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Citation: Yurkevich, M.; Suleymanov,
R.; Ikkonen, E.; Dorogaya, E.;
Bakhmet, O. Effect of Brown Algae
(Fucus vesiculosus L.) on Humus and
Chemical Properties of Soils of
Different Type and Postgermination
Growth of Cucumber Seedlings.
Agronomy 2022,12, 1991. https://
doi.org/10.3390/agronomy12091991
Academic Editors: Evgeny Lodygin,
Evgeny Abakumov, Elena
Shamrikova and Andrea Baglieri
Received: 29 June 2022
Accepted: 19 August 2022
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agronomy
Article
Effect of Brown Algae (Fucus vesiculosus L.) on Humus and
Chemical Properties of Soils of Different Type and
Postgermination Growth of Cucumber Seedlings
Marija Yurkevich 1,*, Ruslan Suleymanov 2,3 , Elena Ikkonen 1, Ekaterina Dorogaya 2and Olga Bakhmet 3
1Institute of Biology of the Karelian Research Centre, Russian Academy of Sciences,
185910 Petrozavodsk, Russia
2Ufa Federal Research Centre, Ufa Institute of Biology, Russian Academy of Sciences, 450019 Ufa, Russia
3Department of Multidisciplinary Scientific Research of the Karelian Research Centre, Russian Academy
of Sciences, 185910 Petrozavodsk, Russia
*Correspondence: svirinka@mail.ru
Abstract:
The possibility of using brown algae in agriculture as an alternative source of nutrients
is currentlyunder study and discussion. Our study aimed to evaluate the effect of F. vesiculosus on
the agrochemical properties of four soil types: Retisol loamy sand soil, Retisolloam, Retisol clay,
and Histosol. The F. vesiculosus waste was added to soil samples at a rate of 0, 0.5, 1.0, 2.0, 5.0, and
10 wt%. The brown algaewaste application significantly decreased soil acidity in the substrates
of all soil types, with the larger increasesfor Retisol loamy sand and Retisol clay than for Retisol
loam and Histosol. The application of F. vesiculosus waste products increased the C content in all
soil types except Histosol. The N and P content in soil substrates were not significantly affected by
algaewaste application regardless of soil type. This study showed that the effect of F. vesiculosus
waste application varies depending on the soil type, with the strongest impact on Retisol clay and the
lowest on Histosol.
Keywords:
Retisolloamy sand soil; Retisol loam; Retisol clay; Histosol; soil acidity; macronutrients;
brown algae; Fucus vesiculosus L.; cucumber
1. Introduction
For further improvement incrop productivity, new ways of soil fertility management,
especially for soils with low nutrient availability, are under study and discussion [
1
–
4
]. The
soils of high latitudes are usually characterized by low natural fertility; they tend to have
a thin humus layer and low content of humus and nutrients available for plants [
5
]. In
northern regions, not only the low natural fertility of soils but also the low temperatures,
inadequate soil water regime, and existence of geomagnetic, gravitational, and radiation
anomalies can be recognized as stress factors limiting plant growth and yield. Agricultural
production has always involved the exploitation of resources, primarily soils. In the
northern regions, soil restoration is extremely slow, so agricultural production should be
carried out with minimal environmental risks using new efficient methods and technologies.
As one of these agricultural methods, brown algae application can be proposed.
Brown algae, which are represented by 1500 species, are the main algae of temperate
and polar regions. Fucus vesiculosus L. is one of the brown macroalgae dominants of
the rocky shores in the North Atlantic and Arctic intertidal zone. The high content of
macro- and microelements, especially nitrogen (N), phosphorus (P), potassium (K), iodine,
molybdenum, and boron [
6
], makes it possible to consider algae as promising natural
fertilizers [
7
–
11
]. Chelating forms of microelements of algae species allows micronutrients
to be readily available to plants. Algae fertilizer, unlike manure and compost, does not
contain weed seeds and spores of fungal pathogens.
Agronomy 2022,12, 1991. https://doi.org/10.3390/agronomy12091991 https://www.mdpi.com/journal/agronomy
Agronomy 2022,12, 1991 2 of 11
When in contact with soil water, the polysaccharides of brown algae improve the
structural and mechanical properties of the surface soil layer [
12
]. Experimental evidence
shows that algae application to soil can promote the physical and hydrophysical charac-
teristicsof soil [
7
,
10
,
13
]. Saadaoui et al. [
14
] showed that algae application couldincrease
the soil content of N, P, and K, thereby increasing soil fertility [
9
–
11
]. Algae, as biobased
material, are known for their ability to increase soil microbial biomass and activity, as well
as the structure of pedobiont complexes [12].
