Submitted to: Book Chapter
Publication Type: Book / chapter
Publication Acceptance Date: 11/1/2005
Publication Date: 12/19/2006
Citation: Banuelos, G.S., Lin, Z.Q. 2006. Reuse of agricultural drainage water in central california: phytosustainability at high levels of salinity and toxic trace elements. Book Chapter. On CD from The Gological Society of London 2006, Special Publications 266, pgs 79-88. Interpretive Summary: There is an increasing trend in reusing poor quality waters for irrigated agricultural production systems. Reusing poor quality water for irrigation can serve two purposes: one is to dispose of drainage water that would otherwise be costly to dispose, and the other is to utilize poor quality drainage water as a water resource for growing crops that have economic value. In this multi-year field study, crops ranging from salt-sensitive (e.g. lettuce) to salt-tolerant (e.g. halophytes) were irrigated with waters of increasing salinity and boron levels. Stand establishment was generally good during the time period of study for the selected crops for each respective component. The subsequent reuse of drainage water resulted in an accumulation of natural-occurring trace elements-boron and selenium-in the soil and a decrease in drainage water quality produced from the various components of the drainage reuse system. Careful monitoring and salt management practices, e.g. leaching, will, however, be absolutely necessary for the soil to sustain the observed plant growth over long-term use. In addition, the presence of residual selenium in the drainage water and eventually in the solar evaporator will need to be strictly controlled because of selenium’s toxic effect on the biological ecosystem.
Technical Abstract: Agricultural drainage waters in Central California contain high levels of salts, boron (B) and selenium (Se), which are potentially hazardous to plants and wildlife. To investigate the plausibility of using plants as recipients for poor quality drainage waters, multi-year field studies were conducted to reuse drainage water on plant species that were salt and B tolerant, and accumulate or stabilize soluble Se from the applied water. Installation of subsurface tile drainage system in cropping fields allowed drainage waters to be collected and subsequently reused as irrigation water on tolerant plant species. The quality of water used for irrigation along the water reuse path changed as follows: electrical conductivity (EC) from 4.5 to 15.2 dS m-1, soluble B from 3.4 to 14.5 mg L-1, and soluble Se from 0.08 to 1.18 mg L-1 Beginning with sensitive and progressing to more salt tolerant plant species, the following plants were irrigated with drainage water that was collected with each subsequent water reuse: lettuce (Lactuca sativa),tomatoes (Lycopersicon esculentum), cotton, (Gossypium hissutm L.), alfalfa (Medicago sativa L.), canola (Brassica napus var. Hyola), sunflower (Helianthus annuus), saltgrass (Distichlis spicata L.), and pickleweed (Salicornia bigeloii Torr.). Stand establishment for the selected crops for each respective component was generally good during the time period of study, except some leaf necrosis was observed in canola. Mean tissue B concentrations were greatest in canola at 226 mg/kg DM and generally under 100 mg kg/DM for the other species. Pickleweed accumulated and volatilized the greatest amount of Se at 13 mg/kg DM and at 620 g/ha year, respectively. After each growing season for the respective crop; soil EC and concentrations of B and Se increased in 0-90 cm depths of soil. Based upon these multi-year studies farmers wanting to grow salt and B tolerant crops with drainage water on a sustained basis will clearly require more information on the following: 1) irrigation management to reduce production of drainage water; 2) economic viability associated with the selected crops; 3) irrigation practices with poor quality waters; 4) salt management strategies, e.g., leaching, to sustain productivity in soils irrigated with drainage water; and 5) disposal strategy for residual Se in solar evaporator.