1. Soil organic matter
Soil organic matter is an important component of the solid phase of the soil. Although the content of soil organic matter only accounts for a small part of the total soil, it has a great impact on soil fertility and soil cultivability. Data show that within a certain range, the content of organic matter is positively correlated with the level of soil fertility . Therefore, soil with too low soil organic matter has low immunity, which is easy to compact and acidify, and crops are easy to get disease.
Studies have shown that if the organic matter in the soil is reduced from 2% to 1.5%, the soil's fertility retention capacity will drop by 14%.
In addition, soil organic matter profoundly affects water storage. One acre of soil, one inch thick, and 2% organic matter can hold up to 121,000 liters of water, and 5% and 8% soils can hold 303,000 and 485,000 liters, respectively.Studies have shown that the increase in soil organic matter from 1% to 3% increases the soil's water retention capacity by 6 times.
Soil organic matter in the end there are those who make use?
（1）. Organic matter promotes the growth and development of crops. Humic acid in soil organic matter can enhance plant respiration, increase cell membrane permeability, and enhance the absorption of nutrients. At the same time, vitamins and some biological hormones in organic matter can promote plant growth and development.
（2）. Organic matter promotes the formation of soil structure, improves soil physical properties, and improves soil structure Humus in organic matter is the main cementing agent for soil aggregates. Soil organic colloid is an indispensable cementing substance to form a water-stable aggregate structure, so it helps the cohesive soil to form a good structure, thereby changing the soil pores and water, The air ratio creates a suitable soil tightness. The viscosity of soil organic matter is much smaller than that of clay particles, only a fraction of that of clay particles. On the one hand, it can reduce the viscosity of cohesive soil, reduce farming resistance, and improve farming quality; on the other hand, it can improve the agglomeration of sandy soil and improve its excessively loose state.
（3）. Organic matter improves soil's fertility retention capacity and buffer performance. The organic colloid in the soil organic matter has a large amount of negative charge and has a strong adsorption capacity. It can absorb a large number of cations and water. Its cation exchange capacity and water absorption rate are several times, even dozens of times larger than clay particles, so it can Improve the soil's ability to retain fertilizer and water, and at the same time improve the soil's acid-base buffer.
（4）. Soil organic matter content is the key to the survival of beneficial soil microorganisms! It is not only a stable and long-lasting substance containing life functions. And it contains almost all kinds of nutrients needed by crops and microorganisms. Therefore, the soil organic matter lacks the soil beneficial microorganisms naturally, but the harmful organisms are mostly! This is also an important factor that makes crops vulnerable to disease!
According to these important properties and functions of soil organic matter, it is not difficult to see that the soil with high soil organic matter content has a higher level of soil fertility, which not only provides rich nutrients for crop growth, but also has strong water and fertilizer retention capacity, which can reduce nutrients. Loss, save the amount of fertilizer and improve fertilizer utilization. The opposite is true for soils with less organic matter. Therefore, the first thing we must consider now is how to improve soil organic matter. Soil improvement is the top priority!
2. Soil pH
Soil pH affects the soil's fertility supply capacity and the healthy growth of crops. Most crops like neutral soil, that is, the pH is between 6.5-7.5. Data show that various mineral nutrients in the soil are most effective when the pH is neutral, and the partial acidity or partial alkalinity of the soil will affect the absorption of some elements, especially trace elements.
In acidic soil, phosphoric acid in the soil is easily combined with iron and aluminum ions to form insoluble substances and be fixed, which affects the absorption of phosphorus by vegetables; potassium, calcium and other elements are easily replaced by excessive hydrogen ions and lost; in addition, acidity The dissolution of copper, zinc, manganese, boron and other trace elements in the soil increases. If micro-fertilizers are added, vegetables may be harmed. In alkaline soil, water-soluble phosphate is easily combined with calcium to form insoluble calcium phosphate, which reduces fertilizer efficiency; it also fixes trace elements such as iron and zinc, causing iron deficiency in vegetables.
When the soil pH is 6-8, the available nitrogen content is high; when the pH is about 6.5, the availability of phosphorus is the highest; when the pH is greater than 6, the soil potassium, calcium, and magnesium content is high; when the pH is 4.7-6.7 ; The effectiveness of boron is high; when the pH is greater than 7, the solubility of boron is significantly reduced.