Brown algae commonly contain high concentrations ofmannitol, which is a chelat-
ing agent useful in controlling soil micronutrient availability by complexing with soil
metal cations. Algae also contain salts of alginic acid, which combine with soil metal ions
to form highmolecular complexes. These complexes improve soil structure and water-
holding capacity and, consequently, increase root and plant growth [
15
–
18
].
М
oreover,
Zaborowska et al. [
19
] showed that algae could be useful for the remediation of soils
contaminated with heavy metals.
Since the industrial processing of seaweed generates a large amount of waste, which
also has nutritional value, then there is a question of their disposal, which, from our point
of view, is not a rational use of nature. In this connection, in our work, we tried to consider
the use of algae waste as an organic fertilizer for low-fertile soils of Karelia, their influence
on the basic chemical properties of soils, and the postgermination growth of cucumber
seedlings (as an assessment of bioproductivity).
Of all species of brown algae, only a small number have been studied to determine
their potential applications as a soil improver [
12
,
20
,
21
]. The brown algae Ascophyllum
nodosum is one of the most widely studied species, but much less information is available,
however, about the impact of F. vesiculosus on soil fertility. Our study aimed to evaluate the
effect of F. vesiculosus on the agrochemical properties of different soil types.
2. Materials and Methods
2.1. Study Site and Soils Description
Four types of soil of the Karelia region (northwest of Russia) (Figure 1) were used in
this study: Retisol loamy sand, Retisol loam, Retisol clay, and Histosol. The soil samples
of Retisol loamy sand soil were collected from a quarry, Retisol loam and Retisol clay
samples were collected from the A horizon of Retisols (5–15 cm), and Histosol samples
were collected from the O horizon of peat soil (10–50 cm).
Agronomy 2022, 12, x FOR PEER REVIEW 2 of 11
fertilizers [7–11]. Chelating forms of microelements of algae species allows micronutrients
to be readily available to plants. Algae fertilizer, unlike manure and compost, does not
contain weed seeds and spores of fungal pathogens.
When in contact with soil water, the polysaccharides of brown algae improve the
structural and mechanical properties of the surface soil layer [12]. Experimental evidence
shows that algae application to soil can promote the physical and hydrophysical charac-
teristicsof soil [7,10,13]. Saadaoui et al. [14] showed that algae application couldincrease
the soil content of N, P, and K, thereby increasing soil fertility [9–11]. Algae, as biobased
material, are known for their ability to increase soil microbial biomass and activity, as well
as the structure of pedobiont complexes [12].
Brown algae commonly contain high concentrations ofmannitol, which is a chelating
agent useful in controlling soil micronutrient availability by complexing with soil metal
cations. Algae also contain salts of alginic acid, which combine with soil metal ions to form
highmolecular complexes. These complexes improve soil structure and waterholding ca-
pacity and, consequently, increase root and plant growth [15–18]. Мoreover, Zaborowska
et al. [19] showed that algae could be useful for the remediation of soils contaminated with
heavy metals.
Since the industrial processing of seaweed generates a large amount of waste, which
also has nutritional value, then there is a question of their disposal, which, from our point
of view, is not a rational use of nature. In this connection, in our work, we tried to consider
the use of algae waste as an organic fertilizer for low-fertile soils of Karelia, their influence
on the basic chemical properties of soils, and the postgermination growth of cucumber
seedlings (as an assessment of bioproductivity).
Of all species of brown algae, only a small number have been studied to determine
their potential applications as a soil improver [12,20,21]. The brown algae Ascophyllum
nodosum is one of the most widely studied species, but much less information is available,
however, about the impact of F. vesiculosus on soil fertility. Our study aimed to evaluate
the effect of F. vesiculosus on the agrochemical properties of different soil types.
2. Materials and Methods
2.1. Study Site and Soils Description
Four types of soil of the Karelia region (northwest of Russia) (Figure 1) were used in
this study: Retisol loamy sand, Retisol loam, Retisol clay, and Histosol. The soil samples
of Retisol loamy sand soil were collected from a quarry, Retisol loam and Retisol clay
samples were collected from the A horizon of Retisols (5–15 cm), and Histosol samples
were collected from the O horizon of peat soil (10–50 cm).
Figure 1. Maps showing the location of the Karelia region.
Figure 1. Maps showing the location of the Karelia region.
