AN ANALYSIS OF THE EFFECT OF CLAY AND ORGANIC MATTER CONTENT ON THE CATION EXCHANGE CAPACITY OF NEW JERSEY SOILS

Cation exchange capacity (CEC), clay content, and organic matter content data were collected for 170 profiles of 49 New Jersey soil series. Regression analysis was used to examine the relationship between CEC and clay and organic matter and to estimate both the CEC of the clay and organic matter and their contribution to the CEC of the soils. The data were partitioned by major soil horizon, geomorphic province, soil orders of Soil Taxonomy, and great soil group and were analyzed to determine both the ability of the partitioning of the data to improve the regression and to define groups having distinct relationships between CEC and clay and organic matter. Multiple regression indicated that 59 percent of the variation in the CEC of all the data could be explained by variation in clay and organic matter contents, with the clay having a CEC of 35 and the organic matter 217 milliequivalents per 100 grams. Partitioning the data by geomorphic province or by soil order proved superior in defining groups of soils with distinct clay and organic matter CEC. Poor correlations were obtained between CEC and clay and organic matter for soils of the Piedmont province or of the Alfisol order, indicating either other sources of CEC or variability in the clay mineralogy, organic matter composition, or both in these classes of data.