3. The total salt of the soil
continues to put a large amount of fertilizer into the soil, and the total salt content of the soil will increase. If the total salt content of the soil reaches a certain range, the soil will have a tendency to salinization, and at the same time, due to the total salt content If the soil solution concentration is too high, it will directly affect the growth of crop roots.
On the one hand, total soil salt can reflect the content of soil mineral elements, and more importantly, it can determine whether the soil is healthy and suitable for planting vegetables. The total salt content of the soil in the greenhouse must be controlled below 2g/kg, so that the soil can always be maintained in a healthy state of sustainable fertilization. Otherwise, once the total salt content of the soil exceeds the standard, then vegetable planting in the soil is like flooding pickles. Light vegetables will grow badly, and serious vegetables will die or even pull up the garden.
4. Trace elements in soil
There is a well-known theory in crop cultivation-the barrel effect, which proves that the yield of crops is determined by the nutrients with the least content. That is to say, if there is a lack of necessary nutrients in the soil, even if other nutrients A large amount of supplementation will not get a good yield.
In crop cultivation, the medium and trace elements in the soil are often lacking in crops due to absorption and consumption and antagonism from other nutrients. On the one hand, it may be that these middle and trace elements are really lacking in the soil. On the other hand, it may be due to the excessive use of other large-scale elements, which inhibits the absorption of these middle and trace elements.
Therefore, under the condition of fully understanding the content of trace elements in the soil, timely supplement the lack of elements, and at the same time rationally use other large elements to avoid mutual antagonism between ions in the soil, thereby improving the absorption and utilization efficiency of trace elements in the soil.
5. Soil microorganisms
There are many types of microorganisms in the soil, including bacteria, fungi, actinomycetes, algae and protozoa. The quantity is also very large, there are hundreds of millions to tens of billions in 1 gram of soil. Most soil microorganisms are beneficial to the growth and development of crops. They have a significant impact on the formation and development of soil, material circulation and fertility evolution. Of course, there are also some unpopular pathogenic microorganisms. So what are the roles of microorganisms in the soil?
First, soil microorganisms can form soil structure. Soil is not simply a simple combination of soil particles and chemical fertilizers. As an active component of soil, soil microorganisms contribute to soil particles through the exchange of oxygen and carbon dioxide through metabolic activities in their own life processes, and the secreted organic acids. A large aggregate structure is formed, and finally a real soil is formed.
Secondly, the most significant effect of soil microorganisms is to decompose organic matter, such as organic fertilizers applied to the soil. Only through the action of soil microorganisms can they decay and decompose, release nutrient elements for crop utilization, and form humus to improve soil structure. And farming.
Third, soil microorganisms can also decompose minerals, and the metabolites of soil microorganisms can promote the dissolution of insoluble substances in the soil. For example, phosphorous bacteria can decompose phosphorus in phosphate rock, and potassium bacteria can decompose potassium in potassium ore to facilitate crop absorption and utilization and improve soil fertility. In addition, the decomposition and utilization of urea is also inseparable from soil microorganisms. These soil microorganisms are like fertilizer processing plants in the soil, processing the mineral fertilizers in the soil into a form that can be absorbed by crops.
In addition, soil microorganisms also have nitrogen fixation. Nitrogen accounts for 4/5 of the air composition, but plants cannot directly use it. Some microorganisms can use their nitrogen fixation effect to convert nitrogen in the air into fixed nitrogen compounds that plants can use. Such soil microorganisms are equivalent to the soil having its own nitrogen fertilizer production workshop.
Microorganisms can also degrade residual organic pesticides, urban sewage and factory waste in the soil, decomposing them into low- or even harmless substances, and reduce residual toxicity.
6. Soil harmful substances
The soil contains all kinds of mineral nutrients, of course, it also contains harmful substances that crops do not like, such as chlorine, sodium ions and heavy metal ions. If these things accumulate in the soil in large quantities, they will harm crops, affect crop growth, and cause Food safety issues. For the soil, the increase of harmful substances is mainly caused by unreasonable fertilization. For example, the use of unqualified fertilizers and fake fertilizers containing heavy metals will increase the harmful substances in the soil and ultimately affect the growth of crops.
Therefore, the scientific and rational use of regular fertilizer products is also an important factor in maintaining the sustainable development of the soil.