ABSTRACT:Porous ceramic cups under constant tension (0.45 bar) were used to extract solutions from undisturbed soil columns. Solution concentration changed with length of extraction time. Significant relationships were found between extraction time and concentrations of P, Ca, and K in soil solution for two sample depths in an Omega loamy sand soil column. At two extraction time classes and at two sample depths, combined data from 12 soil columns representing two soil series reinforce the relationship. As time to extract a sample increases, the sample probably represents solution held by soil at tensions approaching those applied to the ceramic cup. We recommend that the choice of an extraction tension be given consideration in studies using porous ceramic cups under constant tension for monitoring constituents of soil solution. In addition, care must be taken to attain good physical contact between the cups and the soil material.
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