Partitioning runoff and percolation of urban soils in response to precipitation and soil characteristics

Soil nutrient applications are beneficial to plant growth and aesthetic quality, yet have the potential to degrade ground and surface water quality through stormwater nutrient leaching and runoff mechanisms. The fate of soil nutrients has been intensively researched in agricultural production, yet few studies have focused on urban residential landscapes. An examination of soil characteristics in newly constructed urban residential communities within Central Florida was conducted. Mean soil bulk density for over 50% of sampled communities was near 1.75 g cm-3. A majority (90%) of sampled building sites contained coarse-textured sandy soils. Half of sampled sites had soil infiltration rates below the 100-year, 24-hour design storm intensity.;Three soils representing the textural range observed in these communities were used for in-depth runoff and leachate studies. Runoff boxes were constructed and filled with the three soil types. Influences of soil type, soil moisture level, and precipitation intensity on runoff and leachate volume were examined. Low soil moisture (≤ 40% plant available water) or precipitation intensity (2.5 cm hr-1 for 15 minutes) produced zero or near zero runoff and leachate volumes. Higher soil moisture (70 and 90% plant available water) and precipitation intensity (5.1 and 7.6 cm hr-1) levels produced large runoff and leachate volumes. Results suggest measureable stormwater runoff and leachate will occur in barren moist soils of urban residential communities under short interval, high intensity (≥ 5.1 cm hr-1 ) precipitation events.;A 5.7 cm layer of pine bark mulch applied to the soil surface of runoff boxes decreased runoff volumes to zero and near zero values, while leachate volumes were not influenced at moderate precipitation intensity and soil moisture. Physical impedance and absorptive capacity of mulch therefore provides a potential reduction of stormwater nutrient runoff. Addition of six Salvia farinacea transplanted into each lysimeter had no influence on runoff or leachate volumes.