What is humic acid fertilizer? Let us help you understand humic acid!

　　There is a type of fertilizer that serves as a slow-release agent for nitrogen, an efficiency enhancer for phosphorus, a protective agent for potassium, and a chelating agent for secondary and micronutrients—namely, humic acid fertilizer.

　　Humic acid is a natural organic substance that accumulates through geological processes, the decomposition of plant and microbial residues, and a series of chemical transformations. It is derived from the remains of plants and animals found in forests, grasslands, and wetlands, and is rich in organic matter and humic acids. Humic acid is abundantly present in lignite, weathered coal, and peat.

　　Humic acid itself contains essential plant‑growth elements such as carbon, hydrogen, oxygen, and nitrogen, and it also enhances the efficiency of nitrogen, phosphorus, and potassium fertilizers. As a result, humic acid delivers very noticeable yield increases for crops. Compared with the use of conventional chemical fertilizers, applying humic‑acid‑based fertilizers or organic–inorganic compound fertilizers typically boosts yields by 8% to 20% for field cereals and oilseeds, and by 15% to 35% for melons, fruits, vegetables, and other cash crops. Consequently, in agricultural production, humic acid is an indispensable ally for farmers. Now, let’s explore the powerful benefits of humic acid!

　　 The synergistic effect of humic acid on fertilizers

　　Humic acid, by adsorbing, exchanging, and activating numerous mineral nutrients in the soil—such as nitrogen, phosphorus, potassium, calcium, and magnesium—significantly enhances their availability, thereby improving crop nutrition. It also acts as an efficiency enhancer in fertilizers and mitigates the adverse effects of chemical fertilizers on the soil’s physicochemical properties.

　　 1. The effect of humic acid on enhancing the efficiency of nitrogen fertilizers

　　Nitrogen fertilizers are essential for plant growth; the main types are urea and ammonium carbonate. Once applied to the soil, these fertilizers are quickly lost through volatilization and leaching, leaving only about 30% of the nitrogen available for crop uptake.

　　The aromatic rings, hydroxyl groups, carboxyl groups, and other acidic functional groups in humic acids can react with nitrogen to form highly stable new ionic complexes, also known as chelates. These chelates persist in the soil for an extended period, gradually decomposing to release nitrogen, which is then absorbed by plants over time.

　　According to statistics, when the nitrogen released from urea and carbamide is complexed with humic acids, its fertilizer efficacy can last for more than 60 days, increasing the utilization rate of nitrogen fertilizers by over 10%.

　　 2. The synergistic effect of humic acid on phosphate fertilizers

　　After phosphate fertilizer is applied to the soil, phosphorus is immobilized by metal ions in the soil, converting readily available phosphorus into slowly available or unavailable forms.

　　The aromatic rings, hydroxyl groups, carboxyl groups, and other acidic functional groups in humic acid can react with phosphorus, converting it into soluble phosphorus and enhancing its availability, thereby facilitating uptake by plants. According to statistics, the application of humic‑acid‑based fertilizers can increase the efficacy of phosphate fertilizers by approximately 5% to 10%.

　　 3. The synergistic effect of humic acid on potassium fertilizers

　　The functional groups in humic acid can also adsorb and store potassium ions, thereby preventing potassium loss through leaching in sandy soils and mitigating potassium fixation in clayey soils, thus improving the efficiency of potassium fertilizer application by approximately 5%.

　　 The role of humic acid in soil improvement

　　Current scientific research indicates that soil fertility is largely determined by the content of humic acids in the soil. A range of humic acid properties—such as cation exchange capacity, oxygen content, and water‑holding capacity—are key factors underlying its ability to enhance soil fertility and promote plant growth. Most importantly, humic acids can bind with metal cations, oxygen, and hydroxyl groups, releasing these elements gradually for plant uptake. Owing to these characteristics, humic acids exert multiple effects—physical, chemical, and ecological—in soil improvement.

　　First, humic acid can improve the physical structure of soil. It promotes the formation of soil aggregates, enhancing the soil’s ability to retain water and nutrients. In relatively compact soils, such as saline‑alkali soils, it improves aeration and permeability, thereby ameliorating physicochemical properties characterized by strong alkalinity, dispersed soil particles, and poor soil structure, thus optimizing cultivation conditions. Humic acid also exerts significant beneficial effects on white‑slurry soils and red‑soil types. By acting as a binding agent, it helps the soil surface retain moisture, preventing cracking and erosion. Furthermore, it softens the soil, increases its porosity and utilization efficiency, enhances drought resistance, and darkens the soil color, facilitating greater absorption of solar radiation.

　　Secondly, humic acid plays the following roles in improving soil chemical properties: it neutralizes soil acidity and alkalinity, thereby regulating the pH; it can chelate metal cations, facilitating their uptake and utilization by plant roots; it helps retain moisture around crop roots and can dissolve inorganic fertilizers, thus reducing their leaching; it reduces the reactions between phosphorus and calcium, iron, magnesium, and aluminum, or converts these elements from unavailable forms into bioavailable forms that plants can absorb; and it can mitigate the presence of toxic substances in the soil.