How important is soil organic matter?

Soil organic matter refers to the organic compounds containing carbon in the soil in various forms, which are the substances derived from life in the soil and the substances other than soil minerals in the soil. It is the most active part of the soil, the basis of soil fertility, and one of the important indicators to measure soil fertility. It can be said that there is no soil fertility without soil organic matter. Soil without fertility can't grow anything!

So what does soil organic matter do?

1, is the main source of soil nutrients

Organic matter contains various nutrients required for crop growth, and can directly or indirectly provide nitrogen, phosphorus, potassium, calcium, magnesium, sulfur and various trace elements for crop growth. In particular, more than 95% of the nitrogen in the soil is present in the organic state. Since soil minerals generally do not contain nitrogen, the main source of soil nitrogen is provided by the decomposition of organic matter in addition to the applied nitrogen fertilizer. The carbon dioxide produced by the decomposition of soil organic matter can supply the needs of green plants for photosynthesis. In addition, organic matter is also an important source of phosphorus, sulfur, calcium, magnesium and trace elements in soil.

2. Promote the growth and development of crops

Humic acid in organic matter can enhance plant respiration, improve the permeability of cell membrane, and enhance the absorption of nutrients, while vitamins and some hormones in organic matter can promote the growth and development of plants.

3, promote the formation of soil structure, improve soil physical properties, improve soil structure

Humus in organic matter is the main cementing agent of soil aggregates, and soil organic colloid is an indispensable cementing substance for the formation of water-stable aggregate structure, so it helps the clay to form a good structure, thus changing the soil porosity and the ratio of water and gas, and creating a suitable soil tightness. The viscosity of soil organic matter is much less than that of clay particles, and only a fraction of that of clay particles. On the one hand, it can reduce the viscosity of sticky soil, reduce tillage resistance and improve tillage quality; On the other hand, it can improve the agglomeration of sand and improve its excessively loose state.

4, improve the soil fertilizer retention capacity and buffering performance

The organic colloid in soil organic matter, with a large amount of negative charge, has a strong adsorption capacity, can absorb a large number of cations and water, its cation exchange capacity and water absorption than clay several times, or even dozens of times, so it can improve the soil's ability to hold fertilizer and water, but also improve the soil's buffer of acid and base.

5. Promote the activity of soil microorganisms

Soil organic matter supplies the energy and nutrients required by soil microorganisms, which is conducive to microbial activities.

6. Increase soil temperature

The color of organic matter is dark, generally brown to black brown, and the heat absorption ability is strong, which can improve the ground temperature. It can improve the soil heat condition.

7. Improve soil nutrients

Humus in organic matter has complexation, which helps to eliminate soil pollution. For low-yield fields, soil fertility can be improved by increasing the content of organic matter. For high-yield fields, due to the continuous decomposition of organic matter, it is also necessary to constantly supplement organic matter. Humus can form complexes or chelates with phosphorus, iron and aluminum ions to avoid the precipitation of insoluble phosphate and increase the amount of available nutrients.

In addition, soil organic matter can be divided into 6 types according to the type role!

1. Provide various nutrients needed by crops (basic role)

Soil organic matter is gradually mineralized, and nutrients are transformed into simple inorganic forms that are absorbed and utilized by crops and microorganisms. Organic acids and humic acids produced in the conversion process have a certain ability to dissolve soil minerals, promote mineral weathering and release nutrients.

2, enhance the soil's water and fertilizer retention capacity and buffering (chemical action)

Humic acid is loose porous, is a hydrophilic colloid, has a strong ability to absorb water. Humus has a strong ability to adsorb cations. Humic acid is a weak acid and can form a buffer system with its salts.

3, promote the formation of aggregate structure, improve soil physical properties (physical action)

Soil humus is a kind of colloid, and its bonding force and adhesion are greater than sand and smaller than clay, which is suitable for the formation of aggregate structure, so that the water permeability, water storage and air permeability of soil can be improved.

The humic acid color is deep, so that the soil temperature is fast; Large heat capacity, high soil temperature.

4, promote the physiological activity of microorganisms and plants (biological action)

Soil organic matter is the main source of nutrients and energy required by soil microbial life activities. Humic acid is a kind of plant physiological active substance, which can improve the drought resistance of crops and the activity of peroxidase.

5, reduce the pollution of pesticides and heavy metals (environmental effects)

Fixed effect on organic pollutants such as pesticides; Complexation, adsorption and reduction of heavy metal ions.

6. Impact on global carbon balance (ecological role)

Soil organic matter is an important carbon reservoir in the process of global carbon balance.