Nitrogen Dynamics in Rice under Rice-Wheat Cropping System at Khumaltar Condition

Nitrogen fertilization is a key input in increasing rice and other crop production in the world. Realizing the issue, nitrogen dynamics Lalitpur, Central Nepal was studied in long-term experiment under rice-wheat cropping system at rainfed lowland condition of Khumaltar The first objective of the experiment was to assess the contribution of organic, inorganic and biological nitrogen fixation ( BNF ) for the better nitrogen cycling and  utilization of added and residual nitrogen by crops. The second objective was to quantify the  N0 3 - -N and  NH 4 + -N in puddled soil at different soil depths and growth stages of rice in rotation with rice based wheat-cropping pattern.The nitrogen (N) level was used 0,50, and 100 kg N per ha The  NH 4 + -N and  N0 3 - -N dynamic in three soil depth (0-15, 15-30 and 30-60 cm) were monitored and crop performance evaluated in terms of grain and straw yield.The rice grain and straw yield were observed in the higher N-addition and incorporation of soybean stubble.The  N0 3 - -N and  NH 4 + -N in the soil were also higher in the soybean incorporation treatment than in other treatments. Higher  NH 4 + -N was absorbed at maximum tillering stage than after rice harvest.