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ProEnvironment
ProEnvironment 6 (2013) 247 - 253
Original Article
Biochemical and Chemical Properties of Commercial Growing
Media, and Peats from Fen and Raised Bog
SZAJDAK Lech W.1*, Katarzyna STYŁA1, Wioletta GACA1, Teresa MEYSNER1,
Marek SZCZEPAŃSKI1, Jacek S. NOWAK2
1
Institute for Agricultural and Forest Environment, Polish Academy of Sciences, Bukowska 19 Str., 60-809, Poznań, Poland
2
Research Institute of Horticulture, Pomologiczna 18 Str., 96-100 Skierniewice, Poland
Received 10 March 2013; received and revised form 29 March 2013; accepted 7 April 2013
Available online 1 June 2013
Abstract
The investigations were carried out in commercial substrates for rooting, raised bog from the commercial
company and peats from Kusowo bog and Stążka Mire. Each growing medium was divided into three parts and mixed
with IAA. Our investigations have shown that the enzyme activity and concentrations of chemical compounds varied in the
commercial growing media and in peats fens and raised bog. The study has indicated impact of two doses of IAA on the
content of chemical compounds and activity of urease and nitrate reductase. Raised bog from the commercial company
acts increases urease activity and ammonium ions in comparison with commercial substrates for rooting, peats from fen
and raised bog. Our results revealed that higher pH and concentration of total nitrogen corresponds to nitrate reductase
activity in the peat from fen.
Keywords: commercial growing media, fen, raised bog, indole-3-acetic acid.
1. Introduction
Growing media constituents are the basic
components of mixes, which are generally formulated
on a percentage volume basis. Such materials include
peat, composted biodegradable waste, composted
bark, wood fibre, coir, perlite, vermiculite and others.
Growing media constituents can usually be sensually
detected in the mix. Additives include fertilizers,
liming materials, buffering materials, binders, wetting
agents, hydrogels, chemical pesticides, biological
products, dyes and other substances [18].
The substrates not only have to be of good
quality but also completely repeatable and
homogeneous for physical and chemical parameters.
* Corresponding author.
Tel.: +48 618475601; Fax: +48 618473668
e-mail: [email protected]
247
The horticultural growers more and more
frequently use ready-made substrates produced on
industrial scale with the use of homogeneous
components having tightly controlled quality [15].
Nowadays, peat is the most favorable and popular
medium of organic origin. Natural soils contain
organic substances responsible for their productivity
[18]. Humus materials have remarkable absorption
and adsorption and buffer capacity. They can absorb
and adsorb different nutrients and regulate their
uptake, thus contributing to the balanced nutrient
supply to the plants and protecting them from the
damaging salt-effect [20]. Peatlands have been long
recognized as unbalanced ecosystems, in which the
rate of production of organic material exceeds that of
its decomposition [4]. Bogs and fens are globally
dominant wetland classes. They are particularly
important for the global carbon (C) cycle, because
they accumulate peat, a heterogeneous assemblage of
partially decomposed plant materials (about 45%50% C), on annual through millennial time scales.
SZAJDAK Lech et al./ProEnvironment 6(2013) 247- 253
Peat is decomposed predominantly by fungi in the
oxygenated peat horizon (acrotelm) and by bacteria
in the anoxic peat horizon (catotelm). The
degradation of organic matter is often viewed as a
process of facilitation, whereby species of a particular
fungal community alter the substrate sufficiently to
allow other fungal species to become established and
continue the degradation process [30].
Organic nitrogen can play a dynamic role in the
nutrients status of peat ecosystems. Twenty to forty
five percent of the nitrogen associated with humic
acids may consist of amino acids or peptides
connected to the central core by hydrogen bonds [7].
Enzymes are crucial for microbial activity and
nitrogen transformations. Microbial metabolism
within the unusual physical conditions of the peat
environment leads to the release of soluble humic
substances and organic compounds of small
molecular weight: amino acids, alkaloids, vitamins,
fates, antibiotics, phenol compounds, enzymes etc. in
addition to gaseous products such as carbon-dioxide
and methane [12].
Physiological activity of plants is regulated by
many biochemical compounds called hormones.