2.2. Physicochemical Analysis of Soil
The collected air-dried soil samples were sieved with a 2 mm sieve and mixed with
the waste of F. vesiculosus to achieve its content equal to 0, 0.5, 1.0, 2.0, 5.0, and 10 wt%.
All soil substrates were incubated under 21–23
◦
C and 70–80% of the maximum soil water
holding capacity for 60 days.
Agronomy 2022,12, 1991 3 of 11
After incubation, the homogeneous soil substrates were air-dried and sieved with
a 1 mm sieve. The pH
H2O
of soil substrates was measured potentiometrically. Total
soil carbon (%) was analyzed with a total organic C analyzer (TOC-L CPN, Shimadzu,
Japan). Total N concentration (%) was determined by the Kjeldahl method using a Kjeltec
analyzer [
22
]. Available P
2
O
5
(mg 100 g
−1
soil) was determined using flame photometric
methods (SF 2000 OKB Spectrum, SaintPetersburg, Russia) following Kirsanov’s procedure
used in Russia [
23
]. Exchangeable Ca
2+
, Mg
2+
, Na
+
, and К
+
(mg kg
−1
soil) were extracted
with 1MNH
4
Ac buffered to pH 7 and then determined using spectrophotometric atomic
absorption (Shimadzu AA-7000, Kyoto, Japan). Dry residue was obtained by summing the
calculated method (Ca
2+
+Mg
2+
+Na
+
+K
+
), and since the sum of the cations corresponds to
the sum of the anions, then the sum of the cations was multiplied by 2 and converted into a
percentage, following the procedure recommended by van Reeuwijk [
24
]. Analysis of the
chemical composition of F. vesiculosus waste was carried out according to GOST [
25
] and
Zhang et al. [26].
2.3. Germination of Cucumber Seeds in Various Research Media
Uniform seeds of cucumber (Cucumis sativus L., var. Kurag) were used for the germi-
nation and seedling growth test. The seeds were obtained from a commercial supplier and
stored at 4
◦
C until the start of the experiment.In a viability test before germination, seeds
showed 98–100% germination in distilled water. Twenty-four seed replicates were placed
in 9cm Petri dishes with one disk of filter paper and 7 mL of test solution. The test solution
included 0, 0.1, 0.5, 1.0, 2.5, 5.0, and 10.0 g of F. vesiculosus waste extract in 1 L of distilled
water. All dishes were subjected to a germination chamber with conditions maintained at
26
◦
C in the dark with 60
−
70% relative air humidity. Seeds were considered germinated
when the radicle emerged 2 mm from the seed. The number of germinated seeds was noted
down every day after sowing. Twenty randomly chosenseedlings of each treatment were
used for the measurements of growth parameters at the end of 5 days of soaking. The 5-day
seedlings were separated into shoots and roots, and the root and hypocotyl lengths were
measured. Then, the organs were dried at 70
◦
C to weight constancy and weighted. The
ratio between the root and shoot dry biomass was calculated.
2.4. Statistical Analysis
For each treatment, the means were determined with at least three analytical replicates.
The reliability of changes in the studied chemical properties of soils under F. vesiculosus
waste application wasassessed by Student’s test. The effect of F. vesiculosus waste on the
postgerminative parameters of cucumber seedlings and the significant difference between
the treatments were assessed by the least significant difference (LSD) of analysis of variance
(ANOVA). Differences at the p< 0.05 level were reported as significant. All statistical
tests were carried out with Statistica software (v. 8.0.550.0, StatSoft, Inc Dell., Round Rock,
TX, USA).
3. Results
The content of phenolic compounds, proline, alginate (salt of alginic acid, polysac-
charide), mannitol (hexahydric alcohol, low-molecular-weight carbohydrate), as well as
the composition and content of sugars in fucoidan (a complex of high-molecular-weight
sulfated polysaccharides, the main monosaccharide component of which is L-fucose) are
presented in Tables 1and 2.
Agronomy 2022,12, 1991 4 of 11
Table 1.
The content of phenolic compounds (mg gallic acid g
−1
), proline (%), alginate (%), mannitol
(µg g−1),andtotal sugar concentration (mg g−1) in the F. vesiculosus waste used in this study.
F. vesiculosus Material Phenolic Compounds Proline Alginate Mannitol Total Sugar Content
n= 5
Waste 2.10 ±0.03 0.048 ±0.004 7.4 ±0.03 1.1 ±0.1 104.1 ±5.2
Table 2. The composition and content of sugars in the fucoidan of F. vesiculosus.
