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Comparison of Compost and Proprietary Soil Amendments for Vegetation Establishment

Status:  Active
Project Start Date:  05/14/2021

Summary:

Soils disturbed by roadway construction or with poor and/or limited quantity of topsoil resources, often exhibit reduced soil quality. This may lead to reduced soil porosity, infiltration rates, soil structural stability, aggregation, water holding capacity and thereby increased erosion. Hence, sites with poor soil quality can be a challenge to promote better and healthier vegetation establishment and less postconstruction maintenance of erosion damage. The use of organic composts is the most common method to improve topsoil quality on disturbed soils, outside of importing topsoil. Organic composts can reduce or eliminate the use of periodic conventional fertilization, is typically less costly, and can ameliorate local irregularities in surface soil properties. However, good sources of compost are not always available in the vicinity of construction sites in Minnesota which makes proprietary soil amendments a cost-effective alternative. Nearly 14 proprietary soil amendment products are currently in consideration by MnDOT, but limited information is available about the effects and mixing ratios/techniques of these products on roadside vegetation. Previous studies by MnDOT and LRRB has considered the effects of soil amendments on the establishment of salt-tolerant grasses on roadways, development of watering methods/schedules, and selection of suitable species and cultivars. However, these studies did not compare different types of amendments or appropriate mixing ratios/techniques. Hence, more research is needed to better understand how to improve the topsoil quality at construction sites with different types of amendments or appropriate mixing ratios/techniques in order to promote healthier vegetation establishment. Results from this study will be used to provide recommendations on appropriate soil amendment option (mixing ratios/techniques) incorporation for post-construction highway vegetation establishment to reduce costs for site inspection activities as well as reduce the need for corrective actions resulting from inspections and will allow sites to fulfill their NPDES Permit requirements sooner.

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