Effects of foliar application of the mixture of copper and chelated iron on the yield, quality, photosynthesis, and microelement concentration of table grape (Vitis vinifera L.).

• The mixture of copper and chelated iron (Cu-Fe) adhered to grape leaves uniformly. • Grape yield and photosynthesis was improved by application of the mixture (Cu-Fe). • The mixture (Cu-Fe) decreased the Cu accumulate in plant and soil. In the present study, a two-year field experiment was conducted with the V. vinifera 'Kyoho' grape in the Yellow River Delta of China. It tested the effects of the mixture of copper and chelated iron (Cu-Fe), a novel product on the basis of copper-based foliar fertilizer (CFF), on grape microelement concentrations, leaf photosynthesis, quality, and yield of grape plant. Grape yield in 1.0 g L−1 Cu-Fe treatment exceeded the control, Bordeaux mixture, Kocide 2000, and 1.0 g L−1 CFF treatments by 10.1–10.2%, 7.5–9.7%, 4.1–4.3% and 2.6%–3.7%, respectively. Levels of soluble solids, soluble sugars, sugar: acid ratios, and vitamin C, were higher in 1.0 g L−1 Cu-Fe treatment than the control or Bordeaux mixture treatment. Indices of leaf photosynthesis also were increased by spraying 1.0 and 2.0 g L−1 Cu-Fe compared with Bordeaux mixture and control, because of its improved wettability and uniformity on grape leaves. Leaf Fe concentrations in the Cu-Fe treatments were increased by 20.1–48.6% compared with other treatments, and the Cu content of leaves sprayed with 1.0 g L−1 Cu-Fe was significantly decreased by 67.3% compared with the Bordeaux mixture. In 2015, levels of soil available Cu were significantly lower when the mixtures of copper and iron-chelate was applied instead of Bordeaux mixture, because of the lower contact angle on grape leaves. Hence, compared with Bordeaux mixture, application of 1.0 g L-1 Cu-Fe led to higher leaf Fe concentrations, yields, and fruit quality of grape plants, while lowering the levels of Cu within the plants and soil. [ABSTRACT FROM AUTHOR]