A Survey of Soil Properties Affecting Vegetation Establishment Along Nebraska Highways

Vegetation along roadsides is important to prevent soil erosion, provide habitat and filter water running off the road. Along some highways in Nebraska vegetation does not readily establish and persist. It is thought that sodium and bulk density issues are the driving factor behind the lack of vegetation. After a construction project, the shoulder is seeded into the compacted soil, and salts can accumulate in the soil due to deicing agents being used during the winter. The purpose of our study was to determine if the bulk density and sodium are the driving factors of the vegetation cover. We also evaluated how shoulder type and time since seeding affected these soil issues and vegetation cover. The study was conducted by collecting soil samples and identifying vegetation cover from 53 sites in three different regions, the Panhandle, Southcentral and Southeast regions, in Nebraska, USA. The soil was analyzed for pH, electrical conductivity, sodium, chloride, and bulk density. At each site, vegetation was designated into one of four categories, bare ground (\u3e70%), annual vegetation (\u3e70%), perennial vegetation (\u3e50%), and bare ground-annual vegetation mix (~50-50% mix). It was found that sodium and compaction issues had little effect on the establishment and persistence of vegetation. Over half of the sites had high soil sodium levels at both the 0-10 and 10-20 cm depths. The bulk density was found to be normal in the Panhandle and slightly high in the Southcentral and Southeast. The shoulder and time since seeding showed limited effect on the soil variables measured. Although tested soil factors did not have large magnitude in influencing vegetation cover, we suggest post-seeding factors such as snowplows, mowing and traffic could have contributed to the lack of vegetation along highways. Advisors: Martha Mamo and Walter H. Schach