Because of their ability to sop up selenium, some plants have been enlisted in efforts to clean up soils and wastewater that have an excess of this potentially toxic element. Now Agricultural Research Service scientists have shown that the way contaminated irrigation water is delivered to plants affects how much selenium they will absorb from it.
Soil scientist Donald L. Suarez and plant physiologist Catherine M. Grieve, working with soil scientist James A. Poss, found that sprinkling -- rather than flooding -- kale and turnip plants with selenium-laden drainage waters allowed the plants to absorb almost twice as much selenium from the water. Suarez, Grieve and Poss are at the agency's George E. Brown Jr. Salinity Laboratory in Riverside, Calif.
Boosting plants' uptake of selenium creates a place to naturally "store" the element, thereby decreasing the amount of selenium that might otherwise leach into drainage and groundwater.
As a possible additional benefit, the selenium-enriched kale and turnip plants -- as well as other crops irrigated by sprinkling -- could be used to supplement the diets of livestock raised in selenium-deficient regions of the United States. Animals must consume some of this essential nutrient for optimum growth and stress tolerance.
Suarez expects the sprinkler method to work with other crops, so the findings are likely to aid growers who are interested in producing selenium-rich vegetables for health-conscious consumers.
Sprinkling water onto the crops takes advantage of plants' ability to absorb droplets of water through openings in their leaves. Plants can also soak up selenium from water via their roots. But because plant roots screen out some elements, leaf uptake can be a more effective way to capture the selenium.