Compost Controls Erosion at Highway Construction Sites

November 25th, 2002

AMES, Iowa — Using compost at road construction sites can be an effective tool to reduce runoff and erosion. That's the conclusion of a three-year study conducted by Iowa State University.

The research was funded by the Iowa Department of Transportation and the Iowa Department of Natural Resources. Tom Glanville and Tom Richard, researchers in the ISU agricultural and biosystems engineering department, were the project leaders.

The project was designed to compare roadway embankments blanketed with compost to slopes where conventional erosion control practices were applied. Conventional practices normally include direct seeding of erosion control vegetation into native embankment soil or, where the existing soil does not support vigorous plant growth, applying six inches of imported topsoil prior to seeding. These conventional practices work well at most construction sites, but unfavorable weather or poor soil conditions can result in high runoff and erosion before vegetation can get established.

Three types of composted organic wastes were used in the field test — bioindustrial byproducts that included paper mill sludge and grain processing wastes from businesses in the Cedar Rapids area, municipal sewage biosolids and yard waste from Davenport and municipal yard waste from Des Moines.

A rainfall simulator was used to expose test areas to the same effects as those caused by a high-intensity, 30-minute rainstorm. Runoff and erosion measurements were conducted on bare plots to evaluate the damage likely to occur on new construction sites, and again after erosion control vegetation was established.

Researchers said the compost-treated areas produced less than 30 percent of the runoff from conventionally constructed embankments. And while conventional roadside areas began producing runoff within five minutes after rainfall began, areas treated with compost often took 25 to 50 minutes to start producing runoff. "Delayed runoff can translate into significant environmental benefit since rainstorms lasting less than 30 minutes would produce little if any runoff," said Glanville.

Because of the low runoff, researchers also found the compost-treated areas were resistant to erosion. "One of the most important benefits of compost treatments is the immediate erosion protection that's provided before vegetative cover is established," said Richard. "Compost applications on projects completed too late in the year to establish vegetation could provide immediate runoff and erosion control that would help prevent damage that may otherwise occur before the next growing season."

Photographs and further details about the research and its conclusions are on the Web at: http://www.abe.iastate.edu/compost/

Contacts: 

Tom Glanville, Agricultural and Biosystems Engineering, (515) 294-0463
Tom Richard, Agricultural and Biosystems Engineering, (515) 294-0465
Russell Persyn, Agricultural and Biosystems Engineering, (515) 294-4241
Susan Thompson, Ag Communications, (515) 294-0705

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