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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A laboratory experiment was conducted to examine the oxidation of elemental sulphur (Sa) in a red non-calcareous (Typic Haplustalf) soil. Different levels of S° (60 and 100 mesh size) at a rate equivalent to 1000, 5000 and 10000 mg kg were thoroughly mixed with soil and incubated for 120 days at 25°C+2°C. The oxidation was measured by the increase in the concentration of sulphur (SO4-S) in soil. The highest oxidation of 46.3 per cent was achieved when S° was added as finer particles (100 mesh) at a rate of 1000 mg S kg soil. The S' oxidation also resulted marked reduction in soil pH.