Grapes (Vitis vinifera L.) are widely cultivated in Iran. One of the major problems involved in cultivating and exploiting this fruit crop is the deficiency of some nutrient elements including microelements. In general, due to the problems facing most of Iran’s soils such as lime and high pH, and the inability of these soils to absorb microelements, especially iron (Fe), zinc (Zn), and manganese (Mn), foliar application of fertilizers has a significant effect on the quantitative and qualitative traits of grapevine. In addition, leaf spraying due to the high absorption of the elements by the vine can dramatically decrease fertilizer uses and increase the economic efficiency of the berries. It should not be forgotten that the foliar application of nutrient elements also solves the problems associated with the entry of elements into the groundwater and reduces significantly the environmental impact of soil application of fertilizers. Therefore, to solve this problem, the present study was conducted to investigate the effect of foliar application of micronutrients including Fe, Zn, and Mn on qualitative and quantitative characteristics of grapevine cv. Thompson Seedless. The experiment was conducted with four concentrations of Fe, Zn, and Mn combination (0.00, 2000, 3000, and 5000mg/L) with three replications on vines at two times including before flowering (May) and after flowering (June). The results showed that the highest values for bunch length, number of berries, berry length, and total soluble solids were related to June application, and the highest values for bunch width, bunch weight, berry width, and berry weight were observed in May. Therefore, foliar application of microelements to save time and cost is recommended before flowering (in May).
