Most people say black soil, but they don't know that the soil also has a variety of colors. The more famous ones are the black soil in the northeast, the red and yellow soil in the central and southern regions, and the purple soil in the Sichuan region. What kind of magic makes the soil so many colors?

It turns out that the difference in the content of humus and mineral composition in the soil will cause the soil to show different colors. Soil humus evolves from animal and plant residues, and generally adheres to the surface of soil particles. It mainly adjusts the depth of soil color. Black soil generally has a higher humus content, because the humus is black and brown; when the humus content is low, the soil appears gray or off-white, such as Xinjiang gray desert soil. From gray to black, the color changes gradually with the increase of humus content.

Minerals have a more magical effect, because they give the soil a color other than black. For example, iron oxide is a master of color toning in soil minerals. When its content in the soil is high, the soil color becomes reddish or brownish red. Iron oxide is a fickle substance, which changes frequently in the soil. When it interacts with water, it can be transformed into yellow hydrated iron oxide. The low-lying and humid environment is the suitable condition for this change. Therefore, in such places, the soil often appears yellow. When there is poor ventilation and lack of oxygen, the iron oxide in the soil becomes ferrous oxide again. When there is more ferrous oxide in the soil, the soil appears grayish blue. White is often closely linked to changes in salt in the soil. Such as calcium carbonate, sodium carbonate, sodium chloride and other salts, as well as kaolin, aluminum hydroxide and other substances in the soil in powder form, may make the soil appear white.

Purple soil is formed by purple sandstone and shale weathering material. It is widely distributed in Sichuan and is rich in calcium, phosphorus, potassium and other nutrients. The main determining factors for its color are the crystalline iron oxide and manganese contained in it. Compound.

The color of the soil can also be changed. For example, soils that are gray, off-white, dark brown, reddish brown, etc., were mostly white soil, red soil, and yellow soil. After long-term cultivation and application of organic fertilizer, the humus in the soil increased and the soil gradually changed to black.

The color of the soil can reflect the changes in the intrinsic properties of the soil, and it is an important basis for dividing soil layers and studying soil properties. According to the color of the soil, not only can it be judged that the soil is roughly fat and thin, the appropriate crops can be planted in accordance with local conditions, and it is also convenient to "prescribe the right medicine" to improve the soil. The color of the soil also affects the soil temperature. The soil with deep color has strong ability to absorb sunlight and the soil temperature rises quickly, while the soil with light color has weak ability to absorb sunlight and the soil temperature rises slowly. The temperature of the soil is closely related to seed germination, root growth, and microbial activity.