These substances in low quantities move within the
plant from the site of production to the site of action,
however, the mechanism is not known. The
availability of free indole-3-acetic acid (IAA), the
biologically active form of auxin, plays an important
role in the development of a plant through-out its life
cycle. Plant growth regulators (phytohormones) are
organic substances, which in low concentrations,
promote, inhibit or modify the growth and
development of plants. The plant hormone is an
organic compound synthesized in one part of the
plant and trans-located to another. Applications of the
amounts of chemical compounds characterizing
hormonal effect or hormonal-like effect have become
important
agricultural
production
practices,
particularly in horticulture, agriculture, pomology,
floriculture as well as for growing media. IAA seems
to fulfill a considerable function in nature as a result
of its influence on the regulation and development of
plant growth [6, 13, 25, 27].
The aim of our investigations was to compare
biochemical and chemical properties of commercial
growing media with different doses of IAA with
peats from fen and raised bog.
three parts: first part with natural concentration of
IAA (control), second part with an addition of 200 g
kg-1 IAA, third part with addition of 400 g kg-1 IAA.
All experiments were run triplicate and the results
were averaged.
Kusowo bog is located in the West Pomeranian
Voivodship (53°48’57.83” N, 16°32’42.03” E). This
place is most likely the best preserved Baltic type
raised bog in Poland. The “Bagno Kusowo” Nature
Reserve was established in 2005 to protect the major
part of the bog and its adjacent dystrophic pond. The
area of the reserve is 326.56 ha being entirely
included into the “Jeziora Szczecineckie” Natura
2000 proposed Site of Community Importance. The
vegetation of Kusowo bog is dominated by: Drosera
rotundifolia, D. anglica, Vaccinium uliginosum,
Empetrum nigrum, Trichophorum cespitosum, Carex
limosa, Sphagnum balticum, S. centrale, S.
compactum, S. fuscum, S. obtusum, S. russowi, S.
tenellum, S. magellanicum [8].
Stążka Mire is located in northern Poland in the
region of Tuchola Forest on the outwash plain of the
Brda River which was formed during the Pomeranian
phase of the Vistulian glaciation. The mire is situated
within the administration limits of the Tuchola Forest
management area (53°36’17.58” N, 17°57’20.38” E).
This site is in the southern part of the Tuchola
Landscape Park and part of the Stążka River Mires
Reserve. The region was honored with the prestigious
title of the Unesco Biosphere Reserve in recognition
for the sustainable economic development. This mire
covers a total area of 478.45 ha, where the whole
complex of natural peatlands is under protection. The
vegetation of Stążka Mire is dominated by:
Eriophorum vaginatum, Sphagnum fallax, S.
cuspidatum, S. magellanicum, S. fuscum, S.
recurvum, Juncus effuses, Vaccinium oxycoccos,
Pleurozium schreberi, Scheuchzeria palustris, Carex
limosa, Rhynochospora alba, Drosera rotundifolia,
Pinus sylvestris, Ledum palustre, Empetrum nigrum,
Andromeda polifolia, Calluna vulgaris, Alnus
glutinosa and Calla palustris [11].
Soil pH was measured in 1N KCl from air
dried soil samples using a 1:5 v/v soil solution
suspension. The total organic carbon (TOC) was
analyzed on Total Organic Carbon Analyzer (TOC
5050A) with Solid Sample Module (SSM-5000A)
produced by Shimadzu (Japan). Hot water extractable
organic carbon (CHWE) was evaluated on TOC 5050A
equipment produced by Shimadzu (Japan). For the
purpose of investigation of hot water extractable
carbon soil samples were heated in bidistilled water
in 100ºC for two hours under a reflux condenser.
Extracts were separated by the medium porosity filter
paper and analyzed on TOC 5050A facilities. Twice
distilled water from silica glass equipment was used
2. Material and Method
The investigations were carried out in
commercial substrates for rooting, raised bog from
the commercial company (70% vol.) + perlit (30%
vol.) and natural peats located in Kusowo bog and
Stążka Mire. Each growing media was divided into
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SZAJDAK Lech et al./ProEnvironment 6(2013) 247- 253
[19]. Total nitrogen (Ntotal) was evaluated by the
Kjeldahl method.
