Influence of Mussoorie Rock Phosphate on Available Nutrients in a Soybean Sunflower Cropping System

A field experiment was conducted to study the effect of Mussoorie rock phosphate (MRP) as a source of p for a soybean-sunflower cropping system in Vertic Ustropept during June 1989 to February 1990. The P treatments applied at 80 kg ha⁻¹ included superphosphate (SP), MRP, 1:1 mixture of SP and MRP, partially acidulated rock phosphate (PARP). MRP + phosphobacteria and no P. These treatments were imposed with and without FYM at 12.5 t ha⁻¹. Due to the of higher dry matter production (DMP) and grain yield per unit area with increased nutrient uptake, FYM and SP applied plots registered the lowest soil available Nand K after soybean while it was FYM and MRP + SP (1:1) treatments which gave low values of available soil nutrients after the residual crop of sunflower. Citric acid soluble P status of the post-harvest soil of soybean and sunflower crops was high in FYM applied plots while the total P of the soil was not influenced markedly. MRP application recorded slightly higher values of total P as it contributed to the total P pool.