|Sharmasarkar, Shankar - CALIF STATE UNIV FRESNO|
Submitted to: Journal of Plant Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 15, 2001
Publication Date: N/A
Interpretive Summary: Drainage water reuse is a proposed strategy for reducing the volume of saline drainage water produced in the westside of central California. Saline effluent collected in some regions of central California contains trace elements, selenium (Se) and boron (B). Without a means of safely disposing of Se and B-laden drainage water, irrigated agricultural soils producing such an effluent may be taken out of production. In our multi-year field studies we evaluated the growth, salt tolerance, and trace element accumulation in crops and trees that were irrigated with drainage waters containing high levels of salinity, Se, and B. Crops were first established with good quality water and then furrow-irrigated with drainage water based in part on evapotranspiration losses. Results showed that total dry matter yields decreased in the following order for crops surviving at least two growing seasons: canola > broccoli > alfalfa > Indian mustard > alkali sacaton > tall fescue (both tree species died in second year). Concentrations of tissue Se ranged from a low of 1.1 mg/kg in leaves of paulownia trees to a high of 6.2 mg/kg in canola leaves. These low concentrations of Se allow growers to consider safety when utilizing the plant products as Se-enriched animal forage. Long-term studies are essential to evaluate the sustainability of a drainage water reuse system on the better preforming crops as salinity and B levels gradually increase in the soils with continued irrigation of drainage water.
Technical Abstract: Several strategies to utilize or dispose of drainage effluent containing selenium (Se) include disposing of this effluent on salt and boron (B) tolerant crops and trees. Of particular concern in the San Joaquin Valley of central California are the natural-occurring trace elements B and Se. In our multi-year field studies in the westside of central California, the WMRL evaluated plant tolerance and trace element accumulation in different plants and trees irrigated with effluent that had an average composition of sulfate-dominated salinity (EC = 6-10 dS/m), 0125-0.375 mg/L). All field sites were furrow-irrigated with drainage water based in part on evapotranspiration losses. All perennial crops consumed more drainage water than annual crops on an annual basis. Total dry matter yields decreased in the following order for crops surviving at least two growing seasons: canola > broccoli > alfalfa > I. Mustard > alkali sacaton > tall fescue. Selenium levels were greatest in Brassica species (up to 6.2 mg/kg) and B concentrations were generally similar in all leaves from all species. High tissue Cl levels were primarily responsible for the decreased yields, and B to a lesser extent. A sodium sulfate dominated salinity of the drainage water was likely responsible for the low tissue levels of Se in all plants. These low concentrations of Se allow growers the opportunity to utilize the products as Se-enriched forages. Although reusing poor quality water was successful for three years , management of increasing salt and B levels in the soil will be necessary.