F. vesiculosus Material Type of Sugar Sugar Content, %
n= 5
Waste Ribose 4.0 ±0.4
Xylose 12.9 ±1.6
Hexose 10.6 ±0.8
Pentose 26.4 ±2.7
Glucose 5.1 ±0.5
Galactose 23.4 ±2.1
As shown in Table 3, the F. vesiculosus waste application significantly affected soil
acidity. In accordance with the increase in algae content, pH values increased in the
substrates of all soil types used in this study, with alarger increase for Retisol loamy sand
and Retisol clay than for Retisol loam and Histosol. A statistically significant relation was
determined between the algae content and pH values of soil substrates.
Table 3.
The pH values and C, N, P
2
O
5
, Ca, Mg, Na, K, and dry residue content in soils of different
types under F. vesiculosus waste application with arate of 0, 0.5, 1.0, 2.0, 5.0, and 10 wt%.
Treatments pHH2O C Total N Total P2O5Ca2+ Mg2+ Na+К+Dry Residue
% mg 100g−1soil mg kg−1soil %
n = 5
Retisol loamy sand
0 5.41 1.28 0.12 10.2 394.0 18.7 40.6 34.4 0.10
0.5 5.38 1.62 * 0.13 9.7 371.4 22.8 65.1 * 46.1 * 0.10
2.0 6.38 * 1.71 * 0.12 14.3 566.4 51.6 * 139.5 * 65.3 * 0.16
5.0 7.33 * 2.24 * 0.14 13.6 574.1 58.2 * 223.0 * 93.2 * 0.19
10 8.01 * 3.12 * 0.19 13.8 899.8 * 112.3 * 437.4 * 213.3 * 0.33*
Retisol loam
0 5.77 3.96 0.22 162.0 2856 164.1 67.2 379.7 0.69
0.5 5.56 4.71 * 0.23 172.0 3090 253.6 * 104.9 * 270.5 0.74
2.0 5.80 4.94 * 0.21 172.5 2956 284.6 * 177.3 * 357.7 0.76
5.0 5.94 * 5.44 * 0.21 174.7 2975 290.3 * 186.3 * 462.6 * 0.78
10 7.40 * 5.50 * 0.20 165.5 2511 316.2 * 371.6 * 472.4 * 0.73
Retisol clay
0 6.30 0.48 0.18 105.0 630 194.9 99.1 84.2 0.20
0.5 6.89 * 0.66 0.23 111.5 671 191.8 96.7 78.4 0.21
2.0 7.47 * 1.48 * 0.21 107.5 742 * 177.0 155.2 * 79.7 0.23
5.0 8.11 * 1.76 * 0.21 128.3 1073 * 271.3 * 229.2 * 47.9 0.32
10 8.62 * 2.78 * 0.28 122.6 1260 * 249.5 * 379.5 * 92.7 * 0.40*
Histosol
5.49 35.93 1.80 42.3 8914 635.8 81.2 53.2 1.94
0.5 5.34 36.51 1.68 45.5 8849 626.1 82.7 48.4 1.92
2.0 5.39 35.78 1.73 47.3 9357 682.5 232.3 * 67.8 2.07
5.0 5.54 36.31 1.65 65.3 * 8404 682.3 283.2 * 108.9 * 1.90
10 5.71 * 36.93 1.80 60.1 * 9316 832.8 * 633.7 * 180.3 * 2.19
* Significant changes in chemical properties were observed (t
emp
> t
tbl
at p
≤
0.05); in other cases, the changes
were not significant (temp ≤ttbl at p≤0.05).
Agronomy 2022,12, 1991 5 of 11
It is well known that organic matter mineralization causes an increase in the content of
soil organic carbon [
22
,
23
]. The application of F. vesiculosus waste products also increased
the C content in all soil types under the study, except Histosol. The largest increase inC
content was found for Retisol clay, with anincrease of 1.4, 3.1, 3.7, and 5.8 times when 0.5,
2.0, 5.0, and 10% algae were added into the soil, accordingly. For Retisol loamy sand and
Retisol loam soils, the total carbon content increased by 2.4 and 1.4 times, accordingly, in
the treatments with 10% F. vesiculosus waste.
