Crop residue management to sustain soil fertility and irrigated rice yields

Field experiments were conducted on a sandy clay loam soil (deep aquic ustorthent) for five consecutive seasons from wet season (WS) 1998 to WS 2000 with a permanent layout at the Directorate of Rice Research (DRR) farm, ICRISAT campus, India, to study the influence of incorporation of rice straw residues alone or in combination with in situ grown green manure (GM) and straw burning on soil fertility, irrigated rice productivity and pest incidence in comparison with only fertiliser application (control). The residue treatments received uniform doses of N, K, Zn at the same level as that in control plots. The crop residue treatments favourably influenced some of the soil parameters over control. Recycling of crop residues by incorporation or burning increased soil available K and organic carbon significantly over control, while total N content increased by residue incorporation. Bulk density decreased with residue incorporation as compared to control and burning treatments. Yellow stem borer was the only pest observed, with higher white ear damage recorded during wet seasons ranging from 14.2-31.3% in 1999 and 16.8-29.7% in 2000. The damage was higher with straw 1 green manure, apparently reflecting the quantum of N applied through crop residues and fertilisers. The influence of crop residue treatments on yield parameters like panicle and spikelet number was more apparent after two cycles of residue incorporation, recording significant effects on rice productivity in the dry and wet seasons of 2000. Rice yield increased by 1.0 to 1.2 t/ha in DS and 0.4 to 0.8 t/ha in WS.