Humic acid is a principal component of humic substances, which are the major organic constituents of soil, peat, and coal. It’s also a key organic component of many upland streams, dystrophic lakes, and ocean water. The humic acid used in fertilizers is often derived from leonardite, a substance formed from the decomposition of plant material in certain types of soil and rock formations.
Leonardite is a soft, brown, lustrous material that resembles coal and is named after A.G. Leonard, the first director of the North Dakota Geological Survey. It is an oxidized form of lignite, a type of coal, and is found in various parts of the world, including North America, Russia, and China. The oxidation process that transforms lignite into leonardite results in high levels of humic and fulvic acids, making leonardite an excellent source of these beneficial organic
Advantages of Humic Acid Derived from Leonardite
Humic acid has several benefits when used in fertilizers:
- Soil Conditioning: Humic acid improves the structure of the soil. It increases the soil’s capacity to hold and retain water, which is particularly beneficial in arid regions. Moreover, it aids in soil aeration, thus promoting root development.
- Nutrient Uptake: Humic acid enhances nutrient uptake by plants. It facilitates the transport of nutrients from the soil into the plant cells, resulting in healthier and more productive crops. This is especially crucial for micronutrients, which can be difficult for plants to absorb without the assistance of humic substances.
- Stimulates Plant Growth: Humic acid stimulates plant growth by promoting cell division and increasing the rate of photosynthesis. This leads to higher yield and better quality crops.
- Chelating Properties: Humic acid has chelating properties, meaning it can bind to metal ions in the soil, making them more available for plant uptake. This can be especially beneficial in soils with high levels of aluminum or other potentially toxic metals.
- Increases Soil Microbial Activity: Humic acid promotes the growth of beneficial soil microorganisms, which play a vital role in nutrient cycling and disease suppression in crops.
- Environmental Benefits: The use of humic acid in fertilizers reduces the need for synthetic fertilizers, thus helping to reduce the environmental impact of agriculture. Moreover, by improving the soil’s capacity to retain water, humic acid can also help to mitigate the effects of drought and climate change on crop production.
Comparison of core differences in humic acids from different sources
Humic acids are mainly classified into four categories based on their source: lignite humic acid, weathered coal humic acid, peat humic acid, and biochemical humic acid. They differ significantly in their agricultural applications, as detailed below:
1.Soil Improvement Effects
| Functions | Lignite Humic Acid | Weathered Coal Humic Acid | Peat Humic Acid | Biochemical Humic Acid |
| Structure Improvement | Excellent Promotes Long-Lasting Aggregate Formation | Superior Strongest Cementing Effect | Good But Easily Decomposes | Average Short-Term Effectiveness |
| Water Retention Capacity | Strong (Water Holding Capacity +25-40%) | Very Strong (Water Holding Capacity +30-50%) | Strong But Decreases with Decomposition | Medium Lasting for 1-2 Seasons |
| pH Regulation | Strong Buffering Capacity (Adapts to pH 4-10) | Strongest Regulation Capacity Suitable for Saline-Alkali Soils | Medium Buffering Capacity | Limited Dosage Needs Control |
| Heavy Metal Passivation | Strong (Stable Complexation) | Strongest (High Carboxyl Content) | Medium | Weak And Unstable |
2.Nutrient Enhancement Capacity
| Nutrient Type | Lignite Humic Acid | Weathered Coal Humic Acid | Peat Humic Acid | Biochemical Humic Acid |
| Nitrogen Fertilizer Enhancement | Reduce losses by 40-60% Slow release for 15-25 days | Reduce losses by 30-50% Slow release for 20-30 days | Reduce losses by 20-40% | Short-term effectiveness No long-term slow release effect |
| Phosphorus Fertilizer Activation | Increase utilization rate to 35-45% | Strongest Especially good in calcareous soils | Increases to 30-40% | Limited effect |
| Trace Elements | Strong chelating ability Increases availability by 3-5 times | Strongest chelating ability | Medium chelating ability | Some small molecules Have complexing effect |
3.Plant Stimulation Effects
| Physiological Effects | Lignite Humic Acid | Weathered Coal Humic Acid | Peat Humic Acid | Biochemical Humic Acid |
| Root Promotion Effect | Strong and Long-Lasting Root Mass +50-100% | General Mainly Macromolecules | Moderate | Fast-Acting but Short-Lasting Contains Hormone-like Substances |
| Enhanced Photosynthesis | Chlorophyll +20-35% Stable Effect | Chlorophyll +15-25% | Chlorophyll +10-20% | Significant Short-Term Improvement |
| Stress Resistance Induction | Systemic Activation (SOD, etc. +50-150%) | Mainly Chemical Protection | Partial Activation | Fast Stress Response But Poor Sustainability |
| Quality Improvement | Significant Overall Improvement (Sugar Content, Vitamin C, etc.) | Limited Improvement | Some Improvement | Short-Term Appearance Improvement |
Main Advantages, Disadvantages, and Applicable Scenarios
1. Lignite Humic Acid
- Advantages: Comprehensive functions, rich in active substances, stable quality, high cost-effectiveness
- Disadvantages: Requires extraction process; purity depends on processing technology
- Best Scenarios: High-yield cultivation of field crops, quality improvement of cash crops, remediation of moderately to severely degraded soils
2. Weathered Coal Humic Acid
- Advantages: Strongest ability to improve soil physical structure, longest-lasting effect, lowest cost
- Disadvantages: Poor water solubility, weak physiological activity, inconvenient application
- Best Scenarios: Saline-alkali land improvement, treatment of compacted clay soils, ecological projects requiring long-term soil construction
3. Peat Humic Acid
- Advantages: Good natural state, rich in active substances
- Disadvantages: Limited resources, ecological damage from extraction, high cost, moderate duration of effect
- Best Scenarios: Seedling substrate, high-end horticulture, soil conservation in organic farms
4. Biochemical humic acid
- Advantages: Rapid onset, wide availability of raw materials, low production cost, good water solubility
- Disadvantages: Short-lasting effect, unstable quality, higher risk of heavy metal contamination
- Optimal applications: Foliar spraying for topdressing, short-term crop growth promotion, and compounding with other sources of humic acid
In summary, humic acid is not a replacement for traditional fertilizers, but rather an enhancement of them. It transforms “dead” mineral nutrients into “living,” easily absorbed forms; it invigorates “fragile” plants into “robust” individuals; and it restores “pathological” soil to a “healthy” ecosystem. Its benefits are comprehensive and multi-targeted, ultimately achieving six synergistic goals: fertilizer saving, increased yield, improved quality, soil improvement, stress resistance, and environmental protection. It is an indispensable core input for developing green, efficient, and sustainable modern agriculture. The key to maximizing its benefits lies in correctly selecting high-quality humic acid products and combining them with scientific agronomic practices.