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Review

Brown Coal Waste in Agriculture and Environmental Protection: A Review

Institute of Agriculture and Horticulture, Faculty of Agrobioengineering and Animal Husbandry, Siedlce University of Natural Sciences and Humanities, B. Prusa 14 St., 08-110 Siedlce, Poland
*
Author to whom correspondence should be addressed.
Sustainability 2023, 15(18), 13371; https://doi.org/10.3390/su151813371
Submission received: 30 June 2023 / Revised: 25 August 2023 / Accepted: 3 September 2023 / Published: 6 September 2023

Abstract

:
Modern agricultural technologies have contributed to a significant reduction in the amount of soil organic matter. Brown coal waste (BCW), with low energy content, can be used to neutralize this process, contributing to the recuperation of soil fertility and to environmental protection. More studies need to be conducted on organomineral fertilizers based on BCW and applied to soils with low humus content. Apart from increasing soil production capacity in arable fields, BCW could be used for the reclamation of industrially contaminated areas and degraded soils, in the vicinity of motorways and in soilless agriculture. It can also be used as a sorbent of gases emitted from slurry during its storage such as NH3, H2S, mercaptans, volatile fulvic acids (FAs); as a component of sewage sludge compost; as a natural additive to calf feed; and for the production of adsorbents for sewage and wastewater treatment.

