1. What is soil organic matter?

Soil organic matter refers to carbon-containing organic matter present in soil. It includes the residues of various animals and plants, microorganisms and various organic matters that can be decomposed and synthesized. Soil organic matter is an important component of the soil solid phase. Although the content of soil organic matter only accounts for a small part of the total soil, it is extremely important for soil formation, soil fertility, environmental protection and sustainable development of agriculture and forestry. effect.

2. Organic matter content determines soil type

The content of soil organic matter varies greatly in different soils. The high content can reach 20% or more than 30% (such as peat soil, northeast black soil, etc.), and the low content is less than 1% or 0.5% (such as desert soil and aeolian sandy soil). Wait). In soil science, soils containing more than 20% organic matter in the ploughing layer are generally called organic soils, and soils containing less than 20% organic matter are called mineral soils. Under normal circumstances, the soil organic matter content of the tillage layer is usually above 5%.

3. Existence status of soil organic matter

Organic matter entering the soil generally exists in three types of states.

(1) Fresh organic matter: refers to those animal and plant residues that have entered the soil and have not been decomposed by microorganisms. They still retain their original shape and other characteristics.

(2) Decomposed organic matter: After being decomposed by microorganisms, the animal and plant residues entering the soil have lost their original morphology and other characteristics. The organic matter is partially decomposed and tangled with each other, giving it a brownish color. Including organic matter decomposition products and newly synthesized simple organic compounds.

(3) Humus: refers to a brown or dark brown macromolecular colloidal substance that is decomposed and resynthesized by microorganisms. It is closely combined with soil minerals and soil particles and is the main morphological type of soil organic matter, accounting for 85-90% of the total soil organic matter.

4. Soil organic matter requires microbial transformation

The microbial transformation process of soil organic matter is the most important and active process of soil organic matter transformation.