For Retisol loam and Histosol, no significant differences in the total N content were
observed among all algae treatments, but for Retisol loamy sand soil and Retisol clay, the
N content tended to be higher in soil substrates with 5.0 or 10% than with 0% algae. The
significant effect of F. vesiculosus waste application on the content of available P was found
only for Histosol. For this type of soil, the substrates with 5.0 or 10% algae had about a 50%
higher P
2
O
5
content than the substrate without algae. The F. vesiculosus application caused
a significant increase in the content of Ca, Mg, Na, and K ions in substrates regardless of
soil type.
In general, the application of algae residues resulted in an increase in the content of
water-soluble salts in almost all variants of the experiment, with the exception of variants
with Histosol (doses of 0.5 and 5%), but a significant increase was noted only in variants
with 10% addition to Retisol loamy sand and Retisol clay, which may be due to, initially,
the uneven salt content in algae waste and in the soil itself.
Seed germination was not affected by F. vesiculosus waste application and was close to
100% among all treatments (data not shown). Hypocotyl length increased according to the
increase in F. vesiculosus waste extract content (Figure 2a). Among all treatments, the highest
and lowest hypocotyl length was found in 10.0 and 0 g L
−1
treatments, respectively.In
contrast to the hypocotyl length, F. vesiculosus reduced root length (Figure 2b). The root
length of seedling germinated in 5.0 and 10.0 g L
−1
solution was significantly lower than in
other treatments. Regardless of F. vesiculosus waste extract content, no significant differences
in shoot dry mass of cucumber seedlings were found (Figure 2c); however, the root dry
mass of seedlings of 10.0 g L
−1
treatment was the highest among all treatments (Figure 2d).
The increased root mass caused an increase in the root/shoot ratio (Figure 2e).
Agronomy 2022, 12, x FOR PEER REVIEW 5 of 11
It is well known that organic matter mineralization causes an increase in the content
of soil organic carbon [22,23]. The application of F. vesiculosus waste products also in-
creased the С content in all soil types under the study, except Histosol. The largest increase
inС content was found for Retisol clay, with anincrease of 1.4, 3.1, 3.7, and 5.8 times when
0.5, 2.0, 5.0, and 10% algae were added into the soil, accordingly. For Retisol loamy sand
and Retisol loam soils, the total carbon content increased by 2.4 and 1.4 times, accordingly,
in the treatments with 10% F. vesiculosus waste.
For Retisol loam and Histosol, no significant differences in the total N content were
observed among all algae treatments, but for Retisol loamy sand soil and Retisol clay, the
N content tended to be higher in soil substrates with 5.0 or 10% than with 0% algae. The
significant effect of F. vesiculosus waste application on the content of available P was found
only for Histosol. For this type of soil, the substrates with 5.0 or 10% algae had about a
50% higher P2O5 content than the substrate without algae. The F. vesiculosus application
caused a significant increase in the content of Ca, Mg, Na, and K ions in substrates regard-
less of soil type.
In general, the application of algae residues resulted in an increase in the content of
water-soluble salts in almost all variants of the experiment, with the exception of variants
with Histosol (doses of 0.5 and 5%), but a significant increase was noted only in variants
with 10% addition to Retisol loamy sand and Retisol clay, which may be due to, initially,
the uneven salt content in algae waste and in the soil itself.
Seed germination was not affected by F. vesiculosus waste application and was close
to 100% among all treatments (data not shown). Hypocotyl length increased according to
the increase in F. vesiculosus waste extract content (Figure 2a). Among all treatments, the
highest and lowest hypocotyl length was found in 10.0 and 0 g L−1 treatments, respec-
tively.In contrast to the hypocotyl length, F. vesiculosus reduced root length (Figure 2b).
The root length of seedling germinated in 5.0 and 10.0 g L−1 solution was significantly
lower than in other treatments. Regardless of F. vesiculosus waste extract content, no sig-
nificant differences in shoot dry mass of cucumber seedlings were found (Figure 2c); how-
ever, the root dry mass of seedlings of 10.0 g L−1 treatment was the highest among all
treatments (Figure 2d). The increased root mass caused an increase in the root/shoot ratio
(Figure 2e).
dd
bc cd bc ab a
0
10
20
30
40
0 g/L 0.1 g/L 0.5 g/L 1.0 g/L 2.5 g/L 5.0 g/L 10.0 g/L
Hypocotyl lenght, mm
(a)
Figure 2. Cont.
