Assessing capacitance soil moisture sensors for precision irrigation scheduling in wheat crop

Abstract Water resources influence agricultural production, yet efficient utilization, particularly water conservation in irrigation still remains a significant challenge in developing nations. This study aimed to calibrate and evaluate three capacitance soil moisture sensors, namely, capacitive v1.2, capacitive v2.0 and capacitive waterproof sensors for various soil textures at the Indian Agricultural Research Institute (IARI; New Delhi) research farm. The study assessed the sensors’ adaptability for irrigation scheduling and their impact on yield and water productivity in wheat crops during the years 2021–2022 and 2022–2023. Experimental results demonstrated that location-specific calibrated capacitive waterproof soil moisture sensor outperformed the others, with the lowest prediction error statistics, including MAE (0.30 to 0.43), RMSE (0.35 to 0.46) and NMBE close to zero, along with high accuracy (NSE > 0.97). Irrigation scheduling using capacitive waterproof soil moisture sensors of two wheat cultivars (HD:2967 and HD:3086) under three irrigation regimes (Field capacity, 20% and 40% deficit irrigation) indicated that soil moisture sensors measured the soil moisture content closely aligned with the measured values for all irrigation regimes. Grain yields for HD:2967 were 5.66 t/ha and 5.21 t/ha, and for HD:3086, 5.45 t/ha and 4.89 t/ha under field capacity irrigation regimes for 2021–2022 and 2022–2023, respectively. Correspondingly, crop water productivity (CWP) was highest under the 40% deficit irrigation regime, with values reaching 19.8 kg/ha.mm for HD:2967 and 19.42 kg/ha.mm for HD:3086 in 2021–2022. In 2022–2023, the CWP values were 17.35 kg/ha.mm for HD:2967 and 16.74 kg/ha.mm for HD:3086 under the same regime. These findings suggested that soil moisture sensors, when calibrated for specific locations, can effectively manage irrigation water in field crops, thereby improving both grain yield and CWP.