Soil and foliar fertilization affects mineral contents in Vitis vinifera L. cv. 'rebula' leaves

Grapevine nutrient oversupply as well as shortage can both result in unbalanced vine growth and poor grape production. Mineral fertilization is a powerful tool also in viticulture in order to increase yields and improve grape quality. The trial carried out in Slovenian winegrowing region investigated the effects of basic fertilization coupled with soil or foliar applications of fertilizers containing Mg and Fe on the concentration of K, Mg, Fe and Zn in the grapevines leaves at berry set and veraison. The results obtained in a 2-years study (2008-09) with seven different fertilization treatments (along with control) showed that fertilization with K decreased Mg uptake almost on a half comparing to untreated vines, resulting in basal leaves chlorosis. High K/Mg ratio, determining low Mg uptake, was not lowered in our trial neither by foliar spraying nor by fertirigation with MgSO4 solution. On the other hand, Mg application in addition to Fe supply had same effect on soil Zn uptake and its accumulation in the leaf petioles. Moreover, foliar Fe fertilization enhanced Fe levels in blades at berry set and to a lesser extent also at veraison.