R Paul Schreiner*
*USDA-ARS, 3420 NW Orchard Avenue, Corvallis, OR, 97330 (paul.schreiner@usda.gov)

The primary goal of this work was to assess whether a wider vertical shoot-posi­tioned (VSP) trellis achieved by using cross arms can improve yield without compro­mising quality for Pinot noir grown in a cool region. A second goal was to understand how vine density influences the response to a wider trellis. These questions are being examined in a 2 × 2 × 2 factorial vineyard experiment with the following factors: a wide versus narrow VSP trellis; a high versus low in-row vine density; and a low versus high crop load. The vineyard was planted in 2015 (clone 115, 101-14 rootstock) and was irrigated and fertilized to avoid stress during establishment. By 2019, vines were only irrigated in late summer when leaf water potential fell below -1.3 MPa. The crop level treatment was first implemented in 2021 by cluster thinning. Vines grown on the wider VSP trellis intercepted more sunlight near midday and produced larger canopies than vines grown on the narrow VSP in 2021. Leaf area and pruning weights were both 12% greater in the wide VSP vines, although sunlight interception increased by only 7%. Greater pruning weights were also recorded in the wide VSP vines in 2019 and 2020. High-density vines also had greater pruning weights in the prior two years, but this effect was lost in 2021. Leaf water potential was lower in the wide VSP vines on a single measurement day in 2021, but soil moisture was not altered by any treat­ment. Yield was only altered by the crop load treatment imposed, with nonthinned vines producing 40% more fruit. Soluble solids were reduced slightly in these high-crop vines, but pH and titratable acids were not affected. It will be interesting to see how these factors influence productivity and fruit composition in future years.

Funding Support: USDA-ARS