Status of organic carbon and total nitrogen under green manure and varying nitrogen levels in rice-wheat cropping system

Significant increase in soil organic carbon and total nitrogen was observed by using bio-organic sources and bio-fertilizers in rice-wheat cropping system during the present investigations. It was observed that standard INM packages for paddy (N60 + GM + BGA) and wheat (N90 + Azotobactor) enhanced the paddy and wheat yield by 20 and 10 per cent respectively as compared to recommended doses (120 kg/ha) of chemical N. On an average most promising INM doses reflected positive nitrogen balance in soil after harvest of last rotation as +0.03 per cent organic carbon and +0.004 per cent total N with Sesbania rostrata as green manure and recommended dose N 120 kg/ha showed negative N balance as -0.02 per cent organic carbon and -0.001 per cent total N. In case of wheat Azotobactor with 90 kg N/ha gave sustainable nitrogen balance as +0.05 per cent organic carbon and +0.004 per cent total N as compared to recommended dose of N 120 kg/ha which showed negative nitrogen balance as -0.02 per cent organic carbon and -0.002 per cent total N. Application of biofertilizers and green manure alone or in combination with chemical N provided sustainable nitrogen balance after harvest of rice-wheat crop.