Agronomy 2022,12, 1991 6 of 11
Agronomy 2022, 12, x FOR PEER REVIEW 6 of 11
Figure 2.The effect of F. vesiculosus waste extract of 0, 0.1, 0.5, 1.0, 2.5, 5.0, and 10 g L−1 content on
postgerminative parameters of cucumber seedlings. Different letters indicate significant differences
in the means at p < 0.05., (a)—hypocotyl length, mm; (b)–root length, mm; (c)—shoot dry mass, mg;
(d)—root dry mass, mg; (e)—root/shoot ratio.
aab aab a
bc
c
0
10
20
30
40
50
60
70
0 g/L 0.1 g/L 0.5 g/L 1.0 g/L 2.5 g/L 5.0 g/L 10.0 g/L
Root lenght, mm
(b)
ab bab ab ab ab
a
0
20
40
60
80
0 g/L 0.1 g/L 0.5 g/L 1.0 g/L 2.5 g/L 5.0 g/L 10.0 g/L
Shoot dry mass, mg
(c)
bb
bab b
ab
a
0
5
10
15
0 g/L 0.1 g/L 0.5 g/L 1.0 g/L 2.5 g/L 5.0 g/L 10.0 g/L
Root dry mass, mg
(d)
bbbab
b
ab
a
0.00
0.05
0.10
0.15
0.20
0.25
0 g/L 0.1 g/L 0.5 g/L 1.0 g/L 2.5 g/L 5.0 g/L 10.0 g/L
Root/*Shoot ratio
(e)
Figure 2.
The effect of F. vesiculosus waste extract of 0, 0.1, 0.5, 1.0, 2.5, 5.0, and 10 g L
−1
content on
postgerminative parameters of cucumber seedlings. Different letters indicate significant differences
in the means at p< 0.05., (a)—hypocotyl length, mm; (b)–root length, mm; (c)—shoot dry mass, mg;
(d)—root dry mass, mg; (e)—root/shoot ratio.
Agronomy 2022,12, 1991 7 of 11
4. Discussion
Karelia is located within the Baltic crystalline shield with bedrocks, mainly granites,
gneisses, crystalline schists, quartzitesandstones, and gabbro–diabases. The bedrocks are
covered with loose glacial, fluvioglacial, and lacustrine–glacial Quaternary sediments,
which are represented by sands, sandy loams, loams, and clays mixed with gravel, pebbles,
and boulders in places. These deposits, as well as the topography, climate, and vegetation,
have a great influence on the formation of soil cover. The climate of the study area is
cool and humid; the average annual temperature varies from north to south from +0.1
◦
C
to +3
◦
C, and the average annual precipitation is 400–650 mm [
27
]. The vegetation is
represented by the northern and middle subzones of the southern taiga with such main
forest-forming species as pine, spruce, birch, and alder. Meadows are mostly secondary
and arose on the site of former forests and along river floodplains. In areas of dissected
relief, peat bog complexes were formed.
The peculiarities of the natural and climatic conditions of Karelia contributed to the
formation of a wide variety of soils, among which primitive underdeveloped, podzolic,
soddy, marsh, and alluvial soils predominate. Podzolic soils are the most common; they de-
velop under coniferous and coniferousbroad-leaved forests under conditions of a leaching
water regime and the influx of plant residues depleted in ash and nitrogen. All podzolic
soils, depending on their mechanical composition, are divided into two groups—those
formed on sands and sandy loams and on loams and clays. Podzolic sandy and sandy
loamy soils have a clear differentiation of the profile into horizons: forest litter A0, pod-
zolic A2, illuvial B, and soil-forming rock C. The thickness of the forest litter ranges from
2–2.5 cm to 7–9 cm. The podzolic horizon is represented by a whitened thin layer 1–2 cm
with inclusions of fragments of coarse organic matter, passing into the illuvial horizon of
ocher color.The podzols are formed on fluvioglacial and lacustrine sands and sandy and
sandy loamy moraines. Soil-forming rocks are characterized by a low content of dust and
dust particles, which leads to a low rate of organic matter accumulation.The content of
organic matter in the podzol profile is low. Organic matter accumulates on the soil surface
as litter, and its content decreases from 0.9–1.6% in the podzolic horizon to less than 0.1%
in the parent rock. The content and distribution of nitrogen correlates with the content of
organic matter and varies from 0.15% in the podzolic horizon to 0.018% in the parent rock.
