The effects of drought and salinity on KS and RAW managerial coefficients in the efficient water management in maize farms

This study aimed to investigate the simultaneous effects of drought and salinity on irrigation management coefficients in maize farms. A three-year field research was conducted in the form of a 3 × 3 factorial experiment with a randomized complete block design and three replications from 2020 to 2022 in a maize farm, in Aliabad Fashafoye, Qom province, Iran. The applied treatments included three levels of salinity (S₀ = 1.8, S₁ = 5.2, and S₂ = 8.6 dS/m) and three levels of irrigation (W₀ = 100%, W₁ = 75%, and W₂ = 50% of field capacity). Evapotranspiration stress coefficient (K_S) due to W₀S₁ and W₀S₂ treatments was (0.975 and 0.934), (0.974 and 0.932), and (0.962 and 0.935) in 2020, 2021, and 2022, respectively. According to the results, K_S decreased by increasing the salinity level of irrigation water, so a 1-unit increase in salinity level above the tolerance threshold of the crop to salinity decreased K_S by 0.78 and 1.76% for S₁ and S₂, respectively. Moreover, each percent of volumetric moisture decrease from field capacity decreased K_S by 5.9 and 13.3% in W₁ and W₂, respectively. Also, with the increase in the intensity of the stresses, the readily available water (RAW) of treatments decreased. The sole application of salinity stress decreased the decreasing slope of RAW by 3.2%, while the application of both stresses resulted in the decreasing slopes of 4.9, 5.7, and 7.8% at the salinity levels of S₀, S₁, and S₂, respectively, compared to the control. The findings of this study show that the accurate estimation of crop evapotranspiration and RAW can help to improve the irrigation schedule, and the amount of irrigation water used is less than in non-stress conditions due to the reduction of total evapotranspiration and less water uptake in environmental stresses in maize farms.