2011 Annual Report
1a.Objectives (from AD-416)
1. Develop new tools and a knowledge base that will enable decision makers to more effectively manage and conserve water resources.
1.a Design and test sensors that will quantify the level of plant water stress in growing crops and can be used to make irrigation decisions.
1.b Determine the relationship between crop productivity and applied water as a function of environmental factors so that irrigation can be managed for optimal use of all available water.
2. Develop and evaluate techniques and methodologies that maintain efficient agricultural production under deficit irrigation and dryland production.
2.a Design and evaluate water management strategies that optimize water use and crop production with limited well capacity.
2.b Define and evaluate crop management systems to facilitate the transition from irrigated to dryland cropping, considering crop species and varieties, cultural practices, and that incorporate long range weather prediction.
3. Identify changes in soil microbial, chemical, and physical properties affecting soil water availability and develop management practices that impact soil properties to sustain and improve crop production where water supply is in transition from limited irrigation to rainfed production.
4. Develop Best Management Practices based on a growing region's climate variability.
4.a Develop optimal planting strategies that integrate seasonal climate forecast information into agricultural managment.
4.b Develop software tools that provide detailed knowledge of precipitation, temperature stress, and evapotranspiration and demand to producers and plant breeders.
1b.Approach (from AD-416)
Develop and evaluate techniques and methodologies that utilize limited water resources efficiently to maintain economically viable deficit irrigated and dryland agricultural production systems. Develop new approaches, including acoustic detection of xylem cavitation and portable chamber technologies, to quantify the degree of crop drought stress and evaluate new and existing deficit irrigation strategies. Examine irrigation quantity and application rate effects on water use efficiency using the BIOTIC protocol for irrigation scheduling. Explore the efficiency of subsurface drip irrigation for storing water from low capacity wells in the soil during the fallow season. Determine the feasibility of enhancing water infiltration with adapted grasses and use water stored in playa lakes for forage production. Evaluate new crop species and cultural practices for facilitating the transition from irrigated to dryland cropping systems. Determine the effects of crop rotations and residue management systems on soil microbial, chemical, and physical properties including effects on soil water availability, infiltration, and rainfall capture efficiency. Assess the influence of row spacing and planting patterns on water use efficiency of different cropping systems. Use seasonal climate forecasts to develop optimal planting strategies and software tools to provide detailed predictions of precipitation, temperature stress, and evapotranspiration demand for producers and plant breeders. This multifaceted research program will provide the knowledge base for optimizing the use of scarce water resources especially in arid and semi-arid regions where ground water resources are being depleted.
We used measurements of canopy temperature to schedule irrigations using two different irrigation scheduling methods: the Stress Time method and the Stress Degree Hour method. These two irrigation methods are being compared using several criteria, including cotton yield, total water use, water use efficiency, and seasonal irrigation application timing to determine which method is most suitable for cotton growers with limited access to irrigation water or who may wish to practice deficit irrigation.
We are completing the ninth year of a long-term study that compares soil infiltration, erodibility, microbial biomass C, and enzyme activities of C cycling as affected by four dryland cropping systems. Soil microbial biomass C and enzyme activities showed significant differences due to system management history, while tillage produced no significant effects. These trends are important for soil and water conservation because increases in both organic matter quality and quantity can have beneficial effects on soil structure, C sequestration, and water availability for crop production.
We have completed development of the Ogallala Agro-Climate Tool, a PC application that provides estimates of climate statistics, crop evapotranspiration and irrigation demand for a range of crop types over the United States' Ogallala aquifer region. The application can be downloaded from the ARS Ogallala Aquifer Project website at: http://www.ogallala.ars.usda.gov/OgAgCliTool_Install.php.
Temporary playa lakes may help recharge declining aquifers. ARS researchers at Lubbock, Texas, have measured water movement through temporary playa lakes or simply 'playas'. These depressions in the landscape of the Southern High Plains temporarily fill with water following rainfall events. Researchers have found that playas differ in the rate in which water is lost through the playas bottoms and infiltrates into the underlying ground water, including the Ogallala Aquifer. However, over the long-term, about half of the water in playas is lost to the atmosphere through evaporation, while the other half of the water infiltrates the soil and can ultimately recharge the aquifer. This information and datasets are now being used by the Texas Water Development Board and the Llano Estacado Regional Water Planning Group to provide information for policy decisions aimed at best management of West Texas water resources.
Ogallala Agro-Climate Tool PC application. Over the latter half of the 20th century and the first years of the 21st, pumping from irrigated agriculture has led to water level declines in the Ogallala aquifer that have not been compensated for by natural recharge. The drawdown of this important water resource has led to questions about the long-term viability of the area's agricultural economy. The Ogallala Agro-Climate Tool, a Visual Basic application that can be run on Windows 2000, XP, and Vista operating systems, has been developed by ARS scientists in Lubbock, Texas, to provide accurate information about the required irrigation levels for a range of crops, in addition to climate and crop evapotranspiration statistics for the Ogallala region. By providing estimates of the water requirements of the area's major crops, this easy-to-use PC tool may help producers to identify wasteful irrigation practices and conserve the water resource of the aquifer.
Ephrath, J., Timlin, D.J., Reddy, V., Baker, J.T. 2011. Irrigation and elevated carbon dioxide effects on whole canopy photosynthesis and water use efficiency in cotton (Gossypium hirsutum L.). Plant Biosystems. 145:202-215.
Pelletier, M.G., Viera, J., Schwartz, R.C., Lascano, R.J., Evett, S.R., Green, T.R., Wanjura, J.D., Holt, G.A. 2011. Fringe capacitance correction for a coaxial soil cell. Sensors. 11(1):757-770.
Li, H., Lascano, R.J. 2011. Deficit irrigation for enhancing sustainable water use: Comparison of cotton nitrogen uptake and prediction of lint yield in a multivariate autoregressive state-space model. Soil Use and Management. 71(2):224-231.
Mauget, S.A., Leiker, G.R. 2010. The Ogallala Agro-Climate Tool. Computers and Electronics in Agriculture. 74(1):155-162.
Lascano, R.J., Van Bavel, C., Evett, S.R. 2010. A field test of recursive calculation of crop evapotranspiration. Transactions of the ASABE. 53(4):1117-1126.