Grapevine nutritional diagnosis methods for the « Serra Gaúcha » viticultural region, Brazil

Abstract

The methods of grapevine nutritional diagnosis used in Michigan, California, and South Africa were evaluated with the objective to assess and adjust values of these methods for the Brazilian conditions. The study was carried out in 53 vineyards in the Serra Gaúcha viticultural region, State of Rio Grande do Sul, Brazil, from 1995/96 to 1997/98 (25 of these vineyards were Cabernet Sauvignon and 28 Italie Riesling). All these vineyards were conducted in the pergola system. Data of yield, °Brix, total titratable acidity, density, and pH of the grape must, the concentration of macro- and micro nutrients in the leaves as well as data from soil analyses were assessed. The yield of each vineyard and the concentration of the mineral nutrients in the tissue were correlated. The final adjustments were made by means of the method of the critical threshold using the NCRIz criterion. The method of California was the less precise as it neither establishes defined border values for the sufficiency level nor takes some nutrients into account. The method of Michigan needed few adjustments because of its origin; for this it may be considered viable for the nutritional diagnosis, mainly for American cultivars. Out of the three methods, the South African proved to be the most appropriate for diagnosing the nutritional status of the grapevine cultivated in the Serra Gaúcha, because it did not need adjustments for most nutrients.