Water supply and Nitrogen fertilization influence water relations, transpiration, photosynthesis and dry matter accunmlation in the grapevine. In Piedmont (NW Italy) White Muscat is not irrigated, so that water supply is only from rainfall, butNitrogen must be yearly provided to vines. In this report 0, 40, 80 and 160 N units/ha/year have been provided for four years to a grass-covered vineyard after many years without fertilization. Effects on production resulted only after two years. Yield increased with increased N fertilization, but sugar accumulation in the berries decreased and total acidity increased, suggesting a perturbation in the maturation process. Vegetative growth was higher in fertilized plants, and higher was the fraction of shaded leaves (inside the canopy) in relation to sunny leaves that were directly exposed to the sun. In more fertilized, vigourous plants Botrytis damage in berries was higher. 40 N units/ha/year has been suggested as the best compromise between vegetative and productive performances.
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