Abstract
Dry matter and nitrogen (N) and potassium (K) partitioning were determined in the roots and trunks 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 increased until leaf fall. Root N concentration increased from the first of the calendar year, peaked midway between budbreak and anthesis, then decreased throughout the remainder of the growing season in the first year, but remained constant after anthesis in the second year. Root N concentration increased after fruit harvest in 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 N accumulated in the current season’s shoot growth (leaves, stems, and clusters) from budbreak to harvest in the first year of the study and for 4% in 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.
- Received March 2016.
- Revision received August 2016.
- Revision received February 2017.
- Revision received April 2017.
- Accepted April 2017.
- Published online September 2017
- ©2017 by the American Society for Enology and Viticulture
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