Vegetative approach to manage poor water quality in central California

Abstract

Irrigated agriculture is the largest consumer of developed water resources. At the same time, drainage from irrigated lands is one of the major causes of waterlogging and of water pollution. Water availability for irrigation could be enhanced through the proper use of drainage water. Expanding such use would minimize water/logging drainage problems and reduce the hazardous effects of irrigation on the environment. Many drainage waters can be used successfully to grow crops without long-term consequences to some crops or soils. Reuse of saline subsurface drainage water for irrigation is a subject of increasing interest for managing high drainage volumes and sustaining crop productivity in California’s agricultural region of San Joaquin Valley. Typical drainage waters from this part of central California originate from infiltrated water that has percolated through the root zone carrying dissolvable salts, e.g., boron, selenium, chloride, into subsurface drains. Successful use of these collected saline drainage waters requires an adequate understanding of how natural-occurirng salts affect waters, soils, and plants. Proper management and disposal of these drainage waters are difficult because of the high salinity (EC>10 dS/m), boron (>10 mg B/L), and selenium (>150 ug Se/L) levels. Concerns have been reported in different ecosystems, including selenium poisoning in waterfowl and crop toxicities associated with increased salinity and boron in the soil. Environmental concerns related to selenium found in conjunction with boron and salinity have added a new dimension to drainage management and disposal with water-reuse strategies. Information is available regarding the effect of both salinity and boron on plant growth but identification of tolerant species remains an on-going and complex selection process. In the last few years potential plant and tree species have been irrigated with saline and boron-rich drainage waters under greenhouse and field conditions. The accumulation of boron, chloride, and selenium and their effect on dry matter production has been evaluated. Information will be presented on the tolerance of the better candidates among the tested crops.