Effects of nitrogen and irrigation on the quality of grapes and the susceptibility to Botrytis bunch rot

Nitrogen fertilization and irrigation are very important in commercial vineyards. The potential for increasing N fertilizer efficiency in vineyards should be improved with new information on N fertilizer timing, the grapevine's N demand, and maximizing irrigation efficiency. The aim of this study was to investigate the effects of nitrogen and irrigation on the agronomic characteristics of grapes and their susceptibility to Botrytis cinerea. Three nitrogen (0, 60, and 150 kg/ha) and two irrigation (irrigated at 60% of crop evapo-transpiration and non-irrigated) treatments were applied in a commercial vineyard. The results showed the immediate effect of supplying nitrogen in the form of ammonium on chlorophyll synthesis and photosynthetic capacity in the leaves of vines. High levels of N caused a substantial delay in the accumulation of sugars during ripening, while nitrogen fertilization significantly increased bunch weight. Irrigation did not influence chlorophyll concentration, the photosynthetic capacity, leaf N concentration, the susceptibility of grapes to Botrytis bunch rot and bunch weight Some effects of irrigation on the water potential and the chemical composition of wine were found. The results also showed that nitrogen increased the susceptibility of grapes to B. cinerea. There was a tendency of higher susceptibility to B. cinerea of irrigated plants than non-irrigated plants although there was no statistically significant difference. This study showed that nitrogen fertilization and irrigation of the vineyard affected the physiology of plants, the fruit quality and susceptibility to fruit rot. Therefore, nitrogen fertilization and irrigation of vineyards should be undertaken carefully to avoid negative effects and apply the best management practices that optimize N use and irrigation efficiency. The results of this study showed that a dosage of 150 kg/ha of ammonium nitrate is recommended in sandy loam soils with a relatively high pH. Irrigation of vineyards at 60% evapotranspiration rate is also recommended. (C) 2016 Elsevier B.V. All rights reserved.