1、Potential origin and formation for molecular components of humic acids

The humic acids from Ohno et al. (2010) were treated by a process described by Olk et al. (2002) which separates two types of humic acids, those extracted without soil treatment and those extracted after acidification of the soil to release Ca-bound humic acids.

2、Understanding the Role of Humic Acids on Crop Performance and Soil Health

Although HA structure contains many functional groups, the most predominant are phenolic (OH), and carboxylic (COOH) groups (Figure 1) (Nardi et al., 2021).

3、Properties of Humic Acid Substances and Their Effect in Soil Quality

External application of plant-derived humic acid (PDHA) and coal-derived humic acid (CDHA) to wheat growing in two alkaline calcareous soils in pots resulted in considerable spike weight increases in both clayey and sandy loam soils.

4、How to Select the Right Humic Acid and Humate Products for Your

Learn how to choose the best humic acid and humate products for your farm. Improve soil health, boost crop growth, and address specific agricultural needs.

5、Structure and composition of rhizosphere

In particular, the composition and functional groups of humic acid (HA) and fulvic acid (FA) in rhizosphere soil of different crops under land use change from paddy to upland fields are still unclear.

Characteristics and distributions of humic acids in two soil profiles

Characteristics and distributions of humic acid (HA) and soil organic matter (SOM) in a yellow soil profile and a limestone soil profile of the southwest China Karst area were systematically investigated to reveal their evolutions in different soils of the study area.

Humic Acid: A Natural Enhancer of Soil Quality and Crop Productivity

Humic substances, especially humic acid (HA), have emerged as effective natural amendments for improving soil fertility and supporting crop performance. This review provides a comprehensive overview of the role of HA in enhancing soil structure, nutrient availability, and plant growth.

Humic Acids: What They Are and How They Benefit Soil

Humic acids and fulvic acids are both components of humic substances, formed from the same decomposition processes of organic matter. However, they differ in their molecular characteristics and functional roles.

Humic Acid vs Fulvic Acid: Key Differences and Best Uses

Confused between humic and fulvic acid? Learn their differences, benefits, and when to use each for optimal plant and soil health.

Humic Acid In Soil Remediation

Below is an overview of how humic acid contributes to soil remediation, its mechanisms, benefits, and limitations. Humic acid acts as a natural chelating agent, binding to heavy metals like lead, cadmium, and arsenic.

Soil humic acid is a complex organic substance primarily derived from the decomposition of plant and animal residues under microbial action. It plays a crucial role in soil fertility and plant growth. Based on differences in origin and structure, soil humic acid can be classified into two main types:

I. Naturally Occurring Soil Humic Acids

This type of humic acid forms through prolonged microbial transformation of natural organic matter, mainly originating from the decomposition of plant and animal residues (e.g., fallen leaves, animal manure). These materials undergo gradual biochemical breakdown in nature, resulting in humic acids with specific structures and functions. Naturally occurring soil humic acids typically have the following characteristics:

1. Large Molecular Weight and Complex Structure: Due to extended biochemical transformation, naturally occurring humic acids exhibit high molecular weights and intricate structures. These large molecules enhance their adsorption and chelation capabilities in soil, improving water retention and nutrient supply.

2. Versatile Functions: They regulate soil pH, increase organic matter content, improve soil structure, and boost fertility. These properties make them highly valuable for agricultural applications.

3. Environmental Friendship: As products of natural organic matter decomposition, they minimally disrupt ecosystems. Using naturally occurring humic acids reduces environmental harm in agriculture and promotes sustainable development.

II. Synthetic Soil Humic Acids

These humic acids are produced through chemical or biotechnological synthesis, often involving processes like chemical oxidation or enzyme-catalyzed transformation of natural organic materials. Synthetic soil humic acids are characterized by:

1. High Controllability: Their molecular weight, structure, and functionality can be precisely controlled by adjusting synthesis conditions (e.g., temperature, pressure, catalysts). This ensures stability and reliability in agricultural use.

2. High Efficiency: With tailored structures, synthetic humic acids deliver rapid nutrient release, enhance crop yields, and improve soil structure, water retention, and aeration.

3. Economic Viability: While initial costs may be higher, synthetic humic acids offer long-term economic benefits by reducing synthetic fertilizer use, lowering production costs, and improving crop quality and quantity.

soil humic acids分为两类：naturally occurring and synthetic. Each type has unique advantages, and the choice depends on specific agricultural needs.