Effect of crop establishment, nitrogen levels and time of nitrogen application on weed density, weed dry matter and yield of direct seeded rice (Oryza sativa L.)

A field experiment was conducted during 2016 and 2017 at the Agricultural Research Farm, Banaras Hindu University, and Varanasi (U.P.) India. The experiment was laid out in split-plot design with two crop establishment methods viz., C1- Conventional tillage, C2-Zero tillage and four nitrogen levels viz. N1- 90 kg ha-1, N2- 120 kg ha-1, N3- 150 kg ha-1 and N4- 180 kg ha-1 in the main plot and four time of nitrogen application treatment viz. T1: 25% N as basal + 50% N at active tillering stage + 25% N at panicle initiation stage; T2:15% N as basal +22.5% at 15-20 DAS+ 40% N at active tillering stage + 22.5% N at panicle initiation stage; T3: 33.3 % N at 15-20 DAS + 33.3 % at active tillering stage + 33.3 % at panicle initiation stage; T4: 25% N at 15-20 DAS+ 25% N at active tillering stage + 25% N at panicle initiation stage + 25% N at heading in sub-plots for both the years. In case of crop establishment method, significantly lowest weed density (m-2), weed dry matter (g m-2) and higher grain and straw yield was recorded with zero till DSR (C2) compared to conventional DSR (C1) at all the crop growth stages Among the nitrogen levels, 90 kg N ha-1 recorded lowest weed density (m-2), weed dry matter (g m-2) and significantly higher yield was observed with 150 kg N ha -1 which is at par with 180 kg N ha -1 compared to rest of the nitrogen levels at all the crop growth stages during both the year of the experimentation. With regards to time of nitrogen application, lowest weed density (m-2) and weed dry matter (g m-2) was recorded under the treatment (T4) 25% N at 15-20 DAS+ 25% N at active tillering stage + 25% N at panicle initiation stage + 25% N at heading which was at par with treatment (T3) 33.3 % N at 15-20 DAS + 33.3 % at active tillering stage + 33.3 % at panicle initiation stage at 20 DAS. However, at 40 and 60 DAS significantly lowest weed density (m-2) and weed dry matter (g m-2 ) was recorded by treatment (T1) 25% N as basal + 50% N at active tillering stage + 25% N at panicle initiation stage which was at par with treatment (T4) 25% N at 15-20 DAS+ 25% N at active tillering stage + 25% N at panicle initiation stage + 25% N at heading compared to rest of the treatments during both the years of experimentation. However, about grain and straw yield treatment (T3) 33.3 % N at 15-20 DAS + 33.3 % at active tillering stage + 33.3 % at panicle initiation significantly influenced grain yield and straw yield respectively as compared to rest of the treatments and at par with treatment (T2) 15% N as basal +22.5% at 15-20 DAS+ 40% N at active tillering stage + 22.5% N at panicle initiation stage. During both the years of experimentation.