Abstract
Dry matter and N and K partitioning was determined in the roots and trunk of five and six-year-old field-grown Thompson Seedless grapevines over the course of two growing seasons using destructive harvests. Trunk and root dry biomass decreased slightly from leaf fall the previous season until midway between budbreak and anthesis during the current season, at which time dry matter accumulation began and continued to increase until leaf fall. The concentration of N increased from the first of the calendar year in the roots, it peaked midway between budbreak and anthesis, then decreased throughout the remainder of the growing season the first year but remained constant after anthesis the second year. The concentration of N in the roots increased after fruit harvest both years. Total N in the root system somewhat followed a pattern similar to that of N concentration. The concentration of K and total K in the root system varied only slightly throughout the growing season. The loss of N in the trunk and roots accounted for ~ 11% of the N accumulated in the current season’s shoot growth (leaves, stems and clusters) from budbreak to fruit harvest the first year of the study and 4% the second year during the same time frame. Approximately 85% of the increase in total N in the roots and trunk (16.9 g N/vine) after fruit harvest the second year was due to N translocation (14.4 g N/vine) from the leaves as they senesced. Under the conditions of this study, N reserves in the permanent structures of the vine contributed only slightly to the N demand of the current season’s new growth between budbreak and fruit harvest.
- ©2017 by the American Society for Enology and Viticulture
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