Sandy and sandy loamy podzols are characterized by an acid reaction. The absorption
capacity in mineral horizons is low at
−
2–3 cmol (+) kg
−1
; among the absorbed cations,
the content of calcium is
−
0.9–1.1, magnesium
−
0.4–0.6, sodium 0.1–0.2, and potassium
0.07–0.2 cmol (+) kg
−1
. Podzolic loamy and clayey soils are formed on boulderless loams
and are characterized by a high content of silty and fine silt particles, which contributes
to the accumulation of organic matter and mobile elements of nitrogen, phosphorus, and
potassium. Under the forest floor with a thickness of 3–6 cm, the formation of a dark gray
humus-accumulativeeluvial horizon A1A2 with a thickness of 2–15 cm is noted, which
gradually turns into a podzolic horizon A2 (15–30 cm thick) with a brownish tint, under
which there is an illuvial horizon B, smoothly transitioning into the parent rock. The content
of organic matter in the A1A2 accumulative horizon is 1.5–3.8% and gradually decreases
down the profile to 0.15–0.2%; the content of total nitrogen ranges from 0.4 to 0.1%, respec-
tively. Loamy and clayey podzols are characterized by an acid reaction of the medium in
the upper part of the profile and close to neutral in the lower part. The absorption capacity
in the accumulative horizon is 6–8 cmol (+) kg
−1
; among the absorbed cations, the content
of calcium (3.4–3.8 cmol (+) kg−1) and magnesium (2.0–2.2 cmol (+) kg−1).prevails [28].
The development of podzolic soils for arable land leads to a change in the structure of
the profile. The upper horizons, including the A2 podzolic horizon, are completely plowed
up, and the upper part of the B illuvial horizon is plowed up, resulting in the formation of
an arable humus-accumulative plow horizon. Plowing and cultivation of podzolic soils
lead to a change in the reserves of organic matter. As a result of plowing, the conditions for
the decomposition of organic matter are improved (improvement inair and water regimes, a
decrease in acidity, an increase in microbiological activity), which leads to a sharp decrease
Agronomy 2022,12, 1991 8 of 11
in its content. In this regard, there is a need for the constant application of organic fertilizers.
There is also a removal with the harvest and washing out into the underlying horizons
of elements of the mineral nutrition of plants (nitrogen and mobile forms of phosphorus
and potassium), which also leads to the need for their regular application to the soil in
the form of fertilizers. As an alternative source of organic and mineral fertilizers in the
Republic of Karelia, a small amount of cattle manure is used; the absence of large livestock
farms makes it difficult to introduce the required amount of organic matter. Peat soils
are formed under conditions of excessive moisture in deep relief depressions, in hollows
between moraine hills, and among outwash plains. The soil profile is poorly differentiated
into genetic horizons—A0–T1–T2, and the thickness of peat horizons varies from 0.5 to
8 m. These soils are characterized by low ash content (1.5–4%), acid reaction of the medium
(рН
KCl
3–3.5), organic carbon content 30–40%, and total nitrogen content 1.0–2.5%. Peat
soils are infertile and poor in microorganisms, and the processes of the mineralization of
organic matter proceed very slowly. During the period of development and cultivation,
they need liming and mineral fertilizers [29].
The composition of algae often depends on the time of collection and the method of
processing. In our studies, the average proline content was noted in algae processing waste
(Table 1). The free amino acid proline is one of the most common low-molecular-weight
organic osmolytes in higher plants. Proline performs osmoregulatory and cryoprotective
functions and participates in the synthesis of protein molecules. It is also an efficient energy
substrate, a source of carbon, and a reserve for nitrogen.
Alginates form the main structural polysaccharide of many marine brown algae (40%
dry weight). The alginate fraction in algae processing waste is quite high. In the presence
of charges, polysaccharides can behave like polyelectrolytes, which have a special ability
to ionize in aqueous media. Ionization promotes the dissolution of polyelectrolytes and
determines their unique properties. The dissolution of polyelectrolyte is accompanied by
the formation of polyion and counterions. Polyions are mobile and hold many charges
in close proximity so that individual charges are firmly connected to the macromolecular
backbone [30].
The six-hydric alcohol mannitol, isolated from brown algae, is a valuable material.
Mannitol is a low-molecular-weight carbohydrate from brown algae. In the tissues of algae,
it is formed because of the peculiarities of the processes of biosynthesis and assimilation.
Mannitol is one of the first and main products of photosynthesis, acting as a reserve
substance, which is used in the synthesis of structural elements of macrophyte cell walls
and, at the same time, performs an important osmoregulatory function for brown algae [
31
].
The concentration of mannitol in natural algae is hundreds of times higher than in deep
processing waste.
