Nitrogen scheduling, phosphorus management and green manuring for increasing productivity of lowland rice

Field experiment was conducted during dry and wet seasons of 2005, 2006 and 2007 at Pusa, Bihar to assess the effect of phosphorus management in pre-rice green manure crop dhaincha and rice on the biomass production of Dhaincha and its effect on yield and nutrient uptake of succeeding rice crop and residual fertility build up in soil. Dhaincha biomass production increased with increasing phosphorus level and seed rate, achieving 21.89 t ha−1 when entire dose of phosphorus was given to the green manure crop at higher seed rate. The increase in biomass production was 37.2% over no phosphorus to dhaincha. Addition of nitrogen to the soil ranged from 36.7 to 74.4kg N ha−1. Maximum grain and straw yield of rice was recorded when entire dose of phosphorus was added to dhaincha with 75% recommended dose of nitrogen (RDN) to rice crop, however, this remained at par with 50% RDN added to the rice crop. NPK uptake by rice crop also increased significantly due to these treatments. Second experiment was conducted to schedule the nitrogen splitting in summer green manuringrice system to optimize the efficiency of applied fertilizer N through better synchronization between crop demand and supply. Significantly maximum grain and straw yields, and net return was recorded when N fertilizer was applied in three splits as ¼N at active tillering + ½N at panicle initiation + ¼ N at flowering.