GROWTH, YIELD, AND ION RELATIONS OF STRAWBERRY IN RESPONSE TO IRRIGATION WITH CHLORIDE-DOMINATED WATERS

Abstract

Strawberry is listed as the most salt sensitive fruit crop in comprehensive salt tolerance data bases. Recently, concerns have arisen regarding declining quality of irrigation waters available to coastal strawberry growers in southern and central California. Over time, the waters have become more saline, with increasing sodium (Na⁺) and chloride (Cl⁻). Due to the apparent extreme Cl⁻ sensitivity of strawberry, the rising Cl⁻ levels in the irrigation waters are of particular importance. In order to establish the specific ion causing yield reduction in strawberry, cultivars ‘Ventana’ and ‘Camarosa’ were grown in twenty-four outdoor sand tanks at the ARS-USDA U. S. Salinity Laboratory in Riverside, CA and irrigated with waters containing a complete nutrient solution plus Cl⁻ salts of calcium (Ca²⁺), magnesium (Mg²⁺), Na⁺, and potassium (K⁺). Six salinity treatments were imposed with electric conductivities (EC) = 0.835, 1.05, 1.28, 1.48, 1.71, and 2.24 dS m⁻¹, and were replicated four times. Fresh and dry weights of ‘Camarosa’ shoots and roots were significantly higher than those of ‘Ventana’ at all salinity levels. Marketable yield of ‘Camarosa’ fruit decreased from 770 to 360 g/plant as salinity increased and was lower at all salinity levels than the yield from the less vigorous ‘Ventana’ plants. ‘Ventana’ berry yield decreased from 925 to 705 g/plant as salinity increased from 0.835 to 2.24 dS m⁻¹. Relative yield of ‘Camarosa’ decreased 43% for each unit increase in salinity once irrigation water salinity exceeded 0.80 dS m⁻¹. Relative ‘Ventana’ yield was unaffected by irrigation water salinity up to 1.71 dS m⁻¹, and thereafter, for each additional unit increase in salinity, yield was reduced 61%. Both cultivars appeared to possess an exclusion mechanism whereby Na⁺ was sequestered in the roots, and Na⁺ transport to blade, petiole and fruit tissues was limited. Chloride content of the plant organs increased as salinity increased to 2.24 dS m⁻¹ and substrate Cl increased from 0.1 to13 mmol_cL⁻¹. Chloride was highest in the roots, followed by the leaves, petioles and fruit. Based on plant ion relations and relative fruit yield, we determined that, over the range of salinity levels studied, specific ion toxicity exists with respect to Cl⁻, rather than to Na⁺ ions, and, further, that the salt tolerance threshold is lower for ‘Camarosa’ than for ‘Ventana’.

Keywords:

• chloride toxicity
• fruit yield
• ion partitioning
• sodium exclusion

ACKNOWLEDGMENTS

We are indebted to Donald A. Layfield for mineral ion analysis of plant tissues, Nahid Vishteh for ion analysis of the irrigation waters, and Phyllis Nash for statistical analyses. James Poss, James Wood, John Draper and Doug Diaz provided invaluable technical assistance. Sierra-Cascade Nursery, Susanville, CA donated the runner plants, and Sierra-Cascade staff members H. C. Larsen and Christopher Winterbottom generously shared their expertise in strawberry management. The research was supported in part by a grant from the California Strawberry Commission, Dan Legard, Director, Production Research and Information.

This article not subject to US copyright law.Received 23 June 2011; accepted 9 November 2011.