Seasonal variation in leaf nutrient concentration of grapefruit

Leaf samples of ‘Star Ruby’ grapefruit (Citrus paradisi Macf.) were collected from fruiting terminals (FT) and non-fruiting terminals (NFT) at monthly interval during the growing period to study the nutrient dynamics. The mean nutrient concentrations for N, P, K, Zn, Cu and Mn were found higher in the leaves from non-fruiting terminals (2.21%, 0.13%, 2.07%, 20.81 ppm, 10.68 ppm, 17.06 ppm) as compared to fruiting terminals (1.60%, 0.12%, 2.01%, 18.87 ppm, 9.92 ppm, 15.88 ppm). However, the mean nutrient concentrations for Ca, Mg and Fe were recorded higher in the leaves from fruiting terminals (4.10%, 0.412%, 145.50 ppm) as compared to nonfruiting terminals (3.94%, 0.367, 141.51 ppm). Similarly, K, Mg, Zn and Cu contents were higher in younger leaves, while, Ca, Fe and Mn contents were more in older leaves. There were non-significant variations in the content of N, P, K, Ca, Mg, Fe, Zn, Cu and Mn in the leaves from FT and NFT during September-October. The dynamics of leaves micronutrient content showed higher intensity of seasonal variations than the macronutrient content. The regression analysis explained the correlation between type of terminals and the linear regression in leaves accounted 86, 75 and 79% variability in data for the N, K and Mn, respectively.