DOT Project Number:  90-00-LRTF-115

Fiscal Year:  2001

Award:  $5,400.00

Principal Investigator:  Maria Urice, Department of Environmental Science, University of Northern Iowa, murice@netins.net

Summary Report:

EFFECTS OF ANNUAL RYE AND REGREEN COVER CROPS ON SOIL EROSION AND PRAIRIE ESTABLISHMENT IN ROADSIDES UNDER CONSTRUCTION

Departments of transportation in Iowa and other midwest states are increasingly specifying native prairie vegetation to meet a variety of roadside management goals. Temporary cover crops are typically used to minimize soil erosion while prairie roadside plantings are establishing. The Iowa Department of Transportation specifies the use of annual rye as a cover crop with its prairie roadside plantings. Regreen, a wheat x wheatgrass hybrid is gaining popularity as a cover crop with prairie plantings in the Midwest. To compare rates of erosion and prairie species establishment under annual rye and Regreen, research plots were established on a newly constructed highway right-of-way in eastern Iowa. The 1600 square meter research site was seeded in June 2000 using Iowa DOT specifications for native grass plantings, and was divided into ten 8 m x 20 m plots. Five randomly chosen, replicated plots received an annual rye cover crop treatment; Regreen was seeded as a cover crop on the remaining five plots. Plant canopy cover data were collected for two seasons.

Annual rye, when seeded at the IDOT-specified rate of 45 lbs./acre, provided more erosion prevention than Regreen seeded at 15 lbs./acre during the first growing season. Establishment of Regreen, a cool season plant, could have been improved by seeding in early spring or fall.

Annual rye was found to inhibit growth of prairie species. The competition created by annual rye appeared to be responsible for the slower prairie species establishment. An annual rye seeding rate of 45 lbs./acre results in a dense seed coverage of approximately 200/square ft. Quick to establish and aggressive in nature, annual rye seedlings out-compete prairie plants for space and resources. A significantly lower annual rye seeding rate is recommended when the cover crop is used with prairie species.

There was no significant statistical difference in weed canopy cover between treatments. Sources of weeds at the site were existing seed in the soil, straw mulch, and up-slope stabilizing crops.