Evaluating the Use of Fertilizer and Compost on Vegetation Growth, Sediment, and Nutrient Loss

Construction activities often degrade and compact roadside soils, leading to erosion, sparse vegetation, and nutrient loss. Establishing vegetation alongside roads helps improve fertility and reduce erosion, nutrient loss, and sediment runoff. This study evaluated the effects of soil type (topsoil and subsoil) and soil amendments (compost and fertilizer) on vegetation growth and water quality through controlled rainfall simulations. Six large-scale mesocosm boxes (180 cm × 45 cm) with a 1:1 slope were built using soils collected from roadside construction sites in Iowa. Treatments included topsoil (T), subsoil (S), and compost-amended subsoil (CS). Fertilizer was applied only to T and S. The boxes experienced weekly simulated rainfall for 12 weeks, and effluent was analyzed for total suspended solids (TSS), total nitrogen (TN), and total phosphorus (TP). Vegetation growth was monitored weekly via image analysis of green coverage. Topsoil and compost-amended subsoil showed faster growth, reaching 90% coverage after 5 weeks. In comparison, subsoil reached 90% coverage after 9 weeks. Vegetation growth significantly reduced sediment loss, with final values more than 10 times lower than initial levels. Nutrient concentration loss was initially higher across all soils but stabilized over time.