Spatio-temporal Variations of Green Gram Evapotranspiration in Marathwada Region of Maharashtra, India

Despite the crucial role of water in agricultural production, exact estimates of water requirements of field crops are often lacking in many regions of India. This study focuses on estimating crop water needs accurately and exploring spatio-temporal variability of crop evapotranspiration (ET_c) for green gram crop in Marathwada region of Maharashtra, India. The reference evapotranspiration (ET_o) estimated using FAO-56 Penman-Monteith method was used for estimating ET_c for 32-year (1990-2021) across eight districts of Marathwada. Results revealed that the ET _c of green gram in the region increased slightly from 29^th meteorological week (2.3 mm d^-1) to 31^st meteorological week (2.4 mm d^-1). Thereafter, the ET_c increased in 35^th meteorological week to 4.3 mm d^-1 and remained constant during mid-season stage, and later on, it gradually decreased to 2.2 mm d^-1 at the end season (39^th meteorological week). The average daily ET_c of green gram was 3.8 mm d^-1over the entire growing season. Among the eight districts, seasonal ET_c ranged from 280 mm (Dharashiv district) to 240 mm (Hingoli district). Geographical variations exhibited the higher ET_c in southwest and some area of southeast portion of the region, while the northwest portion displayed the lower ET_c values. Mann-Kendall test indicated significantly decreasing trends in weekly ET_c of green gram mainly during two meteorological weeks, i.e., MW-37 and MW-38, across most of the districts, which was further confirmed by the results of Sen’s slope estimator. Farmers in the study area can schedule the application of irrigation for green gram at right time and in appropriate amounts depending upon the specific ET_c values. Thus, findings of this study are useful to farmers and agriculture department by enabling optimized irrigation water management.