Question

Important steps in decomposition are
(a) Fragmentation and mineralization
(b) Leeching and catabolism
(c) Humification and mineralization
(d) All of the above

Answer 1

Hint: It is the breakdown, by physical and biological mechanisms, of organic substances found in the soil. Plant remains, deposited on or in the soil, are known as plant litter. During the formation of humus, the concomitant with the breakdown of litter is the synthesis of meta-stable substances.

Complete answer:
Decomposition is the process of breaking complex organic matter into simpler inorganic matter. There are five steps of decomposition. These are fragmentation, leaching, catabolism, humification, and mineralization. During the fragmentation process, the breaking of detritus into little pieces by detritivores. Leaching is the process of releasing nutrients in the water and seeping into the soil. Catabolism is the process of breaking down complex molecules into simpler molecules. The process of the formation of dark-colored humus on the soil is called humification. Mineralization is the process of degradation of the hummus to release inorganic nutrients.

Additional information: Decomposition is a critical process in the nutrient dynamics of soil. As litter decomposes, microorganisms become inextricably associated with the decaying litter creating a substrate–microbe complex. The microorganisms will decay the litter in order to gain carbon, nutrients, and energy for growth and reproduction. In most freshly deposited plant litter, carbon and energy are relatively abundant and inorganic nutrients are in short supply. In order for the microbial community to produce enzymes, adenosine triphosphate (ATP), and other essentials of metabolism it must accumulate nitrogen, phosphorus, and sulfur, and perhaps other nutrients from the environment.
So the right answer to the above question is ‘All of the above’.

Note: During the early stages of decomposition, nutrients are imported into the substrate–microbe complex, a process called immobilization. As carbon is released via respiration, the ratio between carbon and other nutrients declines. Eventually, the concentration of nutrients is sufficient to meet the needs of the decomposer organisms and both carbon and nutrients will be released from the complex.