Monday, November 13, 2006 - 2:30 PM

Short-Term Sustainability of Drainage Water Reuse on a Forage Crop: Impacts on Soil Properties.

Dennis L. Corwin1, Scott M. Lesch2, James D. Oster2, and Stephen R. Kaffka3. (1) USDA-ARS, George E. Brown Jr. Salinity Laboratory, 450 W Big Springs Rd, Riverside, CA 92507-4617, (2) Dept of Environmental Sciences, Univ of California, Riverside, CA 92521, (3) Dept of Plant Sciences, One Shields Ave, Univ of California, Davis, CA 95616

Drainage water reuse offers a means of providing an additional source of irrigation water and concurrently reducing the volume of drainage water. A long-term (10 years) study was initiated in 1999 on a 32.4-ha saline-sodic field (Lethent clay loam series; fine, montmorillonitic, thermic, Typic Natrargid) located on the west side of California's San Joaquin Valley with the objective of evaluating the sustainability of drainage water reuse from the perspective of impact on soil quality. A preliminary 5-year evaluation is presented. Geo-referenced measurements of apparent soil electrical conductivity (ECa) were used to direct soil sampling at 40 sites to characterize the spatial variability of soil properties (i.e., salinity, Na, B, and Mo) crucial to the soil's intended use of growing Bermuda grass (Cynodon dactylon [l.] Pers.) for livestock consumption. Soil samples were taken at 0.3-m increments to a depth of 1.2 m in August 1999, April 2002, and November 2004. Drainage water varying in salinity from 3-5 dS m-1 has been applied to the field since August 1999. General temporal trends indicate that the overall soil quality has improved with leaching of B from the top 0.3 m of soil, leaching of salinity from the top 0.6 m, leaching of Na and Mo from the top 1.2 m, and initiation of Se buildup in the top 0.3 m. Improved soil quality has resulted in increased forage yields. The short-term sustainability of drainage water reuse from the perspective of impacts on soil quality is supported by the results. The short-term implications are that drainage water reuse on forage is a viable alternative for reducing drainage water volumes thereby reducing the need for evaporation ponds or other disposal facilities. However, the long-term sustainability may be of concern due to Se accumulation and needs further assessment.