Ammonium ions were measured on ion
chromatograph Waters 1515 (USA) equipped with a
1515 Isocratic HPLC pump, conductivity detector
Waters 432, a rotary valve fitted with 20 µL sample
loop and column PRP-X200 (150 x 4.1 mm I.D.)
from Hamilton, protected with a guard column of the
same material (25 x 2.3 mm I.D.). The detection was
monitored at the range of sensitivity of 10 µS. The
column was operated at a temperature of 25°C.
Nitrate ions were measured on ion chromatograph
HIC-6A Shimadzu (Japan) equipped with a LP-6A
Isocratic HPLC pump, conductivity detector CDD6A, a rotary valve fitted with 20 µL sample loop and
column PRP-X100 (150 x 4.1 mm I.D.) column from
Hamilton, protected with a guard column of the same
material (25 x 2.3 mm I.D.). The detection was
monitored at the range of sensitivity 1 µS. The
column was operated at a temperature of 25°C.
For analyses of nitrate reductase activity fresh
soil from each place was pooled together in order to
obtain average mixed sample. The tested soil was
screened through a sieve with 2.0 mm mesh. Nitrate
reductase activity was determined using potassium
nitrate as a substrate and 2,4-dinitrophenol as an
inhibitor of nitrite reductase according to Kandeler
[10]. The field-moist soil samples were incubated
under waterlogged conditions in test tubes and
agitated on a rotary shaker for 24h at 25ºC. Nitrite
released as a result of incubation was extracted with
potassium chloride solution and determined
colorimetrically at λmax=520 nm [22, 23, 25]. Activity
of nitrate reductase in soils was calculated from the
early-prepared analytical curve according to the
Lambert-Beer light absorption law by means of the
least squares formulas.
Urease activity in soils was determined by the
Hoffmann and Teicher method [25, 26, 29]. This
enzyme releases NH3 and CO2 through urea
hydrolysis and is essential in the chain of hydrolysis
of amino compounds. This method involves
determination of the ammonium released by urease
activity when soil is incubated with buffered (pH 6.7)
urea solution and toluene at 37°C for 3 h. The
absorbance of the solution was measured
colorimetrically at λmax=630 nm using a UV-VIS
spectrophotometer Beckman DU®-68 USA. Urease
activity in soils was calculated from the earlyprepared analytical curve according to the LambertBeer light absorption law by means of the least
squares formulas.
Indole-3-acetic acid (IAA) concentrations were
assayed by fluorimetric analysis. Briefly, 2 g of soil
was added to 10 ml 0.1 N NaOH. The mixture was
shaken for 5 h vigorously. Then, the suspension was
allowed to stand overnight. Next day the sample was
centrifuged for 20 min (15,000 g). 4 ml of
supernatant was taken and added to 4 ml of npenthanol. The mixture was shaken for 30 min. After
centrifugation, the mixture was centrifuged by 20 min
(15,000 g). 3 ml of top layer was taken and added to
3 mL 0.1 M phosphate buffer at pH 7.0. The mixture
was shaken for 1 h and next centrifuged for 20 min
(15,000 g). Organic layer was washed 2-times by 2
ml 0.1 N HCl for tryptophane removing. IAA in the
resulting
soil
extraction
was
measured
fluorimetrically in the bottom layer at λexcitation=290
nm and emission=368 nm. The concentration of IAA
was calculated on the basis of the analytical curve,
the IAA concentrations ranged from 50-300 ng mL-1,
prepared similar to investigated soils samples. The
mean fluorescence of IAA concentrations is linear
[25, 28, 29].
3. Results and Discussions
The effects of phytohormone indole-3-acetic
acid (IAA) on plant root tissue are concentration
dependent and can be species specific. Responses to
increasing IAA concentrations advance from the
stimulation of primary root tissue to the development
of lateral and adventitious roots and finally to the
complete cessation of root growth [5]. The highest
IAA concentration was observed in peats from Stążka
Mire (330.46 g kg-1) (table 1). In peats from
Kusowo bog the IAA contents is two times higher
than in raised bog from the commercial company and
1.7 times higher than in commercial substrates for
rooting. The IAA is produced in young leaves, seeds,
stems and exuded from the plant roots. Therefore, in
peat soils where there is natural vegetation we
observed higher contents of IAA phytohormone than
in growing media which was on average 51%. The
addition of 200 g kg-1 IAA contributes to the
increasing IAA concentrations in both commercial
substrates for rooting and raised bog from the
commercial company. However, further addition of
IAA (400 g kg-1) led to the decrease of IAA
amounts to initial value in both growing media (table
1). Szajdak and Maryganova [28] showed much
higher the concentrations of IAA in organic soils than
in mineral soils.
