The fertility of the soil depends mainly on:

Soil fertility mainly includes four aspects: water, fertilizer, gas and heat.

The physical properties of soil are composed of three ratios (solid, liquid and gas phase volume ratios), texture (divided according to the mass percentage of solid sand, silt and clay particles), bulk density (dry soil mass per unit volume of undisturbed soil), porosity and structure (block, columnar, prismatic, nucleus, flake, agglomerate, micro-agglomerate) and so on. These soil indicators are interlinked, and their impact on soil fertility cannot be evaluated in isolation.

In pedology, soil structure is defined as the arrangement and combination of soil particles (single and multi-grain). Soil structure includes two aspects: soil structure and soil structure, which usually refers to soil structure.

Block, columnar, prismatic, nucleated, and flake are poor structures, with small total porosity, mainly small inactive pores, and large ventilation pores between structures, which often become channels for water leakage and fertilizer leakage. Plant roots are difficult to pierce, and dry cracks often tear off the root system.

The aggregate structure is a good structure, not only the total porosity is large, but also there are a large number of large and small pores in the interior, the aggregate is loosely arranged between the aggregates, and there are many large pores, which has the dual roles of water storage and aeration.

Soil fertility is a complex concept, not only with nitrogen, phosphorus and potassium; Calcium, magnesium, sulfur, iron, zinc, selenium and other trace elements, in addition to these also include the content of organic matter, the type and quantity of soil microorganisms, soil aggregate structure, etc., the relationship between them is complex and consistent. Soil fertility can be simply divided into physical fertility, chemical fertility, and biological fertility. Physical fertility simply refers to the aggregate structure of the soil, chemical fertility refers to the previous nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, etc., soil organisms include soil organic matter and various microorganisms in the soil, and the really healthy and fertile soil is the intersection of these three fertilizers.

It is precisely because of the carbon element nutrition in organic matter, physical fertility, especially the coordination of soil aggregate structure and water, air and heat, that various chemical elements can be efficiently absorbed and utilized, and microorganisms can obtain food and ability to multiply in large quantities, thereby promoting the operation of soil biological chain, so organic matter is a participant in the formation of three types of soil fertility, is the core substance of soil fertilizer, and plays an important role in soil fertility.

Refers to the nutrient storage, intensity and capacity factors in the soil, which mainly depend on the quantity and composition of soil minerals and organic matter. Worldwide, the approximate levels of nitrogen, phosphorus, and potassium in most mineral soils are01 and.

The nutrient content of typical farmland in China is: nitrogen; Phosphorus; Potassium. However, the ability of soil to provide nutrients to plants is not directly determined by the amount of nutrients stored in the soil, but by the availability of nutrients. The chemical position of a nutrient in the soil is the main factor that determines the effectiveness of this element.

The chemical niche is an intensity factor that can be expressed in terms of the concentration or activity of the nutrient in the soil solution.

Due to the low concentration of nutrients in the soil solution, they must be quickly replenished after they are absorbed by the plants in order to maintain their concentration in the soil solution, i.e. the intensity factor, at a necessary level. Therefore, the availability of soil nutrients also depends on the amount of solid-phase nutrient elements that can enter the soil solution, often referred to as the capacity factor. In practice, nutrient capacity factors often refer to the number of nutrients that are in a substitutional state (substitution of potassium, isotope substitution of phosphorus, etc.).

The actual availability of soil nutrients, that is, the amount of nutrients actually absorbed by plants, is also affected by the condition of soil nutrients reaching the surface of plant roots, including the interception of nutrients by plant roots, and the mass flow and diffusion of nutrients.

Physical factors. It refers to the texture, structural condition, porosity, moisture and temperature conditions of the soil. They affect the oxygen content, redox and aeration of the soil, thereby affecting the conversion rate and existence of nutrients in the soil, the nature and operation of soil moisture, and the growth capacity and physiological activities of plant roots.

Physical factors have obvious restraining effects on the changes of water, fertilizer, gas and heat in soil.

Chemical factors. It refers to the pH of the soil, cation adsorption and exchange properties, soil reducing substances, soil salinity, and the content of other toxic substances. They directly affect plant growth and the transformation, release and availability of soil nutrients.

The content of soil organic matter is an indicator of soil fertility.

In a broad sense, soil organic matter refers to all carbon-containing organic matter existing in the soil in various forms, including various animal and plant residues in the soil, microorganisms and various organic substances decomposed and synthesized by them.

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

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 soil fertility level within a certain content range under the same or similar conditions.

Soil fertility is a measure of the ability of the soil to provide the nutrients needed for the growth of crops. It is an important indicator reflecting the fertility of the soil, the comprehensive expression of various basic properties of the soil, the most essential feature of the soil that distinguishes it from the parent material and other natural bodies, and the material basis of the soil as a natural resource and agricultural production materials.

Soil fertility is the basic attribute and essential characteristic of soil, the ability of soil to coordinate nutrients, water, air and heat for plant growth, and the comprehensive reaction of soil physical, chemical and biological properties. The four major fertility factors are: nutrient factors, physical factors, chemical factors, and biological factors.