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

      Lyons, S. M.; Gifford, G. F. (Society for Range Management, 1980-05-01)
      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.
    • Impact of Incremental Surface Soil Depths on Plant Production, Transpiration Ratios, and Nitrogen Mineralization Rates

      Lyons, S. M.; Gifford, G. F. (Society for Range Management, 1980-05-01)
      From October 1974 to August 1976, a study was conducted to measure how incremental surface soil depths from the pinyon-juniper type affected plant production, plant transpiration rates, and nitrate nitrogen mineralization rates. The treatments were incremental removals of 7.6-cm soil layers to a depth of 30.5 cm. Plant production and transpiration ratios (or water use efficiencies) were measured in greenhouse studies using Agropyron desertorum grown in specified incremental 7.6-cm soil layers taken from five study sites throughout Utah. Significant decreases in plant production and increases in transpiration ratios were measured for all sites at incremental depths beyond 7.6-cm. These changes in plant production and transpiration ratios were linearly related to the nitrate nitrogen content of the soils (as determined when the soils were collected for use in the greenhouse). Nitrate mineralization rates were measured for two 6-week periods under field conditions at two sites for each of the 7.6-cm incremental soil layers. Nitrate nitrogen mineralization was linearly correlated with the organic carbon content of the soil. Decreased mineralization rates as measured in the field at both sites were reflected in the significant increases in plant water requirements and decreases in production that were measured in greenhouse studies.