University of California Water Resources Center

California Pima cotton production has and been particularly hard hit resulting in acreage declines caused by water supply reductions in the western San Joaquin Valley. Water management methods that improve water use efficiency while maintaining high agronomic yield are of value to the cotton producers that face water supply limitations. We tested structured and predictive approaches to water management and collected field water management information that evaluated our ability to match varying water supply amounts in a way that maximized production and limited economic losses due to reductions in crop quality. Evaluations at four separate sites conducted during the 2005 and 2006 cropping seasons confirmed Pima cotton’s ability to respond favorably to irrigation guidelines recently developed by the UCCE and to modest deficit irrigation approaches that have been developed for Acala type Upland cottons. Variations in soil water storage at each site were large and played a critical role in how Pima cotton responded to in-season water deficits.