The improvement effect of Humic Acid on soil - chemical effect

     Humic acid substances (HS) are an important guarantee for building soil fertility, stabilizing soil quality and maintaining soil safety. Soil fertility refers to the supply of all elements (water, fertilizer, air, heat, etc.) required for crop growth and development, and is also the fundamental characteristic of soil. HS, especially Humic acid, which accounts for more than 60% of soil organic matter, is the core substance of soil quality and plays a decisive role in soil fertility. As a natural macromolecular organic matter, humic acid has many effects on soil, making the soil fertile and generating land productivity by changing the physical, chemical, nutritional and biological properties of the soil. This article will describe it from the chemical aspect.

1. pH regulation and buffering capacity

    The ability of soil to mitigate sudden changes in its system when the pH value changes suddenly is called soil buffering. This buffering capacity is very important for maintaining a stable environment for crop growth and development. The structure of HUMIC ACID is a weak acid-base system, including carboxylic acid-carboxylate and phenolic acid-phenolate buffer systems, so it has a high buffering capacity in a wide pH range. For example, the soil pH in Northeast and North my country is relatively high. Using NHA as an acidifier can stabilize the soil pH value at 5.5~6, overcoming the disadvantage of using sulfuric acid to adjust the pH value, which can easily cause a sharp rise in pH, and significantly reducing the phenomenon of rice seedling rot in early spring due to low temperature.

2. Improve soil cation exchange capacity (CEC) and reduce salt content.

   CEC indicates the ability of soil to absorb bases and replaceable cations, and is an extremely important functional indicator in determining soil fertility. The base exchange capacity of HUMIC ACID is 10 to 20 times that of clay minerals in the soil, and its contribution to the CEC of the entire soil system accounts for 20% to 70%, which shows its huge role. Therefore, HUMIC ACID plays an important role in retaining bioavailable cationic nutrients (such as NH₄⁺、K⁺、Mg²⁺、Ca²⁺etc.) and preventing cation loss.And because the soil has enhanced its ability to replace and bind Ca²⁺ and Mg²⁺ after HA adsorption, and the soil structure is improved, the bases such asNa⁺、CO₃^2-、HCO₃^-、and CI^- are desorbed and leached, playing the role of "isolating salt and suppressing alkali".

3. Regulate redox potential and improve soil electron transfer potential

 HUMIC ACID is the main electron donor (reductant) in soil and the main factor that determines and controls the redox potential of soil. Therefore, it has a great influence on many photochemical, chemical and enzymatic single-electron processes in soil.

4. Buffering and detoxification effects on soil pollutants

  There is still much controversy about the effect of HS on soil heavy metal pollution, but research results tend to show that poorly soluble and insoluble HA-metal complexes can reduce or even eliminate the pollution of harmful heavy metals in soil.

In conclusion, incorporating humic acid and other organic fertilizers is a key method for enhancing soil quality.