Yield, berry quality and physiological response of grapevine to foliar humic acid application

Environmentally friendly grape growing is an important objective of modern viticulture. The aim of the study was to examine the response of two grapevine Vitis vinifera L. cultivars to humic acids (HA) foliar application as biostimulant in order to provide sustainable viticultural practices for farmers. The experiment was carried out under field conditions and repeated in two consecutive years. In order to evaluate the effect of humic acids application, the grapevines were treated with three concentrations: 30 ml.L-1 (HA(T1)), 40 ml.L-1 (HA(T2)) and 50 ml.L-1 (HA(T3)). The grapevines were represented by two grape varieties: cv. Feteasca Regala (cv. FR) and cv. Riesling Italian (cv. RI). Foliar sprays with humic acid derived from vermicompost at a concentration of 50 ml.L-1 induced a significant increase in the total leaf area, yield and total soluble solids. For several measurements performed in plants we found no significant difference between grapevines treated with HA(T2) and those with HA(T3). The experimental results in the present study confirm that foliar application with humic acid may improve growth, yield, and berry quality attributes of grapevine.