Productivity and soil fertility of rainfed lowland rice (Oryza sativa) as influenced by establishment and weed management

Abstract

Field experiments were conducted during kharif season of 2016 and 2017 at the experimental farm of SASRD, Nagaland University, Medziphema to evaluate the effect of establishment methods and weed management on productivity, nutrient uptake, nutrient harvest index (NHI) and residual soil fertility of rainfed lowland rice. Three establishment techniques and six weed management practices were evaluated in split plot design with three replications. Results revealed higher grain (4.24 t ha-1) and straw (5.88 t ha-1) yield, nutrient uptake by grain (53.1, 13.8 and 10.7 kg NPK ha-1) and straw (32.3, 6.2 and 48.8 kg NPK ha-1); available nutrients in post harvest soil (332.5, 20.7 and 12.3 kg NPK ha-1) under system of rice intensification (SRI) whereas conventionally transplanted rice (CTR) recorded least values. Minimum weed dry matter (158.4 g m-2) and nutrient depletion (11.3, 1.9 and 19.9 kg NPK ha-1) was recorded in integrated crop management (ICM) while maximum was observed in SRI. Among the weed management methods, significantly lower weed dry weight (103.4 g m-2), nutrient depletion (7.4, 1.3 and 12.9 kg NPK ha-1) and higher grain (4.59 t ha-1) and straw (6.30 t ha-1) yield was observed under hand weeding (HW) twice at 20 and 40 days after transplanting (DAT). Nutrient depletion by grasses was observed to be higher as compared to sedges and broad leaved weeds. Weed control increased nutrient uptake by rice and decreased nutrient uptake by weeds. Hand weeding at 20 and 40 DAT recorded highest grain yield which was 81% higher over weedy check.