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Characterization of Humic System in Fertilizer Raw Materials


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The aim of the study was to characterize humus system of natural and artificial products. Humus systems from leonardite, lignite biotransformed with Trichoderma sp. (Plantagra), plant materials after pyrolisis (charcoal) and composts are compared. Humus systems are characterized by Kononova-Belchikova's method, and heavy metals content was measured by atomic absorption spectroscopy (AAS). Humic acids from the International Humic Substances Society (IHSS) collection are the standards for humus substances quality of compared products. Data obtained for leonardite indicate that the studied substances from factory, Izmir, Turkey contain humic acids over 94%. Compared to the standard, heavy metals content in these materials demonstrate high amounts. Organic carbon content in the composts is very low compared to the leonardite materials and IHSS collection, where the heavy metals content is lower. Biotransformed lignite is characterized with lower content of organic carbon, but humic acids are with high degree of humification. Results obtained show that the fourth studied humus systems may be used in agriculture on base of the high humic acids content. It is recommended to measure heavy metals content before applying the materials in agriculture.
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Journal of Agricultural Science and Technology A 7 (2017) 11-17
doi: 10.17265/2161-6256/2017.01.002
Characterization of Humic System in Fertilizer Raw
Еkaterina Filcheva1, Rossitza Ilieva2, Kosnstantin Chakalov3, Todorka Popova3, Valentin Savov3 and Mariana
1. Department of Soil Genesis, Geography and Classification, Nikola Poushkarov Institute of Soil Science, Agrotechnology and Plant
Protection, Sofia 1080, Bulgaria
2. Department Common Agriculture, University of Forestry, Sofia 1718, Bulgaria
3. Balkan Plant Science Ltd. Co., Sofia 1000, Bulgaria
Abstract: The aim of the study was to characterize humus system of natural and artificial products. Humus systems from leonardite,
lignite biotransformed with Trichoderma sp. (Plantagra), plant materials after pyrolisis (charcoal) and composts are compared.
Humus systems are characterized by Kononova-Belchikova’s method, and heavy metals content was measured by atomic absorption
spectroscopy (AAS). Humic acids from the International Humic Substances Society (IHSS) collection are the standards for humus
substances quality of compared products. Data obtained for leonardite indicate that the studied substances from factory, Izmir,
Turkey contain humic acids over 94%. Compared to the standard, heavy metals content in these materials demonstrate high amounts.
Organic carbon content in the composts is very low compared to the leonardite materials and IHSS collection, where the heavy
metals content is lower. Biotransformed lignite is characterized with lower content of organic carbon, but humic acids are with high
degree of humification. Results obtained show that the fourth studied humus systems may be used in agriculture on base of the high
humic acids content. It is recommended to measure heavy metals content before applying the materials in agriculture.
Key words: Compost, humic acid, leonardite, lignite, sewage sludge, Trichoderma harzianum, Trichoderma viride.
1. Introduction
Role of humus in soils is diverse. The content and
reserves of N, a major nutrient element in the soil
system, largely depend on the total content of organic
matter. The quantity and characteristics of soil organic
matter have a positive influence on many soil
properties, primarily on the soil physical properties
and the processes of structure formation. Humus
substances interact with mineral colloids, and form
complexes in nature and structure of organo-mineral
compounds and associates as a result of this change
the properties of the mineral colloids. An important
role of soil organic matter is to bind heavy metals and
some organic contaminants in polluted technogenic
soils [1-3].
Corresponding author: Ekaterina Filcheva, professor,
research fields: soil science—soil organic matter, composts,
organic carbon stocks, etc..
The decreasing of soil organic matter is due to the
rapid mineralization of the labile components under
the limited input of organic materials in soils. Major
sources to replenish the loss of organic carbon are
after harvest, such as root residues, organic fertilizers,
composts, humus materials of different origin,
charcoal, etc.. Nowadays, there is a global trend for a
gradually replacement of chemical fertilizers by
natural products. Humic substances are promising raw
material, as they naturally occur in high amounts in
Bulgarian lignites [4].
