Water displacement of soils and the soil solution

Abstract

1. The use of a positive air pressure on closely packed soils decreases the time of recovery and increases the yield of solution obtained by water displacement. 2. Equipment and technique for the recovery of displaced solutions is described. 3. Data from three sandy loams and two silty clay loams are reported. 4. Successive displaced solutions of equal electrical conductivity were obtained from each soil. The concentration thus measured was in each case the same as that of the liquid obtained without the use of displacing water. 5. Concentrations of individual ions in successive portions of displaced solution are uniform in soils at optimum and this also appears to be true at half optimum. 6. There is an inverse proportion between total moisture content of soil and concentration of displaced solution as indicated by measurements of specific resistance. 7. When the solution displaced by water from a given mass of soil was used as displacing agent on another portion of the same soil, the newly displaced solution had the same concentration of electrolytes as the displacing solution. The opinion is expressed that this result indicates that the displaced solution has the same concentration as the solution with which it came in contact in the soil. 8. Typical differences in behaviour of the various solutes in displaced solutions are discussed. 9. The significance and limitations of water extractions of soils are discussed in the light of the results from displaced solutions.