DRIS norms for evaluating the nutrient constraints in pomegranate orchards

A survey was conducted during 2019-20 in Vijayapur district, Karnataka where pomegranate is being extensively cultivated. Leaf samples (n=80) for selecting 8^th pair of leaves (counting from the growing tip) from the new growth in the month of August for February crop collected and analysed for macro and micronutrient status. A data bank was established to develop nutrient diagnostic norms and identification of most yield limiting nutrients using Diagnosis and Recommendation Integrated System (DRIS) approach. The entire population was divided into two i.e low- and high-yielding population based on cutoff yield of 150 fruits tree^-1. Fifty-six nutrient expressions were chosen as diagnostic norms in pomegranate: K/N (0.431), N/S (18.5), P/B (0.002), Ca/S (29.59), B/K (368.7), Ca/P (8.661), Zn/Mg (40.87), B/Zn (8.463), Fe/B (0.759), and Cu/B (0.159) etc. which showed lower co-efficient of variation compared to others and therefore, those might have a greater physiological rationale of pomegranate productivity. Calcium and sulphur were the most yield limiting nutrients in low yielding lime orchards through DRIS indices followed by Boron and Copper. By using mean and standard deviation, five nutrient standards were derived as deficient, low, optimum, high and excess for each nutrient. The optimum leaf N, P, K, Ca, Mg, and S ranged from 1.30 to 1.55, 0.20 to 0.33, 0.41 to 0.67, 1.60 to 2.55, 0.55 to 0.77 and 0.07 to 0.09 per cent, respectively. Similarly, the optimum Fe, Mn, Zn, Cu and B ranged from 89.42 to 166.21, 29.06 to 56.50, 16.23 to 29.97, 18.56 to 34.76, and 169.59 to 226.80 µg g^-1, respectively. The interpretation tool, DRIS thus identified the nutrient imbalances in realizing the higher yield levels. The optimum nutrient ranges can serve as a guide for the routine diagnosis and advisory purpose in pomegranate with regional readjustments for better efficacy.