Effect of seedlings age and plant spacing on growth, yield, nutrient uptake and economics of rice (Oryza sativa) genotypes under system of rice intensification

A field experiment was conducted during the rainy (kharif) season of 2008 and 2009 at Varanasi, to evaluate the effect of seedlings age and plant spacing on growth, yield, nutrient uptake and economics of rice (Oryza sativa L.) under system of rice intensification (SRI). Sixteen treatments were laid out in a split-plot design, keeping combinations of 2 genotypes (‘PHB 71’ and ‘NDR 359’) and 2 spacings (25 cm × 25 cm and 30 cm × 30 cm) in mainplots and 4 seedlings age (8, 10, 12 and 14 days old) in sub-plots with 3 replications. The rice hybrid ‘PHB 71’ showed significantly higher growth, yield attributes and 12.6% higher yield than ‘NDR 359’. This hybrid also gave the highest net monetary returns ( 46,700/ha) and benefit: cost ratio (1.56). Wider spacing i.e. 30 cm × 30 cm gave significantly more tillers/hill (22.7), panicles/hill (21.9) and grains/panicle (168.1) than other spacing. However, plant height (116 cm), leaf-area index (5.0), net monetary returns and yield were significantly higher in closer spacing of 25 cm × 25 cm. The closer spacing resulted in around 12.30% higher grain yield over wider spacing. Amongst the ages of seedlings, 10 days old seedlings resulted in significantly higher growth, yield attributes, net monetary returns and yield than 8 and 14 days old seedlings but remained at par with 12 days old seedlings. The 10 days old seedlings gave 12.8 and 17.6% more grain yield than 8 and 14 days old seedlings, respectively.