Fertilizer Potassium Doses Based on STCR for an Yield Target of 70 qha-1 or Rice Cv. ADT-36

Soil test crop response (STCR) correlation studies were conducted by gradient crop experiment-rice (ADT43) and then Test crop experiment-rice (ADT-36) at an Experimental Farm, Annamalai University, Annamalainagar. The field layout comprised four strips (I, II, III & IV), in which the needed variation in soil fertility for potassium was deliberately created (Dev et al., 1978). After the harvest, each gradient strip was divided into 24 plots which were received 5 levels of nitrogen @ (0, 50, 100, 150 & 200 kgha^-1), four levels of phosphorus (0, 30, 60 and 90 kgha^-1), three levels of potassium (0, 40 and 80 kgha^-1), Two levels of FYM (0.1, 2.5 t/ha^-1) and Azospirillum levels were (0, 2 kgha^-1) (Fractional Factorial Randomized Block Design). Rice(ADT-36) was grown as the test crop. At harvest, grain yield ,K uptake, initial soil available K status and fertilizer K₂O applied were noted plot-wise. The NR kgq^-1, CS% and CF% values for potassium were 1.50, 10.67 and 54.05, respectively. The per cent contribution of K from FYM and FYM+Azospirillum were found to be 28.79 and 29.72, respectively. These data have been transformed in the form of simple equations. The results revealed that at an initial soil available potassium status was 350 kgha^-1, the FK₂O requirement to get an yield target of 70 qha^-1 of rice was 111 kgh^-1 with fertilizer alone, whereas the FK₂O requirement reduced to 86 kgha^-1 with fertilizer+FYM+Azospirillum application.