A significant number of studies focus their attention
on the role of lignin decomposing enzyme systems,
like peroxidase [5, 6]. A new isolate of Trichoderma
atroviride has been shown to grow on low rank coal
as a sole carbon source; T. atroviride ES11 degrades
82% of a particular type of coal over a period of 21 d
[7]. In the previous studies, the possibility for
Characterization of Humic System in Fertilizer Raw Materials
biotransformation of lignite by Trichoderma has been
shown [8]. Some of this material can bio-solubilized
by bacteria (such as Bacillus sp. and Pseudomonas sp.)
in bioreactors, and they have significant physiological
effect on plants [9]. So, the aim of this study was to
characterize humic systems of certain natural and
commercial products with a view to determine their
potential as enhancers of the humus status of soils
treated with them, or their ability to stimulate plants.
2. Materials and Methods
Different materials were compared for humus
system in the study:
(1) Humus substances produced from leonardite in
a factory (YEM-MIKS Company/Ant Organic
Fertilizer-Humic Acid Manufacturer), Izmir, Turkey
were dissolved in distill water (1 g in 250 mL);
(2) Humus substances produced from 1 g of
powdered lignite and biotransformed lignite with
Trichoderma sp. prepared by Research Organization
and Manufacture of Bioproduct (ROMB), Bulgaria;
(3) Composts contain sewage sludge, zeolite and
barks after three months period of aerobic
(4) Plant materials after pyrolisis (charcoal);
(5) The humic acids from International Humic
Substances Society (IHSS) collection were used as a
referent material (etalon).
The fourth series of humic substances are studied
by content and composition of organic carbon by the
following method.
Soil organic carbon content was determined by
modified Turin’s method [10, 11]. The method is
based on dichromate oxidation and digestion at
125 °C, 45 min, in presence of Ag2SO4 and
FeSO4(NH4)2SO46H2O titration, phenyl anthranilic
acid as an indicator.
Soil organic matter composition was determined by
the method of Kononova-Belchikova [10, 11]. Total
humic and fulvic acids (Cextr.) were determined after
extraction with mixed solution of 0.1 M Na4P2O7 and
0.1 M NaOH, while “free” and R2O3 bounded humic
and fulvic acids (CNaOH) were determined after
extraction with 0.1 M NaOH, with ratio of
soil:solution = 1:20 for the extractions. Humic and
fulvic acids in both extracts—Cextr. and CNaOH were
separated by acidifying the solution with 0.5 M
sulfuric acid. Optical characteristics (E4/E6) show the
degree of condensation and aromatization of humic
acids, and it was determined at the optical density λ =
465 nm and 665 nm, respectively.
Nutrient elements were determined with
conventional methods, pH was measured with
pH-meter [12] and heavy metals were measured by
atomic absorption spectroscopy (AAS-Perkin Elmer
3. Results and Discussion
The humus substances produced from leonardite in
Izmir, biotransformed lignite in Bulgaria, composts
and plant materials after pyrolisis are powdered with
dark brown to black color. Their solubility in water is
very good and does not require filtration before testing.
Apparently before the treatment of plants or soils, the
solubility is similar to the standard of IHSS.
Characteristics of humus substances from leonardite
are presented in Table 1. It shows that pH is alkali and
strong alkali reaction. Total organic carbon is lower
compared to the substances of IHSS collection
(etalon). The most similar in content of total organic
carbon is humic powder, compared to the standard,
but the differences show that they are enriched with
humic substances. The high percent of humic acids
(over 94%) was established in the studied materials
from Izmir factory, while, in the etalon it is close to
87%. The remaining preparations contain from 7% to
10% more humic substances compared with the
standard. Optical characteristics (E4/E6) are similar to
those of etalon, which is an indicator for average
maturity [13]. The total content of nutrients is high,
but it is negatively concerning, especially Na content.
