|Lin, Z.Q. -|
Submitted to: Chemosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 15, 2010
Publication Date: September 15, 2010
Citation: Banuelos, G.S., Lin, Z. 2010. Growing Indian Fig Opuntia on selenium-laden agriculture drainage sediment under field conditions. Chemosphere. 26:167-175. Interpretive Summary: Metalloid selenium, a naturally occurring trace element, is primarily found in sedimentary and shale rock formations, like those observed in the Westside of the San Joaquin Valley (SJV) in central California. Soils originating from these geological sources are generally high in trace elements, including boron and selenium. Irrigated agriculture in such arid areas is decreasing because of the increased levels of soluble salts and of the lack of available good quality water. New crops, e.g., cactus, that can survive under drought-like conditions and tolerate the high levels of salts, may be a crop to consider for such adverse areas. In this multi-year study we evaluated the ability of different cactus clones to grow, accumulate, and volatilize selenium from salty soils high in boron and selenium. After 3 years of growth, the different clones tolerated the poor soil conditions, even though they all experienced decreases in height and fruit production. No toxic symptoms were observed on the leaves (cladodes) or on the fruit. All clones volatilized selenium during the growing season, and leaves and fruit accumulated selenium. The findings from this micro field study could be of special importance for the Westside of the San Joaquin Valley when one considers that fresh water supplies are limited and reduced for irrigated agriculture in this region of California. Moreover, the ability of cactus to accumulate, and volatilize selenium, and produce selenium-enriched cladodes and fruit warrants further investigation into larger scale cactus production on the Westside of the San Joaquin Valley.
Technical Abstract: Growing alternative crops for saline and selenium (Se) impacted lands in arid regions, e.g., Western United States, depends upon the plant’s ability to tolerate the presence of high salts and boron (B). In this field study, we planted 2-month old cacti plants on 30 x 1m beds and evaluated the ability of five cactus clones (Opuntia-ficus-indica (L)) with country of origin in parenthesis: clones No. 243 (Brazil), No. 248 (Mexico), No. 250 (Mexico), No. 252 (Mexico), No. 255 (Chile) to tolerate a sediment soil high in sulfate salinity (electrical conductivity of 5 dS/m), high soluble boron (B) of 6 mg/L, and soluble selenium (Se) concentrations of 0.8 mg/L. After 3 years of growth, all clones experienced 15-20% decreases in height and fruit yield compared to the same clones grown under control conditions. Measurements for volatile Se were initiated in year 2, and leaves (cladodes) and fruit were subsampled in years 2 and 3 and analyzed for Se. Rates of Se volatilization ranged from 20 to 80 ug/m2/d for all clones, while plant Se concentrations in (mg/kg DM) ranged from 4.9 to 9.8 in cladodes, 1.5 to 2.6 in fruit flesh, and 4.5 to 10 in seeds among all opuntia clones. The apparent tolerance of the tested clones to the high salt and B soil conditions and their ability to subsequently remove Se from the soils via volatilization and accumulate Se in cladodes and fruit may make opuntia a viable alternative health food crop for the Westside soils of central California. Moreover, opuntia’s ability to survive with a minimum amount of water further support its planting in arid areas where fresh water supplies are severely limited.