Effectiveness of rock phosphate as a source of phosphorus for apple

A long term field experiment was conducted on an acid hill soils with two sources of phosphatic fertilizer viz., single superphoshpate (SP) and rock phosphate (RP) with or without FYM and their mixtures to study the efficacy of sources on phosphorus availability, yield, agronomic efficiency and quality of fruits. The application of rock phosphate alone as well as in combination with superphosphate and FYM exhibited an increasing trend in apple fruit yield. The yield response was maximum with current season application of superphosphate. The fruit yield was better with the application of recommended dose of single superphosphate. However, the yields were at par with residual treatment of rock phosphate (RP 4.0 +FYM) from third year of experimentation. The fruit qualities were not affected by different phosphorus treatments. The highest Olsen's - P was recorded with current season application of SP followed by RP + FYM, SP + RP + and RP alone. On an average, addition of FYM to the rock phosphate increased availability of P by 24 per cent over their alone treatments.