It is the process of breakdown of complex organic substances into simple inorganic substances like carbon dioxide, water and nutrients is called decomposition.
Dead plant remains such as leaves, bark, flowers, fruits, dead remains of animals including faecal matter, constitute detritus, which is the raw material for decomposition.
Decomposition has fallowing steps
a) Fragmentation of detritus
The organisms which feeds on detritus are called detritivores like earthworm, beetles, termites etc. They breakdown of detritus into smaller fragments which increases the surface area of microbial action. The detritus gets converted into nutrient, when it passes through the digestive tracts.
b) Leaching
The water soluble inorganic nutrients produced by decomposition reaches to deeper layer of soil and get precipitated as unavailable salts. Which is called leaching.
c) Catabolism
Decomposers such as bacteria and fungi carryout extracellular digestion. They secrete digestive enzymes on the detritus and convert complex insoluble organic substances into simple soluble organic and inorganic compounds.
d) Humification
The process of formation of humus is called humification. During the process the simplified detritus converted into dark colored amorphous substance called humus. It is two types like acidic found in regions of coniferous forests where decomposition is brought about by bacteria and fungi. Alkaline humus is found in grassland and deciduous forests, where microorganisms and earthworms help in the process of decomposition. Humus is highly resistant to microbial action. It is colloidal in nature and serves as reservoir of nutrients.
e) Mineralization
The formation of minerals is called mineralization. It involves the release of inorganic substances such as carbon dioxide, water and nutrients in the soil.
Factors affecting decomposition
a) The humus blends with the mineral matter of the soil to form a highly fertile colloidal matter.
b) Decomposition is mostly an oxygen requiring process. Anaerobic conditions slow down the rate of decomposition.
c) When the temperature is more than 25 degree Celsius and in the presence of moist conditions results in the fast growth of microflora which help in rapid decomposition of detritus within a few weeks or months. But, when temperature is less than 10 degree Celsius with lot of moisture, then the decomposition of detritus is very slow.
d) Even though the climatic conditions are normal, the decomposition rate of detritus is slower with lignin and chitin.