Effect of age and number of seedlings on weed dynamics, productivity and nutrient uptake of rice (Oryza sativa)

A field experiment was conducted at Darisai, West Singhbhum, Jharkhand during kharif, 2010 and 2011 to find out the effect of age and number of seedlings on rice (Oryza sativa L.) crop. Twenty days old rice seedlings, being on par with 30 days old seedlings, recorded significantly lower density of grassy, broad-leaved as well as total weeds at 30 days after sowing (DAS). Significantly lower dry matter accumulation of weed was recorded by 20 days old seedling which was similar to 30 and 45 days old seedlings. Transplanting two seedlings hill⁻¹ recorded reduced density of grassy, broadleaved, sedges as well as total weeds compared to transplanting three and four seedlings hill⁻¹ at 60 DAS. Transplanting of two seedlings hill⁻¹ also recorded reduced dry matter accumulation by weeds at 30 DAS compared to three and four days old seedlings. Younger seedling i.e. 20 days old, being on par with 30 days old seedlings recorded 30.6 and 43.3% higher grain and 30.8 and 43.1% higher straw yield compared to 40 and 60 days old seedlings, respectively. Transplanting of two seedlings hill⁻¹ being similar to three seedlings hill⁻¹ recorded 10.9% higher grain and 11.1% higher straw yield compared to two seedlings hill⁻¹. Transplanting of twenty days old two seedlings hill⁻¹ recorded significantly higher net return (` 33.7 x 10³ ha⁻¹) and B: C ratio (1.07) than four seedlings hill⁻¹and it was also significantly higher over other combination of age and number of seedlings hill⁻¹.