SOIL ANALYSIS OF A CATENA IN ORDER TO UNDERSTAND THE TERROIR AT JOHNSON SCHOOL VINEYARD, WASHINGTON COUNTY, OREGON

A catena study was conducted across harvest plots at Johnson School Vineyard in Washington County, Oregon in order to understand the soils, the terroir, and possibly find a reason for the range of fruit ripening rates within the vineyard. This 39.6 acre vineyard is located in the Chehalem Mountains AVA and owned by Cooper Mountain Vineyards. The Washington County Soil Survey mapped this area as the Cornelius and Kinton or Helvetia Soil Series. Six soil pits were dug; four of these were along an east-west catena from 341 to 200 feet asl transecting the mapped soils. This vineyard is located on highly weathered basalt bedrock that is overlain by old loess creating well-drained thick soils at elevations greater than 280 feet. Missoula Flood deposits occur at elevations less than 200 feet with a transition zone around 250 feet where the soils reflect a combination of having both parent materials. The catena included the Helvetia and Woodburn Series. These are described as an Ultic Argixeroll and an Aquultic Argixeroll, respectively. The Helvetia soils are well drained with abundant iron concretions in the A horizon, thick Bt horizons with moderate medium subangular blocky structure and common prominent clay films. The Woodburn Series is located at elevations less than 250 feet and had signs of being somewhat poorly drained because of Btg and Bg horizons. The absence of a fragipan suggests that the Cornelius and Kinton Series are unlikely to occur at this site.