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

Abstract

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 29th meteorological week (2.3 mm d^-1) to 31st meteorological week (2.4 mm d^-1). Thereafter,  the  ET_c increased  in  35th  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 (39th meteorological week). The average daily ET_c of green gram was 3.8 mm d^-1 over 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.