1. Introduction

The intensification of agricultural production and the increase in mineral fertilizer use contribute to the accelerated mineralization of organic matter and soil humus, which is the main cause of degradation in agricultural soils. The increasing area of light soils around the world and the low production potential of these soils create the need to seek a way to improve the quality of these soils. The use of high doses of fertilizers, especially mineral fertilizers on light soils, may violate the balance of the soil environment and contribute to soil and groundwater contamination. A great source of permanent organic substance for light soils can be brown coal waste (BCW) with low energy value. It is located on heaps as an overlap of brown coal energy deposits in many countries around the world.
Brown coal waste (BCW) is one of the cheapest energy sources for the electric power industry [1]. Its global resources in currently exploited locations are sufficient to cover about 40% of primary energy consumption. BCW is a caustobiolite, i.e., a carbonaceous sedimentary rock of organic origin, which has undergone the process of carbonization, i.e., enrichment with carbon. The stages of brown coal (BC) formation are as follows: vegetation (primary carbon-forming material) → peat → brown coal → bituminous coal → anthracite. In Europe, brown coal is divided according to its level of carbonization [2]: soft BC, also called earthy brown coal (carbon content (C): 58 ÷ 71%, heat of combustion (Qc): 14.6 ÷ 19.3 MJ kg−1); matt hard BC (C): 71 ÷ 73%, heat of combustion (Qc): 19.3 ÷ 24.4 MJ kg−1); and shiny hard BC (C): 73 ÷ 76%, heat of combustion (Qc): 24.4 ÷ 26.7 MJ kg−1). Lying at a depth of 30–130 m, BC is mined using the opencast method (Figure 1).
Brown coal deposits include seam deposits, tectonically and glaciotectonically disturbed deposits, as well as less common karst, relict deposits, and brown coal flows. Xylite brown coal has a well-preserved wood structure with a predominance of cellulose and lignin. In soft earthy BC, polymolecular amorphous humic acids (HAs) are the main component [3,4].
An important problem for environmental protection is the management of huge amounts of brown coal overburden of earthy varieties and with low energy value [5]. It is most often used for the reclamation of opencast excavations [6,7].
Its direct effect on soil results from its content of chemical elements and compounds necessary for the growth of plants [8,9]. The indirect action on soil results from its physical properties. BCW can reduce the leaching of fertilizer components into deeper soil layers. Brown coal waste, due to a well-developed external and internal surface, has good sorption properties and acts as a natural sorbent [10]. Polish brown coal constitutes of 55–76% humic acids [11]. The Ukrainian brown coal contains a large amount (about 80%) of humic acids. It is proved that humic substances obtained from brown coal of Ukraine allow for the binding of up to 99% of heavy metal ions in complexes [12]. BCW contains plant nutrients [13]. The average content of macronutrients in polish BCW can be presented in a series of decreasing values: C (351) > Ca (18) > S (6.2) > N (4.6) > Mg (2.3) > K (0.4) > P (0.06) g kg−1 and micronutrients: Fe (3039) > Ti (115.8) > Mn (39.6) > B (22.1) > Zn (11.3) >Cu (3.3) >Ni (2.6) > Co (1.4) > Se (0.13) > Mo (0.1) mg kg−1 [13].
The single application lignite-derived humic product called “Nano humus” significantly increased soil-available phosphorus by 63% and potassium by 96% relative to the control; it significantly enhanced total biomass of alfalfa (Medicago sativa L.) by 749%, barley (Hordeum vulgare L.) by 250%, and sea buckthorn (Hippophae rhamnoides L.) by 147%. The beneficial effects of lignite-derived humic substances were exhibited after 2 years [14]. Fulvic Acids (FAs) and humic acids (HAs) from brown coals have significant differences in their chemical and structural-group compositions [15]. FAs are characterized by a high concentration of oxygen—containing aliphatic groups, carboxylic acids, and esters. They are characterized by lower concentration of carbon, hydrogen, and aromatic fragments and a lower aromaticity/aliphaticity ratio [15]. Phytotesting showed that FAs isolated from all the studied of brown coal exhibited biological activity in relation to wheat seeds. FAs exerted the most pronounced stimulating effects on the length of roots and the height of seedlings [15]. Lignite from Visonta (Hungary) has a stabilizing effect on the heavy metals Cr, Pb, and Zn in the case of complex soil contamination with these metals [16]. According to Uzinger et al. [16], lignite did not increase the amount of higher condensation and polymerization humic fractions, but it did increase the cation exchange capacity of the soil. The pH, content C, available nutrients, and electric conductivity (EC) in agricultural soils clearly increase with the addition lignite-based amendment [17,18,19]. The use of humic acid in sustainable agriculture has been advocated, and it has been stated that highly significant increases have been reported recently in potato growth, tuber yields, and quality in plant-growth-promoting rhizobacteria (Bacillus megaterium and Bacillus subtilis) and humic acids (HAs)-inoculated crops [20,21].
The chemical composition of silage maize is the result of treatment, soil and weather conditions, growing methods, and varieties [22,23,24]. The organomineral fertilizer based on brown coal waste in doses 1 Mg ha−1 and 5 Mg ha−1 applied to the preceding crop NPKMgS + 20 kg N ha−1 and NPKMgS + 40 kg N ha−1 plots positively affected maize parameters such as agronomic and physiological efficiency [23]. The addition of urea to brown coal used for crops increases the efficiency of nitrogen use and the yield of these crops [25].
Soil nutrients and organic matter are important factors influencing soil microbe composition [26]. The enzymatic activity of soil depends to the greatest extent on its content of organic matter and nitrogen, its pH and temperature, on mineral and organic fertilizer treatment, on the content of macronutrient, micronutrient, and heavy metals, but also on the fertilizer treatment applied to the preceding crop [27,28]. The mineral fertilizers applied to the preceding crop increased the activities of urease, phosphatases, and dehydrogenases. In order to obtain high enzymatic activity in the soil and a high biochemical index of soil fertility, pre-sowing fertilizers at the level of 100 kg N, 35 kg P, 125 kg K, 12 kg Mg, and 14 kg S per hectare; and top dressing of 20 kg N or 40 kg N per hectare are recommended. At the same time, it is advisable to add 1 t ha−1 or 5 t ha−1 of BCW of low energy value to the preceding crop. An increase in enzyme activity as a response to organic matter application to the soil was also reported by Widmer et al. [29] and Xie et al. [30].
The main purpose of presenting this manuscript in the form of a review article was to provide current knowledge about the multidirectional possibilities of using and developing brown coal waste with low energy value.
According to the authors, this manuscript will contribute to the use of scientific and experimental knowledge in agricultural practice and in the field of environmental protection.

