Analysis of the characteristics of different types of soil, and how to improve soil according to local conditions?

Soil is gradually formed from the weathering of surface rocks over millions of years, with the participation of microorganisms. The different properties of rocks (parent materials) and natural climatic conditions in various regions lead to significant differences in soil texture, cohesiveness, and acidity/alkalinity among different areas. Although soilless cultivation technology is developing rapidly, traditional soil cultivation will still be the mainstream of agricultural development in the future. Soil is fundamental for crop growth and even for ensuring human food security. The quality of soil properties directly affects crop growth, development, yield, and quality formation.
The overall trend of soil properties in China is that acidity gradually increases from north to south, and soil viscosity gradually increases. The soil characteristics suitable for the growth of most crops are: moderate acidity and alkalinity, and suitable sandiness and viscosity. However, due to natural reasons, improper irrigation and fertilization methods, and improper cropping systems, saline-alkali soils and sandy soils in the northwest, acidic and clay soils in the south, as well as saline-alkali and clay soils in some parts of the northeast and central regions, have become important obstacles to crop yield increase and quality improvement.
What characteristics must soil suitable for crop growth possess? What are the impacts of soil with different acidity, alkalinity, and sandiness on crop growth? How should soil with different textures be improved?
This article will address the above issues in conjunction with production practice, aiming to provide reference and guidance for producers.

1、 What are the characteristics of high-quality soil that ensure good crop growth
1. Moderate acidity and alkalinity
After long-term evolution and natural selection, most plants in nature have adapted to neutral soil environments with moderate acidity or alkalinity. However, excessive soil acidity or alkalinity can disrupt the balance between soil nutrient supply, root absorption, and plant needs. For example, the most suitable absorption range for phosphorus is in a neutral environment. When the acidity is too high, it will precipitate with excess aluminum and the roots cannot absorb it; In soil environments with excessive alkalinity, calcium ions in the soil are prone to form carbonate precipitates and lose their effectiveness.
The normal growth of plants often requires symbiotic bacteria in the soil roots to assist in the decomposition, transportation, and absorption of mineral elements. These symbiotic bacteria are sensitive to changes in soil acidity and alkalinity, and acid-base imbalance can cause the stability of symbiotic microbial colonies in plant roots to be disrupted, leading to a decrease in root absorption capacity.
2. Good soil structure
Soil structure mainly refers to the coordination between soil permeability, permeability, water holding capacity, and fertilizer retention capacity. There is a contradictory relationship between the two, and the soil structure that enables both parties to achieve mutual coordination is the "granular structure". The basic characteristics of the "granular structure" can be summarized as follows:
The aggregate structure is formed by the mutual bonding of soil small aggregates. Soil particles with small distances between them combine to form small aggregates, which can bind internal and external nutrients and prevent leaching and waste caused by rainwater infiltration. Therefore, they have good water and fertilizer retention ability, but poor air and water permeability; And these small aggregates combine with each other to form larger aggregates. The distance between small aggregates within the larger aggregates is relatively large, which allows water and gas to flow smoothly, thus having good permeability and breathability, but insufficient water and fertilizer retention capacity.
However, the internal characteristics of small aggregates and the characteristics between small aggregates complement each other in terms of water and fertilizer retention, as well as breathability and permeability, resulting in a coordinated and balanced structure of the aggregates that combines permeability, breathability, and water and fertilizer retention. This is the optimal soil structure for plant growth.

