Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 10, 2001
Publication Date: N/A
Interpretive Summary: There is an increasing trend in using poor quality water for irrigated agriculture in central California. The suitability of poor quality water for irrigation is, however, dependent on both the level of salinity and solute concentration of selenium and boron and the crop's tolerance to salt. Among the ions, selenium is of particular concern because it is reported to cause toxicity in many biological systems, including waterfowl Research by the WMRL has demonstrated that phytoremediation with Brassica crops can be used to manage sele nium in the soil by plant uptake. In this field study broccoli and canola were irrigated with selenium-rich water. Both plants' accumulated selenium and reduced selenium levels left in the soil. Growing broccoli and canola as recipients for Se-laden effluent will likely be preferred choices by the growers because of their familiarity with the crops because of their market value. However, both of these crops swill likely not tolerate high salt and B levels in the soil. thus, salt management will be essential in soils receiving this quality of water for long term use.
Technical Abstract: Many drainage waters can be used successfully to grow some crops without long-term hazardous consequences to crops and soils. Certain ions in saline drainage waters can be specifically toxic to plants, if pres in excessive concentrations. Of particular concern in the San Joaquin Valley of California are Na, Cl, B, and Se. Careful salt management with leaching is problematic in soils loaded with Se from irrigation with salin drainage water. For this reason, an alternative technology, phytoremediation, has been developed for managing Se by plant accumulation. In this two-year study, the WMRL evaluated Se accumulation in canola and broccoli irrigated with poor quality water containing salts, Se, and B under typical field conditions in the westside of central California. Canola was directly seeded on 7.5 ha and broccoli planted as transplants on 2.5 ha. Water used for irrigation had levels of Se (100-300 ug/L), B (3-5 mg/L), and a sodium sulfate dominated salinity (EC = 5-8 dS/m). Soil samples were taken prior and postharvest to a depth of 90 cm and canola and broccoli samples were collected at harvest. All samples were analyzed for Se, B, as well as extractable Se and EC in soil samples. Based upon the total amount of Se applied via irrigation, canola and broccoli extracted 12 and 18% respectively. Additional losses of Se (around 17%), occurred presumably by biological volatilization, in soils planted to both crops. Tissue Se concentrations did not exceed 5 mg/kg DM in both species. Based on two years of data, both broccoli and canola can be safely grown with poor quality water. However, salt and especially B management will be essential in soils receiving this quality of water for a longer period of time.