2. Chemical Properties of Brown Coal Waste Components

The main chemical components of BCW are fulvic acids (FAs), humic acids (HAs), humins (Hs), and bitumen (B). Fulvic acids are organic matter compounds easily soluble in water, alcohol, alkali, and inorganic acids. They are very mobile and of a lighter color and simpler structure than HAs, and they contain less carbon [31]. FAs form more or less stable complex bonds (at pH > 5) with Has, aluminium, and iron hydroxides. HAs are the most important component of brown coal waste fertilizers. They mainly contain carbon, hydrogen, and oxygen, as well as small amounts of nitrogen and sulfur. Aromatic benzene and pyridine rings, alicyclic rings, aliphatic, chains, bridges, and functional groups are the basic elements of their structures. Bridges can be formed by oxygen atoms—O–, nitrogen—N=, and chains or groups of atoms like =NH2 or =CH2. Aromatic rings sharing carbon atoms C–C can also be found. Functional groups are an important component of HAs (carboxyl group—COOH, hydroxyl group—OH, methoxyl group—OCH3 and carbonyl group =C=O) (Figure 2 and Figure 3).
The structure of HAs depends both on the type of brown coal and on the transformations that the initial carbon-forming material underwent in the carbonization process. Active functional groups disappear with increasing degrees of carbonization, which entails the loss of ion-exchange capacity [32,33].
The main physicochemical properties of humic acids (HAs) are porosity, sorption capacity, hydrophilicity, ion-exchange capacity, and swelling capacity [34,35,36]. They are divided into brown HAs (lower N content, lower sensitivity to the coagulating effect of electrolytes, stronger acid character, lower molecular weight) and gray HAs (richer in nitrogen, sensitive to electrolytes, with weak acid character, higher molecular weight than brown HAs, high bonding capacity).
Humins are humic compounds that are formed as a result of dehydration, decarboxylation, and deoxidation of humic and ulmic acids (UAs) at low temperatures, or as a result of strong drying at high temperatures [11,37]. They play a bond-forming role, but they are not very active. Under the influence of microorganisms, they undergo slow and long-lasting mineralization. Bitumen is a mixture of hydrocarbons, tars, and waxes, and it is not very chemically active (fewer functional groups); it is resistant to various external factors.

3. Use of Brown Coal Waste in Agriculture

For fertilizing purposes, brown coal waste is used as an aggregate material with particles smaller than 1 mm or lumps crushed to a fraction of 8 mm (Figure 4).
The main chemical components BCW as well as macronutrients and micronutrients contained in BCW increase the nutrients in maize biomass [24,38]. The diversified chemical composition of BCW results from the type and origin of the excavation as well as the depth and thickness of the collected brown coal overburden. The greatest amounts of carbon, calcium, sulfur, and magnesium were determined in the analyzed materials while the microelements mostly included iron, manganese, and boron, as demonstrated by Symanowicz et al. [13]. Microelements (iron, molybdenum and cobalt) introduced to the soil with brown coal waste can increase the process of biological N2 reduction through bacteria living in the soil [39,40]. BCW and organomineral fertilizers produced on the basis of BCW with a very low energy value can be used for the agromelioration of arable sandy soils. Reclamation fertilizer used in light soil agromelioration consists of organic substances such as BCW (80%), lignite ash, single superphosphate, calcium nitrate, and potassium salt (N—0.15%, K2O—0.2%. P2O5—0.15%, MgO—1.0%, CaO—3.0%, Cu—0.0025%) [41]. Brown coal waste and organomineral fertilizers based on brown coal waste permanently improve the physical and water properties of sandy soils (Table 1 and Table 2). An example of such an organomineral fertilizer is Rekulter.
Rekulter can be used for reclamation of soils and devastated areas. It can be used on defective soils, too heavy and too light, and soils acidified by industry. It is exported and applied to desert soils. The results of a 3-year field study with maize, potatoes, and barley showed an increase in the yield of the test plants after the application of biochar (12.8 t ha−1), and brown coal waste (24.2 t ha−1) by at least 20%, with or without the addition of NPK (90-26-91 kg ha−1) [42].

