Why are there different colors of soil? What determines the color of the soil?

Soil color is actually a reflection of the composition of soil materials and their properties, soil material composition and its properties are determined by different natural conditions, i e soil formation factors, and in different areas, a single color of rocks or minerals of the same color weathering after weathering to form white soil and green soil, in high temperature and rainy areas, due to the circulation of active substances, strong weathering and leaching make the soil silica and other substances lose and desilicon, however, a small amount of fluid iron oxide and alumina are rich in the soil layer, Rich in iron and aluminized, while iron oxide is red.

In the soil, calcium carbonate accumulation layers are formed, which are chestnut or brown respectively, therefore, it is called maroon soil and brown calcareous soil, In cold climatic conditions, a large amount of organic matter provided to the soil by grassland plants for a long time is corroded and accumulated, thus forming fertile black soil, soil humus is generally attached to the surface of soil particles, and its dosage is mainly to adjust the depth of soil color. Black soils are generally high in humus because humus is black and brown.

This is the agricultural proverb, the black soil is oily, not fat but also long grain, its proverb is actually how it came about, and when the humus content is less, the soil is gray or gray-white, like gray desert soil, the color changes from gray to black with the increase of humus content, purple soil He is actually formed by the weathering of purple sandstone and shale, which is widely distributed in Sichuan, rich in calcium, phosphorus, potassium and other nutrients.

The determinants of soil color are mainly crystalline iron oxide and the manganese compounds contained in it, the color of the soil can also be changed, for example, gray, off-white, dark brown, reddish-brown and other soils are mostly original white soils, red soils and yellow soils. Under the action of cultivation and application of organic fertilizer, the humus in the soil has increased, and the soil gradually transitions to black.

The question of why there are different colors of soil and what determines the color of the soil is explained here today.

In all parts of the world, not only the skin color of people is different, but even the color of the clay is also different.

Face the loess with your back to the sky"This sentence describes the hard work of farmers, but why use the color "yellow"? There is also the song that sings, "My family lives on the high slope of the loess, is all the land in my country yellow?"

To understand the color of soil, we first need to know what soil is. Soil is the loose layer of the earth's land surface. It possesses some fertility and plants can grow in it.

The Earth was born 4 billion years ago, but there was no soil at that time. The formation of soil is a long and complex process, which involves the joint action of physical, chemical and biological aspects.

Soil types in the monsoon region of China.

and color from south to north and from east to west with the climate latitude and radial changes produce regular changes from Hainan Island.

In Heilongjiang, the climate changes from warm in the tropics to wet and cold in the cold temperate zone, and the soil color also changes from brown soil and red soil to black soil and dark brown soil.

From Shandong to Xinjiang, the climate changes from warm to dry and cold, and the soil color changes from brown soil, brown soil to brown soil, brown soil to brown lime soil, and brown desert soil.

This color change is influenced by many factors, even in the same soil, the top 10 cm and the 20 cm below are not necessarily exactly the same, the main influencing factors are metals and organic matter.

Soil is made up of 45% mineral solids, 25% air, 25% water, and 5% organic matter. There are also many substances in organic matter, such as carbohydrates.

lignin, nitrogenous compounds, etc. The soil can grow plants because of this 5% organic matter.

Soil is like a small world of recycling, the soil contains a lot of microorganisms, and there are many plants and animals growing on it, and it asks for nutrients from the soil. When these creatures die, their nutrients return to the soil.

The higher the organic matter content of the soil, the darker the color of the soil. Northeast.

The climate is cold, and animals are not active before a large number of human beings cultivate the soil, so we see that organisms nourish the soil, but the organic matter in the soil is not used, and the organic matter is more and more, and the soil is getting darker and darker.

In contrast, the southern region of China has a high temperature and rainy climate, and the surface weathering and soil formation are very active, where the soil is fully dissolved by rainwater, and there is a lot of silica.

and other substances are washed away, only iron oxide.

And silica because of its low fluidity, it is not washed away and collects in the soil, so the color of the soil changes to the color of iron oxide, which becomes red.

In some places at higher latitudes, the climate is generally mild, dry, and with a lot of precipitation.

It is often less than the amount of evaporation, the weathering effect is not strong, and the state of the soil is weak leaching. Here, rain only washes away some soluble substances, but not iron, aluminum, etc. The soil here contains calcium carbonate produced by calcium and plants.

When these calcium carbonates accumulate in the soil, they form brown.

Earthy color. The color of soil under sunlight can reflect the changes of soil intrinsic properties, which is an important basis for dividing soil layers and studying soil properties. The depth of soil color is related to humus.

When the humus content is high, the soil is black, such as the cold black soil in the north; When the humus content is low, the soil is gray, such as the gray desert soil in Xinjiang. The color of the soil is also related to the type of compounds contained in the soil. Iron hydroxide is red.

When the content in the soil is high, the soil will show different degrees of red, brownish-red and brownish-yellow. Silica, calcium carbonate, kaolin, aluminum hydroxide, etc., are white, and when any of these compounds are contained in the soil, it is gray, light gray, or pale yellow.

Because the content of putrefactive biomass contained in the soil in different regions is different, the composition of minerals is different, resulting in different colors of soil. Putrefactive biomass is the carcass of decaying plants, animals and microorganisms, which attach to the surface of the soil, and the color of the soil varies from brown to black because the decaying things are brownish-yellow to black.

The color of the soil in sunlight can reflect the changes in the intrinsic properties of the soil. The colors are minerals, chemical elements, and humus.

In China, the soil mainly has the following colors: black soil, white soil, brick red soil, brown soil, loess, red soil, soil, clay, sand, dark brown soil, white clay soil, gray desert soil, loess soil, red clay, aeolian sandy soil, purple soil, fluvial soil (light meadow soil), swamp soil, rice irrigation silt soil and irrigation desert soil.

Among them, the best quality is the black soil, which is famous for its high organic matter content, fertile soil, loose soil, and optimal for farming.

From a global point of view, there are three places that can be called the black soil region, one is the Great Plain of Ukraine, one is the Mississippi River Basin, and the other is the Songliao River Basin in Northeast China, due to the influence of the temperate monsoon climate, the Northeast region has high temperature and rain in summer, meadow herbaceous plants grow luxuriantly, and a large amount of organic matter accumulates on the ground and underground.

In the long and cold winter, the soil freezes, the microbial activity is weak, and the organic matter slowly decomposes, gradually forming a 60,100 cm humus layer of black soil, and the black soil area in Northeast China is about 700,000 square kilometers, accounting for about 1 5 of the global black soil area.

The soil in various parts of our country has a variety of colors, in addition to the common black and yellow soil, there are also red, white, brown, gray and other colors of soil.