The study looked at how different types of animal manure compost affect soil organic matter. Chicken, pig, and cow manure composts, as well as manure-sawdust composts, were added to soil for 4 years. After this time, soil carbon increased by 25-40% compared to control. Light fraction carbon increased significantly after the second year in all treatments. Manure-sawdust compost had higher light fraction carbon, while manure compost had higher heavy fraction carbon. This shows that carbon from microbiological processes was stabilized faster in manure compost than in manure-sawdust compost.