The present paper studies organic carbon changes in diffrent fractions in a soil treated with different levels of nanozeolite, alfalfa and wheat residue and incubated for 90 days. The results showed that the amounts of light fraction (LF) and heavy fraction (HF) increased with increasing the percentage of nanozeolite and plant residues in the soil. The highest amounts of LF (7.54 g LF/Kg Soil) and HF (11.10 g C/Kg Soil) were found when 30% nanozeolite, 5% wheat and alfalfa straws was added to the soil. Accordingly wheat straw and alfalfa straw were effective for increasing the LF and HF respectively. However they decreased with decreasing the soil organic matter (SOM) from the 1st day of experiment until the 90th day of experiment. In addition to that, soluble organic carbon fraction plays an important role in soil and many ecosystem processes. Soluble organic carbon in hot (2.22 g C/Kgsoil) and cool (1.54 g C/Kgsoil) water fractions increased with the addition of 30% nanozeolite and 5% plant residues particularly alfalfa straw in comparison with control. Although they increased after 30 days of incubation and then they decreased in the continuation of the experiment. In fact, organic carbon (OC) contents in density and soluble fractions increased with application and addition of 30% nanozeolite and 5% plant residues into the soil, However they decreased with decreasing the SOM after 30 days of incubation. This study revealed that, application of nanozeolite and plant residues improve carbon pools in density and soluble fractions and carbon sequestration increase by increasing the OC contents in soil.