An organic growing medium is of excellent
quality if its pedological properties are similar to the
properties of a good-quality natural soil. During the
vegetation period organic materials accumulate in the
soils in the form of plant remains, therefore, the
amount of the heterocyclic nitrogen slowly increases
while the amount of different amino-nitrogen forms
decreases during mineralization and can be easily
bound to the structure of humic acids in the soils. The
available of nitrogen in mineral compounds originate
from these amines during the processes of
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SZAJDAK Lech et al./ProEnvironment 6(2013) 247- 253
ammonification and nitrification [14]. Most of the
plant species are able to absorb and assimilate nitrate
ions (NO3-), ammonium ions (NH4+), urea and amino
acids as nitrogen sources, but the response to a
particular form of nitrogen varies depending on the
species [16].
Table 1. IAA, Ntotal, N-NH4+, N-NO3-, TOC, CHWE, C/N, urease and nitrate reductase activity, pH in commercial growing media, fen
(Stążka Mire) and raised bog (Kusowo)
Raised bog from the commercial
Commercial substrates for rooting
company
(70% vol.) + perlit (30% vol.)
Stążka
Kusowo
Parameters
Control
Control
Substrate + Substrate +
Substrate + Substrate +
Mire
bog
(natural
(natural
IAA (200 IAA (400
IAA (200 g IAA (400 g
concentration
concentration
g kg-1)
g kg-1)
kg-1)
kg-1)
of IAA)
of IAA)
IAA [g kg-1]
-1
Ntotal [g kg ]
142.54
158.37
142.64
122.73
146.49
122.78
330.46
240.54
8.51
9.41
9.40
11.20
12.32
11.42
20.38
10.84
-1
[mg kg ]
14.25
15.49
16.39
69.47
70.89
71.25
17.15
33.40
N-NO3- [mg kg-1]
10.91
24.94
16.74
25.65
21.37
23.16
11.67
22.07
TOC [g kg-1]
474.70
457.90
480.40
432.20
443.10
415.10
544.14
583.18
CHWE [g kg-1]
13.14
11.59
12.93
14.51
15.45
15.70
7.74
12.96
56
49
51
39
36
36
27
54
27.05
25.29
25.52
42.02
44.66
45.38
13.78
12.18
0.76
0.60
0.74
0.02
0.03
0.02
2.32
0.53
4.68
4.52
4.67
2.68
2.69
2.71
7.13
2.68
N-NH4+
C/N
Urease activity
[µmol h-1 g-1]
Nitrate reductase activity
[gN 24h-1 g-1]
pH (KCl)
Our investigations have shown higher
concentrations of the total nitrogen in peats from
Stążka Mire (20.38 g kg-1), and lower in both
commercial substrates for rooting and raised bog
(table 1). This result corresponded with the highest
concentration of IAA in fen. Also commercial
substrates for rooting and raised bog from the
commercial company had similar concentrations of
total nitrogen with various IAA addition (200 g kg-1
and 400 g kg-1) and in control (with natural
concentration of IAA) (table 1). Furthermore, these
investigations have shown higher values of
ammonium ions in peats of raised bog from the
commercial company (from 69.47 to 71.25 mg kg-1).
In the control there was observed smaller
amount of ammonium ions in comparison with
addition of IAA (200 g kg-1 and 400 g kg-1).
Ammonium ions were two times higher in peats from
Kusowo bog (33.40 mg kg-1) than in peats from
Stążka Mire (17.15 mg kg-1). The results have shown
similar contents of N-NH4+ in fen and commercial
substrates for rooting, both with natural concentration
and with additions of IAA (from 14.25 to 16.39 mg
kg-1). Our study confirmed comparable amount of NNO3- in peats from Kusowo bog (22.07 mg kg-1) and
in raised bog from the commercial company, both
with natural concentration and with additions of IAA
(from 21.37 to 25.65 mg kg-1). In peats from Stążka
Mire the contents of nitrate ions were 11.67 mg kg-1
and in commercial substrates for rooting from 10.91
to 24.94 mg kg-1. However, the nitrate ions
concentrations were increased in control (25.65 mg
kg-1) and decreased with various IAA dose in raised
bog from the commercial company (21.37 and 23.16
mg kg-1). Different results were shown for
commercial substrates for rooting. In this commercial
growing media higher amounts of nitrate ions were
observed after various IAA additions (200 g kg-1 24.94 mg kg-1 and 400 g kg-1 - 16.74 mg kg-1) than
in the control (10.91 mg kg-1) (table 1).
