Productivity Evaluation and Nitrogen Dynamics in Rice (Oryza sativa)-Wheat (Triticum aestivum L) Cropping System as Influenced by Crotalaria juncea Green Manuring

A field experiment was conducted during 2001–2002 and 2002 2003 on the mollisols of Crop Research Station at Pantnagar University to find out the effect of green manuring with Sunhemp (Crotalaria juncea) on productivity, soil microbial nitrogen, wet soil ammoniacal nitrogen, organic carbon, total and mineralizable nitrogen status of soil in rice-wheat cropping system. Crotalaria green manuring at 60 days stage resulted in 5746 and 5663 kg rice yield/ha in 2001–02 and 2002–03, respectively. Application of 150 kg N/ha to rice resulted in yield of 6385 and 6521 in 2001–02 and 2002–03, respectively. The wheat yield due to Crotalaria juncea green manuring was 3792 and 3818 in 2001–02 and 2002–03, respectively. Application of 75 and 150 kg N/ha to wheat crop resulted an increase in grain yield of wheat by 36.8 and 106.2% during 2001–02 and 44.6 and 105.7 during 2002–03 over no green manure treatment respectively. Crotalaria green manuring after 60 days of sowing resulted in 64.07 and 70.44 kg soil microbial biomass nitrogen (SMB-N) at 30 days after transplanting stage, while at harvest of rice the amount was 40.78 and 41.11 kg/ha in 2001–02 and 2002–03, respectively. At harvest of wheat the SMB-N was 42.41 and 42.73 kg/ha in 2001–02 and 2002–03, respectively. The wet soil ammonical nitrogen decreased with the age of rice crop and highest (44.2 and 45.9 in 2001–02 and 2002–03) was recorded due to application of 150 kg N/ha at 30 days after transplanting stage.