Modifying soil test based fertilizer p recommendations for targeted yield of rice on a typic haplustalf

The present fertility gradient field experimental technique of evolving soil test based fertilizer recommendations for specific yield target of crops is heavily biased towards high fertility of native and applied nutrients. This inclination vitiates the basic parameter of phosphate and leads to imprecise estimate of soil-P efficiency. Per cent P contribution from soil decreased with an increase in soil test values and it interacts strongly with other nutrients. In a case study with soil test based fertilizer recommendations for rice yield targets, some modifications for computing phosphorus contribution from soils were included. The new soil test based fertilizer calibrations in comparison with the existing ones greatly modified the fertilizer recommendations and were commensurate with response behaviour of crops under field conditions.