soil fertility

Humic Acid: The Kickstart that your Crops need?

Justin PlattBlog, Humic Acid

Humic acid is the primary active ingredient that is the starting point of a healthy, microbially active soil. A good soil is continuously releasing humic acid (or humins), depending on rain, water, soil temperature and other conditions. 

High humic acid levels can increase crop yields. On the other hand, humic acid deficiency can prevent farmers and gardeners from growing crops with optimum nutrition. Thus, adding humic acid inputs to favour the biology of the soil and chemistry can produce better yields and quality. 

The multiple functions associated with humic acid make this high-quality, soluble granule a priority raw material in every sustainable farming practice.

What is humic acid? 

Humic acid definition: Humic acid is a remarkable brown to black product of soil chemistry that is essential for healthy and productive soils. These organic acids are found in prehistoric deposits and exist naturally in soils, peats, oceans and fresh waters. Humic matter is formed through the chemical and biological humification of plant and animal matter and through the biological activities of microorganisms. 

Humic acid comprises a group of molecules that are soluble in water only at higher soil pH values. The molecules bind to plant roots and help plants absorb water and nutrients. One of the most functional components of humic acid is the water-extractable organic carbon (WEOC), which is an important food source for many beneficial soil microbes, especially fungi. 

What is the difference between organic matter and humus?

  • Humus = a general term that describes a group of separate but distinct humic substances.
  • Organic matter = material that is decomposing at various rates in the ground.
  • Humic acid = a humic substance.

What’s the difference between humic acid and fulvic acid?

Both humic and fulvic acids are the final breakdown constituents of the natural decay of plant and animal materials. Humic acid, however, has a larger and more complex molecular structure than fulvic acid. It’s also not absorbed as easily. 

What are the main humic acid benefits to plants? 

The humic acid benefit to plants actually comes from its effect on the soil. Humic acid helps improve the soil structure. It also binds with clay particles to form stable organic complexes that increase the soil’s cation exchange capacity. 

Benefits of humic acid: Did you know? 

Humic acid can hold up to 16x more minerals than clay.

Humic acids are extremely important as a medium for transporting nutrients from the soil to the plant because they can hold onto ionised nutrients, preventing them from leaching away. For example, humic acid can penetrate between clay particles to release potassium for use by plants.

Humic acids are also attracted to the depletion zone of the plant root. When they arrive at the roots, they bring along water and nutrients that the plant needs. The functionalised humic acid molecules act as photosensitisers, retain water, bind to clay, act as plant growth stimulants, and scavenge toxic pollutants. 

Organic humic acids in the soil also promote the return of beneficial fungi which are missing in many soils. They create a crumb structure that increases the permeability of the soil and thus increases nutrient, water and oxygen uptake and retention. Humic acids are microbe-friendly, improve nitrogen efficiency, reduce phosphate lock-up and are an excellent source of water-soluble carbon, which is essential to the creation of healthy soils.

Humic acids also help to clean soil of toxins, pesticides and heavy metals.

Healthy soil (and thus healthy plants) are dependent on adequate humus levels.

Summary of the benefits of humic acid 

  • Soil with high humic acid levels can become more porous with better drainage, resulting in deeper root growth of all plants.
  • Retains water and the ionised nutrients that are produced by the natural cycling of compost, organic biomass, or other sources of fertiliser.
  • Promotes soil structure improvement by promoting fungi to create a crumb structure for better water and oxygen intake and improved root penetration.
  • Stabilises nitrogen and improves nitrogen efficiency (ideal as an additive with urea).
  • Complexes phosphate to reduce lock-ups (ideal as an additive with DAP/MAP, etc.).
  • Natural chelating and complexing agent to help magnify nutrient absorption.
  • Increases the permeability of cells to increase nutrient uptake by up to 40%.
  • Contains an auxin-like growth promotant that can enhance cell division and elongation.
  • Can buffer the effects of excessive elements (particularly sodium), toxic chemicals and heavy metals.
  • PH buffering capacity to help neutralise the problems associated with pH extremes.
  • Features a CEC of 450, which aids in moisture and nutrient retention.
  • Promotes better seed germination in a shorter time.
  • Microbe-friendly.

The economic benefits of humic acid application

By chelating nutrient compounds in the soil, humic acid makes them more suitable for plant utilisation and optimises nutrient supply. This results in an increase in yield of up to 70%, along with a 30% reduction in the use of fertilisers and pesticides. In addition, because humic acid improves the water-holding capacity of soils, the amount of water needed for irrigation can be reduced substantially. 

Soils poor in humus (typically light and sandy soils) stand to benefit the most from humic acid application. 

The ecological benefits of humic acid in soil 

Humic acids offer diverse benefits and profitable and effective solutions for environmental problems and improved sustainability:

Protecting ground water 

Soils with a high humic acid content of humic acids enable low nitrate leaching and optimum nutrient efficiency. A high content of humic acids promotes a well-developed root system, which prevents nitrate and pesticides mixing in with ground water. 

Reducing over-salination 

When water-soluble mineral fertilisers are applied to the soil, this can result in high salt contents in soils and resulting toxicities. Humic acids are able to reduce the level of over-salination and the NH4-toxicity of fertilisers containing ammonia. This means reduced root burning and lowered levels of salt in soils. 

Fighting soil erosion 

Humic acids effectively prevent soil erosion by enhancing root system and plant development and increasing the ability of soil colloids to combine. 

What is humic acid used for in agriculture? 

Humic acid inputs are not fertilisers. Rather, they act as soil conditioners and as biocatalysts and biostimulants for plants. Adding humic material is an excellent way to provide plants and soil with a concentrated natural and organic dose of essential nutrients, vitamins and trace elements. 

Another benefit is that humic acid material does not get consumed as quickly as other organic inputs such as animal manure, compost or peat. Because humic acid decomposes completely, it does not enter into nutritional competition with plants for nutrients such as nitrogen. 

Humic acid application in South Africa

Ideally, humic acid should be added as an input in small amounts (i.e. 1kg/ha monthly), rather than dumping a large amount in one go. A weekly trickle feed (or even a daily feed, if practically possible) is especially beneficial for very sandy soils that don’t have much organic matter to act as a backup release of humic acid.

Humic acids are a key ingredient in developing and maintaining healthy and sustainable soil. They work by promoting the creation of beneficial fungi – which are missing in many soils. These fungi create a crumb structure, optimising soil structure for better water and oxygen uptake and improved root penetration. The effect is better seed germination in a shorter time and improvement in overall crop yield.

The team at Zylem are on hand to explain applications and precautions associated with humic acid. Get in touch to find out more.

Alex bio pic

About the Author: Alex Platt

Alex is Business Development Manager at Zylem. He’s inspired by the potential of regenerative farming and takes a special interest in the technology and products that are moving agriculture in a more sustainable direction.