Effect of field of view of canopy temperature observations on crop water stress index for irrigation scheduling

The monitoring of canopy temperature (T-c) helps to establish appropriate watering methods. This study calculates the crop water stress index (CWSI) for four irrigation regimes in semi-arid region, India. Plots 1, 2, 3, and 4 had soil moisture depletion of 50% (drip system), 25% (drip system), unregulated (farmer replicated flood system), and 50% (flood system) with irrigation. In this work, we examined the value of employing a portable infrared thermometer (IRT) to measure wheat canopy temperature (T-c) at two geographical locations. The IRT field of view is 51.28-5,128 cm(2), or 10-100 cm from the canopy crown. The field of view change from 10 to 100 cm affects T-c and CWSI in the four irrigation treatments, ranging from 0.65 to 2.71% and 9.2 to 36.4%, respectively. The research found that increasing the IRT from 10 to 100 cm reduced slope by 5.7% and intercept by 20.6% in lower baselines. The R-2 for CWSI and soil moisture was 0.78 (10 cm) and 0.77 (100 cm). Drip-irrigated plots are more sensitive to IRT spatial resolution than flood-irrigated plots. The findings suggest that CWSI studies may benefit from specific sample methods for T-c evaluation.