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Abstract
A greenhouse study was conducted in sand cultures to compare the effects of saline irrigation waters applied by two different methods, flooding and above‐canopy sprinkling, on selenium (Se) accumulation by the forage brassicas, kale (Brassica oleracea L., cv. “Premier”) and turnip (B. rapa L., cv. “Forage Star”). The composition of the irrigation water was designed to simulate saline (7 dS m−1) drainage effluent commonly encountered in the San Joaquin Valley of California, and being evaluated for reuse by irrigation of salt tolerant crops. The experimental design was a randomized complete block with two irrigation methods, two plant species (kale and turnip), four Se concentrations (0.25, 0.50, 1.0, and 2.0 mg L−1 Se–SeO4 2−), and three replications. Kale was generally a more efficient Se accumulator than turnip. Shoot Se concentrations in kale and turnip increased with increasing Se in the irrigation waters regardless of irrigation method. Selenium was readily taken up by the leaves of the sprinkled plants to give shoot‐Se concentrations that were two‐ to three‐fold higher than in plants of the same cultivar grown under flood irrigation. Both kale and turnip can accumulate Se to concentrations that would be toxic to animals if exclusively fed this material. These Se‐enriched forages may be useful as an additive to Se‐deficient fodders in order to meet the nutritional requirements of livestock. The potential for phytoremediation of Se contaminated soils or waters is greatly enhanced by sprinkler irrigation via the mechanism of foliar absorption of Se. This enhanced uptake is especially important in the presence of elevated sulfate concentrations, which normally reduce Se uptake by plants.
Acknowledgments
The authors are indebted to Jennifer Hopper for selenium analysis, Donald A. Layfield for mineral ion analysis, and Phyllis Nash for statistical analysis.
