Cation‐Exchange Capacity as a Function of Organic Matter, Total Clay, and Various Clay Fractions in a Soil Toposequence

Abstract

AbstractSoil cation‐exchange capacity (CEC) as determined for A and B horizons of Miami, Celina, Crosby, and Brookston soils was statistically partitioned using multiple linear regression analyses into the following sets of components: [1] organic matter (OM) and total clay; and [2] OM, 2‐0.2µ, and <0.2µ clay. Coefficients of multiple correlation (R) for independent variables used in regression components [2] are of larger magnitude but not significantly different from components [1]. R values for components [1] range from .76 to .87 and for components [2] from .78 to .92. Organic matter contributes most to the CEC in A horizons whereas <0.2µ clay contributes greatest to the CEC of B horizons for soils of this toposequence. With one exception, 2–0.2µ clay is not significantly correlated with CEC in either A or B horizons. The average CEC of OM for Brookston A horizons is lower than for other toposequence members (154 vs. ca. 200 meq/100 g), whereas for B horizons it is considerably greater (361 vs. ca. 290 meq/100 g). The average CEC of fine clay in B horizons progressively increases with decrease in drainage class, varying from about 70 meq/100 g in Miami to 121 meq/100 g in Brookston.