Dr. Gurreet Brar, Fresno State - Determination of Long-term Threshold Limits for Using Saline Water on Pistachios

Co-investigators: Dr. Sharon Benes (Fresno State), Dr. Todd Lone (Fresno State), Dr. Gary Banuelos (USDA-ARS, Parlier CA), Dr. Monika Summenhalter (Cal State East Bay), Dr. David Zoldoske (Fresno State), Dr. Ray Anderson (USDA-ARS, Riverside CA), Dr. Louise Ferguson (UC Davis), Dr. Lu Zhang (UC Davis).

ARI funding commitment: $298,114; Matching Funds: $329,227.

Most crops have little tolerance to drought or saline irrigation water, both of which increase stress making the plants more susceptible to disease and insects, which often leads to lower yield and quality. Pistachios, on the other hand, appear to be relatively tolerant to saline water over short periods of time.

Global warming is expected to increase the frequency, depth and duration of drought in California and the southwestern United States. In response to the record five-year California drought, growers turned to pumping groundwater, which is not without its problems. Pumping groundwater for irrigation is expensive and the water often contains salts, including boron and selenium. Growers use groundwater without a clear idea of how long they can use this lower quality water before it will damage the pistachio trees. Dr. Gurreet Brar’s group will address that issue by determining the threshold levels of Na and B that begin to disrupt cells, injure tissues and reduce pistachio yield. Experiments will be conducted in the field on trees that have been irrigated with saline water for several seasons. They will conduct controlled studies on younger trees to identify mechanisms that are disrupted by irrigating with multiple salinity levels. Their research will examine biophysical parameters affecting photosynthesis, assay biomarkers that are indicative of stress, and use scanning electron microscopy to examine the sub-cellular effects of Na and B loading as the duration of plant exposure to the low-quality water lengthens. This comprehensive study will also include economic modeling to draw out the relationship between saline irrigation and yields. Dr. Brar states the overall goal is to develop sustainability plans that growers can use to manage pistachio crops under an increasingly likely scenario where there is less high-quality water available for California.