Influence of nitrogen and weed-management practices on crop-growth indices and productivity of dry direct-seeded rice (Oryza sativa)

Abstract

A field study was carried out during the rainy (kharif) season of 2019–20 at ICAR-Indian Agricultural Research Institute, New Delhi, to study the effect of nitrogen and weed management practices in dry direct-seeded rice (Oryza sativa L.) for obtaining higher productivity and crop growth. The experiment was laid out in a split-plot design, taking 3 nitrogen treatments, i.e. No N (P and K only), recommended dose of fertilizer (RDF–N : P : K = 80 : 17 : 33 kg/ha) (3 splits of nitrogen application–50% basal + 25% at tillering + 25% at panicle-initiation stage), 50% N from FYM + 50% N as real-time nitrogen management (top-dressing) as per leaf colour chart (LCC) up to panicle-initiation stage in main plots. Four weed-management treatments, viz. unweeded control, weed-free control, Pendimethalin @ 1.5 kg a.i./ha as pre-emergence followed by (fb) brown manuring with Sesbania bispinosa (Jacq.) W. Wight; Syn. S. aculeata [(Willd.) Pers.] (knocking down Sesbania by Bispyribac- Na 25 g a.i./ha at 25 days after sowing (DAS), Pendimethalin @ 1.5 kg a.i./ha as pre-emergence fb Bispyribac -Na @ 25 g a.i./ha at 25 DAS in subplots with 3 replications. Result revealed that, Pendimethalin @ 1.5 kg a.i./ha as pre-emergence fb brown manuring with Sesbania bispinosa significantly increased grain yield (2.78 t/ha) as well as growth indices like leaf-area index (1.8 and 4.4 at 40 DAS and 70 DAS, respectively), crop-growth rate (1.9 g/m² /day, 8.8 g/m² /day at 40 DAS and 70 DAS, respectively), relative growth rate (145.3 mg/g/day and 54.5 mg/g/day 40 DAS and 70 DAS, respectively), net assimilation rate (0.40 g/m² /day 3.49 g/m²/day at 40 DAS and 70 DAS, respectively) and dry-matter accumulation (185.6 g/m² , 591.6 g/m² and 1,144 g/m² at 40 DAS, 70 DAS and harvesting, respectively) to the other treatments. In case of N-management practices, combined use of FYM and LCC-based N management gave the highest grain yield (3.25 t/ha), growth indices like leaf-area index (1.69 and 4.0 at 40 DAS and 70 DAS respectively) crop-growth rate (1.8 g/m²/day, 8.2 g/m²/day at 40 DAS and 70 DAS, respectively), relative growth rate (145.1 mg/g/day and 55.1 mg/g/day at 40 DAS and 70 DAS, respectively) and dry-matter accumulation (168.5 g/m² , 523.2 g/m² and 958 g/m² at 40 DAS, 70 DAS and harvesting, respectively) comparable with RDF application and significantly higher than the plot without N.