Water, sediment, and nutrient runoff from urban lawns established on disturbed subsoil or topsoil and managed with inorganic or organic fertilizers

Urban runoff has become an increasingly important environmental concern in recent years. With increasing urbanization, turfgrass area has substantially expanded in North America, and these lawns are often established on subsoil stripped of topsoil. In this study, 24 turfgrass-type tall fescue (Festuca arundinacea) plots were established on subsoil or topsoil, and managed with inorganic fertilizer (Scott's Turf BuilderA (R)), organic fertilizer (Nature's TouchA (R) with enzymes), or no fertilizer (control). A one-hour simulated rainfall at 8.9 cm/hour was applied to the plots, and the time to runoff initiation and total runoff volume were measured. Runoff water samples were analyzed to quantify the amounts of sediment, N (NH4-N), P, K, and S losses. The results indicated that runoff initiation time was almost half in subsoil lawns (12.5 min) than in topsoil lawns (23 min). The total runoff volume and sediment loss were significantly larger in subsoil lawns (11,900 ml and 3,700 mg, respectively) than in topsoil lawns (2,200 ml and 900 mg, respectively). Although the N, P, K, and S losses in runoff were low, they were significantly higher from the subsoil-based than topsoil-based lawns, and were higher from inorganic fertilizer treated lawns than those treated with organic fertilizer. These results highlight the significance of topsoil preservation in city planning and urban development with respect to urban run-off and water quality and show distinct benefits of organic lawn management practices over the conventional inorganic practices for maintaining urban water quality.