4. Chelation of Heavy Metal Cations by Humic Acids and Fulvic Acids

An increase in the pH value leads to an increase in free negative charges. Under such conditions, free—OH groups appear in the soil solution and enter into chemical reactions with functional carboxyl and hydroxyl groups [43,44,45].
R-COOH + OH → R-COO + H2O
R-OH + OH → R-O +H2O
The brown coal waste stabilizes of Cr, Pb, and Zn (Figure 5) in the soil [16], the extractability of heavy metals (Cd, Cu, Pb, and Zn), and enzyme activity in soil [46]. As a result, humic and fulvic acids acquire a negative charge and combine with positively charged ions (cations) to form organomineral compounds [47,48,49].
The formation of chelated complexes with cations of heavy metals contributes to soil detoxication and increases the availability of plant nutrients [50,51,52,53,54]. The effect of Rekulter on reducing the uptake of Zn, Pb, and Cd by plants presented in Table 3.
One of the heavy metals forming chelates with humic substances is aluminum. Bound to humic acids (HAs) and fulvic acids (FAs), it cannot fix phosphates (V) into unavailable forms, which makes phosphorus more available to plants. It was found that in soil containing 1% of humus aluminum has a toxic effect, causing a reduction in yields even at a content of 1 mg Al 100 g−1 of soil [55].
However, with a humus content of 5–6%, the harmful effect of aluminum is observed only at a content of 15 mg Al 100 g−1 of soil [55]. According Simmler et al. [56], brown coal waste reduces the solubility and plant uptake of cadmium in pasturelands. In these studies, the addition of brown coal, at the amount of 5% by weight of the soil, was the most effective in reducing soluble cadmium in low pH soils. The research conducted by Simmler et al. [56] also showed that the addition of brown coal in the amount of by weight to the soil in the greenhouse experiment reduced the uptake of Cd by Lolium perenne L. by 30%. The formation of chelated complexes with cations Ca2+ (Figure 6) increases the availability of plant nutrients.

5. Interaction of Brown Coal Waste and Mineral Fertilization

Due to its developed porous system, brown coal waste contributes to increasing the uptake of nutrients from mineral fertilizers, reducing the leaching of fertilizer components into deeper soil layers. An example of the interaction between brown coal waste and mineral fertilizers is seen in the study of Tóth et al. [57]. They explored the effect of Humac Agro (HA) on the yield, sugar content in sugar beet, and soil characteristics under conditions of sustainable agricultural management system (Table 4, Figure 7). An agent improving soil properties, under the trade name of HA, was introduced to the market in the territory of Poland. The manufacturer of HA has also obtained permission to use this agent in organic farming. Chemical composition of HA is 68% Has, N—12.8, K—1.2, Ca—16.8 g kg−1 and Zn—64, B—77, Fe—14,502, Cu—19, Se—6 mg kg−1, and in smaller amounts other trace elements [57].
The highest yields of sugar beet (95.97 Mg ha−1) were obtained for variant V3. Humac Agro applied at 500 kg ha−1 resulted in an increase in the sugar yield by 29.6% in comparison to the control (Table 5).
The humus content in the soil, soil pH, and content of available P, K, Mg, B, Mn, Cu, Zn, and Fe were also increased. Other studies conducted by Tóth et al. [58] showed a positive effect of Humac Agro, when used at a dose of 1 t ha−1, on the yield and biometric parameters of switchgrass (Panicum virgatum L.). BCW has the ability to absorb and exchange ions between the soil solution and the solid phase. It can also absorb H2O, CO2, and NH3. Brown coal waste effectively weakens the rapid effect of row mineral fertilization. It improves the composition of soil solutions and increases the uptake of nutrients, especially of nitrogen. It has a positive effect on the uptake of phosphorus and potassium by plants from the soil, and it increases the absorption of iron. Research conducted by Arjumend et al. [59] and Tahir et al. [60] in greenhouse conditions showed improvement in soil properties and nutrient uptake by wheat (Triticum aestivum L.) after application of lignite-derived humic acid.

6. Use of Brown Coal Waste in Cultivation of Vegetables

BCW meets the conditions for ideal substrates [61,62]. It is free of pathogens and, with proper grain size, it has a large maximum and capillary moisture-holding capacity and high porosity. It has a sufficiently stabilized chemical composition. The reaction of BCW is slightly acidic and neutral (pH 6–7), and its salinity is very low (0.2 g dm−3). It can be enriched with standard nutrients like nitrogen, phosphorus, potassium, copper, and zinc, according to the nutritional requirements of the crop [63,64]. With high durability, it is resistant to microbiological decomposition. The organic matter of waste brown coal and biochar has a positive effect on increasing the enzymatic activity in the soil [28,65,66,67]. According to field experiments, when applied as an aggregate material with a particle diameter of up to 20 mm once every 9 years, it increases the content of organic matter from 1.5 to 4% in a 25 cm soil layer. It can be used on light and heavy soils of arable land at a dose of 20–40 t ha−1. Brown coal waste of various grain sizes is used directly as a substrate for tomato [68,69], lettuce and cucumber [70,71], and ornamental plants [70] requiring continuous irrigation. By enriching BCW with super sorbents, a substrate that swells to different degrees when exposed to water is obtained. On very light soils, BCW-based organomineral fertilizers can be used in reclamation doses. Table 6 presents changes in the properties of the rusty soil under the influence of Rekulter fertilizer.