3. Rich in organic matter
On the one hand, organic matter can serve as a fertilizer source to provide the most comprehensive nutrients for crop growth, improve soil structure, increase the viscosity of sandy soil, and increase the looseness of cohesive soil; It is also possible to store available mineral elements in the soil through the formation of soil colloids after decomposition, in order to prevent loss or transformation into ineffective states, and to continuously and steadily provide nutrients for crop growth during plant growth.
At the same time, organic matter can also provide effective buffering for soils with excessive acidity, alkalinity, and high salt content, weakening the adverse effects of soil acidity, alkalinity, and high salt content caused by improper fertilization or irrigation on crops. It can also weaken the damage caused by excessive heavy metal content to crops and the adverse effects on quality,
2、 What are the characteristics of soils with different textures
1. Characteristics and adverse effects of acidic soil
The pH value of acidic soil is below 6.5, and high levels of (H+) and aluminum ions (Al3+) are the main reasons for high acidity. Under acidic environmental conditions, iron ions (Fe2+) and manganese ions (Mn2+) in the soil will also be high.
The adverse effects are mainly reflected in the following points:
Severe nutrient leaching
Due to the thorough weathering of acidic soil, the decomposition and release of mineral elements such as K+inside are relatively complete. In addition, acidic soil is mostly located in rainy areas in the south. Under the leaching of rainfall, these mineral elements that are released and difficult to be adsorbed by soil particles are easily transported to the deep layers of the soil during the process of water infiltration, and cannot be absorbed by the roots, resulting in soil nutrient deficiency and barrenness.
Inhibit the absorption of elements such as P, Ca, Mg, etc
Under acidic soil conditions, excessive aluminum ions, iron ions, and manganese ions will react with calcium and magnesium ions in the soil, resulting in the precipitation of compounds that cannot be absorbed and utilized by plants. Taking phosphorus as an example: phosphorus is already easily adsorbed by the soil and becomes an ineffective state, while free phosphorus forms iron phosphorus, manganese phosphorus and other compounds and precipitates with excess Fe2+and Mn2+, further exacerbating the deficiency of available phosphorus and causing soil phosphorus deficiency.
Disrupting microbial communities
Excessive acidity can also have adverse effects on the microbial community structure in soil, thereby reducing the ability of microorganisms to decompose soil organic matter, lowering the soil's ability to supply nitrogen fertilizer, and even causing nitrogen deficiency. It can also affect the plant cells' ability to absorb and transport mineral elements. For example, high acidity can cause toxicity to leguminous rhizobia that have nitrogen fixing properties, thereby reducing the formation of rhizobium communities and decreasing nitrogen fixing function.
Reduce soil fertility
In terms of tillage properties, acidic soil structures are suitable for cultivation and crop growth with a narrower water content. Often, when the water content is high, it becomes muddy and slippery, and when the water content is low, it forms a "sticky mud" that is as hard as stones.

2. Characteristics and adverse effects of alkaline soil
The pH value of alkaline soil is generally above 7.5, with typical characteristics of a large amount of OH - and a significant increase in Na+.
The adverse effects are mainly reflected in the following points:
Causing plant nutrient deficiency
The presence of excessive Na+can reduce the absorption of nutrients such as P and K due to the antagonistic effect between ions, resulting in plant growth deficiency. Causing physiological dehydration
Under alkaline conditions, the concentration of mineral ions in the soil increases, and the salt content is too high. During plant growth, these water-soluble salts can cause difficulty for the extended roots to absorb water due to their high concentration, resulting in water stress and physiological drought in plants. This leads to adverse growth conditions such as small leaf area, low growth, and stunted growth of crops.
Reduce soil fertility
In terms of soil fertility, soils with high alkalinity undergo significant fluctuations with the increase or decrease of water content, resulting in a narrow range of moisture content suitable for cultivation and plant growth. Drought induced rupture under water deficient conditions can easily tear off roots and cause serious adverse effects on crops.
3. Characteristics of sandy soil
advantage
The soil has relatively large basic particles and large gaps between particles. The soil is loose and has strong permeability and air permeability. Microorganisms in the soil, with sufficient organic nutrients, can rapidly reproduce in large quantities due to the abundant supply of oxygen, thus being able to quickly decompose organic matter and release fertilizer efficiency.
In terms of the growth of crop roots, due to good air permeability, new roots have strong ability to grow and absorb. In terms of soil fertility, sandy soil has a longer suitable cultivation period.

shortcoming
However, due to poor water storage capacity, it is often more likely to cause crop drought and water shortage. Sandy soil, due to its good aeration, often has a larger temperature difference between day and night, which has a negative impact on crop growth.
However, due to the limited number of small gaps, the soil has a weaker ability to store nutrients, often resulting in rapid growth of seedlings in the early stages and insufficient nutrient supply in the later stages, leading to fertilizer loss.
Fertilization guidelines
The characteristics of fertilizer supply determine that the impact on crops is to "produce small seedlings, not old ones". For sandy soil, attention should be paid to late fertilization, and the principle of fertilization should follow the principle of small amounts and multiple times.
4. Characteristics of Viscous Soil
advantage
In contrast to sandy soil, the basic soil particle volume of clayey soil is smaller. For the same weight of soil, there are more soil particles, which results in a larger surface area of the soil under a certain weight. The increase in surface area enhances the attraction and cohesion between soil particles. This results in a stronger mutual adsorption ability between soil particles, with more small gaps and fewer pores, enhancing their ability to retain water and nutrients. Additionally, due to the slow release of fertilizer efficiency, it ensures even supply of nutrients at all growth stages.
shortcoming
The permeability of clayey soil is weakened, and the microorganisms in the soil are unable to obtain sufficient oxygen supply, resulting in a decrease in their vitality and reproductive ability, and a decrease in their ability to decompose organic matter in the soil. Therefore, the release of fertilizer efficiency in clayey soil is relatively slow, which often leads to a relative lack of nutrient supply in the early stage of production. However, with the extension of the growth period, nutrients can often be better guaranteed in the later stage.
In terms of soil fertility, due to the high viscosity of this type of soil, the suitable cultivation time is directly related to the soil moisture content. When the moisture content is low, the soil is often as hard as stones, and when the soil moisture is high, it is often sticky and difficult to walk. Therefore, agricultural activities such as tillage should choose a soil environment with appropriate humidity to ensure efficiency.
Fertilization guidelines
The characteristics of fertilizer supply determine that the impact on crops is "growing old seedlings, not small seedlings". For this type of soil, bottom fertilizer should be applied heavily in production, and early fertilization can be biased to prevent insufficient fertilizer supply in the early stage and reduce it appropriately in the later stage.

