The influence of the thermal factor on the change in the agrochemical properties of leonardite and the effectiveness of Agro.Bio preparations
Numerous chemical analyses of organic raw materials conducted by leading agricultural institutes in Ukraine and a comparison of literature data on the properties of leonardite (a natural mineraloid, oxidized lignite or brown coal, which serves as a powerful organic fertilizer and the main source of humic and fulvic acids) from various deposits show that they all contain significant amounts of nutrients. When properly processed biotechnologically, they become powerful growth stimulants.
It is known that using pure leonardite, especially freshly mined leonardite, as a direct fertilizer is ineffective. This is because the vast majority of nutrients and humic acids themselves are tightly bound, inaccessible to plants. This requires enormous application rates (tons per hectare) and a long period of time for mineralization in the soil.
Leonardite's effectiveness is enhanced through deep physicochemical activation. Agro.Bio's modern technologies convert the insoluble humic acids of the source material into a water-soluble form, introducing them into active agricultural use as highly concentrated preparations, with application rates as low as 1-2 l/ha.
In the search for the most effective methods of raw material activation, much attention is being paid to the thermal treatment of leonardite. In production conditions, a natural thermal factor is the self-heating of organic chips during storage in storage piles, which we have modeled in detail in the laboratory.
MODELING THERMAL ACTIVATION OF LEONARDITE
To study the physicochemical transformations of leonardite during its heating and the influence of this factor on the agrochemical properties of the raw material, a typical lowland material with an average degree of natural decomposition of 25% was selected.
The self-heating process was simulated in a special thermal column (1000 mm high) simulating the profile of a storage pile. Leonardite was heated for 48 hours, creating a temperature gradient from 180–200°C at the bottom to 32–39°C at the top. Subsequent chemical analysis of the horizons revealed key patterns that are now used to optimize the production of Agro.Bio products.
CHANGES IN AGROCHEMICAL PROPERTIES DURING THERMOLYSIS
1. Ammonia absorption capacity
The ammonia absorption capacity of the original leonardite was 0.80%. After heat treatment, it increased significantly and in some places reached 1.5%.
Table 1. Influence of thermal factor on the change in ammonia absorption capacity of leonardite
| Horizons (from the bottom of the column), mm | Weight of leonardite (dry matter), g | Average ammonia absorption capacity, % | Consumption of 25% ammonia water per 1 ton of raw material, l |
|---|---|---|---|
| Original leonardite | 2014.0 | 0.80 | 32.0 |
| — 500 (heating zone) | 681.0 | 1.27 | 50.8 |
| 500 - 1000 | 1020.4 | 1.44 | 57.6 |
| Total for heated | 1701.4 | 1.35 | 54.0 |
While freshly mined leonardite can chemically bind 32 liters of 25% ammonia water per ton, after heating, this figure increases to 54 liters. This directly demonstrates that humic fertilizers prepared from thermally activated leonardite possess significantly greater chemical activity and cation exchange capacity.
2. Nitrogen dynamics
During heating, nitrogen sublimes from high-temperature zones and is subsequently captured by the upper layers of leonardite. The proportion of readily hydrolyzable (available) nitrogen in the leonardite mass increases from 0.030% to 0.078% in the lower horizons and to 0.042% in the upper horizons.
3. Phosphorus mobilization
Phosphoric acid in freshly mined leonardite is typically poorly mobile. However, the amount of P₂O₅, soluble in weak acid, increases significantly after heat treatment, especially in the temperature range of 60–100°C. Overall, the content of mobile phosphorus increased by 27% across the column, confirming its deep mobilization.
4. Activation of humic acids
A key factor in the effectiveness of Agro.Bio products is the concentration of water-soluble humic acids. Analysis showed that thermolysis dramatically alters their mobility.
Table 2. Change in the content of mobile humic acids in leonardite after heat treatment (2014 g dry matter)
| Indicator | Original leonardite (g) | Heated leonardite (g) | Difference (g) |
|---|---|---|---|
| Humic acids soluble in 0.1 N NaOH | 108,756 | 147,125 | +38,369 |
| Water-soluble humic acids | 0.443 | 1,070 | +0.627 |
The content of the most valuable water-soluble humic acids increased more than 2.4-fold (from 443 mg to 1070 mg). Heat treatment (especially in the range of 60-110°C) alters the fractional composition of leonardite, significantly increasing the yield of physiologically active substances.
INFLUENCE ON PRODUCTIVITY (RESULTS OF EXPERIMENTS)
To confirm the agronomic value of thermally activated leonardite, vegetation experiments were conducted on winter wheat and tomatoes.
- Microvegetation experiment with winter wheat (sand crop, NPK background): The most intensive accumulation of green mass (58.7 g versus 53.3 g in the control) and the highest coefficient of nitrogen and phosphorus use from fertilizers were observed when using leonardite heated at a temperature of 60–70°C.
- Vegetation experiment with tomatoes (sand culture): For the experiment, an experimental preparation (humophos) was made from heat-treated leonardite.
Table 3. Effect of humic preparation from thermally activated leonardite on tomato yield
| Nutritional conditions (NPK background) | Fruit yield, g/vessel | % sugars | Ascorbic acid, mg% |
|---|---|---|---|
| Control (mineral water only) | 136.8 | 2.0 | 134.2 |
| A preparation made from fresh leonardite | 201.9 | 1.4 | 219.4 |
| A preparation made from heated leonardite (70°C) | 268.2 | 1.95 | 17.7 |
Experimental plants treated with the activated humic preparation developed significantly better, with stronger stems and darker foliage. Fruit yields from the heated leonardite preparation were almost twice as high as those from the control. Field trials on corn and tomatoes in the Dnipropetrovsk region fully confirmed these results: yield increases from the activated preparation were 1.4–1.5 times higher than from the untreated preparation.
CONCLUSIONS
- During the process of controlled thermal heating of leonardite, a profound change in its physical and chemical properties occurs.
- The proportion of mobile, easily hydrolysable forms of nitrogen increases significantly.
- Poorly soluble phosphorus compounds become bioavailable (the increase in mobile phosphorus was 27%).
- The content of water-soluble humic acids, the main physiologically active component that stimulates plant growth, increases sharply (2.4 times).
- Thermal activation significantly increases leonardite's capacity to absorb cations (in particular, ammonia). This allows it to be used to produce humic fertilizers with the highest concentration of active ingredients.
- The optimal temperature range for activating organic raw materials to mobilize elements and humic acids is 60–80°C.
- Vegetative and field experiments clearly demonstrate that humic preparations obtained from pre-activated leonardite possess colossal biological activity, ensuring a powerful increase in crop yields and maximum absorption of mineral fertilizers by plants.
Agro.Bio Expert Note: Today, Agro.Bio utilizes the most advanced methods of deep physicochemical and cavitation extraction of leonardite, which far surpass the basic thermolysis methods described above. As a result, modern organomineral growth regulators, such as Agro.Bio's Totem and Agro.Bio's Potassium Humate (application rate: 1-2 l/ha), contain an unprecedentedly high concentration of water-soluble humic and fulvic acid salts. Their use allows Ukrainian farmers to reliably manage crop yields, eliminating the need to apply millions of tons of crude leonardite ballast to the soil.