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To develop fertilizer prescription equations based on soil test crop response (STCR) approach for rice-rice cropping sequence, trials were conducted at farmer’s field in Karikalampakkam village, U.T. of Puducherry, during 2015-16. Soil test data, yield and nutrient uptake by successive crops were recorded to calculate four basic parameters viz. nutrient required to produce one quintal of rice, contribution of nutrients from fertilizers, contribution of nutrients from soil and contribution of nutrients from FYM used in developing STCR based fertilizer prescription equations. The per cent nutrient contribution of nutrients from soil (CS), fertilizer ( CF) and FYM (CFYM) were found to be 19.15, 45.90 and 23.27 for N, 12.13,40.16 and 26.98 for P2O5 and 13.76, 79.64 and 41.07 for K2O respectively for rice cv. White ponni. The same for the rice cv.ADT 45 were 13.48, 40.46 and 34.26 for N, 15.81, 44.64 and 19.89 for P2O5 and 10.48, 58.64 and 41.51 for K2O respectively. Based on fertilizer prescription equations and nomograms formulated for a range of soil test values and desired yield target for the cropping sequence. It was revealed that under the treatment NPK + FYM @ 12.5 t ha- 1 , 47, 29 and 34 kg ha- 1 for rice cv.White ponni and 41 , 22 and 27 kg ha- 1 for rice cv.ADT 45 of fertilizer N , P2O5 and K2O, respectively could be saved for attaining target yield of 70 q ha- 1 compared to NPK fertilizers alone.

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Soil Test Crop Response correlation studies were carried out in maize under Integrated Plant Nutrition System (STCR-IPNS) on Typic Rhodustalf of Tamil Nadu, adopting “Inductive cum Targeted yield model”. The basic parameters for the “Targeted yield model” viz. nutrient requirement (NR), contribution of nutrients from soil (Cs), fertilizer (Cf) and farmyard manure (Cfym) were computed from field experimental data. Using these parameters, the fertiliser prescription equations were developed under IPNS and ready reckoner of fertiliser doses were formulated for desired yield target of maize for a range of soil test values. The quantity of fertilizer nutrients that could be saved due to the application of FYM @ 12.5 t ha-1 was assessed to the tune of 40, 20 and 26 kg fertilizer N, P2O5 and K2O respectively, when applied along with the NPK fertilizers. The per cent reduction in fertilizer N, P2O5 and K2O under IPNS increased with increasing soil available NPK.

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