Effects of the Foliar Application of Magnesium and Zinc on the Yield and Quality of Three Grape Cultivars Grown in the Calcareous Soils of Iran

A completely randomized factorial block designed experiment was carried out at Maragheh region during 2007-2008 to evaluate the effects of the foliar applications of magnesium (Mg) and zinc (Zn) on the yield and quality of three grape cultivars. Factor one included three levels of Mg (0, 0.40 and 0.80% MgSO 4 x H 2 O); Factor two consisted of three levels of Zn (0, 0.20 and 0.40% ZnSO 4 .7H 2 O); and factor three involved three cultivars of grape (Vitis vinifera L.) namely ‘Sahebi’, ‘Soltani’ and ‘Ghezel’. The foliar applications were carried out in two stages, namely, during the enlargement of flower buds and three weeks after the flower petals dropped (late spring). Yield and quality characteristics such as total soluble solids (TSS), juice, pH and acidity were determined. The statistical analyses were performed using MSTATC software and Duncan tests. The analysis of variance demonstrated that the main effects of Mg, Zn and cultivars on yield were statistically significant at 1% level; and the interactive effects of the foliar application of Mg and Zn on the yield were significant at 5% level. The highest yield was obtained with the combined foliar applications of Mg and Zn-fertilizers. ‘Ghezel’ variety produced the highest yield of 47.11 tons ha -1 among the three cultivars. The main effects of Mg and Zn foliar application as well as of cultivars were significant. TSS contents were significant at 1% level. The highest pH values were obtained with the foliar application of Mg sulfate at 0.80% and Zn sulfate at 0.40%. Likewise, the main effects of foliar application of Mg and Zn were significant at 1% level in the lowering of juice acidity and K/Mg ratio. Foliar application did not decrease the K/Mg ratio to the desirable level, however in the deficient soils, foliar application was not enough. It means in additional of foliar application, soil application is also necessary for obtaining desirable grape yield and quality.