Interrelations among physical and hydraulic parameters of non-cracking soils

Water movement into soil is influenced by several soil hydraulic parameters that are often interrelated. In this study, data obtained for non-cracking soils are examined for correlations and interrelations among the various parameters. Data on soil texture, bulk density, parameters of three selected infiltration equations (i.e. Kostiakov, Philip and Horton equations), sorptivity and saturated hydraulic conductivity were obtained for a number of field sites in New South Wales, Australia. In addition, the published data on soil texture, bulk density and parameters of an infiltration equation (i.e. Kostiakov equation) for soils in Botswana were also included to extend the range of soil types and field conditions in the present study. There was a very poor correlation between the infiltration parameters of the Kostiakov equation and the soil physical properties such as bulk density and % of sand, silt and clay in the soil. The correlation between the steady-state infiltration rate (b_r) for a site measured with the ring infiltrometer and that (I_s) measured with the disc permeameter was high, but the values of b_r tended to be smaller than those of I_s. On the other hand, there was a poor correlation between the sorptivity (S_r) measured for a site with the ring infiltrometer and that (S_d) measured with the disc permeameter, and the values of Sr tended to be larger than those of S_d. The hydraulic conductivity measured with the core permeameter showed a poor correlation with similar parameters measured using other methods. Also, a high variability in infiltration characteristics was observed although the measurements were made only a few metres apart.