What does the soil consist of? It would seem a simple question. We all know what it is. Every day we walk on it, plant plants in it that give us a crop. We fertilize the earth, dig it. Sometimes you can hear that the earth is infertile. But what do we really know about the soil? In most cases, only that it is the topmost layer of the earth's surface. And this is not so much. Let's see what components the earth consists of, what it can be and how it is formed.
Soil composition
So, the soil is the top fertile layer of the earth. It consists of various components. In addition to solid particles, it includes water and air, and even living organisms. Actually, the latter play a crucial role in its formation. The degree of its fertility depends on microorganisms. In general, the soil consists of phases: solid, liquid, gaseous and “living”. We will analyze what components form them.
Solid particles include various minerals and chemical elements. The soil contains almost the entire periodic table, but in various concentrations. The degree of fertility of the earth depends on the component of solid particles. Liquid components are also called soil solution. This is water in which chemical elements dissolve. There is liquid even in desert soils, but its quantities are scanty there.
So, what does the soil consist of besides these basic components? The space between the solid particles is filled with gaseous components. Soil air consists of oxygen, nitrogen, carbon dioxide and organic compounds. Thanks to him, various processes take place in the earth, for example, the respiration of plant roots and decay. Living organisms - fungi, bacteria, invertebrates and algae - actively participate in the process of soil formation and significantly change its composition, introducing chemical elements.
Soil mechanical structure
What the soil consists of is now clear. But is its structure homogeneous? It is no secret that the soil is different. It can be sandy and clayey or rocky. So, the soil consists of particles of different sizes. Its structure may include huge boulders and tiny grains of sand. Typically, particles entering the soil are divided into several groups: clay, silt, sand, gravel. This is important for agriculture. It is the structure of the soil that determines the degree of effort that must be applied to process it. It also depends on how well the earth will absorb moisture. Good soil contains sand and clay in equal percentages. Such land is called loamy. If there is a little more sand, the soil is friable and easy to process. But at the same time, such soil retains water and minerals worse. Clay soil is moist and sticky. It is poorly drained. But at the same time, it contains the most nutrients in it.
The role of microorganisms in soil formation
From what components the soil consists of, its properties depend. But not only this determines its qualities. From the dead remains of animals and plants, organic matter enters the soil. This is due to microorganisms - saprophytes. They play a critical role in decomposition processes. Thanks to their active activity, the so-called humus accumulates in the soil. It is a dark brown substance. The composition of humus includes esters of fatty acids, phenolic compounds and carboxylic acids. In the soil, particles of this substance stick together with clay. It turns out a single complex. Humus improves the quality of the earth. Its ability to retain moisture and minerals increases. In marshland, the formation of humus mass is very slow. Organic residues are gradually compressed into peat.
Soil formation process
The soil forms very slowly. In order for a complete renewal of its mineral part to approximately a depth of 1 meter, it takes at least 10 thousand years. What the soil consists of is the products of the constant work of wind and water. So where does the soil come from?
First of all, these are particles of rocks. They are the basis of the soil. Under the influence of climatic factors, they are destroyed and crushed, settling on the ground. Gradually, this mineral part of the soil is colonized by microorganisms, which, processing organic remains, form humus in it. Invertebrates, constantly breaking through passages in it, loosen it, contributing to good aeration.
Over time, the structure of the soil changes, it becomes more fertile. Plants also affect this process. Growing, they introduce organic matter into the soil, changing its microclimate. Human activity also affects soil formation. He cultivates and cultivates the land. And if the soil consists of infertile components, then a person fertilizes it, introducing both mineral and organic fertilizing.
Soil classification by composition
In general, a generally accepted classification of soils does not currently exist. But nevertheless it is customary to divide them into several groups according to their mechanical composition. This division is especially relevant in agriculture. So, the classification is based on how much the soil consists of clay:
- loose sand (less than 5%);
- cohesive sandy (5-10%);
- sandy loam (11-20%);
- light loamy (21-30%);
- medium loamy (31-45%);
- heavy loamy (46-60%);
- clayey (more than 60%).
