Mineral Composition of Young Rabbiteye and Southern Highbush Blueberry Exposed to Salinity and Supplemental Calcium

‘Tifblue’ and ‘Brightwell’ rabbiteye blueberry (Vaccinium ashei Reade) and ‘Sharpblue’ southern highbush blueberry (primarily V. corymbosum) were treated with 0, 25, and 100 mM Na as Na2SO4 or NaCl, and 0, 1, 3, and 10 mM supplemental Ca in sand culture in the greenhouse. For rabbiteye plants salinized with Na 2 SO 4 , leaf Na concentrations increased 54-fold and the percentage of total plant Na found in the leaves increased from 9% to 63% with increasing external Na. Calcium supplementation reduced the Na concentrations in leaves by up to 20%. Leaf Ca concentrations increased with Ca supplementation, but accounted for a decreasing percentage of the total Ca found in the plant, since root Ca concentrations were much higher. Root Na concentrations increased with increasing Na treatments to a smaller extent than in the leaves and were also reduced by Ca supplements. Potassium concentrations in leaves and roots decreased with increasing Na treatment levels, particularly in roots, where K concentration was about half at 100 mM Na (as Na 2 SO 4 .) Leaf Na concentrations were up to two times greater when Na was supplied as NaCl compared to Na2SO4. For plants salinized with NaCl, leaf Na + levels increased to 1.1% and did not decrease when supplemental Ca was applied. Leaf Cl concentrations also increased greatly with NaCl, reaching >1.0% (dry weight basis.). Root Cl concentrations also increased with increasing salinity and were not affected by Ca supplements. Ca supplementation led only to a greater Ca concentration in leaves and roots, but this did not alter Na concentrations. Nutrient concentrations in ‘Sharpblue’ leaves, stems, and roots were greater than those of the rabbiteye cultivars, but were influenced by salinity and Ca in essentially the same way. Excess Na, Cl, or both, together with lowered K, were likely the cause of extensive leaf necrosis and may be indicative of a lack of a mechanism to control Na influx into blueberry leaves. Rabbiteye and southern highbush blueberries require optimumquality water to thrive and produce. Water pH levels >7.0, total bicarbonates (HCO 3 ) >1.5 mM, total Na >2.0 mM, and total Cl >4.0 mM indicate poor-quality water (Haby and Pennington, 1988). While the nutrient composition of rain and surface water seldom exceeds these thresholds, it is often inadequate during midsummer and early fall, when irrigation demands are high. Lower-quality groundwater, which sometimes exceeds the thresholds, must then be used. Groundwater in eastern Texas may contain NaCl or NaHCO 3 – salts or both, and often exceeds 15 mM Na, 6 mM Cl, and 10 mM NaHCO 3 – (Texas Department of Health, 1990). The most damaging effects of saline water on rabbiteye blueberry growth are reported to be due to high concentrations of Na rather than HCO 3 – (Haby et al., 1986). Fresh weight gain of potted plants irrigated with well water containing 7.83 mM Na was only SOC. HORT. SCI. 119(2):229–236. 1994. for publication 27 Jan. 1992. Accepted for publication 7 June 1993. on from the Texas Agricultural Experiment Station (paper no. TA d supported in part by the Expanded Research Area Fund of the t station. We thank Fincastle Nursery, La Rue, Texas, and Finch Nursery, C., for generously donating the plants used in this study. The cost of this paper was defrayed in part by the payment of page charges. Under lations, this paper therefore must be hereby marked advertisement solely