Effect of vineyard nitrogen
Background
Nutrition in the vineyard is an important part of viticultural management, given the nature of Australia’s old, weathered and inherently infertile soils. Nitrogen has a significant impact on vine physiology and, as a consequence, is one of the major drivers of vine vigour and production. While there is a significant body of literature on nitrogen nutrition, much of the early work focused on manipulating nitrogen in the vineyard to increase yield. More recently, researchers have extended their studies to look at some grape quality components but there are still areas that are not well understood. We have almost no knowledge of the impact of nitrogen supplementation on the secondary metabolites such as tannins and aroma and flavour compounds. Given that nutrition management is a very important part of any vine management program, we aim to efficiently use nutrient management to produce fruit that meets winery specifications in an economic and envronmentally sustainable manner.
Progress
In the first season of this trial, the results confirmed that the site chosen (Langhorne Creek) was low in nitrogen and thus responded to the application of nitrogen. Initially, the shoots were visibly stunted with very short internodes and small leaves. The application of nitrogen increased the shoot length and the rate of shoot extension (vigour).
As expected, the application of nitrogen fertiliser increased the concentration of ammonia, total amino acids and yeast assimilable nitrogen (YAN) in the berry at each sample date and in a dose dependent manner. In contrast, the yeast non-assimilable nitrogen (YNAN) decreased in response to nitrogen application. While both proline and arginine increased in response to nitrogen, the proline to arginine ratio decreased as has been previously reported in the literature. Interestingly, the application of nitrogen increased the concentration of pathogenesis-related (PR) proteins in the berry at harvest and this included both the thaumatin-like and chitinase proteins. While this is not of great significance for Shiraz wines, being a red variety and one that accumulates relatively low levels of PR proteins, it might have significance for other varieties such as Sauvignon Blanc which accumulate high concentrations of PR proteins that are often associated with haze formation in white wine.
Currently this trial has now been expanded to include small-scale winemaking, and chemical and sensory characterisation of Shiraz wine produced under a variety of vineyard nitrogen regimes is currently being undertaken.
Highlights
- The application of nitrogen fertiliser increased the concentration of ammonia, total amino acids and yeast assimilable nitrogen (YAN) in the berry at each sample date and in a dose dependent manner
Project leader: Dr Sally-Jean Bell
Project team members:
Publications:
875 Bell, S.-J.; Henschke, P.A. Implications of nitrogen nutrition for grapes, fermentation and wine. Aust. J. Grape Wine Res. 11; 242-295 : 2005 (click here to order).