Assessing the impact of nitrogen and weed management on weeds and productivity of dry direct-seeded rice in eastern India

The objective of this study was to identify effective nitrogen and weed management options to manage weeds and improve productivity of dry direct-seeded rice. This study was conducted during kharif 2020 at Central Rainfed Upland Rice Research Station (CRURRS), Hazaribagh, Jharkhand. A split plot design replicated thrice was used. The tested treatments include: three nitrogen (N) doses in main plots, viz. No N, with recommended dose (RDF) of phosphorus (P) and potash (K) only [No N (RDF of P and K)]; RDF: 80 N:17 P:33 K kg/ha with N applied in 3 splits i.e. 50% basal +25% at tillering +25% at panicle initiation stage [RDF (N:P:K=80:17:33 kg/ha)]; 50% N using farm yard manure (FYM) + 50% N as need based top dressing up to panicle initiation stage, using leaf colour chart (LCC) [50% FYM + RTNM (LCC)]. Four weed management treatments assigned to sub-plots include: un-weeded control (UWC), weed-free control (WFC), pre-emergence application (PE) of pendimethalin 1.5 kg/ha followed by (fb) brown manuring with Sesbania aculeata (by knocking down Sesbania at 25 days after seeding (DAS) with bispyribac-Na 25 g/ha), pendimethalin 1.5 kg/ha PE fb bispyribac -Na 25 g/ha at 25 DAS. The grassy weeds were most dominant. Amongst weed management treatments, brown manuring with Sesbania aculeata significantly reduced weed density by 79.6 % and 88.8% and weed dry biomass by 90.6%, and 96.6 % at 40 and 70 DAS, respectively and increased rice grain yield by 31.06 % over un-weeded control. In case of N management practices, the combined use of FYM and LCC based N management produced highest grain yield with reater reduction in weed density, weed dry biomass, WI and increasing WCE (64.1 % and 76.4% at 40 and 70 DAS, respectively) and WCI (70.5% and 72.9% at 40 and 70 DAS, respectively) with highest overall B:C ratio (2.65), proving to be the most profitable combination in the study.