Click image for caption and
other photo information.
magazine feature about glomalin
research by Sara Wright and others.
Glomalin: The Real Soil Builder
By Don Comis
February 5, 2003
An Agricultural Research
Service scientist now has more proof that she has found a key ingredient
responsible for the well-known benefits of soil organic matter.
Sara F. Wright, a soil scientist with the ARS
Systems Laboratory in Beltsville, Md., discovered glomalin in 1996 and
named the substance after Glomales, the taxonomic order of the fungi that
produce the sticky protein. Recently, she used a nuclear magnetic resonance
imager to show that glomalin is structurally different from any other organic
matter component, proving it is a distinct entity.
The fungi live on most plant roots and use the plants' carbon to
produce glomalin. Glomalin is thought to seal and solidify the outside of the
fungi's pipelike filaments that transport water and nutrients to plants.
As the roots grow, glomalin sloughs off into the soil where it
acts as a "super glue," helping sand, silt and clay particles stick to each
other and to the organic matter that brings soil to life. It is glomalin that
helps give good soil its feel, as smooth clumps of the glued-together particles
and organic matter flow through an experienced gardener's or farmer's hands.
Glomalin was long lost in humus, the organic matter that is
often called "black gold." When it did turn up in humus measurements, it was
thought to be a contaminant.
Glomalin is not just the glue that holds humus to soil
particles, it actually does much of what humus has been credited with. Because
there is so much more glomalin in the soil than humic acid, an extractable
fraction of humus, glomalin stores 27 percent of total soil carbon, compared to
humic acid's eight percent. It also provides nitrogen to soil and gives it the
structure needed to hold water and for proper aeration, movement of plant roots
and stability to resist erosion.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.