Why some soils are not high in organic matter

The organic matter in the soil includes various organic substances, microorganisms and various organic substances that can be decomposed and synthesized. Soil organic matter is an important component of the solid phase of soil. Although the soil content is only a small fraction of the total soil, it has extremely important aspects of soil formation, soil fertility, environmental protection and sustainable development of agriculture and forestry.

The following is an introduction to the types of organic matter and the reasons for the lack of organic matter.

1. Types of organic matter.

1. Fresh organic matter: refers to substances that have not been decomposed by microorganisms in the soil, such as plant residues.

2. Decomposition of organic matter: The decomposition of microorganisms makes plant residues lose the characteristics of their original form, and simple organic compounds will cause less damage to the soil.

3. Humus: It refers to brown or dark brown macromolecular colloidal substances that are decomposed and then synthesized by microorganisms. Combined with soil mineral soil particles, soil particles are the main morphological types of soil organic matter, soil organic matter needs microbial transformation, and the transformation process of soil organic matter microorganisms is the most important and active process of soil organic matter transformation.

2. Causes of insufficient organic matter.

1. Planting crop debris and soil biological remains, this kind of organic matter is mainly planted crop remains, but this kind of organic matter is not completely biodecomposed, resulting in more plant pathogens, and joint cropping is easy to produce diseases, resulting in reduced plant yield.

2. Artificial addition: It is mainly made of animal manure and plant residues through fermentation, which is called organic fertilizer, and the natural fermentation of farmers is also a kind of organic fertilizer. At present, 80% of the organic fertilizers on the market are not completely fermented, and such organic fertilizers are easy to burn the roots when used directly in the root system, and the plants are not easy to absorb the nutrients in them.

3. Solution.

The addition of organic fertilizer can increase the content of organic matter in the soil, among which the fermentation and decomposition of animal and plant fertilizers also contain amino acids, nitrogen, phosphorus and potassium, medium and trace elements, which not only increases soil fertility, but also chelates with fertilizers in the soil, improves fertilizer utilization efficiency, and increases the effective period of fertilizers. At the same time, it provides living space for microorganisms and soil organisms, promotes the reproduction of microorganisms and soil organisms, and thus increases soil permeability.

Organic matter in the soil accumulates slowly, and some soils can be lost due to excessive cultivation and planting. Therefore, in the process of planting, we should also pay attention to the protection of soil fertility.

This is because there are some soils whose nutritional value is not particularly high, and there is a lack of humus in the soil, so it will lead to low organic matter and low acidity and alkalinity.

Because some soils do not have a strong ability to retain water and nutrients, nutrients are easily lost, so the organic matter is not high.

Soil organic matter refers to all carbon-containing organic matter existing in the soil in various forms, including various animal and plant residues, microorganisms and various organic substances decomposed and synthesized in the soil.

In a narrow sense, soil organic matter generally refers to a special, complex and relatively stable type of polymer organic compounds (saprotic acid) formed by the action of microorganisms in organic residues.

Soil organic matter is an important component of the solid part of the soil, is one of the main components of plant nutrition, can promote the growth and development of plants, improve the physical properties of the soil, promote the allergic activities of microorganisms and soil organisms, promote the decomposition of nutrients in the soil, and improve the role of soil fertilizer retention and buffering.

It is closely related to the structure, aeration, permeability, adsorption and buffering of soil, and is usually positively correlated with soil fertility level within a certain content range under the same or similar conditions.

Soil organic matter is mainly found in plants, animals and microbial residues, among which higher plants are the main ones. The first organisms that appear in the parent material in the original soil are microorganisms. With the evolution of organisms and the development of soil formation process, animal and plant residues and their secretions have become the basic soil organic matter.

In natural soils, ground-based vegetation residues and root systems are the main source of soil organic matter, such as trees, shrubs, grasses and their litters, which provide a large amount of organic residues to the soil every year.

In agricultural soil, the soil organic matter is wider, mainly including crop stubble, human and animal manure, and scraps of industrial and agricultural by-products (such as distiller's grains, ammonium papermaking waste liquid, etc.); municipal solid waste, sewage; the remains and secretions of soil microorganisms, animals (e.g. earthworms, insects, etc.); All kinds of organic fertilizers (manure, humic acid fertilizer, sludge and soil miscellaneous fertilizer, etc.) are applied artificially.

Summary. Definition: A general term for the various products and synthetic products of different stages of decomposition of all animal and plant residues formed in the soil and added externally.

Definition: A general term for the various products and synthetic products of different stages of decomposition of all animal and plant residues formed in the soil and added externally.

