Efficiency of Leonardite Application on Gray Forest Soil
Experiments on gray forest soils in Chernihiv region have demonstrated high agronomic efficiency of leonardite.
Chemical Characteristics of Leonardite
Table 3. Chemical characteristics of leonardite obtained by different methods
| Fertilizer | On dry coal, % | In coal ash, % | Water solubility of preparation, % | Cu, % | Zn, % |
|---|---|---|---|---|---|
| Experiment #1 | |||||
| Treated with ammonia water | 4.24 | 2.98 | 45.27 | 0.1 | 0.001 |
| Oxidized with HNO₃ and treated with ammonia water | 8.80 | 4.08 | 62.70 | — | — |
| Experiment #2 | |||||
| Treated with ammonia water | 4.38 | 3.14 | 52.60 | 0.01 | 0.001 |
| Oxidized with HNO₃ and treated with ammonia water | 9.42 | 4.52 | 92.61 | — | — |
| Experiment #3 | |||||
| Treated with ammonia water | 4.04 | 2.68 | 80.12 | 0.01 | 0.001 |
| Treated with ammonia water at 150°C | 6.50 | 3.44 | 79.90 | — | — |
Experimental Conditions
In experiments with spring wheat (variety #1 and variety #2), oats and vegetable crops, leonardite prepared in experiment #2 was used; in corn experiments - leonardite from experiment #1. Leonardite efficiency was compared with 25% ammonia water, a highly effective fertilizer widely used by agricultural enterprises. Field experiments followed mandatory agronomic requirements for crop cultivation.
Wheat Experiment (Variety #1)
Conducted on light gray forest soil using paired method with 10 replications according to scheme:
- No fertilizer;
- Leonardite — 0.5 t/ha;
- Leonardite — 1 t/ha;
- 25% ammonia water — 240 l/ha.
Wheat Experiment (Variety #2)
Conducted on dark gray forest soil with 4 replications according to scheme:
- No fertilizer;
- Leonardite — 0.4 t/ha;
- Leonardite — 0.8 t/ha;
- 25% ammonia water — 240 l/ha.
Corn Experiment
Conducted on gray forest soil with 4 replications according to scheme:
- No fertilizer;
- Leonardite — 2 t/ha;
- Leonardite — 0.8 t/ha;
- Leonardite — 0.8 t/ha with Amino Energy liquid supplement (0.005% concentration, 1 l per nest);
- Water — 1 l per nest.
Amino Energy supplementation was applied three times during growing season: at sowing, June 24 and July 23.
Oats Experiment
Conducted on gray forest soil with 3 replications according to scheme:
- No fertilizer;
- Leonardite — 2 t/ha;
- Leonardite — 2 t/ha + Mind Extra (2 l/ha).
Vegetable Crops Experiments
Potato and beet experiments used same fertilizer variants as oats.
Field experiments were conducted on plots of 1000, 800, 200, 50 and 40 m². Yield was measured by sample sheaves and total harvest.
Vegetation Experiments
Along with field experiments, vegetation experiments with corn and oats were conducted in 5 kg soil containers. To study humic fertilizers' effect on root nutrition, agrochemical and biochemical analyses of soils and plants were performed.
Characteristics of Gray Forest Soils
Gray forest soils of Chernihiv Region's Forest-Steppe represent transitional stage from podzolic to chernozem-like soils. Humus horizon acquires chernozem properties while deeper horizons retain features of sod-podzolic soils. Humus content and humus horizon thickness determine gray forest soil varieties.
