Efficient use of rock phosphate by rice-groundnut cropping system in an acid soil

Low grade Udaipur rock phosphate (6.4% P) and its mixture with superphosphate were applied either to kharif rice or rabi groundnut at a dose equal to the P requirement of both the crops. The residual effects of P were studied on the subsequent rabi crop (groundnut) or kharif crop (rice). Application of phosphate as per requirements of both the crops to one of the crops and growing the subsequent crop on residual P was better than individual application of P to each of the crops. 1f yield increase and P-recovery of both the crops are taken into account, rabi application of P to the groundnut crop and growing the kharif rice on residual P was found to be re efficient than the other way round. Application of 1:1 mixture of SSP with URP proved to be ore effective than rock phosphate alone and was either at par or better as compared to SSP. The residual effect of 1:3 mixture on rice yield was significantly superior to 1:1 mixture.