Response of leaf parameters to soil applications of iron-EDDHA chelates in a peach orchard affected by iron chlorosis

Knowledge of iron (Fe) deficiency parameters implied in diagnosis is fundamental to establish the effectiveness of applied amendments. In the present work, the effects on different plant parameters of three doses (10, 20, and 40 g/tree) of two commercial brand Fe-EDDHA chelates (Ferrishell plus and Group Carla Val F.E.A 6 Superior) were analyzed in a peach orchard affected by iron chlorosis. The treatments were applied into soil by injection at the beginning of June. Fe-EDDHA application produced a minimum increment of 25% leaf surface and an 8% increment in foliar fresh weight. The lowest dose affected chlorophyll content significantly, producing an increase of 21% in relation to the control, whereas higher doses did not significantly increase the chlorophyll content. Active Fe in leaves augmented as the dose was increased, but total Fe in leaves only increased after applying greater doses of chelate, showing that active Fe is a more sensitive parameter to plant iron status than total Fe. Stepwise regression analysis indicated that P and leaf area explain 61% of the variability in chlorophyll. The leaf area was positively correlated with chlorophyll showing that Fe deficiency limits leaf growth. P content was also positively correlated with chlorophyll. Active Fe and chlorophyll concentration were not well correlated although chelate application produced differences in both variables among treated trees and the control. Chelate type affected P concentration in leaf, with Carla Val producing higher P content than Ferrishell plus. The main difference between both chelates lay in its K content. Attending to chlorophyll content, the optimum dose in peach trees affected by iron chlorosis varied for each chelate type. When low to medium doses of Fe chelate were applied, good responses were obtained.