2007 Annual Report 1a.Objectives (from AD-416) 1. Improve infiltration and minimize soil water evaporation for increased soil water storage for efficient use of soil water under dryland and deficit irrigated cropping systems. 2. Develop conservation tillage and residue management systems that optimize crop and integrated crop-livestock productivity and restore degraded soils. 3. Adapt, refine, develop, and implement soil water and crop simulation models to evaluate alternative agronomic and water management strategies, specifically for a semi-arid, advective environment for dryland and deficit irrigated lands. 1b.Approach (from AD-416) Tillage practices that retain residue on the soil surface typically improve water availability to crops by increasing infiltration and/or ameliorating micrometeorological factors that drive the evaporation process. Because of limitations in sensor technology, past research studying water storage and use by crops has not elucidated the tillage induced changes in short-term processes that govern water infiltration, redistribution, and evaporation. Knowledge of the relative importance of each of these processes during a growing season will facilitate refinement of models to simulate seasonal water balance and assist in assessing the merits of alternative management practices. In addition, long-term studies used to quantify cumulative benefits of reduced tillage to increase crop yield, water use efficiency, and soil conservation for established wheat-sorghum-fallow crop rotations will be modified for comparisons of tillage benefits on annual sorghum-cotton crop rotations. Therefore, several experiments focusing on different hydrological aspects and time scales will investigate management effects on soil water and availability to crops. 4.Accomplishments ESTIMATING FIELD SOIL WATER BALANCE: Quantification of the hydrologic balance at high temporal resolution is necessary to evaluate field scale management effects on soil water storage. Scientists within the Soil and Water Management Research Unit at Bushland, Texas, developed a hybrid method to estimate soil hydraulic parameters based on water contents measured using Time-Domain Reflectometry in plots throughout a field. The new procedure permits the calculation of sub-daily rates of drainage, evaporation, and infiltration required for comparing soil management alternatives, and overcomes some of the scale-related difficulties associated with traditional methods. (NP 202, Soil Water Component; Problem Area 2, Soil Management to Improve Soil Structure and Hydraulic Properties) 6.Technology Transfer Number of web sites managed 1 Number of non-peer reviewed presentations and proceedings 8 Number of newspaper articles and other presentations for non-science audiences 3 Review Publications Baumhardt, R.L., Anderson, R.L. 2006. Crop choices and rotation principles. In: Peterson, G.A., Unger, P.W., Payne, W.A., editors. Dryland Agriculture. American Society of Agronomy Monograph Series No.23. Madison, WI: American Society of Agronomy. p. 113-139. Baumhardt, R.L., Salinas-Garcia, J. 2006. Dryland agriculture in Mexico and the U.S. Southern Great Plains. In: Peterson, G.A., Unger, P.W., Payne, W.A., editors. Dryland Agriculture. American Society of Agronomy Monograph Series No. 23. Madison, WI: American Society of Agronomy. p. 341-364. Baumhardt, R.L., Tolk, J.A., Howell, T.A., Rosenthal, W.D. 2007. Sorghum management practices suited to varying irrigation strategies: A simulation analysis. Agronomy Journal. 99:665-672. Unger, P.W., Fryrear, D.W., Lindstrom, M.J. 2006. Soil conservation. In: Peterson, G.A., Unger, P.W., Payne, W.A., editors. Dryland Agriculture. American Society of Agronomy Monograph Series No. 23. Madison, WI:American Society of Agronomy. p. 87-112. Unger, P.W., Payne, W.A., Peterson, G.A. 2006. Water conservation and efficient use. In: Peterson, G.A., Unger, P.W., Payne, W.A., editors. Dryland Agriculture. American Society of Agronomy Monograph Series 23. Madison, WI:American Society of Agronomy. p. 39-85. Schiere, H.B., Baumhardt, R.L., Van Keulen, H., Whitbread, A.M., Bruinsma, A.S., Goodchild, A.V., Gregorini, P., Slingerland, M.A., Hartwell, B. 2006. Mixed crop-livestock systems in semiarid regions. In: Peterson, G.A., Unger, P.W., Payne, W.A., editors. Dryland Agriculture. American Society of Agronomy Monograph Series No. 23. Madison, WI: American Society of Agronomy. p. 227-291. Peterson, G.A., Unger, P.W., Payne, B.A., Anderson, R.L., Baumhardt, R.L. 2006. Dryland agriculture research issues. American Society of Agronomy Monograph Series. 23:901-907.