Growth of ‘Thompson Seedless’ Grapevines: II. Nitrogen Distribution

Abstract

Nitrogen content and concentration were determined on field-grown ‘Thompson Seedless’ grapevines in the San Joaquin Valley of California. Individual vine replicates were harvested throughout the growing season over a 3-year period. There was a linear increase in vine N content from budbreak to 1000 growing degree days (GDDs) later. During this time, the accumulation of N was primarily in the stems and leaves. Subsequent to 1000 GDDs, the increase in vine N was due to the accumulation of N in the clusters. Throughout the season, N concentration in all vine parts decreased. The increase in cluster N content did not appear to occur at the expense of N remobilization from the vegetative structures measured in this study. On a single date, the N concentration of leaves varied throughout the canopy—the outer layer of leaves contained 3.2% N, while leaves in the interior of vine contained 2.4% N. The loss of N from the vine through leaf fall and cane pruning was about 20 and 15 g, respectively. The data were similiar from year to year with regards to both N concentration and content in leaves, stems, and clusters when plotted vs. GDDs. The approximate requirement of N for current season’s growth of ‘Thompson Seedless’ grapevines used for raisin production was 75 g/vine, or 84 kg·ha -1 .