Yield and HVI Responses to Water Deficits in Pima and Acala Cotton

The need to develop new water management approaches that increase both the uniformity and efficiency of application is one a primary driver in the move to increase the water use efficiency of cotton.  Additionally, many US cotton belt growers and researchers are working to develop and implement deficit irrigation approaches that work to cut back on applied water while attempting to retain high production levels.  The desired goal is that with improvements in application technology, irrigation timing and volume can be managed and linked to farming systems that consider the cost and availability of irrigation inputs. A two year study was conducted that investigated water deficit impacts on commercial Pima and Acala cotton yield and quality.  Four irrigation regimes containing a range of high, low and moderate water stress treatments were established on a deep, well-drained, clay loam soil in western Fresno County to determine the impacts of water stress on field productivity and HVI quality parameters.  We monitored field applied water, soil moisture content, and plant water stress throughout the season.  From this information, we developed crop water use estimates, plant water stress duration and intensity estimates that were related back to yield and fiber quality data.  Field evaluation techniques for scaling water stress intensity treatments were successful and found to be useful as predictive indices of crop yield and quality responses.  The approaches presented suggest that when water prices or availability are marginally beneficial to whole field economies, irrigation practices can be modified with some predictive accuracy of how relative yield and quality respond to planned irrigation deficits.