The objective of this work was to evaluate the effect of the plastic greenhouse on the maturation of Red Niagara (Vitis labrusca L.) grapevines. The experiment was carried out in Bento Gonçalves, RS, Brazil, from July 1994 to January 1995. There were two cultural systems (greenhouse and natural condition) and three pruning times for each system (July 21 and August 1st and 11). The variables evaluated in the must were ºBrix, density, pH, total acidity, and ºBrix/total acidity. Grapevines cultivated in the greenhouse accelerated the process of maturation in all pruning times. Grape maturity was anticipated from 17 to 25 days (average of 21 days) when reached 15ºBrix and from 20 to 33 days (average of 27 days) with 18ºBrix, varying according to the pruning time. However, considering the greenhouse effect on both the grapevine phenology and the pruning time, grapevines early pruned showed an anticipation of harvest of 32 days when compared to the normal pruning time in the Serra Gaúcha region. This anticipation of grape maturation could allow prices five times higher when harvested with 15ºBrix than those obtained with grapes grown in the natural condition.
protected crop; plasticulture; table grape; viticulture
