Rootstock Tolerance to Soil Salinity: Impact of Salinity on Popular Grape Rootstocks Grown in Contrasting Soil Types

The major goal of this study is to define the tolerance of particular winegrape rootstocks for saline irrigation conditions. This project addresses a problem of major importance for irrigated vineyards in California. The rootstocks and soil types in this study have been specifically selected for their relevance to the California winegrape industry. The soil types in the study area are extensive in the central and southern Coast Ranges, an area of rapid vineyard expansion. During the first year, we accomplished two major goals:

1. Vineyard site selection, soil sampling and soil characterization.
   The two selected vineyard sites are underlain by contrasting soils. Site 1 contains soil profiles in the Arbuckle series, classified as fine-loamy, mixed thermic Typic Haploxeralfs. These soils contain a thick argillic (clay) horizon and have moderately slow to slow permeability. Site 2 contains soils of the Hanford series, with parent material rich in coarse sand and gravel. These soils are classified as coarse-loamy, mixed, non-acid, thermic Typic Xerorthents. They are coarse textured, welldrained soils with little to low runoff and moderately rapid permeability. These two distinct soil types should provide good contrast for the irrigation studies proposed in this project. Soil chemical analysis is currently underway and will lead to a soil map of the area.
2. Grafting and planting of 10 rootstocks and own-rooted controls at each of the two vineyard sites.
   During the first year of this project, ten different rootstocks were grafted with Cabernet Sauvignon scion and planted at the two designated vineyard sites. A total of 352 vines were planted at each site. Eighty-eight vines (8 replicates of each rootstock plus ownrooted controls) were planted in each of four rows; the four rows will each be subjected to different saline irrigation conditions beginning in Year 2. The rootstocks were selected based upon their popularity and known hardiness in salt-affected soils; for comparison, a few rootstocks with expected intermediate and low salt tolerance were also included. The final list of rootstocks included 101-14 Mgt, 110R (Richter), 1103 P (Paulsen), 140R (Ruggeri), 1616C (Couderc), Harmony, Freedom, Ramsey (Salt Creek), Schwartzmann, and St. George. Ownrooted Cabernet Sauvignon vines (clone 7) were used as a control. The plants are currently being monitored for growth characteristics but were too small for tissue sampling and analysis to be carried out during Year 1.

Having accomplished these two important goals during Year 1, we hope to proceed during Year 2 to begin the irrigation studies, along with detailed soil water sampling and plant tissue sampling. This project benefits from excellent cooperation with an industry collaborator, who also supplies field labor and some technical support.