Brown manuring as a tool of weed management and contributor to nitrogen nutrition of direct wet seeded rice

Field experiments were conducted for two kharif seasons of 2012 and 2013 at Hyderabad to study the impacts of brown manuring (BM) with Sesbania aculeate and nitrogen fertilization of direct wet seeded rice (DWSR) performance. BM crop putting up 1.21 t ha-1 dry biomass (3.09 t ha-1 fresh biomass) in 30 days has accumulated 35.7, 3.9 and 17.2 kg ha-1 nitrogen (N), phosphorous (P) and potassium (K), respectively. BM has reduced the weed biomass production (g m-2) in DWSR by 40.5% and thus reduced their N-P-K uptake (kg ha-1) by 2.22-0.23-2.03 over no BM treatment (5.15-0.51-4.56 kg ha-1 N-P-K). Though BM has improved rice grain yields of DWSR significantly (0.15 t ha-1), the increases in net income were non-significant (921 Rs. ha -1) over no BM. Nitrogen fertilization of DWSR @120 kg ha-1 was found promising from both yield and economics point of view. The yield and economic benefits of BM to DWSR can be derived when no N was applied (0.38 t ha-1 and Rs. 3286). The BM crop on average contributed 9.93 kg N ha-1 and this contribution was highest (14.9 kg ha-1) when DWSR received no N.