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.
3. Progress Report
Though current off-the-shelf technology precludes development of affordable technology that can discriminate the waveform differences between AEs arising from cavitation events and from other sources, component costs continue to fall. We are currently relating Acoustic Emissions to plant water status of plants in the field using a more expensive system. Attempts to locate and evaluate inexpensive components continue. We used measurements of canopy temperature to schedule irrigations using two different irrigation scheduling methods: the Stress Time method and the Stress Degree Day method. These two irrigation methods are being compared against cotton yields and water use efficiency criteria to determine which method is better for cotton growers with limited access to irrigation water. We have conducted yearly soil samplings from the research plots in order to evaluate selected soil chemical, microbial and biochemical properties that may provide indications of more favorable conditions for plant growth (i.e., increases in soil water) in soil under alternative management compared to continuous cotton. Soil samplings and field measurements for water infiltration and availability will be done this fall 2010. We can now predict winter rainfall over the central U.S. based on the previous spring's Pacific sea-surface temperatures (SST). Advanced statistical methods were used to look for ways to predict summer rainfall based on previous winter SST, but similar predictive relationships were not found. Lacking such relationships, future work will develop summer crop management tools that rely only on detailed climatological data. In subobjective 2.a.2, the field experiment is running one year behind schedule due to weather-related delay in 2008. This year, treatments are being administered to the cotton crop, but very high rainfall this year may limit growth and yield differences due to irrigation levels. Due to 15 months without a research technician and subsequent hire of a fresh natural resources graduate, subobjective 3.2 and 3.3 are behind schedule. Although the crop is growing well, problems with the data acquisition are still being addressed. The new research technician is climbing a steep learning curve of electronics and instrumentation, and this is his last challenge to get the field and lab experiments running reliably. The system used depends on MS-DOS to run a computer that controls a Tektronix 1502 cable tester. It is uncertain how long we will be able to maintain this installation due to the increasing complexity of available computers and the scarcity of the Tektronix cable testers.
1. An open chamber system for measuring canopy gas exchanges in cotton. Crop plants absorb carbon dioxide (CO2) from the atmosphere during photosynthesis and lose water (H2O) back to the atmosphere during transpiration. Measurements of CO2 and H2O fluxes of crop plants are essential to understanding the impacts of crop species and varietal selections, as well as environmental variables and cultural practices, on crop productivity. Scientists at the Wind Erosion and Water Conservation Laboratory at Big Spring and Lubbock, Texas, have developed and tested an open or flow-through chamber system that can be left in the field for extended periods and that continuously measures whole canopy gas exchanges across wide ranges of canopy leaf areas and soil water contents. Six identical chamber systems have been built. This system allows simultaneous measurement of photosynthesis, water use and water use efficiencies in cultivar trials for plant breeders and for agronomists testing new agricultural practices. This information is useful for growers, policy makers and researchers in identifying effective agricultural practices aimed at increasing water use efficiency and on-farm profitability.
Mauget, S.A., Zhang, X.J., Ko, J. 2009. The tactical value of ENSO forecast information to dual-purpose winter wheat production in the US Southern High Plains. Journal of Applied Meteorology and Climatology. 48(10):2100-2117.