Humic acid fertilizer is an efficient and environmentally friendly fertilizer that plays a significant role in agricultural production. The following are the main roles and functions of humic acid fertilizer: 
Humic acid fertilizers can increase the organic matter content of the soil, improve soil structure, enhance the soil's water and nutrient retention capacity, and increase the soil's acid-base buffering capacity. These functions effectively enhance soil fertility and promote plant growth. 
Humic acid in humic acid fertilizers can promote the development of plant root systems, increase the plant's absorption capacity for water and nutrients, enhance the plant's stress resistance, and thereby promote plant growth. Additionally, humic acid can stimulate physiological metabolism and promote growth and development. 
Humic acid fertilizers can enhance the photosynthesis efficiency of crops, increase their yield and quality. Humic acid can also improve the utilization rate of various nutrients in the soil, reduce the loss of chemical fertilizers and enhance their effectiveness. 
The organic matter in humic acid fertilizers can improve the soil environment, inhibit the growth of harmful microorganisms in the soil, and reduce soil pollution. At the same time, humic acid can also promote the micro-ecological balance in the soil and enhance the soil's self-purification ability. In addition, humic acid can loosen the plough layer soil, disrupt the accumulation of salts, reduce the salt content in the topsoil, and play a role in salt isolation. 

Enhancing the efficacy of other fertilizers
Humic acid fertilizers have an enhancing effect on phosphorus and potassium fertilizers. The acidic functional groups such as aromatic nuclei, hydroxyl groups, and carboxyl groups in humic acid can react with phosphorus elements, turning them into soluble phosphorus and increasing the activity of phosphorus elements. Similarly, the functional groups in humic acid can also absorb and store potassium ions, improving the utilization rate of potassium fertilizers by 348%. 
In conclusion, humic acid fertilizers have significant effects in enhancing soil fertility, promoting plant growth, increasing crop yield and quality, and improving soil environment. Therefore, in agricultural production, the rational application of humic acid fertilizers can effectively increase the yield and quality of crops, while also being beneficial to protecting the ecological environment and promoting sustainable agricultural development.