Using agroclimatic approach for crop planning under rainfed condition in Darbhanga district of Bihar

Abstract

Agroclimatic analysis with historical weather data for assessment of crop potential under rainfed condition is called for effective decision making purposes for sustainable crop production under changing climatic scenario. An agroclimatic study was conducted for Darbhanga district of Bihar using database of 1980-2012 comprising three locations, viz., Darbhanga, Hayaghat and Jale for efficient crop planning in coarse, medium and fine textured soils. Results revealed that average annual rainfall computed was 1109.8±340.7 mm. More than 30 mm rainfall per week was found to occur during 24 standard meteorological week (SMW) to 36 SMW (11 June-9 September) and more than 50 mm per week occurred during 26 to 36 SMW (25 June-9 September). Total annual water surplus values were 483 mm during 23 to 43 (4 June-28 October), 408 mm during 26 to 42 (25 June-21 October) and 375 mm during 26 to 42 SMW (25 June-21 October) in coarse, medium and fine textured soils, respectively. Year-wise lengths of growing periods (LGP) were worked out based on index of moisture adequacy (Ima). Mean LGP of the district based on Ima was 143±19 days in coarse, 180±30 days in medium and 209±36 days in fine textured soils. Darbhanga, Hayaghat and Jale blocks recorded LGP of 161, 177 and 167 days, respectively. Hargreaves’ moisture availability index (MAI)≥ 0.34 extended from 19 to 42 (7 May-21 October), 23 to 40 (4 June-7 October) and 26 to 38 SMW (25 June-23 September) at 25, 50 and 75% probability levels, whereas MAI≥ 0.75 prevailed from 23 to 42 (4 June-21 October), 28 to 39 (9 July-30 September) and 27 to 35 SMW (2 July-2 September) at 25, 50 and 75% probability levels, respectively. Crop planning based on LGP has been suggested for the district in different soils for sustainable crop production under rainfed condition.