The Effect of Iron, Zinc, and Calcium Trunk and Root Injections on Fruit Characteristics and Leaf Mineral Content in...

This study evaluated the effects of trunk and root injections of iron (Fe), zinc (Zn), and calcium (Ca) on fruit characteristics and leaf mineral composition of "Mazafati" date palm (Phoenix dactylifera L. cv. "Mazafati") under orchard conditions in Kerman Province, Iran. A randomized complete block design with nine treatments was applied to 15-year-old palms: trunk injection of ferrous sulfate (25, 75, 150 g L^-1), root injection of ferrous sulfate (75 g L^-1), trunk injection of zinc aminochelate (2, 4 g L^-1), trunk injection of calcium aminochelate (3, 5 mL L^-1), and an untreated control (n = 3 replications). Fruit physical traits and leaf mineral concentrations were measured at the rutab stage and ~100 days post-injection, respectively. Data were analyzed using ANOVA, Pearson correlation, and stepwise regression. Trunk injection of Fe at 150 g L^-1 maximized flesh weight (16.38 g) and seed weight (1.31 g), while Zn at 4 g L^-1 yielded the highest total fruit weight (17.59 g). Fe injection significantly increased leaf Fe, Mg, and Ca concentrations; Zn injection elevated leaf Zn and K but reduced Fe and Mg. Pearson correlations revealed positive Fe-Mg (r = 0.42) and Fe-Ca (r = 0.38) associations, and negative Zn-Mg (r = -0.41) and Zn-Fe (r = -0.30) interactions. Stepwise regression identified fruit flesh weight and leaf P as the strongest predictors of fruit weight (R ² = 82.1%, p ≤ 0.01). Trunk injection of Fe (150 g L^-1) and Zn (4 g L^-1) at optimized dosages significantly improved key fruit traits and leaf mineral status in "Mazafati" date palm. However, observed nutrient antagonisms (e.g., Zn-Fe, Zn-Mg) underscore the need for balanced fertilization strategies. This approach shows promise for enhancing productivity in calcareous soils where conventional uptake is limited, though multi-season trials and economic analyses are recommended before wide-scale adoption.