Our experimental data have shown that CM HA is significantly
different from S4 HA, and that the HA fraction
isolated from CM treated soil at the end of the amendment
trials is likely to contain both CM HA and S4 HA. This fact
has allowed to assess that the CM organic matter is effectively
present in the amended soil and contributes to
change the nature of the soil organic matter pool and the
soil properties. However, the nature and content of CM
HA in soil have been shown not enough to fully explain
the increase of soil cation exchange capacity (CEC) after
amendment. This fact is consistent with the data in Table 1
showing that all three humic fractions (HA, FA and HU)
contribute to the change of the soil organic matter composition
with the HU fraction being the major contributor to