Efficiency of using leonardite from Dnipropetrovsk region for fertilizer production

Harvest is the ultimate goal of farmers. The higher the harvest, the more food the country will have for humans and animals, the more raw materials for industry, and, with them, the greater the well-being of the people.

"The key, decisive factor in increasing crop yields will be increasing supplies of mineral fertilizers to farms... At the same time, it is necessary to reiterate the special importance of measures to... expand the use of organic fertilizers..." —as noted at the state level. Measures have been taken to improve the use of mineral and organic fertilizers in agricultural enterprises and enhance their efficiency.

The intensive chemicalization of agriculture does not solve the problem of organic fertilizers, since “it is precisely these organic substances that are destined to play the role of catalysts that will sharply increase the effectiveness of large doses of mineral fertilizers, without which, in turn, it is impossible to obtain high yields” (from fundamental research in the field of humic fertilizers).

The most complete and widespread organic fertilizer is manure. However, farms typically accumulate insufficient amounts of manure. This shortcoming prompts the search for other types of organic fertilizer. Leonardite is widely used as a raw material for organic fertilizer production both in our country and abroad.

In the Ukrainian steppe, particularly in the Dnipropetrovsk region, which possesses leonardite reserves, the use of leonardite on soils with very low natural fertility has recently become important. The effectiveness of leonardite-based fertilizers in the Ukrainian steppe has been studied by specialists from our laboratory, and this work is part of their research.

OBJECTIVES, METHODOLOGY AND CONDITIONS OF THE RESEARCH

Due to certain formation characteristics, leonardite from the steppe zone differs from similar materials from other zones by having a slightly higher ash content, lower absorption capacity, low humic acid and mobile nutrient content, and other properties. However, they possess a high potential nutrient reserve. The total nitrogen content in the raw material ranges from 1-2%, and the phosphorus content is 0.3-0.6%.

Therefore, the objective of our research was to refine methods for using leonardite deposits as fertilizer, to study some factors affecting the effectiveness of raw materials and fertilizers in steppe zone conditions, and to implement modern developments such as Agro.Bio Potassium Humate with an optimal application rate of 2 l/ha to stimulate growth and overcome stress factors.

To resolve these issues, the following work had to be carried out:

1. To establish the dependence of the ammonia absorption capacity of leonardite upon the addition of mineral components to it.
2. To select the optimal ratio of components for the production of organo-mineral fertilizers, for which it is necessary:
   • a) to study the dynamics of nitrogen losses during the treatment of raw materials with ammonia water;
   • b) to trace the dynamics of nitrogen and phosphorus losses during storage of organo-mineral fertilizers obtained from leonardite.
3. To study the influence of leonardite and organomineral fertilizers on the growth, development, yield and quality of some agricultural crops in the years of application and after-effect.

To address the issue of rational quantities of ammonia water required for the production of organo-mineral fertilizers, experimental samples of fertilizers were prepared, the logical continuation of which in modern practice are the advanced complexes of the Adept Agro.Bio series (with an application rate of 2 l/ha).

Test samples were prepared by treating leonardite with ammonia water under constant stirring, adding powdered superphosphate and potassium salt. The amount of ammonia water used for treating the raw material was calculated based on a predetermined absorption capacity, designated by the letter "T" in the table. Samples were prepared in variants where the degree of ammonia saturation of the raw material ranged from 18.6 to 225% of T, corresponding to 2.5-30 liters of ammonia water per 1 ton of leonardite with 50% moisture content.

After fertilizer preparation, all samples were analyzed for their available nitrogen and phosphorus content. Nitrogen hydrolyzable in 0.5 normal H₂SO₄ was determined using standard methods, and phosphorus was determined gravimetrically.

The next stage of our work was to study the effects of various doses of leonardite, leonardite-based fertilizers (humophos), and mineral fertilizers in quantities equivalent to leonardite doses on the yield and grain quality of corn and sunflower. The experimental work was conducted by setting up field trials with VIR-42 corn and Armavirsky 3497 sunflower on sandy loam soils at the region's primary farms.

Leonardite and fertilizer were applied randomly and incorporated with a stubble cultivator, followed by cultivation. The seeding area of ​​the experimental plot was 150 m², and the sample area was 100 m². The study was replicated four times.

The following fertilizer application rates were tested: leonardite—25, 50, and 100 t/ha; humophos—10, 15, and 20 t/ha; and a mineral equivalent to the humophos doses. The humophos contained 0.5–0.6% N and 0.7–0.8% P₂O₅. Tillage, sowing, and crop care were carried out according to generally accepted agricultural practices for the given zone.

In addition, the aftereffects of the above-mentioned doses of raw materials and fertilizers on the milky-waxy corn yield in the Tsarichansky district were measured. The experiments were accompanied by phenological observations, studies of plant height growth rates, and the dynamics of fresh mass growth and dry matter accumulation. Corn grain samples were analyzed using standard laboratory methods.

