The relationships between SSA and air-dry moisture content of the soils, and between SSA and cation exchange capacity (CEC), were also investigated.
was used, where y is the SSA measured by pNP, and x is either air-dry moisture content or the CEC, and a and b are coefficients.
These variations are reflected in the wide range of CEC and air-dry moisture content values.
Relation between cation exchange capacity (CEC) and air-dry moisture content of soils with measured and calculated specific surface area (SSA) Soil Soil property Measured SSA CEC (cmol(+)/kg) All soils Non-allophanic soils Air-dry moisture All soils content Non-allophanic soils Calculated SSA CEC (cmol(+)/kg) All soils Excluding smectitic soils Air-dry moisture All soils content Excluding smectitic soils Soil Regression Correlation property equation coefficient (r) Measured SSA CEC (cmol(+)/kg) 13.26 + 0.56x 0.616(**) 14.31 + 0.62x 0.726(**) Air-dry moisture 13.36 + 5.19x 0.566(**) content 7.30 + 8.69x 0.894(***) Calculated SSA CEC (cmol(+)/kg) 15.93 + 0.32x 0.480(*) 0.63 + 1.07x 0.854(***) Air-dry moisture 11.09 + 0.48x 0.693(***) content 6.59 + 6.79x 0.819(***)
For topsoils, and omitting allophanic samples, the relation between pNP surface area and air-dry moisture content is highly significant (r = 0.894; P less than] 0.001) (Fig.
This correlation allows SSA of an independent set of soils to be predicted from their air-dry moisture content with 89% of the variations in SSA being accounted for.