Dried biotransformed lignite prepared by Research
Characterization of Humic System in Fertilizer Raw Materials
Table 1 Characteristics of humus substances from leonardite.
Humus substances pH C (%) Humic acids (%) in the
substances E4/E6 P (%) K (%) Na (%)
Combi 2 7.95 24.69 100.00 6.11 0.047 20.24 15.31
Copper-zinc humate 8.30 24.95 93.82 5.81 0.071 19.26 6.15
Houmphos dry 8.80 21.73 96.38 5.88 3.471 33.0 2.15
Humix powder 8.50 27.88 100.00 6.08 0.072 20.12 2.31
Fer humate 7.50 25.49 94.90 6.23 0.080 18.40 23.37
Etalon from IHSS 7.60 29.9 86.58 5.89
Table 2 Characteristics of humus substances in biotransformed lignite.
Biotransformation with
Total organic
carbon (%)
С in pyrophosphate
extract Humic acid Fulvic acids Е4:Е6
T. viride St-4 33.99 19.72a (58.02)b 15.76 (46.45) 3.96 (11.65) 7.16
T. viride AU 33.35 19.72 (59.13) 13.94 (41.80) 5.78 (17.33) 7.23
T. harzianum St-118 34.00 20.61 (60.62) 12.63 (37.15) 7.98 (23.47) 7.15
T. viride BB-100 34.23 21.12 (61.70) 13.40 (39.15) 7.72 (22.55) 7.09
T. harzianum ABT 33.69 20.00 (59.36) 14.75 (43.78) 5.25 (15.58) 7.64
a: % of sample mass; b: % of the total carbon.
Table 3 Characteristics of nutrient elements, dry mass and heavy metals in Plantagra (mg/L).
Index Plantagra (T. harzianum + P. chlororaphis + P. putida)
Dry matter 15,100
Total organic carbon 5,341
Total N 456.26
Р2О5 164.00
К2О 4,150
NaO 285.00
CaO 281.61
MgO 50.00
Fe 20.00
Mn 0.27
Cu 0.24
Zn 5.47
Organization and Manufacture of Bioproduct (ROMB)
was brown globular powders with gray green hue.
Variants 1 (T. viride St-4) and 2 (T. viride AU) are
with a slight greenish tint, while 3 (T. harzianum
St-118), 4 (T. viride BB-100) and 5 (T. harzianum
ABT) are barely noticeable gray and very strong
greenish hue. This is due to the formation type of
microflora. The preparations are virtually insoluble in
Data presented in Table 2 show there is no
substantial difference in biotransformation with T.
viride St-4 and T. harzianum ABT, but there is
substantial difference of difference strains of
biotransformation of organic substances to fulvic
acids. The advanced stage of humusformation in
biotransformed lignite with strains T. viride St-4
formed 46% humic acid and less fulvis acids 11.65%
of the total carbon, and St-118 formed 37.15% humic
acid and the maximum fulvic acids 23.47%. It is
similar for T. viride BB-100, where contains 22.55%
fulvic acids of the total carbon. Referent strains T.
viride AU and T. harzianum ABT contain humus
substances with low condensation and aromatization,
probably because process of biodegradation prevails
Characterization of Humic System in Fertilizer Raw Materials
and this short inoculation process is not sufficient to
form more mature humic acids.
Humus substances in coal are in a high stage of
maturity. Method of impact with micro-fungi allows
to break chains, where low molecular compounds with
a higher physiological activity are formed [14]. The
chelated forms of Cu and Zn promote the
biodegradation of lignite, increasing the fulvic acids,
while Ca and Mg increase the content of humic acid
up to 97%-99.8% [8, 15].
Plantagra is a product developed on the bases of
alkali hydrolysis of biotransformed lignite from
Stanyansi with strains T. harzianum and T. viride. It is
with dark brown color and balanced natural content of
biogenic elements. It is intended to treat plants and
peat mixture in combination of hydroponic solution.
