Déficit hídrico regulado na fase de maturação da uva “Superior Seedless” na Região do Vale São Francisco.

Abstract

The viticulture in the São Francisco Valley region has been growing at a significant pace in this decade, being responsible for about 90% of table grape export of the country in 2004. Irrigation practices have been adjusted in order to meet the need to culture water e to reduce irrigation water costs. The aim of this work was to evaluate the Superior seedless table grape when subjected to controlled water in the maturation stage of the grape, the water use efficiency and post-harvest performance, in the submédio region of the São Francisco River, in Casa Nova, Bahia. The statistical design was in random blocks, in a factorial scheme of 3x3 with four replicates, with timing of irrigation cut-off of irrigation depths (at 21,13, and 5 days before harvest) and three liquid blades of irrigation applied ( 100% ETc, 50% ETc and 0% ETc) and an additional treatment which represented the grower´s practice. The vines used between 335 mm and 390 mm of water in the production cycle, with a water economy of 48.5%and 94.5% for the deficit treatments in relation to the treatment that received the highest amount of water during the maturation stage of the grape. The soil water matric potential varied from -4 kPa beforematuration up to a maximum -73.6 kPa during treatment application. Water use efficiency varied between 6.42 kg.m-3 to 9.32 kg.m-3 of water , and the pre-dawn leaf water potential ranged from -0.1 MPa to -0.25 MPa and mid-day leaf water potential between -1.0 MPa and -1.8 MPa. The average grape diameter, bunch weight and yield were not significantly affected at the Duncan´s 5% level, however the number of bunches varied between 29 to 38, with weights of from 610 g to 690 g. The firmness was not influenced by the regulated deficits applied in the post-harvest conservation. The values of SS, AT and the SS/TA relationship at harvest were all equal or higher than export standards, ranging from 15.9 ºBrix to 17.2 ºBrix, 0.43 g of tartaric acid/100ml of juice to 0.467 g of tartaric acid/100ml of juice and SS/TA relationships between 35.66 and 39.72. In the post-harvest conservation period the values of SS varied from 15.81 ºBrix to 16.68 ºBrix, the TA varied from 0.42 g of tartaric acid/100ml of juice to 0.46 g of tartaric acid/100ml of juice, whereas the SS/TA varied from 37.76 to 36.35 at 28 days from cold chamber storage.