Efficiency of Mussoorie Rockphosphate for Rice in Acid Soil of Assam

Field experiments were conducted to assess the fertilizer value of Mussoorie Rock-phosphate in an acid soil in terms of direct effect on summer rice and residual effect on kharif rice. Results showed that although the direct effect was not statistically significant, the residual effect as well as direct plus residual effect taken together, as judged by grain yield and total phosphorus uptake were significant. There was practically no advantage due to increased fineness of rockphosphate beyond 60 mesh. It is suggested that in assessing the fertilizer value of rockphosphate its residual effect must be taken into account.