Rye–Srg rotations than the Srg–Ct, while continuous cotton (Ct–Ct) had the lowest value. Only soil under Srf–Rye had higher total C than the other dryland cropping systems. These preliminary findings are demonstrating that knowledge of SOM composition can be important for soil and water conservation under dryland, and they can predict SOM changes not detected with C content analyses. Wind erosion instrumentation has been field tested at a separate location and has proved reliable. The form for the flume intake sections had been built, and epoxy resins intended for the composite intake section have been secured for testing. The design of water-borne sediment collection devices has been modified to conform to low-relief terrain. Recently published manuscript developed the upper and lower base lines for calculating the Crop Water Stress Index (CWSI) for cotton. Software bugs for applying deficit irrigation using CWSI have been corrected. PALMS and Cotton2K were merged into a single model named PALMSCot. The PALMSCot model is a landscape-scale model that operates on a 20×20-m grid and to a soil depth of 2 m and is mechanistic and is based on the balances of water, energy, carbon, and nitrogen. The fundamental processes of cotton transpiration and photosynthesis are based on exchanges of water and carbon between the plant and the atmosphere. The model was tested for the major soil series of the Texas High Plains. Manuscripts are under preparation describing the model and field validation. Instrumentation has been assembled, calibrated, and programmed for use in work under subobjective 2C. Continuing drought has rendered extraction of the monolith without soil structural failure difficult if not impossible. Soil monoliths will be extracted when the profile is stable and moist throughout. All other necessary aspects of this investigation are complete. A web application that helps Southern High Plains cotton producers determine optimally profitable irrigation levels for cotton under specified commodity price and production cost conditions was developed and deployed. Two papers describing the application are under review. Initial work was carried out in designing a MYSQL database for climate trends website. Analysis of long-term records of temperature, precipitation, and stream flow data was carried out to identify patterns of intra- to multidecadal climate variability over the continental US. High-resolution GPS data of selected playas were generated. Access to a large playa was obtained from a landowner and extensive instrumentation began. The double ring infiltrometers developed are being installed into a playa bottom to examine the effects of sediment transport into playas on infiltration rates and aquifer recharge. A new type of pollination bird-resistant bag was developed that allows sorghum breeders to reduce/eliminate time required to replace over sorghum panicles damaged by birds. A new procedure to analyze sorghum seed morphology and yield using image analysis was developed.
1. Ogallala Agro-Climate Tool PC application. A web application for cotton irrigation management on the U.S. Southern High Plains was developed. Given the basically irreversible depletion of the Ogallala Aquifer via center pivot irrigation, there is a need for decision support tools that show the effects of varying deficit irrigation levels on yields and profits. ARS researchers at Lubbock, Texas, developed such a web-based support tool, which can be found on the Ogallala Aquifer Project's web site at www.ogallala.ars.usda.gov/CottonIrrigationTool. Companion papers describing the application have been submitted to Computers and Electronics in Agriculture. By calculating and displaying irrigation's profit effects under varying lint price, production cost, and well capacity conditions, this tool provides information about irrigation's cost-effectiveness, which might help to reduce irrigation waste and optimize the agricultural value of the aquifer's water.
2. Crop identified for in situ precipitation catchment forage production. Playas occupy between 3 to 5% of the land area in the Southern High Plains but are at best marginal farmlands primarily because of unpredictable flooding events of varying length, and because the soils within these basins are clayey. These playas are ephemeral lakes: depressions that flood with runoff from the surrounding uplands after periods of intense or prolonged rainfall. A team of researchers from the ARS in Lubbock, Texas, aimed to identify whether a flood-tolerant, native forage species, eastern gamagrass, could be used as part of a forage production system that made use of precipitation runoff from surrounding areas. Eastern gamagrass seeds are especially well suited to playas and can withstand flooding for months. The study also showed that eastern gamagrass plants can grow on playa soils and survive both infrequent flooding and prolonged periods of drought. The results clearly demonstrate that this species is capable of growth in these wetlands and might be incorporated into a precipitation-catchment forage production system or as part of other wetland restoration or development efforts.Allen, V.G., Brown, C.P., Kellison, R., Green, P., Zilverberg, C.J., Johnson, P., Weinheimer, J., Wheeler, T., Segarra, E., Acosta Martinez, V., Zobeck, T.M., Conkwright, J.C. 2012. Integrating cotton and beef production to reduce water withdrawal from the Ogallala Aquifer in the Southern High Plains: I. Ten-years of effect on water use and productivity. Agronomy Journal. 104(6):1625-1642.