INFLUENCE OF GREEN MANURING ON SOIL QUALITY IMPROVEMENT, FERTILIZER ECONOMY AND MONETARY ADVANTAGES OF GM-T. AMAN-MUSTARD CROPPING PATTERN

Abstract

Six field experiments and one laboratory experiment were conducted at Sher-e-Bangla Agricultural University during uninterrupted years of 2015-2016 to 2016-2017. The main objective of the experiments was to evaluate the impact of different kind of green manures on soil nutrient balance through adding biomass and N-accumulation along with its subsequent impact on crops yield and monetary advantages under Green manure-T. Aman rice-Mustard cropping patern.The green manure crops viz. Deshi dhaincha (Sesbania aculeata), African dhaincha (Sesbania rostrata), sunnhemp (Crotolaria juncea L.), Mungbean (Vigna radiata), Blackgram (Vigna mungo), Cowpea (Vigna unguiculata), Ipil-ipil (Leucaena leucocephala) and Mimosa (Mimosa pudica) were grown during two consecutive years for establishing a new cropping pattern of GM-Rice-Mustard. Fifty days-old green manure crops were incorporated after in situ cultivation and then both T. aman (subsequent crop) and mustard crops (following crop) were grown with recommended dose of N and half of recommended dose of N ha-1 in 1st year (2015) for T. aman rice and recommended dose and half recommended doses of NPK fertilizers in 2nd year (2016) for T. aman rice as well. Results

showed that, the biomass incorporation reduced the N applicationin rice. The biomass from Sesbania rostrata , Sesbania aculeata and Crotalaria juncea with decreasing levels (half of recommended dose of NPK fertilizer) of fertilizer in T. aman rice gave the yield which was at par to increased level (recommended dose) of fertilizer application. Incorporation of Sesbania rostrata and Sesbania aculeata added more organic matter and nitrogen to the soil prior to T. aman rice planting. However, the higher grain yield of subsequent T. aman rice (BRRI dhan66) was recorded at both from recommended and half of recommended dose of Nha-1and NPK with S. rostrata and S. aculeata followed by C. juncea and V. unguiculata incorporation as compared to control (no green manures). Green manuring (S. rostrata and C. juncea) residues incorporation prior to rice transplanting substantially increased (1549 kgha-1 and 1309 kgha-1for 2015 and 2016 respectively) the yield of the succeeding crop mustard as well. In case of mustard, S. rostrata incorporated plots gave the highest seed yield followed by C. juncea and V. unguiculata. The nutrient balance of soil after incorporation of different green manure crops specially S. rostrata, S. aculeata and C. juncea showed positive balance of nutrients than other green manures. Inclusion of S. rostrata as a GM crop in the GM-Rice- Mustard cropping sequence showed higher rice equivalent yield (REY) and production efficiency. This cropping sequence gave on an average 67% higher rice equivalent yield (REY) compared to the existing Fallow-Rice-Mustard sequence.