7. Organomineral Fertilizers Based on Brown Coal Waste

There are many organomineral fertilizers on the market based on brown coal waste. The following are some examples: Humi Brown Gold, Carbohumic, Carbomat ECO, Greenmix. On the basis of BCW, it is possible to produce organomineral fertilizers, with an addition of microelements, to be applied to arable land before the growing period. On the basis of the three-year studies using polyfoska® M-MAKS (NPKMgS) (Group AZOTY, Police, Poland), potassium salt and urea in the cultivation of maize for silage, the optimal dose of mineral fertilizers NPKMgS + N1 (pre-sowing 100-35-125-12-14 kg ha−1 and a top dressing of 20 kg N ha−1), and NPKMgS + N2 (pre-sowing 100-35-125-12-14 kg ha−1 and a top dressing of 40 kg N ha−1) can be recommended [23]. The organomineral fertilizer (Figure 8) based on BCW in doses of 1 Mg ha−1 and 5 Mg ha−1 applied to the preceding crop on NPKMgS + 20N1 and NPKMgS + 40N2 plots positively affected maize parameters (agronomic efficiency, physiological efficiency).
Additionally, organomineral deacidifying fertilizers can be applied pre-sowing to winter plants and in the spring to legume plants [25,72,73]. BCW can be used as a natural fertilizer for the reclamation of devastated, defective, sandy, and desert soils, as well as those acidified by industry. Liquid organomineral fertilizers based on BCW are also produced (e.g., Humolist, Ecopost, Hydrocomplet). To obtain humin-mineral and slow-acting fertilizers, BCW can be treated with various chemicals (KOH, HCl, HNO3, H3PO4, and compounds of magnesium, iron, zinc, and manganese). As a result of these reactions, humic-mineral, nitrohumine-mineral, and micronutrient fertilizers are obtained (e.g., Nitro Sulfer NPK, Tohumus, Tohumus Ekstra).

8. Ecological Aspects of Brown Coal Waste Application to Sandy Soils

Maciejewska [74], and Kwiatkowska-Malina and Maciejewska [75] found positive effects of BCW, on the productivity of sandy soil, by weakening its acidic reaction and increasing its sorption capacity. Owing to BCW application, fertilizer doses can be increased and still be environmentally sustainable. Additionally, an increase in the total content of organic carbon and in soil buffer properties was found [76]. Due to the chelating properties of humic acids (HAs) binding metal cations (Cd2+, Pb2+, Zn2+, Al3+), the uptake of heavy metals by plants is limited [45]. Humic acids from BCW are of higher aromaticity and are more resistant to thermal destruction than HAs from soil humus (according to elemental composition analysis, infrared spectroscopy and differential thermal analysis). They contain more carboxyl and hydroxyl groups [77]. The protective effect of BCW organic matter on light soil physical properties is manifested in a reduction in total and capillary porosity and an increase in soil water-holding capacity by an average of over 50% [10]. Brown coal waste and organic-mineral fertilizers based on brown coal waste permanently improve the physical and water properties of light soils (Table 7 and Table 8). An example of an organic-mineral fertilizer is Complete R. Complete R consists of 85% organic matter, 10% lignite ash, and small amounts of macronutrients and micronutrients. The organic matter consists of waste lignite and peat in a volume ratio of 7:3 [78].
Additionally, BCW can be used as a sorbent of gases emitted from slurry during its storage (NH3, H2S, mercaptans, volatile fulvic acids). Brown coal waste can be used with other minerals as a natural feed additive for calves [79]. It is used to produce adsorbents for wastewater and sewage treatment, and for reclamation of contaminated areas [80]. BCW has a chance to become a valuable environmentally friendly raw material used for the reclamation of devastated and degraded land and the improvement of poor-quality soils with a significant deficit of manure [81]. BCW protects the environment and groundwater from pollution. There are already fertilizers made on the basis of waste brown coal intended for ecological production (e.g., Florovit Eko, Florovit Agro, Florahumus, Humus Active, Folorovit Pro Natura, EkoDarpol).

