Humification and Mineralisation
ஹியூமஸ் உருவாக்கம் மற்றும் கனிமமாக்கல்
Decomposition is not a single step; it is a race between accumulation and release. If humus did not resist microbial action, soil fertility would vanish in weeks. Understand this balance, or lose marks on the simplest cycle questions.
The idea
Humification converts detritus into a dark, amorphous substance called humus. This humus is highly resistant to microbial decomposition and undergoes slow degradation. Mineralisation is the subsequent phase where microbes break down humus to release inorganic nutrients like CO2, water, and minerals back into the soil.
Why it matters
Humus acts as a reservoir of nutrients, and mineralisation ensures these nutrients become available for plant uptake.
NEET lens
NEET focuses on the 'resistant' nature of humus and the 'inorganic' end-product of mineralisation. Do not confuse the two; humification is accumulation, mineralisation is release. Expect a matching-type question or a statement-based question on the sequence of decomposition steps.
Clinical significance
In the human gut microbiome, a failure in similar degradation processes leads to malabsorption and dysbiosis. Just as soil requires mineralisation for plant life, our body requires microbial breakdown of complex fibers to release essential short-chain fatty acids. Without this, metabolic homeostasis collapses.
Introduction
Humification and mineralisation are the last two steps of decomposition: humification forms humus, and mineralisation releases inorganic nutrients from it.
Core concept
Humification leads to accumulation of a dark coloured amorphous substance called humus that is highly resistant to microbial action and undergoes decomposition at an extremely slow rate. Being colloidal in nature, it serves as a reservoir of nutrients. The humus is further degraded by some microbes, and release of inorganic nutrients occurs by the process known as mineralisation. The earlier steps are fragmentation (by detritivores such as earthworm), leaching (water-soluble nutrients go down into the soil and get precipitated as unavailable salts) and catabolism (bacterial and fungal enzymes degrade detritus into simpler inorganic substances).
Go deeper
Because humus releases nutrients slowly, it acts like a slow-release fertiliser for soil.
From Class 10
The dark, crumbly soil under old leaves is humus. Slowly, microbes break it down and release nutrients plants can use.