Data in Table 3 show that the developed product
demonstrate a qualified amendment due to the high
organic carbon content, nutrient elements and very
low heavy metals content.
Field experiments on maize hybrids Kn 435, Kn
509 and Kn M625 with humic substances took place
in the Maize Research Institute in Knezha in
2008-2009. The organic fertilizer was administered by
foliar feeding in the 8-10 leaf phase. The rate of
introduction was 50 mL/ha for each iteration. Two
additional fertilizer rates were tested on Kn 435 with
800 mL/ha and 1,200 mL/ha. The results show that
treating with 1,200 mL/ha Plantagra increases yield
with 12.27%. Especially clear is the trend of increasing
protein content in the range of 2.27% to 18.62% on the
tested hybrids [16]. Treatment of poinsettia with humic
substances from biotransformed lignite (Plantagra)
improved N nutrition with urea. The ornamental quality
of the culture became better [17].
Biodegradable lignite with Trichoderma sp.
further biodegraded in bioreactor with bacteria Bacilus
sp. and Pseudomonas sp. allows to obtaining liquid
bio-humates with very good water solubility. They are
dark brown, subject to filtration for separate minerals
and form microflora. They are liquid or dried in
powder dryer, and have a slight smell of ammonia.
Nutrients are well balanced and they also have an
incentive effect, so they are good bio-fertilizer. They
contain, according to the manufacturer, live
microorganisms, which further increase the impact of
their application.
As shown in Table 4, dry material of
biotransformed soluble humic substances is 33.11% of
the total organic carbon, while the standard is 29.99%.
In this biotransformation and alkaline hydrolysis, the
percentages of extractable fulvic acids increase and
their relative content to the total carbon increases from
10.94% in biotransformation lignite to almost twice
Тable 4 Characteristics of biotransformed lignite and Plantagra.
Index Biotransformed lignite Plantagra dryed in pulverize dryer
Dry mass (%) 59.55 91.90
Total organic carbon (%) 43.13 33.11
С (%) in NaOH and Na4P2O7 24.59а (57.01)b 26.42a (79.79)b
Humic acid (%) 19.87 (46.07) 20.01 (60.43)
Fulvic acids (%) 4.72 (10.94) 6.41 (19.35)
N (%) 1.46 1.22
P2O5 (%) 0.086 1.46
K2O (%) 0.44 18.03
Na2O (%) 0.20 0.54
CaO (%) 5.82 4.58
MgO (%) 0.78 0.56
Fe2O3 (%) 1.42 1.01
Al2O3 (%) 2.24 1.43
S (%) 1.82 1.43
a: % of soil mass; b: % of the total carbon.
Characterization of Humic System in Fertilizer Raw Materials
Table 5 Characteristics of charcoal.
Substances pH C (%) P (%) K (%) Na (%) Cu (mg/kg)
Plants after pyrolisis 6.50 30.44 0.05 0.25 20.00 20.00
Table 6 Characteristics of composts after three months of aerobic composting.
Treatments pH C (%)
Humic acids (%) of the total
carbon of composts E4/E6 K (%) Na (%)
Sewage sludge (SS) 6.80 16.08 7.77 8.15 0.043 0.011
SS + zeolite (Z) 6.80 13.68 8.19 7.55 0.371 0.050
SS + barks (B) 6.80 13.56 7.74 10.43 0.061 0.010
SS + Z + B 6.80 12.12 9.24 7.22 0.197 0.029
SS+ modified Z + B 6.50 13.86 7.28 12.90 0.480 0.061
The modified zeolite according to Ref. [18].
Table 7 Heavy metals content in humus substances (mg/kg).
Materials Cu Zn Pb
Combi 2 9,575 14,375 153.0
Copper-zinc humate 10,600 9,375 143.0
Houmphos dry 35.00 775 95.0
Humix poweder 37.50 95.0 20.0
Fer humate 75.00 323.0 100.0
Biotransformed lignite 29.80 53.00
Plantagra 37.40 66.50
Sewage sludge (SS) 491.00 2,285 64
(19.35%) in Plantagra dryed in pulverize dryer.
