Characterizing Willamette Valley Soil Moisture and Grapevine Response under Drying Seasonal Conditions

Soil moisture, weather data, and vine growth response were measured in 2020 in one vineyard location that had Pinot noir of the same vine age, clone and rootstock growing in three soil types, including volcanic soils (Saum), sedimentary soils (Dupee), and marine sediment soils (Willamette Woodburn). Soil sensors measured soil moisture, soil temperature, and electrical conductivity for each soil type. Soil probes were installed to a depth of 18 and 36 inches under[1]vine and in the middle of the alley between rows. Soil moisture remained relatively consistent through much of spring, with the start of soil moisture decline beginning in mid-June. This occurred shortly after bloom, and continued throughout the rest of summer, when there was little to no precipitation. Vine growth measures of leaf area and lateral count did not vary in-season, but dormant season pruning weights show that the most vigorous vines grew in the Willamette[1]Woodburn soil. Vine vegetative vigor was similar for Dupee and Saum. Soil moisture decline was greatest at the 18” depth and varied less at the 36” depth, and the greatest decline occurred with Willamette-Woodburn, suggesting that the higher vigor vines required more water from the soil profile than vines in the other two soil types. Leaf water potential did not show clear differences in vine water stress of the three soil types. Berry weight lagged slightly for Willamette-Woodburn, but there were no differences in the overall growth curve through development. By harvest, yields were similar from each soil type. However, the Willamette Woodburn had lower Brix and sugar per berry compared to the other two soil types. Data analysis from the 2020 season continues as of this reporting. This research will continue through two additional growing seasons (2021 and 2022).