The Combination Effect of Potassium and Iron on Fruit Yield and Quality, Raisin and Cold Tolerance of Grapevine

In order to investigate the effect of foliar application of potassium sulfate (K2SO4; 0, 1.5 and 3 percent) and iron chelate (Fe-EDDHA; 0, 0.5 and 1 percent) on fruit set, fruit yield and quality, leaf mineral nutrient content, raisin yield and autumn and winter cold tolerance of ‘Bidaneh-Sefid’ grapevine, a factorial experiment was done based on randomized complete blocks design in a commercial vineyard in Bahareh village of Malayer city during 2016-17. The highest fruit set percentage and yield was achieved in 1.5 percent of K2SO4 in combination with 0.5 percent iron chelate. Berries K, Fe and Mn concentration had a positive and significant correlation with fruit yield per vine. Raisin yield was found to be highest in combined treatments of 1.5 percent K2SO4 and 1 percent Fe-EDDHA and the lowest raisin yield was related to control vines. The highest autumn cold hardiness was recorded in K2SO4 (3%) × Fe-EDDHA (1%) treated vines. However, the highest winter cold tolerance was achieved in K2SO4 (3%) × Fe-EDDHA (0.5%) treated vines. The lowest cold tolerance was observed in control vines. There was a positive and significant correlation between cold tolerance and K content and negative correlation with Mg concentration. Totally, the highest fruit and raisin yields and their desirable qualities were obtained with K2SO4 and Fe-EDDHA at moderate concentration. However, the highest buds cold tolerance was obtained with the combination of these fertilizers at higher doses.