Enhancing water productivity in sugarcane cultivation by integrating basal crop coefficient with deficit irrigation

Water productivity (WP) is a critical factor for sustainable agriculture, particularly in water-scarce regions. This study integrated locally calibrated, cultivar-specific basal crop coefficients (K cb ) to apply deficit irrigation strategies for optimizing irrigation management and enhancing WP in sugarcane cultivation. Field experiments with a commercial sugarcane variety (Khon Kaen 3, KK3) were conducted in two weighing lysimeters to assess actual evapotranspiration (ET a ), crop yield, and WP over two growing seasons in central Thailand. The first lysimeter cultivated sugarcane under full irrigation (FI), managed near field capacity to establish a standard non-stress condition, while the second lysimeter used a 50% management allowed depletion (50% MAD) deficit strategy. The SIMDualKc model used the field data to derive K cb values for the local KK3 cultivar, ensuring that the coefficients reflected cultivar-specific physiological traits and Central Thailand's Tropical Savanna (Aw) climate while aligned with the FAO-56 K cb framework. The calibrated K cb values reflected the crop's phenological water demands and were 0.15, 1.11 and 0.49 for initial growth, mid-season and late-season stages, respectively. The AquaCrop model was then configured with the calibrated K cb values, validated against lysimeter and secondary regional yield data, and employed to predict yields, crop evapotranspiration, WP, and irrigation frequencies under various irrigation scenarios. The simulated results revealed that the moderate deficit irrigation regimes (25% and 50% MAD) significantly reduced crop water use while maintaining competitive sugarcane yields. In contrast, the rainfed system demonstrated yield losses due to rainfall variability. The findings provide a sustainable framework for supporting adaptive irrigation practices.