The effect of humic acid on soil improvement

       In addition to the physical and chemical aspects, this article will explain the improvement effect of humic acid on soil from three aspects: nutrient activation and storage, biological effects, and improvement of acid-base desertified soil.

1. Activation and storage of nutrients

The nutrients required by plants are continuously accumulated and provided through the fixation and mineralization process of soil HS.Some experts believe that N, P, and S can exist in the complex organic polymers and HS structures of the soil, and alkaline nutrients such as inorganic cations Ca²⁺, Mg²⁺, and K⁺ exist on the surface of soil organic matter. Trace elements such as Mn²⁺, Cu²⁺, Fe²⁺, and Zn²⁺ exist in the form of organic complexes; the storage and release of nutrients are generally carried out through two basic processes: N, P, and S are mainly biological processes, and trace element cations are mainly physical and chemical processes. Practice has shown that even if chemical fertilizers and trace fertilizers are not applied at the same time, soils that have been applied with HA for many years can still release a considerable amount of P, S, and other cationic elements. The reason is that HS activates the fixed elements. A large amount of research data shows that the storage, activation, and effectiveness of HA on soil nutrients are positively correlated with the amount of Humic Acid added, and are also related to the environmental pH, the source and composition of Humic Acid.

2. Biological effects

The activity of soil organisms and microorganisms has a significant impact on soil fertility, and HS can provide the main energy source for soil organisms and microorganisms, help establish populations, and promote beneficial activities, including promoting the adsorption and transformation of toxic metals or organic elements by soil microorganisms and their metabolites, reducing their toxicity. Bacteria, actinomycetes, fungi, algae, protozoa, nematodes and even some large organisms (such as earthworms) living in the soil are related to the content and transformation of organic matter or HS. A large number of experiments at home and abroad have shown that the application of HA can significantly promote the activity of microbial communities and increase the activity of enzymes. According to the measurement, the number of fungi and enzymes increased after the application of HA is: aerobic bacteria about 100%, actinomycetes 30%, silicate bacteria 90%, fiber decomposing bacteria 500%, cellulase 6%~50%, phosphatase 8.4%~46%, protease 14%~43%; ammonia bacteria and nitrogen-fixing bacteria increased by an average of about 40%, and the total microbial activity (measured by CO2 release method) increased from 5.58% of the control to 10%~20%, among which peat HA had the best effect.

3. Effect of using HA soil conditioner

1. Improvement of saline-alkali land

Soil salinization is a global problem. There are about 955 million hectares of saline-alkali land in the world, and about 99 million hectares in my country, accounting for 10.3% of the world. Among them, about 13 million hectares of saline-alkali land have the potential for agricultural development and utilization, accounting for more than 10% of my country's cultivated land. A large number of studies at home and abroad have shown that under saline-alkali stress conditions, HA can reduce the conductivity of soil media, increase aggregate content, improve soil water retention and cation exchange capacity, and protect plant growth.

2. Improvement of acidified soil

Since the 1980s, soil acidification in my country has become increasingly serious. The pH of almost all soils has dropped by 0.13~0.80, and the acidification has a tendency to expand. At present, most of my country's acidic soils are concentrated in the red soil area in the south. This type of soil has poor structure and excessive water. The soil particles absorb water and disperse into a paste. When it is dry, it becomes dense and hard. A large amount of acidic substances such as Fe and Al that are not easy to flow accumulate in the soil. In addition, Fe3+, A13+, etc. can easily fix phosphorus, reducing the effectiveness of phosphorus. Studies have shown that the effect of applying humic acid calcium (magnesium, silicon) substances in acidic soil is very obvious. Low-grade coal powder with high HA content can also be compounded with alkaline substances such as lime, calcium magnesium phosphate fertilizer, and electric coal.

3. Improvement of desertified soil

my country is one of the countries most seriously affected by desertification in the world. The water and fertilizer retention capacity of desertified soil is poor. Therefore, improving the water and fertilizer retention capacity of desertified soil and promoting plant growth on desertified soil are major issues in the restoration of poor quality soil. The application of humic acid substances can greatly increase the content of 0.25mm water-stable microaggregates and the total amount of microorganisms, which is conducive to the production and reproduction of microorganisms. The test results show that soil organic matter, HA, and soil organic-inorganic composite content are positively correlated with the application amount of activated lignite.

Various practices have shown that the application of HA substances can provide plants with the nutrients they need, create a favorable living environment for soil organisms and microorganisms, and have a significant effect in improving acidic, alkaline and desertified soils.