"Glue" That Makes Good Soil Found

By Don Comis
October 2, 1997

Farmers and gardeners have always believed they could tell good soil by its feel. There may be some truth in that bit of lore. Researchers have discovered a new protein in soils that may be the "glue" that holds good soil together, from Texas to Timbuktu. The protein, secreted by certain soil-dwelling fungi, appears to be what gives a good soil the stable structure that old hands know will support abundant crop growth.

The soil protein, named glomalin [pronounced GLOM-uh-lin], is unusual in its strength as a glue and in its ubiquity in soils. Glomalin was discovered and named by Sara E. Wright, a soil microbiologist with the Agricultural Research Service in Beltsville, Md.

Glomalin coats soil particles and helps hold them together in clumps called aggregates that farmers and gardeners have long seen as the tiny grains of "good soil" sifting through their fingers.

Wright found that higher glomalin levels improve soil structure--easing the passage of air and water through soil and thereby aiding plant yields. The glomalin level in soil is an objective measure that can be used to choose the best farming practices. Already Wright has found that tillage tends to lower glomalin levels.

Wright gave glomalin its name because the gooey substance is secreted by a group of soil fungi called Glomales through long hair-like filaments. The fungi are found worldwide living in a beneficial relationship on the roots of many plants.

An in-depth article on glomalin appears in the October issue of Agricultural Research magazine. The article can also be found on the World Wide Web at:

/is/AR/archive/oct97/glomalin1097.htm

Scientific contact: Sara E. Wright, ARS Soil Microbial Systems Laboratory, Beltsville, Md., phone (301) 504-8156, fax 504-8370, swright@asrr.arsusda.gov.