A Rapid Routine Method for Obtaining Soil Solution Using Vacuum Displacement
- Jeff Wolt and
- John G. Graveel
Vacuum displacement, a modification of traditional column displacement utilizing 75-g soil samples and a mechanical vacuum extractor, was compared to centrifugation as a method for obtaining unaltered soil solution for comprehensive analysis. Soil solutions were displaced by the two procedures from field-moist Lily (Typic Hapludults), Memphis (Typic Paleudalfs), and Etowah (Typic Paleudults) soil samples having varied chemical and physical properties. Solutions obtained were analyzed for volume of solution recovered, pH, EC, Ca, Mg, Mn, K, Na, NH4, Cl, NO3, SO4, P, and percent ion difference. Vacuum displacement was more efficient than centrifugation in terms of man-hour requirements and sample turn-around time. Smaller volumes of soil solution (usually <5 mL) were obtained by vacuum displacement compared to centrifugation, necessitating analytical techniques adapted to uL-volumes of solution. For the most part, both methods resulted in analate concentrations with coefficients of variation <5% and ion differences <12%. Exceptions were NH4, K, and Na, which were sometimes present at concentrations approaching the limits of detection for the procedures employed. Although significant differences in analate concentrations between the two methods were observed, few of the measured differences would lead to interpretive difficulties for the solution components and soils considered.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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