Identifying the potential to apply deficit irrigation strategies in cotton using large mobile irrigation machines

Irrigation water restrictions in the cotton industry have increased the focus on improving water use efficiency. regulated deficit irrigation (RDI) has been found to improve the water use of efficiency of cotton under drip irrigation. Partial rootzone drying (PRD) has been commercially implemented in grapevines and found to increase the water use efficiency for a variety of crops. This paper investigates the potential to improve cotton water use efficiency using RDI and PRD strategies applied with lateral move machines. A range of RDI treatments (71 % - 100 % evapotranspiration replaced) and a PRD and non-PRD treatment were applied to a crop of Sicot 180 during the 2002/2003 cotton season. No yield reduction was found between the fully irrigated and the 50% RDI treatment that received 1.05 ML/ha less water. Crop WUE was found to increase from 0.94 bales/ha to 1.17 bales/ha as the irrigation water applied was reduced from 100% to 79 % of evapotranspiration replacement. No difference in physiological growth and yield was found due to the implementation of the PRD treatment. Further work is required to confirm the RDI results, further explore the application of PRD strategies using these machines, and to more fully understand the physiological response of cotton to imposed soil moisture deficits applied either by volume (RDI) or space (PRD).