Effect of nitrogen and potassium fertilization on productivity and fruit quality of ‘crimson seedless’ grape

The effect of the nutritional status of grapevine 'Crimson Seedless' on growth, fruit set and quality was studied in two growing periods.The vines were treated with three nitrogen rates (24, 36, 48 kg/ha.)combined with three potassium levels (240, 285, 330 kg/ha).Increasing N supply enhanced N-concentrations in the petioles.N-fertilization also increased K concentrations in the petioles.The K-fertilization variants themselves did not alter the K content of the petioles.High Nfertilization improved vegetative growth (leaf area, cane diameter) and reduced bud burst, bud fertility and fruitfulness.Excessive N-supply negatively affected yield per vine by reducing the number of fruit clusters.Cluster size, however, was improved with increasing N-nutrition whereas the number of berries per cluster and the cluster compactness remained unchanged.The single berries were bigger (size, weight) and their shape remained typically for the cv.The amount of juice per berry increased and fruit firmness decreased in the high N-variants.The only effect of high K fertilization was an increase of total soluble solids and a decrease of acid concentration.Anthocyanin contents generally showed a high variability in the experiment.Therefore, the color of berries might be more regulated by the ripening process than by the fertilizer treatments.