Evaluation of groundnut stover management strategies in a legume-rice rotation

Groundnuts grown after rice often lead to a gap of 1-3 months between legume harvest and planting of the next rice crop in many parts of Southeast Asia. To identify the best stover management strategy in such systems, the effect of methods of application (surface application vs incorporation), complementary mineral (NPK) additions and time of incorporation of groundnut stover on growth of rice KDML 105 and on decomposition (litter bag) was assessed. Groundnut provided 7500 kg ha(-1) of stover corresponding to a recycling of 100 kg N ha(-1), 10 kg P ha(-1) and 74 kg K ha(-1) which resulted in higher seed yield of the succeeding rice compared with removing stover from the field. Initially, low leaf area index where stover was incorporated 6 and 13 days before transplanting indicated a negative effect of decomposing stover; however, rice plants fully recovered subsequently. N application at panicle initiation did not have a significant effect on dry matter yields, although it increased seed N contents, especially those of the early stover application treatments. Neither N application nor omission of PK fertilizer at rice transplanting had any significant effect on rice growth suggesting groundnut stover is an effective basal fertilizer. N accumulation in rice increased with decreasing time of stover application before rice transplanting probably associated with rapid N (and K) release from residues. Storage of residues and application shortly before rice transplanting led to a better recycling of N but the associated seed yield gains were small and probably not sufficient to make it an attractive alternative for farmers.