摘要 : The present study was carried out at the Indian Agricultural Research Institute, New Delhi, for three crop years (2000-2001 to 2003-2004) to find out the effect of rates and sources of phosphorus on production and phosphorus balan... 展开 The present study was carried out at the Indian Agricultural Research Institute, New Delhi, for three crop years (2000-2001 to 2003-2004) to find out the effect of rates and sources of phosphorus on production and phosphorus balance in a rice-wheat system. Phosphorus application significantly increased productivity and P uptake of rice-wheat cropping system and resulted in an increase in extractable P (0.5 M NaHCO₃) content in soil. Mussoorie rock phosphate with phosphorus solubilizing bacteria inoculation (MRP+PSB) at 35 and 52.5 kg P ha^-1 was similar to 17.5 and 35 kg P ha^-1, respectively, as diammonium phosphate (DAP) in terms of productivity and P uptake of rice-wheat cropping system but significantly superior in terms of PSB population and CO₂ evolution in soil. The P balance was generally more positive for MRP+PSB than for DAP and the highest P balance was observed with the application of 52.5 kg P ha^-1 as MRP+PSB. At the end of three cycles of rice-wheat cropping system,net change in extractable P content in soil increased with increasing rate of P application and was highest with the application of 52.5 kg P ha^-1 as MRP+PSB to each crop of every year of the three years of study. The present study, thus, indicates that P requirement of a rice-wheat cropping system can be met with 35-52 kg P ha^-1 as MRP to each crop with PSB inoculation. 收起