What are Humic Acids and their sources?

1. Humic matter is formed through the chemical and biological humification of plant and animal matter and through the biological activities of micro-organisms. (Ill.1). The biological center, the main fraction of natural humic matter, are the humic acids, which contain humic acidand fulvic acid. Humic acids are an excellent natural and organic way to provide plants and soil with a concentrated dose of essential nutrients, vitamins and trace elements. They are complex molecules that exist naturally in soils, peats, oceans and fresh waters. The best source of humic acids are the sedimentation layers of soft brown coal, which are referred to as Leonardite. Humic acids are found in high concentration here. Leonardite is organic matter, which has not reached the state of coal and differs from soft brown coal by its high oxidation degree, a result of the process of coal formation (bog>peat>coal), and high humic acids content as well as higher carboxyl groups.

Compared to other organic products, Leonardite is very rich in humic acids. While Leonardite is the end product of a humification process lasting 70 million years, the formation period of peat, for instance, is completed within only a few thousand years. The difference between Leonardite and other sources of humic acids lies in its property that Leonardite is extremely bioactive through its molecular structure. This biological activity is about five times stronger than other humic matter as one kilogram Leonardite corresponds to about 5 kilogram of other organic sources of humic acids. In terms of humic acids content, one liter of Liqhumus (liquid concentrate) is equivalent to 7-8 metric tons of organic manure. Similarly, one kilogram of Powhumus (concentrated powder) is equivalent to about 30 metric tons of manure.

Leonardite is not a fertilizer. It acts as conditioner for the soil and as bio-catalyst and bio-stimulant for the plant. Compared to other organic products, Leonardite enhances plant growth particularly (biomass production) and fertility of the soil. Another advantage of Leonardite is its long-term effectiveness, as it does not consume up so quickly as animal manure, compost or peat. As Leonardite is completely decomposed, it does not enter into nutritional competition with plants for nutrients such as for nitrogen. This is not the case with incompletely decomposed compost, whereby the organic substances in soil are rapidly consumed up by micro-organisms and mineralized entirely without humus formation. Our Leonardite- based products improve the soil structure up to five years. 



2. Benefits of Humic Acids?

Current scientific studies show that the fertility of soil is determined to a very large extent by the content of humic acids. Their high cation-exchange capacity (CEC),the oxygen content as well as the above average water holding capacity are the reasons for the high value of using humic acids for improving soil fertility and plant growth. The most important feature of humic acids lies in their ability to bind insoluble metal ions, oxides and hydroxides, and to release them slowly and continually to plants when required. Due to these properties, humic acids are known to produce three types of effects: physical, chemical and biological. 

2.1. Physical Benefits:

Humic acids physically modify the structure of the soil.

  • Improve the structure of soil: Prevent high water and nutrient losses in light, sandy soils. Simultaneously convert them into fruitful soils by way of decomposition. In heavy and compact soils, aeration of soil and water retention are improved; cultivation measures are facilitated.
  • Prevent soil cracking, surface water runoff and soil erosion by increasing the ability ofcolloidsto combine.
  • Help the soil to loosen and crumble and thus increase aeration of soil as well as soil workability.
  • Increase water holding capacity of soil and thus help resist drought.
  • Darken the color of the soil and thus help absorption of the sun energy.

2.2. Chemical Benefits: 

Humic acids chemically change the fixation properties of the soil.  

  • Neutralize both acid and alkalinesoils; regulate the pH-valueof soils.
  • Improve and optimize the uptake of nutrients and water by plants.
  • Increase buffering properties of soil.
  • Act as natural chelator for metal ions under alkaline conditions and promote their uptake by the roots.
  • Rich in both organic and mineral substances essential to plant growth.
  • Retain water soluble inorganic fertilizers in the root zones and reduce their leaching.
  • Possess extremely high cation-exchange capacities.
  • Promote the conversion of nutrient elements (N, P, K + Fe, Zn and other trace elements) into forms available to plants.
  • Enhance the uptake of nitrogen by plants.
  • Reduce the reaction of phosphorus with Ca, Fe, Mg and Al and liberate it into a form that is available and beneficial to plants. The productivity of particularly mineral fertilizers is increased considerably.
  • Liberate carbon dioxide from soil calcium carbonate and enable its use in photosynthesis.
  • Help to eliminate chlorosis due to iron deficiency in plants.
  • Reduce the availability oftoxicsubstances in soils.  


