Rootstock Tolerance to Soil Salinity: Impact of Salinity on Popular Grape Rootstocks Grown in Contrasting Soil Types
Summary (by Objective): To date, we have accomplished several major goals: Objective 1: Soil Characterization; Monitor the impact of salt accumulation on soil solution chemistry and nutrient balance. The two vineyard sites were selected based on preliminary soil analyses during Year 1. During Years 2 and 3, we performed additional, detailed chemical and physical analyses of the two contrasting soils. 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. In year 4, we applied a saline solution to the soil through the drip system and sampled the soil solution after the salt application. In Year 5, two additional salt applications will be performed; plant tissue and soil solution will be monitored concurrently in order to determine the relationship between soil properties and plant growth and nutrition. Objective 2: Determine the tolerance of a panel of ten rootstocks to irrigation water containing four different salinity levels. (a) Grafting and planting of 10 rootstocks and own-rooted controls at each of the two vineyard sites. The planting scheme was described in section IV above, and a map of one of the vineyard sites is provided in Appendix A. (b) Monitoring of the plants. As expected, some losses among the grafted rootstocks occurred during the first winter. Missing plants were replaced during Year 2 using additional grafted vines provided by the nursery, which had been designated for this purpose. During the warmest weeks of the summer, supplemental irrigation was given to the developing vines to prevent further losses. Subsequent losses, which were minimal, have not been replaced due to the larger size and maturity of the plants. (c) Application of saline irrigation solution. During Year 4, the irrigation system was locally modified to allow the application of solutions with a salinity level of 1.75 mS, 3.5 mS and 4.5 mS. The saline solution was applied using water-powered non-electric chemical injectors coupled with the drip line, during a single, 30-hour irrigation event that was coordinated with the vineyard management staff. The soil solution was sampled following the irrigation event using suction lysimeters buried at depths of 6 and 12 inches, and the chemical analysis of these solutions is ongoing. Leaves and petioles were again sampled at 2, 4 and 6 weeks after the saline solution was applied. The blade tissues are currently being analyzed for chloride ion (Cl-) content, as a marker for salt uptake by the plant tissue. The samples from week 4 are also being analyzed for other macro and micronutrients, as was done for the bloom and veraison samples. Results of these analyses are anticipated in Spring, 2012. In Year 5, two additional applications of saline solution will be performed and the results intensively monitored.