Thirty samples from sites representingmajor physiographic regions
and soil groups in Alabama were available from a previous study
(Ou, 2013). The soils from the SFC were dried in a mechanical oven at
60 °C and pulverized to pass a sieve with 0.85-mm apertures—the
same procedure that was used for the other samples. Dry samples
were stored in plastic bags until used in analyses.