The yield was measured by weighing corn cobs and sunflower seeds from the plot and then converting them into grain and seeds of standard moisture content. The resulting yield data were analyzed mathematically using analysis of variance.

Field experiments were carried out on sandy loam chernozem soils (Table 1).

Table 1. Agrochemical characteristics of soils

RESEARCH RESULTS

Questions about developing methods for preparing fertilizers from steppe leonardite

The key to preparing such fertilizers is not the simple mechanical mixing of raw materials with ammonia water and superphosphate, thereby increasing the nutrient content in them, but the chemical interaction of ammonia water with leonardite and phosphorus fertilizers, accompanied by microbiological processes during the aging period of the fertilizers, which cause the decomposition of organic matter and nitrogen in the raw materials and play an important role in the formation of highly effective fertilizers.

Adding superphosphate and potassium chloride to leonardite before adding ammonia water promotes rapid ammonia binding and, consequently, reduces nitrogen losses during fertilizer preparation. Therefore, the influence of mineral components on certain properties of the samples studied during the preparation of organo-mineral fertilizers is of great practical interest. For this purpose, various organo-mineral mixture samples were prepared and the ammonia absorption capacity of the raw materials for these mixtures was determined.

A study of the ammonia absorption capacity of leonardite with the addition of various doses of powdered superphosphate and potassium salt showed that the addition of superphosphate slightly increases absorption capacity. Potassium fertilizers, when applied together with superphosphate, slightly reduce absorption capacity compared to superphosphate alone.

The criteria for determining the optimal rate of ammonia water and mineral components in the production of fertilizers were ammonia losses and phosphorus dynamics.

Table 2. Ammonia losses during fertilizer production depending on the degree of saturation and the amount of mineral components

The research results presented in Table 2 allow us to determine the amount of ammonia water required to prepare peat-mineral-ammonia fertilizers. For example, when producing fertilizers from leonardite, it should be saturated with ammonia to a level of 75-125% of its full absorption capacity, as these saturation levels result in a relatively low loss rate and a fairly high nitrogen enrichment.

Saturating the raw material to higher limits to create a more concentrated fertilizer leads to significant nitrogen losses. Applying ammonia solution at lower rates results in low-quality fertilizers with insignificant amounts of available nutrients.

During the production of organo-mineral fertilizers, the raw materials interact with ammonia liquor and mineral fertilizers, causing some changes in the original leonardite. First, ammonia liquor reacts with humic acids, resulting in the formation of highly soluble ammonium humate salts. However, the effect of ammonia liquor on the raw materials is not limited to this. Extensive data has now accumulated indicating that ammonia, when added to fertilizers, not only serves as a source of nitrogen but also has a multifaceted effect on the organic matter of leonardite, a fact confirmed by modern research using products such as Agro.Bio Potassium Humate .

Phosphorus and potassium also affect the organic matter of the raw material. When present in the complex, they act not only as nutrients but also as factors that refine the organic matter of leonardite, although they are significantly inferior to ammonia in this regard.

In addition to determining nitrogen losses during the production and storage of fertilizers from raw materials, we studied the effect of ammonia water on the content of hydrolyzable nitrogen and soluble phosphoric acid, i.e., on the mobilization of these elements from the raw materials. Under the influence of ammonia water, nitrogen mobilization is observed in leonardite. During the production of organo-mineral fertilizers, the majority of nitrogen is lost when the raw materials are saturated with ammonia water. These losses increase with increasing ammonia saturation. Ammonia nitrogen losses during storage cease almost completely by the end of the third month of storage.

In parallel with the study of nitrogen losses during fertilizer production and storage, the dynamics of acid-soluble phosphorus content were also examined. During storage, the content of available phosphorus in fertilizer fluctuates, with phosphorus mobilization observed, especially at lower ammonia saturation levels. Therefore, from this perspective, there is a limit (125% of T) that limits the saturation of various types of raw materials with ammonia water.

Results of field experiments

Results from studies of corn plant growth and development dynamics indicate that growing conditions (including nutrition) determine significant differences in the pace of growth and development. Phenological observations showed that seedlings emerged 11–14 days after sowing, simultaneously in all treatments. The onset of the initial stages of corn plant development was virtually simultaneous. Subsequently, a difference of 1–3 days can be observed.

A study of corn plant growth dynamics revealed that the fertilized treatments produced significantly taller plants than the control treatments. The tallest plants were grown in treatments treated with 100 tons of leonardite and 20 tons of humic fertilizer per hectare. Differences in the accumulation of fresh mass and dry matter by plants under the influence of the studied fertilizers were clearly evident.

