Effect of Nitrogen, Zinc, Boron, and Magnesium and Time of Foliar Application on Quality and Quantity of Rainfed Grapevine

In order to investigate the effect of nitrogen, zinc, boron, and magnesium and the time and stages of foliar application on the grapevine (Vitis vinifera L.), a factorial experiment in the form of a randomized complete block design was conducted for three years. Treatments consisted of 12 fertilizer treatments including C1 (Control), C2 (N), C3 (Zn), C4 (B), C5 (Mg), C6 (N + Zn), C7 (N + B), C8 (N + Mg), C9 (Zn + B), C10 (N + Zn + B), C11 (Zn + B + Mg), and C12 (N + Zn + B + Mg) and two spraying times (T1= One-stage foliar application in the bud swelling stage and T2= Two-stage foliar application in bud swelling stage and after fruit formation). The results showed that nutrient foliar application treatments at two foliar application times and in three consecutive years did not have a significant effect on vegetative growth characteristics, including leaf area size and branch diameter, but it had a significant effect on yield components and fruit quality like cluster weight, berry weight, berry size, the yield of each shrub, anthocyanin, soluble solids (TSS) and total acidity (TA) of fruit. The tripartite interaction of year, foliar application time, and nutrient treatment had a significant effect on yield, panicle weight, and anthocyanin. The highest average of fruit yield per tree in three years was observed in C2 (N), C3 (Zn), and C4 (B) treatments, respectively, and almost all treatments showed a significant difference compared to the control. The grapevines that received no dietary treatment, along with C10 (N + Zn + B) and C11 (Zn + B + Mg), had the lowest fruit yields, respectively. Therefore, it can be concluded that despite the usefulness of spraying nitrogen, zinc, and boron nutrients, the use of nutrients together has negative effects on rainfed grapes.