Response of rice (Oryza sativa) varieties to graded levels of nitrogen under aerobic culture

A field experiment was conducted during 2006 and 2007 at Agricultural College, Naira on the response of rice (Oryza sativa L.) varieties to graded levels of nitrogen. Plant height, leaf area index, root volume and dry matter production were the highest with Vasundhara and 120 kg N/ha at all the stages during both the years of study. Panicles/m2, filled grains/panicle, grain yield (4.51 and 4.30 t/ha) and straw yield and nitrogen uptake by grain and straw were also significantly higher in the variety Vasundhara. Increasing levels of nitrogen progressively enhanced panicles/m2, filled grains/panicle, grain and straw yield and nitrogen uptake by grain and straw only up to 120 kg N/ha. Varieties and nitrogen levels interacted significantly and the highest grain yield and economics were recorded with Vasundhara at 120 kg N/ha and it was found to be optimum combination for aerobic rice.