OENO One (May 2019)
Seasonal vine nutrient dynamics and distribution of Shiraz grapevines
Abstract
Aim: The nutrient reserves in the grapevine perennial structure perform a critical role in supplying the grapevine with nutrients when demand cannot be sustained by root uptake. The seasonal changes in these reserves largely depend on the developmental stage and the associated growth requirements. These stored reserves are, in turn, influenced by environmental conditions and vineyard management practices, such as production levels and water availability. The aim of this study was to assess the nutrient dynamics of a major wine grape variety grown in Australia to determine the key nutrient uptake periods and to understand the mobilization patterns throughout a season. Methods and results: The own-rooted 10-year-old Shiraz vines used for the trial were located in the Riverina, which is a hot inland grape-growing region in New South Wales, Australia. Uniformly sized vines, identified by trunk circumference, were selected for 11 excavation dates with four replicates, from a month before bud-burst to leaf-fall. The above-ground section of the vines were separated into the different perennial, vegetative and reproductive organs. The below-ground section of the vines were obtained in an allocated area (6 m2/vine) and were excavated to a depth of 1 m, and the roots were separated into rootstock and three root sizes. Sub-samples of each tissue were freeze-dried and the remaining tissues were oven-dried at 70°C, and for both procedures the dry weight (DW) was recorded. For the nutrient analysis, the tissue sub-samples were ground up, and nutrients were determined with an nitrogen analyzer and an ICP-OES. The annual organs showed the highest nitrogen (N) concentrations in spring, with the leaves having 3% and inflorescences 2.5%, but stem N concentration was highest at the end of the season with 0.7% DW. Root N concentrations are at least double the other perennial sections, with these reserves declining early in the season and being replenished by leaf-fall. The changes in concentrations for perennial sections are similar for the other macro nutrients, but differ for Ca and S in the annual tissues. The N content of the perennial structure declined considerably until flowering, with a sharp increase after harvest. The majority of the N uptake occurred four weeks before flowering and four weeks before veraison, and more than half the N of the vine was allocated to the annual organs at harvest. Other macro nutrients show a pattern of decline and replenishment in the roots and wood and most nutrients were taken up predominantly four weeks prior to flowering. Conclusions: An important finding from the study revealed that the amount of each nutrient allocated to the perennial structure and annual parts varied between the nutrients. This understanding of the nutrient dynamics will lead to an optimization of individual nutrient status and supply for grapevines. Significance and impact of the study: This is the first time that whole-vine nutrient levels were followed through the season under Australian conditions and on a wine grape variety for all macro nutrients. Such information is critical to allow precise prediction and modeling of grapevine nutrient requirements.
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