3、 How to improve soils with different properties
Whether it is acidic, alkaline, sandy or clayey soil, the application of Organic Fertilizer can improve soil properties. The colloids formed by the decomposition of organic matter can adsorb excessive H+or OH - ions, thereby reducing the adverse effects of excessive H+or OH - on crop growth in the soil; On the other hand, these colloids can weaken the bonding ability between clay soil particles, making them more loose and breathable; The bonding ability between particles in relatively loose sandy soil can also be enhanced, thereby increasing its ability to store nutrients and water.
1. Acidic soil
Apply quicklime
The most direct way is to apply lime (quicklime, calcium oxide, turns into calcium hydroxide when it comes into contact with water, which is a typical alkaline substance) before plowing. The appropriate amount of lime to be applied is about 50 pounds per mu of land per year, until the pH is adjusted to near neutral. It should be emphasized that in areas with organic matter content, the application of lime will make the soil harder and the tillage properties worse. In addition, it will chemically harden with sulfate ions produced due to the application of fertilizers containing sulfate ions, forming calcium sulfate, which is the main component of gypsum. Therefore, in order to prevent acid adjustment from reducing tillage properties, a certain amount of decomposed organic fertilizer needs to be applied.
Apply alkaline fertilizer
Ash from plants and trees is alkaline, and can be applied according to the standard of 50 kilograms per acre per year; Other commonly used fertilizers that exhibit alkalinity include ammonium bicarbonate, calcium magnesium phosphate fertilizers, and nitrate fertilizers (crops, especially vegetables, have a preference for nitrate nitrogen, where one nitrate can exchange an equivalent OH - from the plant root system to neutralize soil acidity).
2. Alkaline soil
Application of sulfur powder
Sulfur powder is widely used for soil improvement in blueberry cultivation. The main principle of regulating soil alkalinity is that sulfur atoms are widely present in the soil under the action of sulfur bacteria, ultimately forming sulfuric acid, which can effectively neutralize excessive OH - in the soil.
Apply acidic organic compounds
A better choice is peat soil and pine needles, both of which are acidic (the pH value of peat soil in some southern regions can reach 3.5). They not only balance the acidity and alkalinity, but also improve soil structure. They can also be used as soil acid regulating fertilizers for rice seedling cultivation.

3. Sandy soil
Sticky sand
Mixing highly viscous silt, river mud, and pond mud into it to increase its viscosity is labor-intensive and costly, and requires sufficient cost review and justification before adoption;
deep plowing
Mixing the more viscous soil in the deep soil with the sandy soil in the surface layer to increase soil viscosity is a relatively low-cost and operationally feasible method for a shallow sandy soil plot;
4. Cohesive soil
Sand mixed with stickiness
Mixing river sand and other materials with freshly made soil, and then tilling and mixing them evenly, is also a labor-intensive method that requires careful cost accounting before deciding whether it is cost-effective;
other measures
Secondly, grass beach, vermiculite, perlite, etc. can be applied to increase the proportion of large pores; For soils with sandy patterns in deep layers, deep plowing can be used to increase porosity and reduce viscosity, which is also an efficient method.

Conclusion
Applying decomposed organic fertilizer is a universal and effective method for improving various poor soils. However, currently, China's crop straw has been facing the problem of how to deal with it under the background of banning burning. With the premise of solving the cost, returning straw to the field has huge promotion and application space in improving soil.
In addition to improving soil properties themselves, it is also possible to adjust the types of cultivated crops according to local conditions to adapt to soil characteristics. For example, tea trees, azaleas, and blueberries all prefer acidic soil. Among them, blueberries have a suitable pH range of 4.5-5.5 for growth and are typical acid loving plants. Economic crops with strong salt alkali tolerance include goji berry and jujube (both can tolerate a pH value of around 8.5). Plants with strong salt alkali tolerance, such as sesbania, reed, and alkali plant (able to tolerate pH 8-9 alkalinity), have relatively low economic viability. Due to the limited number of plants suitable for growth in strongly alkaline soils, the focus should be on expanding the plant growth area and quantity, protecting and improving the environment, rather than economic development and utilization.