Compared the characteristics of biotransformed
lignite and Plantagra, it was established that
pyrophosphate-extracted organic carbon and humic
acids prevail in the Plantagra product (Table 4).
Nutrient elements content are similar for both
Charcoal is a plant biomass derived materials,
produced from pyrolisis with black color. The main
benefits occur with additions of biochar, such as
enhance plant growth, suppress gas emissions, store
carbon in a long term stable sink, reduce soil acidity,
improve soil water handling characteristics and
increase soil levels of available nutrients. Product,
obtained by pyrolisis, easily crush to fine black dust,
demonstrates good characteristics with favorable pH,
high percent carbon content and nutrient elements
(Table 5).
Composting is a proper way to maintain and
increase soil fertility. Five compost obtained after
composting of different materials were listed in
Table 6. Sludge (SS) from wastewater treatment plant,
Sofia, Bulgaria, is rich in organic matter and nutrients,
Zeolite (Z) is from the Rhodopes mountain, Bulgaria
and barks (B) are from conifers. These materials are
mixed in various proportions and were aerobically
composted for three months [18]. Best results for
humic acids content and optical characteristics
(maturity degree of humic acids) were in the treatment
of SS + Z + B. Neutral pH is very favorable for plant
growth, but the content of total organic carbon and
humic acids are lower than standard (etalon) and
humic substances from Izmir, Turkey. Optical
characteristics showed a low level of maturity. Humic
acids in composts are bound to alkali-earth ions,
which has a positive effect on both the soil and water
physical properties and reduce the risk of washing of
mobile organic substances down the profile depth.
These variants were studied where pot experiments
with polluted and unpolluted soils were carried out.
The results obtained manifested improvement of soil
fertility compared to the control variants [18]. The
Characterization of Humic System in Fertilizer Raw Materials
maximum humic acids and lower ratio E4/E6 (more
condensed humic acids) are formed in the treatment
SS + Z + B. This one could be recommended as the
best variants as a soil amendment.
The content of heavy metals in biotransformed
lignite and Plantagra is low (Table 7). Some of the
substances of Izmir factory contain high amounts of
Cu and Zn, which is related to their use in agriculture
in certain circumstances. SS contains high amounts of
Cu and Zn, due to the including of industrial waters in
purification of waters. In the presence of zeolite and
barks, after a period of composting, respectively,
maturation of compost and doses of application
allowed their use as a soil amendment.
4. Conclusions
To be mentioned, application of different
substances for soils and plants treatment will
increasingly become nowadays more applicable in
agriculture. Characteristics of the products presented
in this paper provide valuable information on the
content and composition of organic matter, maturity
of humic substances and content of heavy metals. This
information is of great importance in the application
of humic preparations (the amount and level of their
application). It is necessary for manufacturers,
businessman, consultants and users in relation to the
production, dissemination and application of humic
substances. Depending on the objectives, the farmer
may choose a different product derived from
leonardite, lignite, charcoal or composts.
Studied soluble humic preparations are similar or
superior to standard in their quality. This indicates that
manufacturers strive to achieve a standard quality of
humic preparations. Biosolubilizated preparations are
intended for the stimulation of plants, because they
contain more fulvic acids.
Biotransformed lignites with different Trihoderma
strains have more variable ratio between humic acids
and fulvic acids, which means that they are intended
for treatment of various types of soils.
Application of amendments in sludge composting
accelerates composting process and improves the
quality of compost. Combining barks and zeolites as
additives is better than submitting zeolites only.
It is recommended for application of charcoal to
different additives, as sewage sludge, composts, etc., as
amendments to soils.
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... The basis of our research is represented by standard quantitative methods for determining the contents of organic matter as well as HAs and FAs within organic matter. Our previous studies proved that there is a good correlation between the composition of the humic products as a mixture of humic acids (HAs) and fulvic acids (FAs) and their optical characteristics of spectral measurements at wavelengths of 300, 445, 665 and 850 nm (Filcheva et al. 2017). ...
