2019 ASHS Annual Conference

Strawberries are the third most valued crop in California ($2.3 billion) and the most sensitive to salinity. Limited information on the salt tolerance and chloride damage, associated with degrading quality of irrigation water, has led to significant yield losses in recent years. Strawberry yields, soil salinity and salts content in leaf blades of the two most popular public cultivars in California (Fronteras and Monterey) were assessed under eight salinity treatments on a randomized complete block design experiment in a commercial field located in Oxnard, CA during the 2017/2018 production season. The treatments consisted of increased salinity content of irrigation water, and they were determined based on irrigation water analysis from 40 commercial fields conducted during the prior season. The crop was planted on October 2017, and the salinity treatments were applied through the irrigation water delivered through the drip tape from November 2017 through June 2018. Irrigation amounts and timing were decided based on daily evapotranspiration estimations from a local weather station and based on tensiometer readings, respectively. Water-powered injectors mixed concentrated salt solutions with the irrigation water delivered on every irrigation from November 2017 to June 2018. The treatments consisted of two levels of elevated sodium adsorption ratio (SAR, 4.6 and 6.6), three levels of chloride (4.2, 7.7 and 11.7 meq/L), and two levels of elevated sulfate (18.3 and 26 meq/L of SO4). There were 60 drip irrigation events (2.0 acre-feet), and 54 harvesting days from December 2017 through June 2018. Composite soil and leaf blade samples were collected from each plot at early, mid and late production stages and analyzed for pH, ECe, Ca, Mg, Na, Cl, B, HCO3, CO3 and SO4-S (soil samples), and N, P, K, S, B, Ca, Mg, Zn, Mn, Fe, Cu, Na and Cl (leaf blade samples). Marketable yields of Fronteras were significantly (P<0.05) reduced with increasing chloride levels of 7.7 and 11.7 meq/L (13 and 17%, respectively). Although yields of all other treatments were lower than the control treatment, those differences were not statistically significant (P>0.05). Yields of the cultivar Monterey were not significantly affected by any treatment. Yield reduction of the cultivar Fronteras started before plant symptoms evident. Cull rates of both cultivars were not affected by the salinity treatments. Overall, the findings of this study conclude that the cultivar Fronteras is highly susceptible to elevated chloride levels, and that salinity effects on strawberry yield is cultivar dependent.