The accumulation of organic matter is
determined by the balance between net primary
production and decomposition rate, which are
controlled by the climate, type of vegetation, water
table level and soil nutrient status and acidity [3].
Natural wetlands store large amounts of carbon and
loss of CHWE has proved to be important for
ecosystem carbon budgets. CHWE is involved in many
processes such as mobilizing trace metals, nutrient
cycling acidification and hydrophobic contaminants
and is related to a microbial activity [21]. In our
investigation lower contents of TOC were measured
in commercial substrates for rooting (from 457.90 to
480.40 g kg-1) and raised bog from the commercial
company (from 415.10 to 443.10 g kg-1) in
comparison with peats from Stążka Mire (544.14 g
kg-1) and Kusowo bog (583.18 g kg-1) (table 1).
Additionally, our research pointed out an increase
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SZAJDAK Lech et al./ProEnvironment 6(2013) 247- 253
TOC between peat soils and growing media to 20%.
The investigations have shown a decrease of CHWE in
peat of fen (7.74 g kg-1) and increase in peat from
raised bog (12.96 g kg-1), commercial substrates for
rooting (from 11.59 to 13.14 g kg-1) and raised bog
from the commercial company (from 14.51 to 15.70
g kg-1) (table 1). This decrease of CHWE between peats
from Stążka Mire and growing media was 44%.
The C/N ratio varied in different commercial
growing media, and in peats from fen and raised bog.
These investigations have shown that the C/N ratio
ranged from 36 to 39 in raised bog from the
commercial company and from 49 to 56 of
commercial substrates for rooting (table 1). However,
C/N ratio values were higher in control (without of
IAA) in both raised bog from the commercial
company and commercial substrates for rooting in
comparison with the same growing media with IAA
addition (200 g kg-1 and 400 g kg-1). The lowest
C/N ratio was 27 in peats from fen. In peats from
Kusowo bog C/N was similar to commercial
substrates for rooting (table 1). According to Ilnicki
[9] the C/N ratio above 30 implies lower degree of
decomposition organic matter.
Soil enzymes are the mediators and catalysts of
biochemical processes important in soil functioning
such as nutrient mineralization and cycling,
decomposition and formation of soil organic matter.
Specifically, the assessment of the activities of
hydrolases can provide information on the status of
key reactions that participate in rate limiting steps of
the decomposition organic matter and transformation
of nutrients in soils [31]. Urease is one of the most
commonly assayed soil enzymes as it greatly
influences the hydrolysis of urea to ammonia and
carbon dioxide. Therefore, urease is an extracellular
enzyme implied in the nitrogen cycle and is a
representative of the soil metabolic capacity.
However, the alkaline and aerobic conditions,
together with the ammonium accumulation during the
urease activity assays, tend to enhance the
nitrification process in soils [2]. Our results showed
that urease activity in peats from fen and raised bog
was lower (13.78 and 12.18 µmol h-1 g-1) than the
mixture of commercial substrates and IAA (from
25.29 to 45.38 µmol h-1 g-1). Correspondingly, the
concentrations of ammonium ions were higher in
peats from raised bog from the commercial company
with different IAA additions than commercial
substrates for rooting and peat soils. It is related to a
higher urease activity in raised bog from the
commercial company than in peat soils to 71% and
commercial substrates for rooting to 41%. The results
suggested that the urease activity can vary depending
on different growing media.
Denitrification plays an important role in
nitrogen cycle. However, information on the rates of
this process from horticultural growing media is rare
in the literature. Amha and Bohne [1] hypothesized
that the rate of denitrification from the horticultural
peats is influenced by the respective peat-forming
environments. They suggested that the rate of the
denitrification from a given horticultural peat is
influenced by the availability of easily decomposable
carbon source to heterotrophic microorganisms and
managements. An enzyme involved in the first step
of this process is nitrate reductase leading to gaseous
products (N2O and N2). The nitrogen oxides act as
terminal electron acceptors in the absence of oxygen.
