Fragmentation involves the breaking down of detritus into smaller pieces by organisms such as earthworms. This process increases the surface area available for microbial action and helps in the breakdown of
organic matter into simpler substances. 
(1) Catabolism occurs under aerobic conditions.
(2) Leaching refers to the movement of water-soluble nutrients to the bottom layers of the soil, away from the reach of plant roots.
(4) Humus is a stable form of organic matter and it undergoes decomposition at a slower rate.