Determining Variability in Characteristics of Residential Landscape Soils that Influences Infiltration Rates

Although composed mostly of sand, observations of new urban residential communities in Florida suggested relatively wide ranges in clay content and importation of offsite soils. Often these communities are constructed around surface water where heavy summer rains and intense landscape maintenance present concerns for surface water contamination. Due to land sculpturing, soil compaction and importation; onsite soil physical properties may differ from soil maps developed decades before. How much change and what changes occurred has seldom been quantified. This study examined soil characteristic data from diverse, newly constructed urban soils and examined relationships with soil infiltration rates. Samples were collected from 40 lots in nine newly established urban residential communities within Central Florida to quantify textural composition, bulk density (Db), moisture retention, and pore size distribution. Most lots (90%) contained sandy soil dominated by micropores (58% total mean pore space). Variability of Db was low with most communities exhibiting high soil compaction (>1.7 g cm-3), which may indicate potential plant root penetration concerns. Mean soil infiltration rates among communities were high (11 to 64 cm hr-1), with large variations (2.0 to 111.1 cm hr-1). Correlations between soil moisture retention volumes, Db, and infiltration rate did not occur. However, soil texture was a significant predictor of infiltration rate. Relationships between infiltration rates and soil characteristics were poor (r2 = 0.43) and suggest direct measurement of infiltration rate may be necessary. High infiltration rates, despite compaction, indicate reduced potential for surface water contamination if a sufficient natural fetch separates landscapes from water bodies.