Abstract

Water scarcity emerges as a prominent threat to the vegetative and reproductive phases of cotton plants. However, water deficit stress induces a reduction in stomatal conductance, altering the interplay between plant water and nutrients, and Irrigation water productivity (IWP). The relationship between IWP and cotton yield under deficit irrigation remains unclear in the irrigated area of Hyderabad, Sindh, Pakistan. The experiment was conducted at experimental stations of Agriculture Research Institute in Tandojam at two different sites during the cotton growing season 2022. The design of this study was based on a split-plot in RCBD including five deficit water stress levels (control treatment (existing irrigation practice 75 mm of water irrigation−1), 20% drought stress of existing irrigation, 20% drought stress of existing irrigation practice at alternate irrigation (even), 30% drought stress of existing irrigation practice and 20% drought stress of existing irrigation practice at alternate irrigation) and soil types. The findings revealed significant differences in soil moisture contents (SMCs) across all treatments, with a notable reduction in plant height and yield correlating with increased water stress. Despite variations in water stress and soil types affecting the number of opened bolls, the cotton yield and IWP demonstrated a decline, though not significantly under certain irrigation treatments. Across the deficit irrigation levels, 20% drought stress of existing irrigation practice at alternate irrigation (even) could significantly decrease yield by 6% and reduce IWP by 5% as compared to control treatment. However, the maximum IWP was recorded in the silt loam as compared to silt clay loam, respectively. The validation and calibration method of the CROPGROW-DSSAT model was designed to estimate cotton yield and IWP. The substantial R2 value indicates a strong concordance between the model-calibrated and observed data, signifying the CROPGROW-DSSAT model's ability to simulate cotton yield and WUE under deficit irrigation strategies within the specific regional climate conditions of Hyderabad. Therefore, it is suggested that the specific deficit irrigation strategies may maintain cotton yield production while reducing water usage, with variations observed between different soil types.