2.3. Biological Benefits:

Humic acids biologically stimulate the plant and the activities of micro-organisms.

  • Stimulate plant enzymes and increase their production.
  • Act as an organic catalyst in many biological processes.
  • Stimulate growth and proliferation of desirable micro-organisms in soil.
  • Enhance plants natural resistance against disease and pest.
  • Stimulate root growth, especially vertically and enable better uptake of nutrients.
  • Increase root respiration and root formation.
  • Promote the development of chlorophyll, sugars and amino acidsin plants and aid in photosynthesis.
  • Increase vitamin and mineral content of plants.
  • Thicken the cell walls in fruits and prolong the storing and shelf time.
  • Increase germination and viability of seeds.
  • Stimulate plant growth (higher biomass production) by accelerating cell division, increasing the rate of development in root systems and increasing the yield of dry matter.
  • Increase the quality of yields; improve their physical appearance and nutritional value.  

Optimal Utilization of Nutrients


fig. 2.1: Increased nutrient deposit by humic acid

fig. 2.2: Ca-Bridge between clay and humus

fig. 2.3: Growth is controlled by the scarcest resource

Effect in soils


In sandy, poor in humus soils, humic acid coats the sand particles, increases the cation exchange capacity (CEC) and increases the ability of the soil to retain nutrients and water. Nutrients, in particular nitrate, are not leached out to the groundwater but together with water retained in the soil, so that they remain available for the plants (s. fig. 2.4, 2.5, pic.1)

fig. 2.4: Sandy soils poor in humus can’t retain nutrients

fig. 2.5: Effect of the cation exchange capacity to sandy soils

pic. 1: Sandy soils without humic substance


Humic acids aerate compacted soils and improve their structure. Thus water, nutrients and roots can penetrate the soil more easily (s. fig. 2.6, 2.7, pic. 2).

fig. 2.6: Compact, hardly penetrable soil structure 

fig. 2.7: Humic acids aerate compact soils

pic. 2: Compacted clay soil without humic substance


Salts are split up by the high cation exchange capacity (CEC) of Humic acids. Cations (e.g. Ca and Mg) are bound and chelated. The high osmotic pressure within the root area is reduced
(s. fig. 2.8, 2.9, 2.10, pic. 3)

fig. 2.8: Splitting
of salt

fig. 2.9: Salinized groundwater in a soil

fig. 2.10: Humic acids reduce the effects of salinity

pic. 3: Highly Solinized soil


Due to their high buffer capacity humic acids neutralize cidic soils. Acid caused stress for the plant roots is educed. Elements harmful for plants, especially aluminium and heavy metals, are bound firmly and immobilized by humic acids. Thus their toxicity is reduced and phosphate bound by aluminium is released (s. fig. 2.11, 2.12). 


As a result of the high pH value many essential nutrients and trace elements are not present in plant available form. Humic acids buffer the high pH and convert nutrients and trace  lements into plant receptible form by complexion. Phosphate bound by calcium is resolubilised and made available (s. fig. 2.11, 2.12).

fig. 2.11: Comp. scheme of light sandy, heavy clayey and rich-in-humus soils

fig. 2.12: Humic acids optimise the soil for root development


The addition of humic acids accumulates the organic matter in the topsoil. The erosion is effectively reduced by intensified root formation and stabilizing clay-humus complexes (s. fig. 2.7). 


