Dynamics of inorganic fractions of nitrogen in an ustifluvents soil on incorporation of organic manures and mineral nitrogen in rice

Field experiments were conducted during Kharif 2007 and 2008 in sandy clay loam soil to study the effect of organic sources and urea on N transformation and yield of rice. The treatments consisted of addition of different organics viz., composted coir pith (CCP), green manures (GM), sugarcane trash compost ( STC), vermicompost (VC), poultry manure (PM) and FYM applied at 100% RDN and combination of above organics @50% N and urea@50%N besides 100% RDN as urea and control. The results revealed that addition of organics or mineral N or both significantly improved rice yields over control in both years. The highest grain yield (5067, 5050 kg ha-1) and straw yield (6490, 6398 kg ha-1) was noticed with vermicompost (50% N) + urea (50% N) which was on par with poultry manure (50%N) + urea (50%N) but superior to rest of the treatments. Rice yield was more with 100% Urea N compared to 100% RDN as organics alone. The best treatment caused 34.2% increase in grain yield over control, 1.36% over 100% urea N. Integrated use of organics and urea recorded higher concentration of ammonium and nitrate nitrogen compared to their individual addition. The N forms were more under vermicompost amended soil followed by green manure and poultry manure. The mineral N was higher at initial stages and decreased with crop growth.