Impact of Incremental Surface Soil Depths on Infiltration Rates, Potential Sediment Losses, and Chemical Water Quality

Abstract

A study was conducted between October 1974 and August 1976 to measure the effects of incremented surface soil depths on infiltration rates, potential sediment production, and chemical quality of runoff water. The treatments were incremental removals of 7.6-cm soil layers to a depth of 30.5 cm on two pinyon-juniper sites in Utah. Hydrologic parameters were measured at each 7.6-cm incremental soil depth using a Rocky Mountain infiltrometer. With one exception, no significant differences occurred in infiltration rates among treatment depths during either 1975 or 1976 at either the Blanding (southeastern Utah) or Milford (southwestern Utah) site. A significant change in infiltration capacities was noted between the 1975 and 1976 field seasons when data from both treatment depths and study sites were pooled. There were no significant differences in potential sediment production between sites or among treatment depths at a site. In terms of chemical water quality, a significant change in phosphorus content of runoff waters was observed at the Blanding site between the 1975 and 1976 field seasons. Significant differences in potassium concentrations were found between sites and among soil depths. Nitrate concentrations were very low in runoff waters from all soil depths at both sites.