It's important to note that corn plants produce intensive leaf production during the first stages of growth. Before panicle formation, leaf weight is 1.5 to 2 times greater than stem weight. During panicle formation, stem weight is 1.5 to 2 times greater than leaf weight. At the milky-wax stage, cob weight is twice that of stem weight. This pattern persists across all experimental treatments, but manifests itself differently. Intensive leaf, stem, and cob production occurred in treatments with 100 tons of leonardite and 20 tons of humophos per hectare.

Corn plants continued to accumulate fresh mass until the milky-wax stage of grain maturity. Subsequently, until full maturity, fresh mass weight decreased, due to water loss from the seeds during ripening and from the tissues of leaves, stems, and husks during aging. Variations in plant growth rates during the growing season significantly impacted corn yield (Tables 3 and 4).

Table 3. Effect of leonardite on corn grain yield

Table 4. Effect of organo-mineral fertilizers on corn grain yield

Analyzing the data in Table 3, it should be noted that only pure leonardite applied at a rate of 100 t/ha yielded the highest increase in corn grain yield (4.9 c/ha, or 19.5%). Applying 25-50 t/ha yielded slightly smaller increases.

Table 4 shows that increasing the application rates of humic fertilizer and an equivalent set of mineral fertilizers increases corn grain yield. The most effective of the tested humic fertilizer rates for corn was 20 t/ha (an increase of 9.1 c/ha, or 36.7% over the control). Furthermore, for prompt crop support during the growing season, the researchers recommend the use of modern corrective fertilizers, such as Adept Agro.Bio (2 l/ha).

Leonardite and humophos had a similar effect on sunflower yield (Tables 5 and 6).

Table 5. Effect of leonardite on sunflower yield

Table 6. The effect of organo-mineral fertilizers on sunflower yield

The effectiveness of fertilizers cannot be assessed solely by grain yield. Our research also examined the effect of fertilizers on crop quality (protein, fat, and starch content).

• Protein: Grain protein content increases with increasing fertilizer doses. When leonardite was applied, the grain with the 100 t/ha dose had the highest protein content (9.78%), while when humophos was applied, the grain with the 20 t/ha dose had the highest protein content (10.17%). Compared to the control, protein content increased by 1.14% and 1.59%, respectively.
• Fat: The highest percentage of fat and its yield per hectare was in the variants with the application of 100 tons of leonardite and 20 tons of humophos per hectare (an increase compared to the control of 0.47 and 0.71%).
• Starch: There is an inverse relationship between the accumulation of starch and other nutrients (protein and fat). Under the influence of fertilizers, starch content decreases slightly in favor of protein and fat.

To study the aftereffect of leonardite and fertilizers in the first year of aftereffect, corn was sown for harvesting at the milky-wax stage for silage (Tables 9 and 10).

Table 9. Effect of leonardite after-effect on the yield of milky-waxy corn

Table 10. Effect of aftereffect of fertilizers on the yield of milky-waxy corn

Leonardite doses of 50 and 100 t/ha the following year after application gave a relatively high increase in the yield of milky-wax ripeness corn (27-33 c/ha, or 28.4-34.7%), which indicates the prolonged effectiveness of the raw material in the aftereffect.

CONCLUSIONS

• When preparing organo-mineral fertilizers from leonardite, mineral components introduced into the raw material somewhat increase the ammonia absorption capacity.
• When determining the rate of application of ammonia water, the ammonia absorption capacity of the raw material should be taken into account.
• During the treatment of leonardite with ammonia water, ammonia volatilization and nitrogen mobilization from the raw material itself occur simultaneously. When the raw material is saturated with ammonia to more than 112% of its full absorption capacity, nitrogen loss outweighs mobilization.
• The optimal rate of application of ammonia water in the production of organo-mineral fertilizers should be considered to be values ​​for raw materials with an average absorption capacity within the range of 3-3.5% of the dry matter weight, and for powdered superphosphate - 2.5-3%.
• The greatest increase in corn grain was obtained in the variant with the application of 20 t/ha of humus phosphate (9.1 c/ha, or 36.7% compared to the control).
• The fertilizers used have a significant effect on the quality of the crop, increasing the protein and fat content.
• Leonardite and fertilizers based on it are also effective in terms of after-effects, with humophos at doses of 15 and 20 t/ha having a stronger after-effect on crop yields than the original raw material in its pure form.

Agro.Bio Expert Note: The results of agrochemical studies and field trials demonstrate that leonardite reserves in the Steppe Zone of Ukraine are fully suitable for the production of highly effective organomineral fertilizers for agricultural crops. Agro.Bio specialists continue to develop the field of advanced leonardite processing described in classical works using cutting-edge biotechnology. Modern products developed by our experts, such as Agro.Bio Potassium Humate and a range of integrated solutions with an optimal application rate of 2 l/ha, enable the full exploitation of the natural potential of humic acids. This ensures prolonged plant protection from stress, maximum mobilization of macro- and microelements in the soil, and stable yield growth in various agroclimatic zones of Ukraine.