... Based on our previous studies, we present data on the extinction of HAs at different wavelengths. For example, we introduce a wavelength of 300 nm established as the maximum wavelength (Filcheva et al. 2017). Our research is in agreement with other studies which reported that spectra of HAs and FAs are similar, but the extinction values decreased with increasing wavelengths (Eshwar et al. 2017). ...
Full-text available
Purpose The application of different humic products for the treatment of soils and plants has increased in recent years. The characteristics of humic products, such as the content and composition of organic carbon and the maturity, provide valuable information which is essential for an adequate application. Such information is crucial for manufacturers, business consultants and users involved in the production, distribution and implementation of humic products. This article presents the correlation between the quantitative indicators of commercial humic products and their spectral characteristics via measurements in the ultraviolet spectrum at 300 nm, in the visible area at 445 and 665 nm and in the near-infrared spectrum at 850 nm. Materials and methods We evaluated humic products (liquid and solid) of different origins. Via wet combustion, the content of total organic carbon in humic products can be determined. The precipitation of humic acids from the starting solution determines the composition of the humic products in terms of humic acids (HAs) and fulvic acids (FAs). The dissolution of HAs determines their concentration by titration, while the specific extinction can be assessed via spectrophotometry via measuring the absorption of HAs spectra at the following wavelengths: 300, 465, 665 and 850 nm. The degree of aromaticity and condensation of humic products determines the optical density of the HAs via the E4/E6 ratio. Results and discussion The content of total organic carbon varied widely from 0.55 to 37.5% across all groups. The content of carbon in HAs, as a percentage of the total carbon in fulvic-type humic products, ranged from 1.29 to 16.00%, while in humic-type products, it ranged from 51.43 to 91.92%. The minimum value of the E4/E6 ratio was 2.97, while the maximum value was 6.35. We observed a direct relationship between the dominant type of acids in humic products and the E4/E6 ratio. Conclusions The optical density of HAs indicates their quality characteristics. The presented optical characteristics for humic products show that there is a direct relationship, especially between HAs/FAs and E4/E6 ratios. Measurement at 300 nm (E300) in the near-ultraviolet area and at 850 nm (E850) in the near-infrared area can increase the range of the spectral study.
... Researches have shown that total organic C in dry matter is 33.11 %; 20.01 % of it belongs to C of humine acids, while the percent of fulvic acids C is 6.42 %. Full characterization of Plantagra with topical information on the organic matter composition, the maturity of the humus substances, the content of heavy metals, etc., has been done by Filcheva et al. (2013). In our experiment, the product was applied through pre-sowing treatment of the planting material at norm 150 ml/100 kg planting material (PTPM). ...
... ,Ilieva (1986), Filcheva and Ilieva (2012),Ilieva and Filcheva (2013, 2014) and etc. ...
Conference Paper
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Abstract:The investigation was carried out in a stationary field trial at DAI on Haplic Chernozems. It included a 15 Triticum aestivum L. varieties. These varieties were grown against four backgrounds of mineral fertilization: 1. Control (untreated); 2. Suprefos (350 kg/ha); 3. Suprefos + ExcelOrga (175+175 kg/ha) and 4. ExcelOrga (350 kg/ha). It was found that under unfavorable parameters of some main agronomy factors, such as previous crop and no nitrogen nutrition prior to !"#$"%&"&'(")(*+,,+,*"#-".($/%,(,&"0.$+,*" wheat vegetation, the choice of a suitable variety was determining for the formation of productivity and the physical properties of the grain. The annual main soil fertilization with Suprefos contributed to higher productivity of wheat with 16.3% (2014-2015). Under conditions of permanent drought during the grain filling stage, the combined application of main soil fertilization with the ExcelOrga and presowing treatment of the seeds with Plantagra contributed to 23.0 % increase of the mean wheat productivity. Cultivars Dragana, Kalina, Enola and Kristi demonstrated high productivity in combination with very good physical properties of the grain. These varieties %$("01+&%)2("-#$"*$#3+,*"3+&'"&'("%)#4("52#3-+,.1&6"practices for plant nutrition. Keywords: wheat, organic fertilizers, low-input nutrition.
