Comparison of laboratory and field determined saturated hydraulic conductivity and prediction from soil particle size

F.A. Gumbs


A very simple apparatus is described for measuring saturated hydraulic conductivity (SHC) above a water table in the field. The horizontal com-ponent of SHC measured by laboratory and field techniques was studied at the 0-30cm, 30-60cm, 60-120cm and 120-180cm depths at two sites about 150 m apart on River E tale sandy loam. The mean laboratory measured values were usually greater (by a factor of between 15 and 15) than the field values and replicates were more variable. The soil profiles at the two sites differed in appearance and in particle size distribution and this latter in-fluenced the SHC. SHC was significantly positively correlated with the coarse sand content and regression equations involving coarse sand content were good at predicting the SHG as measured in the field. The multiple regression equation of SHC with the four particle sizes (coarse sand, fine sand, silt and clay) had the highest variable proportion for regression but the F ratio was Significant only at P= 005. The simple linear regression (SHC= -062 + 011 per cent coarse and) should be adequate for soil survey work and for calculating drain spacing. In this soil type SHC increased markedly as the bulk density decreased from 14g/cm3 (porosity of 48 per cent). A bulk density of l4g/cm3 may be critical for adequate water relations in this soil type.

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