Question

what is humus and how its form

Answer 1

Humus is, "A more or less biologically stable, dark, amorphous material formed by the microbial decomposition of plant and animal residues." The formation of humus begins when the residues from plants and animals comes in contact with microbial life in the soil. Much of the carbon compounds contained in those residues are proteins, carbohydrates and energy for the various bacteria, fungi and actinomycetes involved in the decay process.

Answer 2

Humus is dark, organic material that forms in soil when plant and animal matter decays. When plants drop leaves, twigs, and other material to the ground, it piles up. This material is called leaf litter. When animals die, their remains add to the litter.