In the anaerobic conditions nitrate ions are reduced to
nitrite ions and this enzyme is the catalyst of this
conversion [22, 24]. Our results have shown the
highest nitrate reductase activity in peat from Stążka
Mire (2.32 gN 24h-1 g-1) and the lowest in raised
bog from the commercial company (from 0.02 to
0.03 gN 24h-1 g-1) (table 1). The obtained results
indicate similar nitrate reductase activities in
commercial substrates for rooting (from 0.60 to 0.76
gN 24h-1 g-1) and in peat from Kusowo bog (0.53
gN 24h-1 g-1) (table 1). Additionally, our results
revealed that higher pH and concentration of total
nitrogen corresponds to nitrate reductase activity in
peats from fen.
One of the most influential factors affecting the
microbial community in soil is pH. This parameter
strongly influences abiotic factors, such as carbon
availability, nutrient availability and the solubility of
metals. In addition, soil pH may control biotic
factors, such as the biomass composition of fungi and
bacteria soils [17]. Optimum pH of growing media is
dependent on plant species but generally a range
between 5.00 and 6.50 is desirable. All the
commercial growing media and peat-soil samples
represented acidic to slightly acidic and neutral
properties. The highest pH was detected in peats from
Stążka Mire (7.13) and the lowest in raised bog from
the commercial company substrates (from 2.68 to
2.71) and in peats from Kusowo bogs (2.68).
However, in commercial substrates for rooting, pH
ranged from 4.52 to 4.68 (table 1).
4. Conclusions
The enzyme activity and concentrations of
chemical compounds varied in the commercial
growing media and in fens and raised bog. The
study has shown impact of two doses of IAA on the
content of chemical compounds and the activity of
urease and nitrate reductase.
Our investigations have shown higher
concentrations of the total nitrogen in peats from
Stążka Mire and lower in both commercial
substrates for rooting and raised bog.
251
SZAJDAK Lech et al./ProEnvironment 6(2013) 247- 253
[9] Ilnicki P., 2002, Torfowiska i torf. Poznań, Wyd. AR,
606
These results revealed that the nitrate ions
concentrations were increased in the control (with
natural concentration of IAA) and decreased with
various IAA dose in raised bog from the commercial
company. Opposite phenomena were related to the
changes in commercial substrates for rooting. In this
commercial growing media high amounts of nitrate
ions were observed after various IAA additions than
in the control.
Raised bog from the commercial company
increases urease activity and ammonium ions in
comparison with commercial substrates for rooting,
fen and raised bog.
Our results have shown the highest nitrate
reductase activity in peats from Stążka Mire and the
lowest in raised bog from the commercial company.
[10] Kandeler E., 1996, Nitrate reductase activity. In
Methods in soil biology, Schinner F., Öhlinger R.,
Kandeler E., Margesin R. (Eds), Springer-Verlag. Berlin
Heidelberg. pp. 176-179
[11] Lamentowicz M., K. Tobolski,E. A. D. Mitchell,
2007, Palaeoecological evidence for anthropogenic
acidification of a kettle-hole peatland in northern Poland,
The Holocene, Vol. 17, no. 8, 1185-1196
[12] Makoi J. H. J. R., P. A. Ndakidemi, 2008, Selected
soil enzymes: Examples of their potential roles in the
ecosystem, Afr. J. Biotechnol., Vol. 7, no. 3, 181-191
[13] Martinez-Morales L. J., L. S. Soto-Urzúa, B. E. Baca,
J. A. Sánchez-Ahèdo, 2003, Indole-3-butyric acid (IBA)
production in culture medium by wild strain Azospirillum
brasilense, FEMS Microbiol. Lett., Vol. 228, 167-173
Acknowledgements
This work was supported by a grants No. N N310
310139 and N N310 310 039 founded by Polish
Ministry of Education. Thanks are extended to Teresa
Stachecka for technical support.
[14] Mengel K., 1996, Turnover of organic nitrogen in
soils and its availability to crops, Plant Soil, Vol. 181, 8393
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