Development of Leaf Nutrient Norms and Identification of Yield-Limiting Nutrients Using DRIS in Sapota cv. Kalipatti

A survey was conducted in 106 orchards growing sapota cv. Kalipatti in Raichur, Dharwad and Belgaum districts of Northern Karnataka for developing leaf nutrient norms through Diagnosis and Recommendation Integrated System (DRIS) for nutrient management. Leaf samples collected were processed and analyzed for macro-and micronutrient status and a data bank was established. The entire population was divided into two sub-groups, namely, low-and high-yielding types to derive the norms. Fifty-five nutrient expressions were chosen as diagnostic norms using DRIS, which have shown higher variance and lower coefficient of variation that are found to have greater diagnostic precision viz., N/K (1.731), N/Ca (0.928), Mg/N (0.360), Fe/N (99.89), N/Cu (0.104), N/B (0.037), Mg/Ca (0.329), Ca/B (0.040), Mg/S (1.103), Fe/Mg (278.6), Mg/Zn (0.037), Mg/B (0.013), Fe/Zn (10.39) etc. The nutritional balance index (NBI) indicated an overall imbalance of nutrients based on sum of the indices, irrespective of sign. Diagnosis of nutrient imbalance through DRIS indices indicated that potassium, boron and zinc to be the most common yield-limiting nutrients in the orchards. In addition, five nutrient ranges/standards were derived using mean and standard deviation as deficient, low, optimum, high and excess for each nutrient, to serve as a guide for diagnostics. Optimum leaf N ranged from 1.51 to 2.09%, P from 0.06 to 0.15% and K from 0.83 to 1.44%. The optimum concentration ranged from 1.36 to 2.34% for Ca, 0.54 to 0.68% for Mg and 0.48 to 0.80 for S. Among the micronutrients, optimum Fe, Mn, Zn, Cu and B concentrations ranged from 109 to 206 mg kg^-1, 49 to 99 mg kg^-1, 13.3 to 21.9 mg kg^-1, 3.76 to 9.10 mg kg^-1 and 34.8 to 66.8 mg kg^-1, respectively, for sapota cv. Kalipatti.