Soil organic matter generally refers to carbon-containing organic compounds that exist in the soil in various forms, including the products of animal, plant and microbial residues in the soil at different stages of decomposition and synthesis. Different types of soil have different organic matter: the organic matter of forest soil is dominated by litter; The soil organic matter of grassland vegetation was dominated by roots. The soil organic matter of cultivated land mainly includes cultivated crop residues, root exudates and organic fertilizers (green manure, compost, manure and manure, etc.) applied to the soil every year.

The content of soil organic matter varies greatly in different soils, with high levels of up to 20% or more than 30% (e.g. peat, some fertile forest soils, etc.), and low content of less than 1% or e.g. desert soils and aeolian sandy soils. In pedology, the soil containing more than 20% organic matter in the tillage layer is generally called organic soil, and the soil containing less than 20% organic matter is called mineral soil. In general, the soil organic matter content of the tillage layer is usually more than 5%.

The average carbon content of organic matter is 58%, so the content of soil organic matter is roughly double that of organic carbon.

Type. The organic matter that enters 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 morphological and other characteristics.

For forest soils, it generally refers to the litter layer of litter. It is equivalent to a in the description of soil profile morphology. Layer.

2) Decomposed organic matter: through the decomposition of microorganisms, the animal and plant residues that have entered the soil have lost their original morphology and other characteristics. The organic matter has partially broken down and is entangled with each other, giving it a brown color.

These include organic matter decomposition products and newly synthesized simple organic compounds. For forest soils, it generally refers to the F layer (fermetation) in the litter layer. This layer is generally a in the morphological description of the soil profile.

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

For forest soils, it is generally referred to as the h layer (humus) in the litter layer. In the description of soil profile morphology, it is usually denoted as a together with the above F layer. Layer.

Soil organic matter is related to light, atmosphere, water, temperature, microorganisms, various chemical elements, etc.

Broadly speaking, soil organic matter refers to all carbon-containing organic matter that exists in the soil in various forms, including various animal and plant residues, microorganisms and various organic substances decomposed and synthesized in the soil.

In a narrow sense, soil organic matter generally refers to a special, complex and relatively stable type of polymer organic compounds (humic acids) formed by organic residues through the action of microorganisms. Wu is blind.

Soil organic matter is an important component of the solid phase part of the soil, which is one of the main components of plant nutrition, which can promote the growth and development of plants, improve the physical properties of the soil, promote the activities of microorganisms and soil organisms, promote the decomposition of nutrients in the soil, and improve the fertilizer retention and buffering properties of the soil. It is closely related to the structure, aeration, permeability, adsorption and buffering of soil, and is usually positively correlated with the level of soil fertility under the same or similar conditions and within a certain content range.

Organic filial piety refers to the substances composed of carbohydrates, proteins, fats, nucleic acids, etc., which come from living organisms, as well as their decomposition products. These substances can be biodegraded in nature and converted into forms such as carbon dioxide, water and fertilizer.

The main nutrients of the soil include nitrogen (N), phosphorus (P) and potassium (K), among which organic matter cannot be directly absorbed and utilized by plants, but it is the key factor to maintain the long-term fertility of the soil. Because organic matter is rich in elements such as carbon and nitrogen, it can release nutrients in the form of particulate organic nitrogen and inorganic nitrogen through microbial decomposition, while also increasing soil water retention and permeability, and promoting the formation of soil agglomeration structure.

Therefore, organic matter plays an important role in the soil and can be supplemented by plant residues, compost, soil animal manure, etc. When there is a severe lack of organic matter in the soil, the productivity of the soil will be limited, affecting the growth and yield of crops.

Site conditions are a combination of various natural environmental factors that affect the formation and growth of forests, and are composed of many environmental factors: topography. Including altitude, aspect, slope shape, slope, micro-terrain, etc.; Soil includes soil type, soil thickness, humus layer thickness and humus content, soil erosion, texture, structure, compactness, pH value, gravel content, parent material type and weathering degree, etc. Hydrology.

Including groundwater level depth and seasonal variation, groundwater salinity and salinity composition, whether there is seasonal water accumulation and its duration, flooding potential, etc.; Creature. Including the distribution of plant species, species coverage, abundance and dominant species, community types, and pest and disease status. Human activity. It includes the historical evolution and current situation of land use, and the role of various human activities on the above-mentioned environmental factors.

The classification of forest land, as well as the management methods and methods, must consider the quality of the site. The site lease and grinding conditions of the transformed forest land play a decisive role in the selection of afforestation tree species, the growth and development of the plantation, the yield and the quality, and different afforestation technical measures must be adopted on the afforestation land under different site conditions.

Excerpted from Encyclopedia of Chinese Resources Science).