Effect of Humic Fertilizers on Root Nutrition
Table 4. Nutrient dynamics in gray forest soil fertilized with leonardite (spring wheat sowing)
| Experiment variant | pH (water) | pH (saline) | NH₄, mg/100 g | NO₃, mg/100 g | P₂O₅, mg/100 g | K₂O, mg/100 g |
|---|---|---|---|---|---|---|
| June 12, 2019 | ||||||
| No fertilizer | 6.5 | 5.7 | 1.25 | 3.11 | 1.97 | 9.5 |
| Leonardite 0.5 t/ha | 6.4 | 5.7 | 5.04 | 5.76 | 3.25 | 14.0 |
| Leonardite 1.0 t/ha | 6.4 | 5.7 | 7.80 | 6.80 | 5.57 | 15.8 |
| 25% ammonia water 240 l/ha | 6.0 | 5.2 | 5.00 | 6.67 | 5.36 | 16.2 |
| August 11, 2019 | ||||||
| No fertilizer | 6.3 | 5.3 | 3.00 | 1.87 | 8.40 | 3.4 |
| Leonardite 0.5 t/ha | 6.4 | 5.3 | 4.17 | 3.24 | 13.70 | 10.4 |
| Leonardite 1.0 t/ha | 6.4 | 5.3 | 3.02 | 5.00 | 16.60 | 11.4 |
| 25% ammonia water 240 l/ha | 6.2 | 5.5 | 4.00 | 2.74 | 16.10 | 14.0 |
Leonardite at 0.5 t/ha introduced 22 kg total nitrogen, at 1 t/ha — 44 kg. 240 l of 25% ammonia water introduced 50 kg nitrogen per ha. Nitrogen nutrition conditions were most favorable with high leonardite dose, maintained until end of growing season. With ammonia water, nitrogen availability decreased by season's end.
Table 5. Nitrogen content in differently fertilized soil
| Experiment variant | Total nitrogen, % of dry soil weight | Total nitrogen, t/ha | Mineral nitrogen, % of total nitrogen |
|---|---|---|---|
| June 12, 2019 | |||
| No fertilizer | 0.224 | 6.72 | 0.77 |
| Leonardite 1 t/ha | 0.319 | 9.57 | 2.08 |
| 25% ammonia water 240 l/ha | 0.233 | 6.99 | 2.41 |
| August 11, 2019 | |||
| No fertilizer | 0.242 | 7.26 | 1.23 |
| Leonardite 1 t/ha | 0.280 | 8.40 | 2.75 |
| 25% ammonia water 240 l/ha | 0.209 | 6.27 | 1.85 |
Effect on Potassium and Phosphorus Content
Gray forest soils have low soluble potassium reserves. Leonardite and ammonia water application increases soluble potassium content through soil's silt fraction. Exchangeable potassium is displaced by ammonium cations. Phosphate accumulation is slightly higher with ammonia water, but fertilized plots show increased acetate-soluble phosphates.
Effect on Soil Reaction
Soil solution pH slightly decreases with leonardite, while ammonia water causes more pronounced acidification. High dispersity of humic acids in leonardite results in less impact on soil organic matter compared to ammonia water.
Humus Substance Dynamics
Table 6. Humus substance dynamics in light gray forest soil (wheat sowing, 0-20 cm horizon)
| Experiment variant | Humus, % of dry soil weight | Humic acids (by C), % of soil weight | Humic acids, % of total C | Water-soluble humus (by C), % of soil weight | Water-soluble humus, % of total C |
|---|---|---|---|---|---|
| June 12, 2019 | |||||
| No fertilizer | 3.41 | 0.2106 | 10.6 | 0.01363 | 0.68 |
| Leonardite 1 t/ha | 4.73 | 0.3376 | 12.2 | 0.01527 | 0.55 |
| 25% ammonia water 240 l/ha | 4.76 | 0.2743 | 9.9 | 0.02023 | 0.73 |
| August 11, 2019 | |||||
| No fertilizer | 2.89 | 0.1456 | 8.6 | 0.01450 | 0.86 |
| Leonardite 1 t/ha | 3.19 | 0.2236 | 11.9 | 0.01789 | 0.96 |
| 25% ammonia water 240 l/ha | 3.07 | 0.1459 | 8.4 | 0.01909 | 1.07 |
Humus Changes
Leonardite application increases humus content through humic substances. Ammonia water increases humus by enhancing plant root systems. Leonardite-fertilized soils show increased humic acid content, while ammonia water reduces their share, increasing water-soluble humus.
Conclusions
Leonardite demonstrates high agronomic efficiency on gray forest soils, improving nitrogen nutrition, increasing humus and soluble potassium content, with less soil acidification compared to ammonia water.