Climatic water balance for assessment of growing season in the eastern Indian state of Bihar

Abstract

Correct evaluation of water availability period in a region is vital to ensure sustainable crop production. In this backdrop, an agro-climatic study was carried out for the eastern Indian state of Bihar to evaluate the onset, cessation and length of growing period (LGP) by employing climatic water balance model for effective crop suitability planning under rainfed condition. For this purpose, historical weekly rainfall data of 110 rain-gauge stations for a period ranging from 30 to 55 years, normal weekly potential evapotranspiration (PET) and available water holding capacity were used. Lengths of growing periods (LGP) for coarse, medium and fine textured soils in each individual district of the state were worked out based on weekly values of moisture adequacy index (Ima), which is the ratio of actual evapotranspiration (AET) to PET. Thematic maps of onset, cessation and length of growing period for delineating agroclimatic potential were generated using geographical information system (GIS) to identify the optimum planting schedule, safe growing period and climatic suitability of rainfed crops across various districts in the state. Results indicated a wide variation in LGP, which ranged from 121 to 272 days over different districts in the state. Based on LGP, rainfed crop potential and cropping plan in different districts of Bihar have been worked out for sustainable crop production under rainfed condition.