| |
Native
grasses like switchgrass may contribute to
soils with higher levels of glomalin, a
glycoprotein that helps store carbon and
may increase the value of the grass as a
source of ethanol. |
Switchgrass May Mean Better Soil
By
Don Comis
July 17, 2008
Soils with
native grasses such as switchgrass have higher
levels of a key soil component called glomalin
than soils planted to non-native grasses,
according to a study by the Agricultural
Research Service at two locations in
Mandan, N.D.
Kristine Nichols, a microbiologist with
the
ARS Northern Great Plains Research Laboratory
in Mandan, conducted the study. Glomalin is a
sugar-protein compound that might trigger the
formation of soil. The more glomalin in a
given soil, the better and less erosion-prone
that soil probably is.
In 2004,
Nichols collected soil from under grass plots
established between 1987 and 2002. The amount
of glomalin in the soil increased as the
degree of interdependence between plants and
the arbuscular mycorrhizal fungi increased.
These fungi produce glomalin and live inside
plant roots and the surrounding soil. That
interdependence is greatest in warm-season
native grasses such as switchgrass, blue grama,
big bluestem and indiangrass.
Further
evidence that soils underneath native grasses
are higher in glomalin came from another study
on rangeland areas at Mandan and near Platte,
S.D.
In an earlier
study, Nichols analyzed samples from
undisturbed soils with native vegetation in
Maryland, Georgia and Colorado. According to
her analysis, glomalin stored a large
percentage of the carbon found in those soils
and contributed greatly to soil fertility. On
average, glomalin stored 15 percent of the
soil carbon, with the highest amount—30
percent— in a Colorado soil and the lowest
amount—9 percent—in a Georgia soil. These
results are similar to those from other soil
samples taken around the world.
The increased
glomalin and underground carbon storage
observed with switchgrass adds to its value as
a potential source of cellulosic ethanol.
Nichols uses
glomalin measurements as a quick guide to
evaluate how "soil-friendly" farming or
rangeland practices actually are. She
originally worked with soil scientist Sara
Wright, who discovered and named glomalin in
1996. Wright has since retired.
Read more about the research in the July
2008 issue of Agricultural Research
magazine.
