Subsurface nutrient processing capacity in agricultural roadside ditches
Chloride, Denitrification, Iowa, NO3-N, Nutrients, Phosphorus, Roadside ditches
Science of the Total Environment
Roadside ditches located throughout urban and rural landscapes are integral components of watershed-scale hydrologic processes but their capacity to reduce nutrients in the subsurface environment has not been investigated. In this study, vegetation, soil and groundwater conditions were characterized in six roadside ditches in the 66 km 2 Lime Creek watershed in eastern Iowa. Shallow water table wells were installed at 17 locations in six transects and sampled monthly in 2017 to evaluate spatial and temporal patterns. Vegetation characteristics were surprisingly diverse but was not found to be a significant factor in water quality patterns. Groundwater NO 3 -N concentrations were <1 mg/L in wells at two transects and were observed to decrease from upgradient to downgradient positions at four locations (average 60% reduction). Water table levels were very shallow (<0.3 m) at nearly all sites, and the loamy and organic rich ditch soils appeared sufficiently anaerobic for subsurface processing of NO 3 -N via denitrification to occur. Groundwater dissolved reactive phosphorus concentrations did not vary systematically among the sites whereas two of the roadside ditches had Cl concentrations indicative of road salt encroachment. With estimated NO 3 -N reductions equivalent to typical wetland N reductions we recommend consideration of roadside ditches to serve as “linear wetlands” for watershed-scale treatment of nonpoint source pollution.
Original Publication Date
DOI of published version
UNI ScholarWorks, Rod Library, University of Northern Iowa
Schilling, Keith E.; Streeter, Matthew T.; St. Clair, Martin; and Meissen, Justin, "Subsurface nutrient processing capacity in agricultural roadside ditches" (2018). Faculty Publications. 666.