Fertilization with ZnO and ZnSO ₄ : Mineral analyses in Vitis vinifera grapes cv. Fernão Pires

Nutrition of the world population has become a concern, making research for strategies to enhance crop production necessary. Thus, the study of nutrients and the interactions between them is highly necessary since they are important for plant physiology and influence the growth of crops. Zinc is an essential micronutrient required for normal function of plants. Its deficiency is associated with losses in yield and nutritional quality. Vine, being a crop susceptible to Zn deficits, is among the most cultivated fruit plants in the world. In this study, the reactions of the variety Vitis Vinifera Fernão Pires, located in a field in Palmela, Portugal (N 38º 35'41.467 '' W 8º 50'44.535”), to three foliar sprays of ZnO and ZnSO₄ with concentrations of 150 g ha^-1 and 450 g ha^-1 were studied. Using a XRF analyzer, the mineral content of the grapes and leaves was determined, which showed increases in the contents of Zn. It was found that the highest concentration (450 g ha^-1) of ZnSO₄ and ZnO, led to increases of 1.3 and 1.9-fold respectively. Importantly, XRF analysis confirmed that K and P contents of ZnO and ZnSO₄-treated plants are similar to controls, indicating that there are no significant antagonistic and/or synergistic effects. Furthermore, to study the conditions of nutrient availability in the soil, parameters such as pH, organic matter and humidity were evaluated. This work showed that fertilization with ZnSO4 and ZnO was effective in increasing the concentration of Zn, without negatively affecting the contents of the crucial nutrients K and P, which is important to improve crop quality.