NITROGEN AND WATER MANAGEMENT STRATEGIES FOR WINE-GRAPE QUALITY

The effects of vineyard nitrogen (N) application timing and irrigation strategy on fruit quality and amino-N (proline and arginine) composition of Vitis vinifera 'Shiraz' were investigated. Three irrigation treatments (PRD, RDI and standard practice (STD) were factorialised with three nitrogen (N) applications (bloom to veraison, post-harvest, and split application bloom to veraison/post-harvest). No interactive effects of N and irrigation treatments were found. However, RDI decreased yield, decreased berry size, achieved ripeness (22.5 °Brix) earlier and increased berry anthocyanin concentration compared with STD. PRD had no effect on yield, berry anthocyanin concentration or berry weight, but the vines were harvested one week earlier than were the STD vines. A high level of N applied at bloom to veraison delayed ripening, and resulted in a lower berry anthocyanin concentration. Juice arginine concentration was highest in response to bloom to veraison N application, and decreased with irrigation treatment in the order: STD > PRD > RDI. PRD and RDI decreased the proline concentration in the juice compared to STD. RDI and post-harvest N application increased the juice proline:arginine ratio. These results suggest that N application timing and irrigation strategy can have implications for the fermentation process as well as fruit quality.