a pH determined in 0.01 M CaCl 2 in a 1:2.5 soil:water suspension.
b Natural moisture content. Amount of water per mass of dry soil (gravimetric water content of field moist soil).
c Mass percentage of carbon determined by dry combustion.
d Mass percentage of particle size distribution determined by sieving and sedimentation (clay < 2, m m, 2 m m < silt < 20 m m, 20 m m < fine sand < 200 m m,200 m m < coarse sand < 2000 m m).
e CEC 7 : Cation exchange capacity determined by the ammonium acetate method(pH 7) (cmol(þ)/kg).
f Sum of exchangeable base cations (Ca 2þ , Mg 2þ , Na þ , K þ )/CEC 7 *100.
g Extractable aluminum and iron determined by the dithionite-citratebicarbonate method (mmol/kg).
h Clay minerals determined by powder X-ray diffraction.