Emission of nitrous oxide from rice-wheat systems of Indo-Gangetic plains of India

Nitrous oxide (N₂O) accounts for 5%of the total enhanced greenhouse effect and responsiblefor the destruction of the stratospheric ozone. The rice-wheat cropping system occupying 26 million ha ofproductive land in Asia could be a major source ofN₂O as most of the fertilizer N in this region isconsumed by this system. Emission of N₂O asinfluenced by application of urea, urea plus farm yardmanure (FYM), and urea plus dicyandiamide (DCD), anitrification inhibitor, was studied in rice-wheatsystems of Indo-Gangetic plains of India. Total emissionof N₂O-N from the rice-wheat systems varied between654 g ha^-1 in unfertilized plots and 1570 g ha^-1 in urea fertilized plots. Application of FYM and DCDreduced emission of N₂O-N in rice. The magnitude ofreduction was higher with DCD. In wheat also N₂O-Nemission was reduced by DCD. FYM applied in rice had noresidual effect on N₂O-N emission in wheat. In riceintermittent wetting and drying condition of soilresulted in higher N₂O-N emission than that ofsaturated soil condition. Treatments with 5 irrigationsgave higher emissions in wheat than those with 3irrigations. In rice-wheat system, typical of a farmer'sfield in Indo-Gangetic plains, where 240 kg N isgenerally applied through urea, N₂O-N emission is1570 g ha^-1 (0.38% of applied N) and application ofFYM and DCD reduced it to 1415 and 1096 g ha^-1,respectively.