Evaluation of Wheat Yield and Water Productivity for Drip and Flood Irrigated Treatments Based on Maximum Allowable Deficit, Crop Evapotranspiration, and Conventional Practices

Assessing grain yield (GY), irrigation water productivity (IWP), and irrigation crop water use efficiency (ICWUE) provides valuable insights into optimizing irrigation water use while maintaining crop yield. For this purpose, irrigation is varied either in crop phenological stages or based on the maximum allowable depletion/deficit (MAD) or crop evapotranspiration (ET_C) or ratio of irrigation water to cumulative pan evaporation. No study has been identified that analyzed and compared GY, IWP, and ICWUE for drip and flood irrigated treatments based on MAD, ET_C, and conventional practices for wheat. This study analyzed and compared GY, IWP, and ICWUE among drip-irrigated (DI) and flood-irrigated (FI) treatments based on MAD, ET_C, and conventional practices by conducting field experiments for the wheat crop during 2023-24. The treatments were 50% MAD (DI), 50% MAD (FI), 100% ET_C (DI), 80% ET_C (DI), 80% ET_C (FI), 60% ET_C (DI), 40% ET_C (DI), and conventional practice replication (referred to as farmers’ field replication). Compared to farmers’ field replication, GY increased by 30.5%, 16.9%, 23.2%, 15.6%, 9.6%, and 0.4% in 50% MAD (DI), 50% MAD (FI), 100% ET_C (DI), 80% ET_C (DI), 80% ET_C (FI), 60% ET_C (DI) treatments, respectively. Furthermore, compared to the farmers’ field replication, the irrigation amount in 50% MAD (DI), 50% MAD (FI), 100% ET_C (DI), 80% ET_C (DI), 80% ET_C (FI), 60% ET_C (DI), and 40% ET_C (DI) reduced by 16.4%, 7.9%, 18.3%, 36.8%, 33.9%, 52.4%, and 65.5%, respectively. IWP values in 50% MAD (DI), 50% MAD (FI), 100% ET_C (DI), 80% ET_C (DI), 80% ET_C (FI), 60% ET_C (DI), 40% ET_C (DI), and farmers’ field replication were 29, 23.6, 28, 34, 39.2, 50.3, and 18.6 kg/ha-mm, respectively. For the same level of irrigation, IWP and ICWUE were higher in DI treatments compared to FI treatments. The values of IWP and ICWUE in 50% MAD (DI) increased by 23.1% and 41.5%, respectively compared to 50% MAD (FI). Similarly, IWP and ICWUE in 80% ET_C (DI) increased by 20% compared to 80% ET_C (FI). Among the treatments, the 50% MAD (DI) and 100% ET_C (DI) produced significantly higher GY of 5336.2 kg/ha and 5036.3 kg/ha, respectively. Between these two treatments, GY was higher in 50% MAD (DI). This can be attributed to the MAD in the 100% ET_C (DI) treatment reaching 67% during the high-water demand growth stage, which exceeded the MAD level in the 50% MAD (DI) treatment. This study suggested that with the priority to produce the higher grain yield and save irrigation water (16.4 to 18.3%) as compared to existing irrigation practices followed by the farmers in the study region, 50% MAD (DI) or 100% ET_C (DI) treatment must be employed. With the priority of saving the highest irrigation amount (52.4 %) without compensating for the GY, 60% ET_C (DI) can be utilized by the farmers in the local region.