Differential Susceptibility of Strawberry to Salts

Strawberry is a primary crop in five counties in coastal California, with an annual value of $ 1.4 billion.  Strawberry is sensitive to injury from salts, abundance of which is measured with soil electrical conductivity (EC). Even though current EC threshold for yield reduction is 1 dS/m, several strawberry fields have excellent production in soils with EC 4–6 dS/m. Thus, we investigated the specific salt and ion effect on strawberry in summer and fall-planted bare-root strawberry in typical 1.2 m-wide raised beds covered with plastic mulch in clay loam soil near Santa Paula, CA. Four plants were watered by hand nine times during initial 3-week establishment period with 250 mL/plant of one of the four salt solutions (each salt at EC 5, 10, 15, or 20 dS/m) or with distilled water. At EC 5 dS/m potassium sulfate or sodium sulfate did not significantly reduce plant size or fruit production in summer or fall strawberry, while plants irrigated with sodium chloride or calcium chloride were 65% or 85% smaller than distilled water irrigated plants. At greater EC values plant size declined 50% to 80% for the sulfates and no live plants were observed in plots irrigated with chlorides at EC >5 dS/m. A similar trend was observed for fruit production. The negative effects of all salts were more pronounced in summer, likely due to higher evapotranspiration rates, lack of rain and greater susceptibility of proprietary variety to salt damage compared to fall-planted 'Benicia'. The study identified specific salt and ion effects on strawberry and emphasized the need for testing of the irrigation water for those ions instead of relying solely on EC measurements for production management decisions.