Rootstock Tolerance to Soil Salinity: Impact of Salinity

During Years 1 thru 3 of this project, we made progress towards all three Objectives. For Objective 1, we identified two suitable vineyard plots containing contrasting soils, then sampled and characterized the soil profiles present within these plots. The results of these analyses confirmed the differences in morphology and texture between the two soils, and also revealed differences in cation exchange capacity, hydraulic conductivity, and plant available water. These differences will likely have a significant impact on plant growth and nutrient uptake. For Objective 2, we grafted and planted the various rootstock-scion combinations at both sites. By the end of Year 2, the plants were sufficiently large and well established that we were able to sample petioles and blades at harvest time. Following discussions with the vineyard management staff, the research team decided collectively that the vines were still too small to safely begin treatment with saline water conditions during Year 3. Accordingly, during Year 3 we proceeded with Objective 3, continuing to study baseline differences in plant nutrient uptake, comparing the 10 different rootstocks to one another within a single soil type, and comparing vine replicates grown on identical rootstocks in the two contrasting soil types. There were significant differences between rootstocks for all nutrients studied. In most cases, the rootstock rank order was similar for vines grown on the Alfisol and those grown on the Entisol; however, there were many exceptions to this trend. For the coming year, as described in the renewal application for Year 4, saline irrigation will begin in spring 2011. In Years 4 and 5, plant nutrient uptake and soil solution chemistry will be monitored concurrently in order to determine the relationship 2 between soil salinity and plant nutrition, and to compare rootstocks. This study constitutes a limited rootstock trial employing a panel of 10 rootstocks commonly used in California, comparing two soil types that are also common in California winegrowing regions. This project has high potential for generating information of relevance to California winegrape growers, as it will be one of the most comprehensive studies to date analyzing the effects of soil salinity on specific rootstocks.