A Comparison of Field and Laboratory Estimated Water Relations of a Vertisol

A comparison of field and laboratory estimated water relations of a Vertisol is presented. The data on laboratory determined moisture retention collected on soil cores revealed a systematic difference attributable to profile depth. At the same suction the moisture retained by the soil increased with depth. The field determined retention curve did not quite resemble the laboratory determined one. The data further revealed that the predicted values of hydraulic conductivity K_(θ following pore size model provided an excellent agreement with K_(θ) estimated following instantaneous profile method in the tensiometer range, when the K values at 0.36 cm³/cm³ moisture content were matched. The computed values of K_(θ) based on the field estimated moisture content suction curve (corrected for over burden pressure) deviated as much as 5 times of the field estimated K. Such deviations may well be within the spatial variability in field estimated K_(θ). It is concluded that for most purposes the pore-size distribution method for determining may be useful even for soils exhibiting over burden pressure.