Humic acids increase the ability of the soil to retain water. Thus water is available for the plants in dry periods too. That way drought caused stress situations to the plants are avoided and the wastage of precious water is reduced.


Humic acids increase the efficiency of pesticides,fungicides and herbicides and immobilize their harmful residues.

3. Ecological Benefits of Humic Acids:

The ecological benefits of humic acids are diverse and present profitable and effective solutions for environmental problems and the preservation of the environment. 

First of all, soils with a high content of humic acids are a guarantee for low nitrate leaching and for optimum nutrient efficiency. A well-developed root system, which is achieved by a high content of humic acids, prevents that nitrate and pesticides mix in with ground water (s.fig 3.1). Futhermore, a low content of nitrate is an indicator and a prerequisite for appropriate organic agriculture. It happens very often that growers use fertilizers more than plants can take up. This leads to nitrate concentration in soil, which is later to be found in ground water. A purification plant, which should sink contaminated water under a value of five milligrams NO3-N per liter in complicated flows, means very high material costs at the same time. (

Important: Instead of curing the symptoms (water contamination) only, the root causes (nitrate leaching) should be fought against with.

Secondly, humic acids reduce the over-salination problem in the application of watersoluble mineral fertilizers. Humic acids are able to decrease high salt contents in soils and thus the resulting toxicities. Especially the NH4-toxicity of fertilizers containing ammonia is reduced, which is of great importance for young plants particularly. Generally, humic acids reduce root burning which comes about through excessive salt concentrations in soils after fertilization; in case of permanent high levels of salt in soils, these are reduced. Furthermore, when humic acids are mixed with liquid fertilizers, the undesirable smell is diminished.

Thirdly, humic acids are an effective means to fight against soil erosion. This is achieved both by increasing the ability of soil colloids to combine and by enhancing root system and plant development. Leonardite and humate-based products are certificated for organic agriculture by renown organizations and institutions of agriculture worldwide (s.fig 3.1). 

fig. 3.1: Reduction of nitrate leaching

4. Economic Benefits of Humic Acids:

Humic acids chelate nutrient compunds, especially iron, in the soil to a form suitable for plant utilization. Thus, the nutrient supply of plants is optimized. High increases up to 70% in yield, accompanied by a reduction up to 30% in the use of fertilizers and pesticides, as well as better and healthier growth of greengrass, ornamentals, agricultural crops and woods can be attained with the regular application of first-quality humic acids. Furthermore, water holding capacity of soils is increased considerably, which means that the use of water can be reduced substantially. 

Best economic results can be obtained in light and sandy soils poor in humus as well as on recultivation fields. The diverse positive impacts of humic acids are to be observed particularly in such soils. This is true for almost all soils in dry and warm regions. As a result of the high mineralization rate of organic substances, providing these soils with stable humic acids is indispensable for the maintenance and improvement of soil fertility. 

Humintech® offers a complete palette of products which successfully fulfil the needs of different soil conditions and plants (s. fig. 4.1). 

As a result, soils treated with Humintech® products secure qualitative and quantitative increases in yield and reduce material and labour costs, Humintech extensive product line of the highest quality has been designed to suit the demands of a healthy community.  

fig. 4.1


  • German Organic Fertilizer and Humic Substance Producers
  • Humic & Fulvic Acids: The Black Gold of Agriculture?
  • The Humus Cycle: by Dr. William Jackson
  • Defintion of soil organic matter: by Jerzy Weber
  • Humus, Still a Mystery?: by Paul Sachs
  • What's Humus? What's the Funktion of Humus?: by Martina Rüthnick
  • Research regarding Arkansas lignite and its possible use as a soil amendment: by Dr.Kline
  • Humic Acids as Object of Environmental Research: by Heise, Karl-Heinz, Brendler, Vinzenz
  • A review of humus and humic acids: by T. L. Senn, A. R. Kingman
  • Röntgenmikroskopie von Huminkolloiden: by Jürgen Thieme, Jürgen Niemeyer