Evaluation of Leaching Strategies for Salinity Control On Drip Irrigated Table and Wine Grapes.

Irrigation of table and wine grapes in arid environments results in salinity buildup between the rows, the extent depending on soil texture irrigation rates and climatic conditions. Since grapes are sensitive to salinity, the management issue is, how much leaching is necessary and what is the best method of leaching. In this experiment we evaluated salinity leaching resulting from either no additional leaching (control) or application of two volumes of water equivalent to 5 and 15 cm of water during the vine dormant season in wine grapes. Leaching was either by either drip or sprinkler, for a total of 5 treatments and 3 replications. We evaluated two soil types in a coastal CA climatic regime and one sandy soil under a southern CA interior valley regime. We utilized both soil samples and a 56 electrode electrical resistivity system to determine 2 dimensional water and salinity profiles within the plots. Based on these two sets of measurements we established that on sandy soils leaching by sprinkler was more effective than by drip using equivalent quantities of water. At the sites with soils of higher clay content leaching at depth was comparable for both irrigation system in the interrow area and drip resulted in better leaching in the vine row region in the upper depths of the profile.