Humic Substances in Plant Nutrition

In agriculture, maximizing crop production while maintaining soil health is a key challenge. Humic substances play a crucial role in meeting this challenge. From improving soil fertility to enhancing plant growth, humic substances are gaining recognition as powerful natural agents for sustainable agriculture.

What Are Humic Substances?

Humic substances are a broad and complex group of organic compounds that form as a result of the natural decomposition of plant and animal material in the soil. These substances are integral to soil health, playing a significant role in soil fertility, nutrient cycling, and plant growth.

Humic substances are the end products of humification, a long-term process in which organic material is broken down by microorganisms and environmental factors. They are rich in carbon and other essential nutrients and can be classified into three primary categories which differ in solubility:

• Humic Acids (HA) are the most well-known and widely used form of humic substances. They are characterized by their relatively large molecular size and dark color. They are soluble in water at neutral and alkaline pH, however insoluble at acidic pH. Humic acids are primarily responsible for improving soil structure and nutrient and water retention.

• Fulvic Acids (FA) are a smaller, more soluble form of humic substances that are lighter in color than humic acids. They are also rich in oxygen and have a lower molecular weight, which makes them highly mobile and capable of entering plant cells with ease. They are soluble in water at any pH. These properties allow fulvic acids to play a crucial role in improving nutrient availability for plants.

• Humins are the most stable and insoluble fraction of humic substances. Unlike humic and fulvic acids, humin does not dissolve in water, even at extreme pH levels, which makes it less directly involved in nutrient transport. However, humin plays an essential role in soil stabilization and long-term soil health.

These three categories of humic substances each bring unique benefits to the soil and plants and together form a comprehensive system that supports plant growth and quality.

Why Are Humic Substances Used in Plant Nutrition?

Humic substances are vital to plant nutrition because they directly influence the availability of nutrients, the health of the soil, and the overall growth of plants.

• Improving Nutrient Availability

One of the key ways humic substances benefit plants is by improving the availability and uptake of essential nutrients. They act as chelators and nutrient carriers – binding with nutrients so that these are more easily absorbed by plant roots.

Fulvic acids, in particular, are known for their ability to move through plant membranes, facilitating the uptake of nutrients directly into the plant. This helps ensure that crops receive the right balance of nutrients needed for optimal growth and development, resulting in stronger, healthier plants.

• Enhancing Soil Structure and Health

Humic substances also improve the physical properties of soil. They help increase soil organic matter content, which is essential for maintaining soil fertility. By enhancing soil aggregation, humic substances improve the structure of soil, allowing for better water retention, drainage, and root penetration. This is especially important in compacted or poorly structured soils, where root growth and nutrient absorption can be limited.

In addition to improving soil texture, humic substances increase the cation exchange capacity (CEC) of soils. This refers to the soil’s ability to retain and release positively charged nutrient ions, which are crucial for plant health. By improving CEC, humic substances help prevent nutrient leaching and ensure that nutrients are available to plants when they need them.

• Boosting Microbial Activity

Soil health is heavily influenced by microbial life, and humic substances play a key role in supporting a thriving soil ecosystem. They serve as an energy source for beneficial soil microorganisms, such as bacteria and fungi, that help decompose organic matter and convert nutrients into forms plants can absorb.

The increased microbial activity in the soil can also help improve disease resistance by outcompeting harmful pathogens. Humic substances encourage the growth of beneficial microorganisms, such as mycorrhizal fungi, which form symbiotic relationships with plant roots, enhancing nutrient and water absorption.

• Increasing Plant Stress Resistance

Plants exposed to environmental stress—such as drought, high salinity, or extreme temperatures—can suffer reduced growth and yield. Humic substances have been shown to help plants manage stress by improving water retention, boosting antioxidant activity, and promoting the synthesis of stress-related proteins. As a result, plants treated with humic substances are often more resilient to adverse conditions.

• Supporting Sustainability

The use of humic substances aligns with the growing demand for sustainable agricultural practices. By enhancing nutrient availability and improving soil health, humic substances reduce the need for synthetic fertilizers and chemical additives, which can have negative environmental impacts. They promote a more organic approach to farming, supporting long-term soil fertility and reducing the risk of nutrient runoff into water sources.

Humic substances also help with carbon sequestration in soil. Their ability to increase soil organic matter and improve soil structure makes them an important tool for reducing carbon emissions and mitigating climate change.

How Are Humic Substances Applied in Agriculture?

Humic substances can be applied directly to the soil, mixed with irrigation water, or used as foliar sprays. Farmers can apply humic substances to improve soil health before planting, or use them as a supplement during the growing season to enhance nutrient uptake and plant growth. Humic substances degrade slowly and efficiently over a prolonged timeframe and they do not compete with plants nor consume nutrient.

Thanks to their properties, humic substances are also very effective when used together with mineral fertilizers The synergistic effect of combining humic substances with fertilizers results in more efficient nutrient utilization promoting sustainable agricultural practices. This combination can lead to stronger plants and higher crop yields, making it a valuable strategy for modern farming, also with significant economic benefits.

ICL Solution with Humic Acids

ICL introduced the Nova Humic product range that integrates essential NPK nutrients with micronutrients and humic acids to enhance plant growth and soil health. This innovative water-soluble product line is designed for fertigation, ensuring easy application through various irrigation systems. Humic acids in the Nova Humic range improve soil structure, increase nutrient availability, and boost microbial activity, which results in more vigorous plants and improved yields. It is a step forward in agricultural practices, with a focus on sustainable and effective plant growth.