9. Conclusions

In modern agriculture, there is a rapid process of mineralization and degradation in organic matter. Based on the review of the thematic literature presented, brown coal waste (BCW) can be recommended for direct or indirect agricultural use. BCW, with low energy content, can be used to neutralize this process, contributing to the recuperation of soil fertility and to environmental protection. More studies need to be conducted on organomineral fertilizers based on BCW which are applied to soils with low humus content. Apart from increasing soil production capacity in arable fields, BCW could be used for the reclamation of industrially contaminated areas and degraded soils in the vicinity of motorways and in soilless agriculture.
Further research on the use of brown coal waste should be focused on the production of permanent organomineral fertilizers for individual plants that are grown on soils with low organic matter content.

Author Contributions

Conceptualization, B.S. and R.T.; writing—original draft preparation, B.S. and R.T.; writing—review and editing, B.S. and R.T.; visualization, B.S. and R.T. All authors have read and agreed to the published version of the manuscript.

Funding

This research was financed from the science grant by the Polish Ministry of Education and Science, research task number 36/20/B.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. Differentiated geological sections of brown coal deposits [2].
Figure 1. Differentiated geological sections of brown coal deposits [2].
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Figure 2. Model of humic acids [10].
Figure 2. Model of humic acids [10].
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Figure 3. Model of the linear structure of humic acids [10].
Figure 3. Model of the linear structure of humic acids [10].
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Figure 4. Ground brown coal waste (BCW) used in agriculture [Phot. B. Symanowicz].
Figure 4. Ground brown coal waste (BCW) used in agriculture [Phot. B. Symanowicz].
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Figure 5. Scheme of the formation of chain or ring chelates, M2+—metal cations [11].
Figure 5. Scheme of the formation of chain or ring chelates, M2+—metal cations [11].
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Figure 6. Scheme of the formation of humic-calcium or fulvic-calcium chelates [11].
Figure 6. Scheme of the formation of humic-calcium or fulvic-calcium chelates [11].
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Figure 7. Field experiment. (a) Control treatment; (b) beets fertilized with a dose of 250 kg ha−1; (c) beets fertilized with a dose of 500 kg ha−1; (d) whole plant sugar beet of individual objects fertilizer [57]. (Phot. J. Karahuta).
Figure 7. Field experiment. (a) Control treatment; (b) beets fertilized with a dose of 250 kg ha−1; (c) beets fertilized with a dose of 500 kg ha−1; (d) whole plant sugar beet of individual objects fertilizer [57]. (Phot. J. Karahuta).
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Figure 8. Organomineral fertilizer (a) applied to the preceding crop (b) maize grown for silage [23].
Figure 8. Organomineral fertilizer (a) applied to the preceding crop (b) maize grown for silage [23].
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Table 1. Selected physical properties of light soil after application of Rekulter [41].
Table 1. Selected physical properties of light soil after application of Rekulter [41].
Years of ResearchDose Rekulter
(t ha−1)
Specific Density
(g cm−3)
Bulk Density
(g cm−3)
Total Porosity (%)Air
Capacity (%)
102.601.5540.2211.00
402.511.4940.6210.78
802.471.4242.307.48
1602.401.3443.155.45
502.601.5739.4720.55
402.531.5339.5518.30
802.481.4441.8011.40
1602.421.3843.186.05
Table 2. Selected water properties of light soil subjected to agromelioration with Rekulter [41].
Table 2. Selected water properties of light soil subjected to agromelioration with Rekulter [41].
Years of ResearchDose Rekulter
(t ha−1)
Hygroscopic Water (%)Moisture at the Time of Sampling by Weight (wt.%)Volumetric Humidity at the Time of Sampling (vol.%)Capillary Water Capacity by Weight (wt.%)Volume Capillary Water Capacity (vol.%)Field Water Capacity (%)
