Journal of Crop Production and Processing

Application of humic acid as an organic acid derived from humus and other natural resources along with iron could be beneficial to overcoming, at least in part, the nutrients deficiencies in the grapes. In order to evaluate the effects of humic acid and iron on fruit yield and concentration of nutrient elements in the leaf of grape, a factorial experiment based on a randomized complete block design in three replications was done during growing season of 2013- 2014. The treatments included combinations of humic acid (control, 1 and 2 per thousand) and ferrous sulfate (control, 1 and 2 per thousand), sprayed in two steps (i.e. before flowering and two weeks after fruit set). The results indicated that treatments significantly increased the grapes fruit yield, e.g. the maximum yield (8.27 kg per plant) was obtained when 2 per thousand of iron sulfate was applied. The above treatments significantly affected nitrogen, iron, zinc and copper content of leaves. Foliar application of ferrous sulfate increased leaf iron concentration, i.e. the highest (189.6 mg per kg tissue) iron content was observed at the presence of 2 per thousand ferrous sulfate treatment.  Positive correlations were observed between the leaf iron concentration with fruit yield, cluster weight, berry diameter, leaf chlorophyll concentration and TSS of fruit. Hence, foliar application of humic acid and iron sulfate (e.g. each at a two per thousand concentrations) in vineyards might be effective in increasing quality and quantity of grapes.