Fucoidans are complex high-molecular sulfated polysaccharides of brown algae, the
main monosaccharide component of which is L-fucose. In addition to fucose, fucoidans
can also contain other monosaccharides: xylose, mannose, glucose, and galactose. Seasonal
fluctuations in the content of fucoidans in brown algae of the White and Barents Seas are
significant and vary within 5–17% depending on the order, genus, and species of algae.
The structure and properties of fucoidans also differ between brown algae species [
32
].
Analysis of the main polysaccharide of F. vesiculosus, fucoidan, also showed the presence of
significant differences in the concentration of sugars (Table 2).
The rate of soil organic matter mineralization is affected by many factors, including
soil texture, granulometric composition, and clay content in the soil [
33
]. Among all
studied soil types with different granulometric compositions, Retisol clay demonstrated
the largest extent of organic carbon accumulation when brown algae waste was added into
the soil. Clay minerals play an important role in stabilizing soil organic matter [
34
] and its
accumulation in the soil [
35
]. Vidal et al. [
36
] showed that the addition of clay minerals to
organic composts not only contributed to the accumulation of organic carbon in the soil
but also increased the productivity and yield of agricultural plants.
Agronomy 2022,12, 1991 9 of 11
Peat soils are among the largest carbon stores in the terrestrial biosphere [
37
] due
to the low rate of organic matter decomposition [
38
]. Waste addition did not affect the
carbon content of Histosol, possibly due to the insufficient incubation time for the microbial
community to adapt to the new, less acidic soil conditions. Moreover, the soil microbial
activity could be limited by toxic macronutrients included in the composition of the waste
and the lack of macronutrients, primarily nitrogen, due to a change in the C:N ratio.
Soil microbial community activity regulates the rate of organic matter decomposi-
tion [
39
]. The process of mineralization of organic matter is accompanied by the production
of greenhouse gases, including CO
2
[
40
,
41
]. Organic matter mineralization and CO
2
pro-
duction can also occur in saline soils [
42
]. As a result of the dissolution of a part of CO
2
in
soil water in the presence of various salts, carbonates and bicarbonates are formed, which
lead to a change in the acid–base properties of soils toward alkalization [
43
]. Carbonate
formation can also be the result of microbial processes. Thus, the waste application could
initiate the production of salt carbonates due to the reaction of soil CO
2
and salt cations
supplied with algae or released during the decomposition of algae waste [
44
]. The algae
application caused an increase in pH in Retisol clay, Retisolloam, and Retisol sandy loams,
but not in Histosols due to their greater degree of mineralization.
5. Conclusions
This study showed that the effect of F. vesiculosus waste application can vary depend-
ing on the soil type. The highest rate of mineralization was found for the Retisol clay,
apparently due to the high content of clay minerals, which play an important role in the
stabilization of organic matter, and due to the low initial level of soil organic matter. In-
creased mineralization led to an increase in the content of organic matter in the soil, with
the largest increase observed in treatments with the highest application rate of algae (10%).
The lowest mineralization rate was found for Histosol, which may be due to insufficient
time for acclimation of the microbial community to changed conditions, as well as the
toxicity of sea salts introduced with algae and the change in soil C:N ratio.
The appearance of soil CO
2
and sea salts (Ca
2+
, Mg
2+
, Na
+
, and K
+
cations) on algae
leaves or the release of cations due to the mineralization of algae waste can lead to the
formation of soil carbonates and bicarbonates, which can reduce the acidity of Retisol clay,
Retisol loam, and Retisol loamy sand. The algae application did not affect the acidity of
Histosol, apparently due to the low degree of soil mineralization.
Author Contributions:
Conceptualization, investigation, formal analysis, writing—original draft
preparation, M.Y.; methodology, project administration, R.S.; writing, E.I.; validation, visualiza-
tion E.D.; review and editing O.B. All authors have read and agreed to the published version of
the manuscript.
Funding:
This research was funded by the Ministry of Science and Higher Education of the Russian
Federation, grant numbers 122031000052-2 and AAAA-A18-118022190102-3; the Russian Foundation
for Basis Research, grant number 19-29-05174; and partly by the Russian Science Foundation, grant
number 22-16-00145.
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Data Availability Statement: Not applicable.
Acknowledgments:
Experimental facilities for this study were offered by the Core Facility of the
Karelian Research Centre of the Russian Academy of Sciences.
Conflicts of Interest:
The authors declare no conflict of interest. The founding sponsors had no role
in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the
manuscript; and in the decision to publish the results.
Agronomy 2022,12, 1991 10 of 11
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