Current Research on Geography, Earth Science and Environment Vol. 9

Rainfall variability is a major source of water stress in rainfed pulse production during the kharif season. This study evaluated whether rainfall-deviation thresholds derived from the Water Requirement Satisfaction Index (WRSI) could support drought-related crop-condition monitoring in Telangana, India. Blackgram, greengram and redgram were examined at 20 representative locations in Medak, Warangal and Mahabubnagar districts, respectively. Gridded rainfall and maximum and minimum temperature data for 2000–2015, together with soil information, were used in a soil-water-balance framework to estimate rainfall deviation, potential crop evapotranspiration, actual crop evapotranspiration and seasonal WRSI. Rainfall-deviation frequencies were assessed for 2000–2016. Deficit rainfall occurred more frequently at the blackgram locations, whereas normal rainfall was more common at the greengram and redgram locations. WRSI classifications indicated predominantly mediocre crop conditions for blackgram and average-to-good conditions for greengram and redgram. The coefficients of determination for rainfall–WRSI relationships ranged from 0.26 to 0.77 for blackgram, 0.35 to 0.94 for greengram and 0.57 to 0.96 for redgram. Rainfall-deviation thresholds for blackgram were broadly interpretable across the assessed soil conditions, while thresholds for greengram and redgram varied with soil type and depth. The findings indicate that WRSI-based thresholds may assist comparative monitoring of drought-induced water stress when crop characteristics and soil water-holding conditions are considered.