DRIS standards for identifying yield-limiting nutrients in Khasi Mandarin and their relationship with fruit yield on acidic soil of the eastern Himalayas, India

Abstract

Mandarin fruits are the most widely grown citrus fruits in the world, particularly in the eastern Himalayas of India, which is the primary center of citrus diversity. Diagnosing potential nutritional imbalances using leaf tissue analysis is a mandatory practice for a higher yield. Regarding the nutritional diagnosis of Khasi mandarin plants, particularly in the acidic soil of the hilly ecology of the Eastern Himalayas, India, there is currently no information available. Therefore, the present study was conducted to identify nutrient constraints, establish leaf-based diagnostic recommended and integrated system (DRIS) norms, and determine nutrients’ relationship with fruit yields in 144 orchards. The result showed that the DRIS indices predicted a nutritional optimum value for Khasi mandarin: 2.26–2.83% N, 0.11–0.16% P, 1.86–2.07% K, 1.85–2.12% Ca, 0.33–0.48% Mg, 170.10–225.10 mg kg−1 Fe, 74.03–83.43 mg kg−1 Mn, 1.24–2.45 mg kg−1 Cu, and 19.84–21.28 mg kg−1 Zn. The DRIS norms identified the nutrients Zn, P, Ca, K, N, and Mg as deficient to low levels (14.15→2.14), while Fe, Mn, and Cu were at high to excessive levels (5.50→18.25). The nutritional balance index had a significantly negative relationship with the fruit yield. Leaf nutrient concentrations of N (0.909**), P (0.827**), K (0.867**), Zn (0.833**), Ca (0.827**), and Mg (0.592**) had a significant positive correlation with fruit yield. The finding will facilitate the correct interpretation of leaf nutrient analysis, and the norms developed will enable a precise intervention through nutrient management for higher yields in mandarin citrus.