Chemical Effects of Humic Acid on Soil
Ability to regulate and buffer PH - Soil buffering is the ability of soil to moderate the abrupt change of its system when pH changes sharply. This buffering property is very important for maintaining the stability of the environment for crop growth and development. The structure of HA is a weak acid-base system, including carboxylic acid-carboxylate, and phenolic acid-phenolic acid salt buffer system, so it has a high buffering capacity in a wide PH range.
Increase soil cation exchange capacity (CEC) and reduce soil salt content - Humic acid has 10-20 times the salt-based exchange capacity of clay minerals in the soil, and contributes 20%-70% to the CEC of the whole soil system. Therefore, humic acid plays an important role in retaining cationic nutrients that can be used by organisms and preventing cationic loss.
Regulate the redox potential and improve the electron transfer potential of soil - Humic acid is a major electron donor (reducing agent) and a major factor determining and controlling soil redox potential and thus has a great influence on many photochemical, chemical and enzymatic electronic processes in soil.
Buffering and reducing poisonous effects on soil pollutants. In fact, the effect of humus on soil heavy metal pollution is still controversial, but some research results tend to suggest that poorly soluble and insoluble HA-metal complexes can reduce or even eliminate harmful heavy metal pollution. In addition, humic substances interact with pesticides and other pollutants through adsorption, photosensitivity, and catalysis, which has a great impact on the accumulation, retention, flow, transport, degradation, biological activity, and phytotoxicity of organic matter.