N, P, and K supply to Pinot noir grapevines: Impact on berry phenolics and free amino acids

Authors: Schreiner, Roger; Scagel, Carolyn; Lee, Jungmin

Submitted to: American Journal of Enology and Viticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2014
Publication Date: 3/15/2014
Publication URL: http://ajevonline.org/content/65/1/43.abstract
Citation: Schreiner, R.P., Scagel, C.F., Lee, J. 2014. N, P, and K supply to Pinot noir grapevines: Impact on berry phenolics and free amino acids. American Journal of Enology and Viticulture. 65:43-49.

Interpretive Summary: The impact of nutrient supply on Pinot noir berry composition was investigated in a pot-in-pot, sand culture vineyard. Grapevines were grown with varying nutrient supply (nitrogen, phosphorus, and potassium) and managed to minimize differences in vine water status and shading of fruit, eliminating indirect effects on berry chemistry. Vines grown under reduced nitrogen supply had lower levels of amino acids and YANs but higher levels of some phenolics. Results show that reducing nitrogen supply can improve berry color (anthocyanins), but this positive effect on berry composition did not occur until crop yield and berry YAN were greatly depressed. An increase in berry tannins and phenolic acids under low N supply, however, may be possible before yield is significantly reduced.

Technical Abstract: Understanding the direct role that the macro nutrient supply (N, P, and K) has on berry chemistry was evaluated in Pinot noir grapevines grown in sand culture using a pot-in-pot system. Self-rooted Pinot noir vines were grown for three years under three reduced levels of either N, P, or K supply while holding all other nutrients constant. Vines were managed to minimize differences in vine water status (altering irrigation to achieve similar daily soil moisture content) and fruit cluster solar exposure (altering leaf pulling to achieve similar cluster irradiance) due to varying nutrient supply, so that indirect effects on berry chemistry could be largely eliminated. Berry chemistry was evaluated in the second and third years after different nutrient supply treatments were imposed. Results showed that low N, but not low P or K, altered berry free amino acid (FAA) and phenolic profiles. Low N vines reduced FAA and resulting yeast assimilable nitrogen (YAN) in both years by up to 70% with certain FAA’s altered more than others, thus changing berry FAA profile. The concentration of anthocyanins also increased in low N vines after the third season, with bigger increases in delphinidin- and petunidin-based anthocyanin. Condensed tannins and total phenolic acids were increased in low N vines across both years. Results indicate that low N supply alters YAN to the greatest degree, while anthocyanin enhancement does not occur until yield and berry size were also reduced. Increased concentrations of tannins and phenolic acids may occur under low N supply prior to reductions in yield and berry size.