Assessing reserve nitrogen at dormancy for predicting spring nitrogen status in Chardonnay grapevines

Abstract

Context and purpose of the study – Nitrogen (N) supply strongly influences vine productivity and berry composition, matching availability and uptake requirements of vines during the growing season is essential to optimize vine nutrition. The nutritional status of grapevines is commonly assessed by the determination of petiole nutrient concentrations at flowering. The reserve N could also be an earlier indicator for grapevine N status, this work aimed to assess how the petiole levels relate to these perennial N reserves.

Material and methods – Five Chardonnay vineyards were planted two years prior and one Riverina vineyard 10 years prior to study commencement. The N levels in various perennial tissues and in the petioles at flowering were determined in these vineyards; vine productivity and berry ripeness were also assessed.

Results – The application of N fertiliser generally increased petiole N levels at bloom, the winter N reserves in root and spur tissues had a strong relationship with spring N status. A spur N concentration between 0.3 to 0.4 % and root N concentrations of 1.0 % relating to the lower value of the adequate range in the petiole at flowering (0.8 %). The determination of root and spur N during dormancy could assist in assessing N status, allowing for adjustment of N supply earlier in the season, prior to petiole levels at flowering are determined. However, it would be expected that the uptake between burst and flowering will alter petiole levels, which would be influenced by N fertiliser applications and by soil processes that are influenced by soil temperature and moisture.