Finding growth factor in soil Research: Scientist identifies naturally occurring protein that improves plant production.

October 25, 1997|By Dennis O'Brien | Dennis O'Brien,SUN STAFF

Sara Wright has spent years trying to answer a simple question: What is it that makes the good earth good?

What gives some soil that moist, granular feel that tells farmers and gardeners when they sift it through their fingers that this is productive and life-sustaining?

After five years of research, the Beltsville Agricultural Research Center scientist thinks she has an answer.

It is a protein -- unknown until now -- secreted by different types of fungus that holds soils together like a glue.

Wright, a soil microbiologist at Beltsville's soil microbial systems lab, has discovered the protein, named it and for the past year has been cultivating it and studying its effect on soil.

She calls it glomalin, a derivative of Glomales, the scientific name for the root-dwelling types of fungus that secrete the newly discovered protein through their hair-like filaments.

Wright says glomalin gives soil its granular structure, improves its content, eases the passage of air and water and improves its ability to sustain plant life.

It is, she says, the difference between a soil that can sustain crops and plain old dirt.

"Natural soil that is in good condition has a life to it, just like any other living organism. But a lot of things that happen in agriculture, like tractor plowing, wreak havoc with soil," Wright, 57, of Laurel says.

Her discovery is important because glomalin levels can be measured in soils, which will enable scientists to detect and choose the best ways to till soil and apply fertilizer to maximize productivity, she says.

Other scientists agree.

Ted M. Zobeck, a soil scientist at an Agricultural Research Service lab in Lubbock, Texas, says scientists have searched for decades to find the glue that holds soils together and keeps them productive.

Wright's discovery solves part of the puzzle, he says.

"Science is a process of building blocks, and this is a significant finding, one of those building blocks," Zobeck says. "But only time and further studies will tell how significant it is."

He says soil experts have long suspected that the key to healthy soil was some component of mycorrhizal fungi, a ubiquitous root-dwelling fungus that attaches itself to the roots of plants and helps them gather nutrients and hold water. But he says no one knew it was a protein secreted by the fungus -- until Wright's discovery about a year ago.

"What she's discovered is that there may be fundamental reasons why these mycorrhizal fungi have the effect they do, holding the soil together the way they do," Zobeck says.

Scientists say the study of soils is aimed at keeping the earth productive and preventing disasters such as the Dust Bowl of the 1930s, when degraded soils and years of drought ruined farmers across Oklahoma and Texas.

While the Dust Bowl was dramatic, soil degradation is a common problem, experts say.

A United Nations study estimated that 17 million acres of farmland is taken out of production each year worldwide because of soil degradation caused by overtilling and soil erosion.

"A lot of people think of soil as dirt but, in fact, it's a resource, and it takes management of that resource for it to continue producing," says Pat Millner, research leader of the Beltsville lab where Wright is assigned.

Wright, who has been working on glomalin since she arrived at Beltsville in 1992, has found that heavy tilling and the use of phosphorus-rich fertilizers tend to lower glomalin levels and damage soils. She published her findings in the summer 1996 issue of Plant and Soil and expects to have another article updating her work published in the same journal in the next five or six months.

Wright says that her work has confirmed what farmers have long known: that untilled soil is richer and better at producing crops. But now scientists know why -- because untilled soil has a higher content of glomalin.

"This gives us a way to measure soil quality and to stabilize the soil or come up with ways to build depleted soil back up again, over a short period of time," she says. "We're talking two to three months, instead of years."

Wright's lab is filled with evidence of her work and its results.

In a basement storage room, she is growing grass under artificial lamps to produce the fungus that secretes glomalin. The grasses, which range from about six inches to about three feet high, are needed to serve as hosts for the types of fungus that secrete glomalin, she says.

Wright also has taped to a refrigerator several plastic bags of soil that she has washed in a solution to reveal glomalin content.

A bag filled from a heavily tilled cotton field near Lubbock, shows a fine-grained, dried-out soil that looks as if it would disappear in a summer wind.

Alongside are bags filled with soils of a slightly better quality -- untilled soils from Texas.

And then there is the best grade -- a bag of untilled "Hagerstown soil," common throughout the mid-Atlantic states. It contains the rich brown earth that farmers crave and has the highest content of glomalin, Wright says.

"This is the quality of soil that people are looking for," she says, sifting it through her fingers.

Pub Date: 10/25/97

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