Soil Test Crop Response (STCR)-Fertilizer Nitrogen Recommendations for an Yield Target of 70 qha-1 of Rice

A field experiment was carried out at an Experimental Farm, Annamalai University, Annamalainagar. The needed variation in soil fertility was deliberately created by dividing the field into 4 equal strips viz., I, II, III and IV. An exhaust crop of rice cv. ADT-43 was grown to enable through interaction between the nutrients in soil and added fertilizers. After the harvest, each gradient strip was divided into 24 plots. Treatments consisted of 5 levels of N (0, 50, 100, 150 & 200 kg ha^-1), 4 levels of P₂O₅ (0, 30, 60 and 90 kg ha^-1), 3 levels of K₂O (0, 40 and 80 kg ha^-1), 2 levels of FYM 0, 12.5 t/ha^-1 and 2 levels of Azospirillum, 0, 2 kg ha^-1 (Fractional Factorial Randomized Block Design). Rice (ADT-36) was grown as the test crop. At harvest, by using grain yield, N uptake, initial soil available N status and fertilizer doses applied the basic data viz., nutrient requirement kg ha^-1, soil and fertilizer nutrient efficiencies (%) were estimated for making fertilizer N recommendation. There was considerable reduction in the quantities of fertilizer N due to IPNS.