Water Use Efficiency and Cotton Yield As Affected By Irrigation Termination Dates

Terminating irrigation at an appropriate date could not only ensure good cotton yield, but also increase water use efficiency (WUE). In this study, the CROPGRO-Cotton module within the Decision Support System for Agrotechnology Transfer (DSSAT) Cropping System Model (CSM) was used to simulate the effects of various irrigation termination dates on cotton WUE and yield under full and deficit irrigation conditions implemented in a field experiment at Halfway, TX during 2010 to 2013. The treatment factors include irrigation capacity (0 mm/day, Low (L); 2.5 mm/day, Medium (M); and 5.1 mm/day, High(H)) and irrigation application within three specific growth stage windows of pre-bloom, peak bloom, and post peak bloom. Three irrigation treatments of HHH, LMH, and LMM were considered in this study. Preliminary results from the 2010-2013 simulations indicated the ideal irrigation termination periods for cotton in case of HHH, LMH and LMM treatments at Halfway as the third week of August, first week of September and second week of September, respectively. These DSSAT simulations have been extended to 1977-2016 period, and the results from these simulations are currently being analyzed to determine the optimum irrigation termination periods for cotton in case of dry, normal and wet growing season conditions.