ASHS 2024 Conference

Over 85% of California's bearing pistachio acreage is located in soils with moderate (4 dS/m) to extremely high (16 dS/m) saline. Several previous studies have demonstrated that pistachios can be grown profitably even in moderately saline soils, with optimal soil salinity (ECe) maintained at approximately 4.5 - 6 dS/m. One common practice to reduce the salinity level in rootzone is to apply good quality water during dormant season. As the availability of good quality canal water for in-season irrigation and dormant season leaching declines, growers are relying more on semi-saline pumped groundwater, particularly in the San Joaquin Valley Westside. It would be beneficial to understand if the volume of dormant season leaching could be reduced, if in-season methods of leaching could be effective, and how to use moderately saline water most efficiently for both dormant and in-season leaching. Current methods for managing salinity through dormant leaching rely on one-dimensional models assuming complete surface wetting. We are exploring alternative approaches, investigating the effectiveness of single and double drip lines in managing root zone salinity using in-row, in-season leaching fractions and small volume pulsed dormant leaching. Preliminary results showed that generally, all leaching treatments, (in-season leaching, dormant leaching and the combination of both, applied with both single and double hose lines, significantly decreased soil ECe relative to the control, reducing ECe values of 13-22% relative to their respective controls. All the leaching treatments also effectively prevented boron from accumulating in the soil relative to the control. No clear effects of line configuration, double versus single line, were detected in soil levels. These findings indicate that treatments are effectively reducing salinity or at least preventing the increases observed in the control. Leaf analysis showed that in-season leaching, with/without dormant leaching, significantly increased leaf nitrogen and phosphorus, and reduced leaf boron accumulation.