Defining phosphorus requirements for Pinot noir grapevines

Authors: Schreiner, Roger - Paul; OSBORNE, JAMES - Oregon State University

Submitted to: American Journal of Enology and Viticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/8/2018
Publication Date: 10/1/2018
Citation: Schreiner, R.P., Osborne, J. 2018. Defining phosphorus requirements for Pinot noir grapevines. American Journal of Enology and Viticulture. 69(4):351-359. https://doi.org/10.5344/ajev.2018.18016.
DOI: https://doi.org/10.5344/ajev.2018.18016

Interpretive Summary: The phosphorus requirements for grafted Pinot noir grapevines were evaluated over four years using a pot-in-pot vineyard that allowed for precise control of phosphorus supply. The impact of phosphorus on vine vegetative and reproductive growth parameters, and on fruit composition and fermentation behavior of musts was used to define phosphorus needs and were equated to leaf and petiole tissue tests. Phosphorus supply had the greatest impact on must phosphorus levels, but the lowest must phosphorus reached here had no impact on yeast fermentation. Phosphorus limitation influenced canopy size and yield when leaf blades at veraison had 0.10% phosphorus or less. Phosphorus did not alter flower development in Pinot noir, opposite of previous research in other cultivars. Guidelines for managing phosphorus in Pinot noir are given.

Technical Abstract: A study to examine the phosphorus (P) requirements for Pinot noir was carried out using a microplot vineyard where P inputs were carefully controlled. Pinot noir grafted on 101-14 rootstock was exposed to four levels of P supply delivered via fertigation beginning in their fourth growing season. Vine nutrient status, productivity, and must chemistry were studied over four years (2012-2015), and fermentation dynamics were evaluated over three years (2012-2014). Phosphorus supply primarily influenced vine productivity by reducing leaf area at veraison and reducing yield which occurred after 3 years only in vines that received no P fertilizer. Flowering and fruit set were not altered by low P status. Phosphorus supply had the most significant impact on must P levels that were reduced in the two lowest P supply treatments the first year that P was altered. However, must P concentrations as low 32 mg P/L did not influence the time for yeast to complete alcoholic fermentation. These findings suggest that P limitation reduces canopy size and yield of Pinot noir before it alters flowering parameters or reduces must P concentrations to a level low enough to alter fermentation. A P concentration of 1.0 g P/kg DW in leaf blades at veraison is proposed as the critical level where P reduces growth and yield of Pinot noir when vines are cropped at levels typical for premium wine production in the region. Growers should closely monitor vine P status when leaf blade P at veraison approaches 1.2 g P/kg DW in western Oregon Pinot noir vineyards to account for sampling and laboratory error.