Project Goal: The goal of this project was to
demonstrate the feasibility of using selected agricultural crops and trees with
economic value to remove selenium from soils and water, thereby reducing
selenium loading from irrigated lands, to underground drainage waters, and
intimately, to water of the Uncompahgre and Gunnison Rivers.
Developed on behalf of the Gunnison Basin Selenium Task Force, and
administered by the Shavano Soil Conservation District, this four-year
experiment was designed to test the ability of certain crops to pull
selenium out of the ground. Studies in other areas of the country with
high selenium soils have shown that in addition to native species,
certain agronomic crops naturally accumulate selenium at high levels in
their plant parts, or even release some selenium to the atmosphere as a
non-toxic gas.
Selenium removed by phytoremediation, is selenium that is not available
for leaching by irrigation water into the groundwater and river system.
This is good news for the rivers and creeks of the Uncompahgre Valley -
some of which have highly elevated concentrations of selenium. This is
also good news for the birds and fish of the area, which may develop
reproductive problems and even deformities as a result of these high
selenium levels.
Located on the Meaker Farm just north of Montrose, the first
phytoremediation test plots were established. Over 4,000 poplar trees
of three different varieties were planted. In addition, a
fescue/birdsfoot trefoil mix, canola, and kenaf (a fast-growing annual
tree), were started. At a field day held on July 18, 2001, organized by
CSU Cooperative Extension and the local NRCS offices, interested
individuals were able to come out and view the phytoremediation plots.
The trees, just three months after planting, were almost three feet
tall, and the canola had already gone to seed.
As the crops mature, samples of their roots, shoots, and if necessary,
seeds, will be collected, cleaned, and prepared for selenium analysis
at the lab. Samples will also be collected to evaluate selenium
concentrations in the surrounding soils, groundwater, and surface
water. In this way, scientists hope to develop an understanding of how
effective these crops may be in reducing overall selenium
concentrations in nearby waterways.
An important component of local selenium reductions may also
be related to reducing the amount of irrigation water applied to the
crops, thereby limiting the amount of deep percolation water that seeps
from these fields. After the first two years of establishment, the
poplars in particular will be able to access the relatively shallow
groundwater table in the area. For sale of poplars to chipboard or
other commercial buyers, it is estimated that six to seven years of
growth are needed to reach a suitable caliper. Over this period, their
reduced need for irrigation may add up to significant reductions in the
amount of selenium flushed from deeper soils into the river system.