100.479.8315.3318.7129.0010.10
400.4910.7516.0020.0929.9410.83
800.6213.0518.5724.4134.7713.15
1600.8117.3323.1629.0438.6915.65
500.473.435.4312.1218.936.55
400.523.685.6113.9421.247.50
800.636.489.3821.0830.2711.40
1600.8310.2814.1226.8937.0914.58
Table 3. The effect of Rekulter on reducing the uptake of Zn, Pb, and Cd by plants. Rekulter dose 150 t ha−1 [10].
Table 3. The effect of Rekulter on reducing the uptake of Zn, Pb, and Cd by plants. Rekulter dose 150 t ha−1 [10].
ElementsSeradella
(%)
Triticale
(%)
Maize
(%)
Rape
(%)
Spinach
(%)
Zn5050505040
Pb5050503030
Cd4030505030
Table 4. Doses Humac Agro (HA) and basic nutrients (NPKS) in the cultivation of sugar beet (kg ha−1) [57].
Table 4. Doses Humac Agro (HA) and basic nutrients (NPKS) in the cultivation of sugar beet (kg ha−1) [57].
TreatmentsHumac AgroNPKS
V1094.834.9100.028.0
V225094.834.9100.028.0
V350060.334.9100.028.0
Table 5. The yield of sugar beet roots, sugar content in sugar beets, and sugar yield [57].
Table 5. The yield of sugar beet roots, sugar content in sugar beets, and sugar yield [57].
Fertilization Variant—Humac AgroRoot Yield
(Mg ha−1)
Relative to Control (%)Sugar Content
(kg Mg−1)
Sugar Yield
(Mg ha−1)
Relative to Control (%)
072.81100.0184.313.42100.0
250 kg ha−186.39118.7176.515.25113.6
500 kg ha−195.97131.8181.217.39129.6
Mean85.06125.2180.715.35121.6
Table 6. Changes in properties of proper rusty soil under the influence of Rekulter fertilizer. Remedial doses [10].
Table 6. Changes in properties of proper rusty soil under the influence of Rekulter fertilizer. Remedial doses [10].
Years of ResearchDose Rekulter
(t ha−1)
pHKClHh (cmol(+) kg−1)Degree of Base Saturation
(%)
Ct
(g kg−1)
Nt
(g kg−1)
Mg2+
(mg kg−1)
Ca2+
(mg kg−1)
K+
(mg kg−1)
H2PO4
(mg kg−1)
104.74.139.37.60.64.086.08.02.0
406.12.080.210.80.837.0257.017.012.0
806,80.993.914.50.974.0556.030.023.0
1607.40.498.922.11.1141.01504.042.047.0
504.82.838.88.70.56.082.090.02.0
406.01.674.911.50.730.0201.014.07.0
806.21.388.315.00.836.0386.022.014.0
1606.60.498.222.70.994.0889.028.030.0
Table 7. Changes in the physical properties of light soil made of loose sands after application of the organomineral fertilizer Complete R [78].
Table 7. Changes in the physical properties of light soil made of loose sands after application of the organomineral fertilizer Complete R [78].
Years of ResearchDose Complete R
(m3 ha−1)
Density of the Solid Phase of the Soil (g cm−3)Density of the Dried Soil in 105 °C (g cm−3)Total Porosity (%)Air
Capacity (%)
102.681.6039.19.8
502.561.5738.79.5
1002.481.4840.47.6
2002.361.4041.75.1
402.671.6040.514.0
502.571.5639.111.3
1002.481.4342.410.3
2002.341.3741.76.3
Table 8. Selected water properties of light soil after application of the organomineral fertilizer Complete R [78].
Table 8. Selected water properties of light soil after application of the organomineral fertilizer Complete R [78].
Years of ResearchDose Complete R
(m3 ha−1)
Hygroscopic Water (%)Moisture at the Time of Sampling by Weight (wt.%)Volumetric Humidity at the Time of Sampling (vol.%)Capillary Water Capacity by Weight (wt.%)Volume Capillary Water Capacity (vol.%)Field Water Capacity (%)
100.458.915.018.029.39.72
500.499.315.918.229.99.99
1000.6310.216.721.232.711.45
2000.7616.322.825.136.613.55
400.452.55.216.326.28.8
500.472.96.217.327.99.3
1000.635.58.922.332.212.1
2000.707.210.624.834.813.4
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Symanowicz, B.; Toczko, R. Brown Coal Waste in Agriculture and Environmental Protection: A Review. Sustainability 2023, 15, 13371. https://doi.org/10.3390/su151813371

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Symanowicz B, Toczko R. Brown Coal Waste in Agriculture and Environmental Protection: A Review. Sustainability. 2023; 15(18):13371. https://doi.org/10.3390/su151813371

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Symanowicz, Barbara, and Rafał Toczko. 2023. "Brown Coal Waste in Agriculture and Environmental Protection: A Review" Sustainability 15, no. 18: 13371. https://doi.org/10.3390/su151813371

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