Grapevine irrigation scheduling in the Po Valley sub-humid area

摘要

The aims of the trial, carried out from 1987 to 1998 on Trebbiano grafted on SO4, was to identify the most suitable irrigation regime in order to reach an high must quality level, to check the possibility to apply RDI on grapevine in the Po Valley and to evaluate the effectiveness of leaf temperature and crop water stress index (CWSI) for the irrigation scheduling of the grapevine. In the first phase of experimentation (1982-92) four irrigation regimes were compared: Rainfed; 50 percent, 100 percent and 150 percent of ETc replenishment. The water supply increases tile yield in the first three years (+23 percent), with relevant economic effects. This was related to the reduced competition between the vegetative and the reproductive sink in the first stages of the vineyard life. The 1982-92 average yield increase due to the irrigation was about 14 percent. No significant differences were observed among the ETc replenishment. The quality characteristics were the same in the rainfed as well as in theirrigated thesis. The leaf temperature in the irrigated treatments was less of about 2 deg C than in the rainfed. The results show that infrared thermometry can be used for tire grapevine irrigation scheduling whit a CWSI threshold of 0,4. In the secondtrial phase (1993-98) the tests in comparison were: ETc - water supply from the flowering end to the veraison, and RDI - water supply only during the fruit enlargement stage (from the cluster closure to the veraison), both according to the daily calculation of a water balance. In the subplots were compared the same irrigation regimes considered in the former phase. The RDI technique allows a reduction in the water use which ranges from 16,5 percent, in rainy years, to a maximum of 52,9 percent in dry years. The yield was not influenced by the application of the RDI technique, neither was the quality of the must. The vegetative growth was not modified in a significant way too. No interaction was observed among the irrigation regimes and the ETc and RDItechniques.