Evaluating temporary soil stabilization methods for road construction sites in Illinois

Background/Question/Methods

When road construction sites are to be inactive for several months, establishment of temporary vegetation cover is required to stabilize soils and prevent erosion. Currently the Illinois Department of Transportation prescribes seeding with a mixture of perennial rye (Lolium perenne) and oats (Avena sativa), regardless of date or location within Illinois. Our objective was to evaluate the effectiveness of the currently prescribed method against alternative combinations of seed mix, soil preparation, and mulching methods. We performed experiments at four sites spanning the range of climatic zones within Illinois, with seeding occurring at each site four times throughout the year (late fall, winter, spring, summer). Factorial combinations of ten seed mixes by two soil preparation methods (rough or fine till) by three mulching treatments (none, straw, straw mat) were tested, with three randomized blocks per planting at each site. Vegetation cover was determined both visually and using analysis of digital photographs in Adobe Photoshop. Analysis of variance was used to identify which combinations of seed mix, soil preparation, and mulching produced the highest cover one month after seeding.

Results/Conclusions

Our results suggest that the current specification should be changed: the perennial rye and oats mix was not the best performer at any site in any season. Annual ryegrass (Lolium perenne ssp. multiflorum) achieved the highest vegetative cover at most sites and in most seasons.  The main exceptions were that cereal rye (Secale cereale) performed best at the southernmost site in fall and sudex (Sorghum bicolor) performed better than annual ryegrass in the southernmost site in summer. Mulching with either straw or mat was generally beneficial. Rough soil preparation generally produced higher cover, probably because the fine till increased soil compaction, leading to lower germination rates. Annual ryegrass is a non-native species that is not currently of concern in Illinois, but is listed as invasive in other states, so if it is to be prescribed for temporary soil stabilization care will need to be taken to ensure that it does not set seed and escape into surrounding sites. We included two native seed mixes in our experiments but neither achieved satisfactory cover. This was most likely due to excessive seed predation; higher seeding rates or alternative mulching methods may give better results.