Impact of Fertilization On Sediment and Nutrient Runoff Losses During Roadside Revegetation.

Runoff events from roadsides during vegetative establishment can transport sediment and nutrients offsite, leading to a reduction in surface water quality. Evaluation of the environmental impact of Mississippi Department of Transportation (MDOT) establishment practices is lacking. A study was conducted to evaluate the influence of N and P sources and rates, and fertilization timing on sediment and nutrient loss during vegetative establishment. In July 2011 and June 2012, stainless steel runoff frames (0.75 x 2.0 m) were installed on a roadside near Starkville, MS. A bahiagrass (Paspalum notatum Flugge), tall fescue (Festuca arundinacea Shreb), sericea lespedeza [Lespedeza cuneata (Dum. Cours.) G. Don], and common bermudagrass [Cynodon dactylon (L.) Pers.] mixture was seeded within each frame. Eight fertilizer treatments consisting of 73.5 or 147 kg N and P₂O₅ ha^-1 as 13-13-13, poultry litter, ammonium nitrate, stabilized urea, polymer coated urea, or diammonium phosphate were applied immediately after seeding. Runoff from natural and simulated (30 minute duration, 66 mm hr^-1 intensity) rainfall was collected and analyzed for PO₄^3--P, total P (TP), NH₄⁺-N, NO₃^-+ NO₂^- -N, total N (TN), and total solids (TS). Results suggest inorganic N and P losses were the greatest in the first runoff event following fertilization. Differences in PO₄^3--P and NH₄⁺-N lost during runoff from natural and simulated rainfall occurred between fertilizer sources. Total N and P were positively correlated with TS in runoff. These results will assist vegetation coordinators in choosing fertilization programs that reduce potential offsite nutrient movement during runoff events.