2007 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. 4.Accomplishments An Open System for Measuring Canopy Gas Exchanges: There is an urgent research need for the ability to monitor crop water loss to the atmosphere and crop carbon dioxide uptake from the atmosphere under a wide range of experiments from the field to the greenhouse. We have completed construction of three chambers we call CETA (Canopy Evapo-Transpiration and Assimilation) chambers and are currently testing these chambers for their ability to monitor crop water loss. Using these chambers, we compared plant water loss to the air against water loss of these same plants using a weighing scale. We found good agreement between the CETA chambers and the weighing scales. (NP201 Problem area 2) Managing Soil Properties through Dryland Cropping Systems Intensities: The transition from irrigated to dryland production is occurring in the Southern High Plains region due to the low recharge to the Ogallala Aquifer, which supplies the water for our agricultural activities. Increasing organic matter content of the soil can improve the water storage-reservoir for dryland crop production in both cotton and sorghum. The High Biomass Crop Dryland Study was successfully established on USDA-ARS land near Lubbock, Texas, in 2003 and it is currently in its fifth growing season. Current data is showing 1.7 times higher soil microbial biomass and 2 fold increases in enzyme activities and soil nutrient cycling under crop rotations with a winter cover crop such as cotton-rye-sorghum and haygrazer-rye compared to continuous cotton or cotton-sorghum rotations. In addition, soil organic matter content is higher under a rotation of hay (alfalfa-sorghum-rye) compared to the other rotations studied. Significant differences in water infiltration rates through the soil were found among cropping systems under no-tillage compared to conventional tillage. However, lint yield of cotton have been similar in continuous cropping compared to the cotton in rotations, and this was dependent on the amount of rainfall. Continuation of this long-term study is vitally important for the long-term evaluation and confirmation of these trends, and their implications in water management and crop productivity in dryland farming. (NP 201-Problem area 2.5 Cropping and Tillage strategies to best use limited water supplies) Improved Statistical Forecast Methods for Agricultural Management Simulations: Simple statistical methods to predict winter rainfall based on preceding El Niño indicators can be used to predict future climate for farmers. In order to improve these forecast systems currently in use, three mathematical methods were applied to the problem of forecasting U.S. winter precipitation. Over the Southern High Plains a "two-tier" method was found to provide the best predictive ability. This result may provide greater forecast value for winter wheat management. In the shorter term, we suggest that these management simulations based on this improved forecast method could be used in computer simulation games designed to introduce winter wheat producers to the use of these climate forecasts for agricultural production decisions. (NP 211 Component: Develop new tools and a knowledge base that will enable decision makers to more effectively manage and conserve water resources. Problem Areas: Problem Area 2, Irrigation Water Management and Security, and Problem Area 5, Watershed Management, Water Availability, and Ecosystem Restoration) 6.Technology Transfer Number of newspaper articles and other presentations for non-science audiences 4 Review Publications Baker, J.T., Gitz, D.C., Payton, P.R., Wanjura, D.F., Upchurch, D.R. 2007. Leaf gas exchange to quantify drought in cotton irrigated based on canopy temperature measurements. Agronomy Journal. 99(3):637-644. Timlin, D.J., Fleisher, D.H., Kim, S., Reddy, V., Baker, J.T. 2007. Evapotranspiration measurement in controlled environment chambers: a comparison between time domain reflectometry and accumulation of condensate from cooling coils. Agronomy Journal. 99:166-173.