UPSC Civil Services Model Paper 8

Decomposers break down complex organic matter into inorganic substances like carbon dioxide, water, and nutrients and the process is called decomposition .
Dead plant remains such as leaves, bark, flowers, and dead remains of animals, including faecal matter, constitute detritus, which is the raw material for decomposition.
The important steps in the process of decomposition are fragmentation, leaching, catabolism, humification, and mineralization.
Detritivores (e.g. earthworms ) break down detritus into smaller particles . This process is called fragmentation .
By the process of leaching, water-soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts.
Hence, Statement 1 is correct.
Bacterial and fungal enzymes degrade detritus into simpler inorganic substances . This process is called catabolism .
It is important to note that all the above steps in decomposition operate simultaneously on the detritus.
Humification and mineralization occur during decomposition in the soil.
Humification leads to the accumulation of a dark-coloured amorphous substance called humus that is highly resistant to microbial action and undergoes decomposition at an extremely slow rate.
Hence, Statement 2 is correct.
Being colloidal in nature it serves as a reservoir of nutrients .
The hummus is further degraded by some microbes and the release of inorganic nutrients occurs by the process known as mineralization.