Efficiency of foliar application of different sources of iron with zinc sulfate on increasing the quantitative and qualitative characteristics of pistachio ‘Ahmad Aghaei’

Due to the calcareous and high pH of the soil in most pistachio growing areas of Iran, the absorption of some elements such as iron and zinc from the soil by pistachio trees is difficult. Under these conditions, foliar application of nutrients is a better way to supply nutrients to deficient plants than to soil application. For this purpose, the efficiency of foliar application of different sources of iron along with zinc sulfate on the quantitative and qualitative characteristics of pistachio ‘Ahmad Aghaei’ was investigated in a completely randomized design with three replications. The experiment was carried out on 8-years old pistachio trees (cv. Ahmad Aghaei), which had been grafted on Fandoghi rootstock, at a commercial orchard in Pakdasht, Iran. Iron citrate (0.2 and 0.4%), iron sulfate (0.2 and 0.4%) or iron chelate (0.1 and 0.2%) in combination with zinc sulfate (0.1 and 0.2%) was carried out in early June and early July (at the filling stage). Pistachio fruits were picked up during the commercial harvest period, when the fruit reached a physiological maturity stage signalled by a reddish hull. The results of analysis of variance revealed that the effect of treatments on all studied traits was significant. The highest splitting rate (%) was obtained by iron citrate 0.4% + zinc sulfate 0.2%. The results of the Pearson correlation coefficients among the traits showed that there is a negative correlation between splitting rate (%) with small nut (%) and blankness (%) as well as a positive correlation with dry weight of 100 nuts, which shows that weight of nuts is the main cause of splitting rate. Foliar application of different sources of iron in combination with zinc sulfate led to a significant reduction in small nut (%) and blankness (%) so that the highest these two traits were related to control 1 (distilled water) and control 2 (common fertilization in the region). The fresh weight of 100 nuts from 140 g in control 1 reached to highest level (162.3 g) in iron citrate 0.4% + zincn sulfate 0.2%. The highest dry weight of 100 nuts was also related to this treatment. Foliar application of different sources of iron with zinc did not significantly increase total chlorophyll compared to controls. According to this study, in pistachio orchard with sandy loam soil in Pakdasht region, spraying of trees with different sources of iron (especially iron citrate) in combination with zinc sulfate could improve the qualitative and quantitative characteristics of pistachio.