Abstract
To study the effect of groundnut crop residue and chemical fertilizers on subsequent rice crops of Groundnut-T. Aus rice- T. Aman rice cropping pattern, the residues of the groundnut crop were incorporated before transplanting of the following T. Aus rice and four chemical fertilizer doses viz., 0, 33, 66 and 100% of recommended doses were tested with or without groundnut crop residue in T. Aus rice and T. Aman rice. Significantly higher grain and straw yields of T. Aus rice (4.65-4.87 t ha⁻¹ grain and 5.00-5.23 t ha⁻¹ straw) and T. Aman rice (4.04-4.51 t ha⁻¹ grain and 4.29-5.30 t ha⁻¹ straw) were obtained from the use of groundnut residue + 66% recommended fertilizer doses. Both higher grain and straw nutrient uptake were found in groundnut residue incorporated plots. But the uptake of nutrients increased with the increase of applied fertilizers irrespective of with or without groundnut residue incorporation. The balance of N, P, S and Zn was positive but K showed negative balance. After two years of cropping, the available P, S and Zn content in soil increased. Soil organic matter content increased in few cases where groundnut crop residue was applied but total N and exchangeable K content in soil decreased in most cases. In a separate trial with N rate after incorporation of groundnut crop residue in T. Aus rice and its subsequent effect on T. Aman rice additional N rate showed that application of only 20 kg N ha⁻¹ (against 60 kg N ha⁻¹) in T. Aus rice and 60 kg N ha⁻¹ (against 80 kg N ha⁻¹) in T. Aman rice were sufficient for maximum grain and straw yields indicating the benefit of groundnut crop residue incorporation in raising crop productivity and maintaining soil fertility in Groundnut-Rice-Rice pattern.