Assessing climatic risk in terms of water availability to the crops in drought prone tract of Bihar

Abstract

An agroclimatic study was conducted to assess the climatic risks in fitting of rainfed crops based on weekly probabilistic values of Moisture Adequacy Index,(MAI) which is the ratio of actual evapotranspiration (AET) to potential evapotranspiration (PET). MAI was estimated at 50 and 75 per cent probability levels, compared to water demand of crops at different phases of growth and thereby to identify appropriate planting schedules for maize and rice based cropping systems in coarse, medium and fine textured soils in different districts under drought prone region (Zone IIIB) of Bihar. The AET was calculated by climatic water balance method using historical weather data. The results revealed that the crops grown in coarse textured soil had to endure greater water stress of different magnitudes at different phases of crop growth than those in medium and fine textured soils. During kharif season, maize could be successfully grown without water stress at any phases of growth across various districts and soils. Although adoption of crops during rabi season becomes risky, toria could be fitted in the cropping sequence for this drought prone region in fine textured soil. Results emanated from the study were of practical implication for field application and for breeding appropriate varieties matching with water availability period. The identification of water stress during different phenological phases of crops at varying risk levels could be useful for scheduling of irrigation.