Investigating the effect of limited climatic data on evapotranspiration-based numerical modeling of soil moisture dynamics in the unsaturated root zone: a case study for potato crop

Root water uptake (RWU)-based numerical modeling was employed for simulating the moisture dynamics in the unsaturated root zone of potato (Solanum Tuberosum L.) crop, wherein crop evapotranspiration (ETc) is an important input parameter. Richard’s equation incorporating a nonlinear RWU model was considered in the study. Reference evapotranspiration (ET0) was computed using full climatic data (combination-based methods) and limited climatic data (radiation, temperature and pan-evaporation-based methods). The crop coefficients (Kc) during different stages of the crop growth were adjusted for the local agro-climate (humid subtropical) following the FAO-56 Kc modification procedure. ETc estimated from different ET0 methods using the FAO-56 crop coefficient approach was compared with the field ETc obtained through the water balance approach. The methods Penman–Monteith (PEN–M) (combination-based), FAO-24 radiation (RAD) (radiation-based), Hargreaves-Samani (HAR) (temperature-based) and Snyder (SD) (pan-evaporation based) performed better in their respective categories. Soil moisture values simulated using the numerical model (considering ETc computed from PEN-M, HAR, RAD and SD) were graphically and statistically compared with the field observed soil moisture. Results indicate that a field soil moisture depletion of 30% corresponds to the simulated soil moisture depletion of 15%, 25%, 28% and 40%, based on ETc inputs from SD, HAR, PEN-M and RAD, respectively. The results augment the investigations on the influence of limited climatic data on the simulated irrigation schedules of the potato crop. The study has significance in effective irrigation scheduling in water deficit areas having different scenarios of climatic data availability.