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Compost from municipal sewage sludge, bark plus zeolite, and zeolite alone were used in this study to evaluate their influence on soil properties and humus characteristics. Two incubation experiments were conducted in two low humus content soils from Bulgaria (Typic Xerochrept) and Greece (Typic Rhodoxeralf). Soil alone, soil with zeolite, and soil with compost in various rates were incubated for 90 days (24±1°C, moisture content about 60% of field capacity). The experimental design was randomized complete blocks with four treatments each replicated four times. At the end of incubation experiment samples were taken, and the basic chemical properties as well as humus composition were determined. The pH, electrical conductivity and NO3-N concentration were determined in samples taken every 15 days. The results showed that zeolite increased soil pH and exchangeable potassium (K). Compost increased available phosphorus (P) in the low P Bulgarian soil and electrical conductivity. A strong positive relationship between electrical conductivity and NO3-N was recorded. Soil pH was negatively correlated with NO3-N concentration for Bulgarian soil. Composted sewage sludge also significantly increased soil organic matter content and led to formation of condensed humic acids.
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For several years it has been known that fungi and bacteria can attack and even liquefy low rank coals. This review covers the progress in coal biotechnology and microbiology, mainly during the last decade, from describing the first effects to elucidating the mechanisms used by the microorganisms. More than one mechanism is responsible for microbial coal degradation/liquefaction: oxidative enzymes (peroxidases, laccases), hydrolytic enzymes (esterases), alkaline metabolites and natural chelators. Due to the heterogeneous structure of coal, which is described in one section, and for economic reasons the review focuses on the enzymatic depolymerization of brown coal. Approaches which seem not so promising are discussed (anaerobic, reductive pathways, chemical pretreatment). Finally the possible applications and products in this field are summarized, as lignite with a worldwide production of about 940 million tons a year will continue to play an important economic role in the future.
Maize hybrids, cultivated without irrigation, are considerably influenced by seasonal climate changes. The selected by us hybrids from FAO groups 500 and 600 have a very high productivity. The purpose of the study is to determine by a comparative test the influence of 3 groups of bio-stimulators on both the changes in mineral nutrition and the changes in grain quality of maize hybrids Kn 509 and Kn M 625. 13 variants are tested in each hybrid, with 4 repetitions in a variant and average 50 plants per repetition. The plants are treated in 8- 10th leave phase with all of the preparations in a dose of 500 ml/ha. 3 groups ofproducts are examined (bacterial—containing species from genera Bacillus and Pseudomonas; humic—in combination with vitamins, hydrolase's enzymes or Trichoderma; chelate compositions of Cu, Zn, Fe, Mn, B, Mo, Co + Pseudomonas sp.) The one-time treatment of the 2 hybrids doesn't have a proven effect on the yield. Leaf diagnostics in the flowering phase shows that bacterial preparations improve the assimilation of P, hydrolase's enzyme preparations balance the excessive assimilation of Mg, and humic acids and chelate compositions improve the assimilation of N. All of the examined preparations increase the protein content of corn. Regarding Kn 509, humic and enzyme preparations increase the protein production per unit of area from 17 to 19%, and regarding the Kn M 625 hybrid—from 9 to 17%. Bacterial and enzyme preparations increase the lipid content in the grain of Kn M 625 to 40%.
Preparations, containing humic substances become more and more popular in modern technologies for organic farming during the past years. The purpose of the study is to determine both the influence of the supporting agent?modified zeolites?during biodestruction of lignite by T.harzianum, and the possibility for using the formed humic substances as a matrix for immobilization of enzyme systems. The influence of chelate form of Fe, Cu, Mn, Zn, Co, Ca, Mg in composition with natural zeolite (clinoptilolite?Eastern Rhodopes, Bulgaria?ammonia form) upon the biotransformation of humic substances from lignite is studied. Lignite from Stanyantsy Mine is inoculated with T.harzianum 10? CFU/g; modified zeolites with concentration 20g/100g lignite are added to the medium. Research data show that N-zeolites, modified with Cu, Zn, Mn and a combination of them, and used as a supporting agent during the biotransformation of lignite by T.harzianum, affect the humification and the formation of enzyme systems depending on the concentration of the saturating micro element. Zinc ions have a lower influence, and manganese ions slow down the humificaion to some extent. Zeolite components, modified with Mn increase the activity of polyphenol oxidase and decrease the activity of peroxidase. Zeolite enrichment with Zn increases the activity of polyphenol oxidase and peroxidase, and the increased concentration of Cuions in zeolites lead to an increased activity of polyphenol oxidase and peroxidase.
Humic acids from lignite deposits in Bulgaria were characterized with respect to the concentration of oxygen-containing functional groups. The following ranges were determined, in mequiv g−1: total acidity 5.1–6.8; carboxylic groups 3.5–4.5; phenolic OH groups 1.6–2.3; ketone groups 1.0–2.0; quinone groups 1.0–1.3; and methoxyl groups 0.3–1.3. Yields of high- and low-molecular fractions were monitored by g.p.c. on Sephadex G-50. The molecular mass for the lower molecular fraction was ~ 4000u. On the basis of the elemental composition, molecular mass and distribution of oxygen in functional groups, a concept for lignite humic acid structure was developed.
The question was investigated, whether chelators alone can solubilize different lignites. For that purpose the influence of eight chelators were tested on different pretreated or natural lignites. The effects of the pretreatment and of the concentration of chelators were studied. The results show that different chelators have different influence on different lignites. Oxidative pretreatment enhances the solubilization. At low chelator concentrations only leonardite is solubilized to remarkable degree.Ammonium oxalate is one of the most effective agents. The results confirm that chelators alone are not able to solubilize lignites with a very low ash or oxygen content.
A new isolate of Trichoderma atroviride has been shown to grow on low rank coal as the sole carbon source. T. atroviride ES11 degrades approximately 82% of particulate coal (10 g l(-1)) over a period of 21 days with 50% reduction in 6 days. Glucose (5 g l(-1)) as a supplemented carbon source enhanced the coal solubilisation efficiency of T. atroviride ES11, while 10 and 20 g l(-1) glucose decrease coal solubilisation efficiency. Addition of nitrogen [1 g l(-1) (NH(4))(2)SO(4)] to the medium also increased the coal solubilisation efficiency of T. atroviride ES11. Assay results from coal-free and coal-supplemented cultures suggested that several intracellular enzymes are possibly involved in coal depolymerisation processes some of which are constitutive (phenol hydroxylase) and others that were activated or induced in the presence of coal (2,3-dihydrobiphenyl-2,3-diol dehydrogenase, 3,4-dihydro phenanthrene-3,4-diol dehydrogenase, 1,2-dihydro-1,2-dihydroxynaphthalene dehydrogenase, 1,2-dihydro-1,2-dihydroxyanthracene dehydrogenase). GC-MS analysis of chloroform extracts obtained from coal degrading T. atroviride ES11 cultures showed the formation of only a limited number of specific compounds (4-hydroxyphenylethanol, 1,2-benzenediol, 2-octenoic acid), strongly suggesting that the intimate association between coal particles and fungal mycelia results in rapid and near-quantitative transfer of coal depolymerisation products into the cell.
Comparative Characteristics of Soils in Bulgaria in Content, Composition and Stocks of Organic Matter
  • E Filcheva
Filcheva, E. 2004. "Comparative Characteristics of Soils in Bulgaria in Content, Composition and Stocks of Organic Matter." Habilitation thesis, NCAS, Institute of Soil Science "Nikola Poushkarov", Sofia.