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Citation: ˇ
Cabilovski, R.; Manojlovi´c,
M.S.; Popovi´c, B.M.; Radojˇcin, M.T.;
Magazin, N.; Petkovi´c, K.; Kovaˇcevi´c,
D.; Laki´cevi´c, M.D. Vermicompost
and Vermicompost Leachate
Application in Strawberry
Production: Impact on Yield and
Fruit Quality. Horticulturae 2023,9,
337. https://doi.org/10.3390/
horticulturae9030337
Academic Editor: Toktam Taghavi
Received: 18 January 2023
Revised: 25 February 2023
Accepted: 26 February 2023
Published: 3 March 2023
Copyright: © 2023 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
horticulturae
Article
Vermicompost and Vermicompost Leachate Application in
Strawberry Production: Impact on Yield and Fruit Quality
Ranko ˇ
Cabilovski, Maja S. Manojlovi´c , Boris M. Popovi´c, Milivoj T. Radojˇcin, Nenad Magazin ,
Klara Petkovi´c *, Dragan Kovaˇcevi´c and Milena D. Laki´cevi´c
Faculty of Agriculture, University of Novi Sad, Trg Dositeja Obradovi´ca 8, 21 000 Novi Sad, Serbia
*Correspondence: klara.petkovic@polj.uns.ac.rs
Abstract:
Recycling organic waste is most important for preserving natural resources. The research
objective was to quantify the effect of the application of vermicompost and vermicompost leachate
on the yield and quality of strawberries and compare it with a standard fertilization program
with mineral fertilizers during a 3-year production cycle. Five fertilization treatments were studied:
control—without fertilizer (Ø); vermicompost (V); vermicompost + foliar application of vermicompost
leachate (VL); vermicompost leachate through fertigation and foliar application (L); and mineral
NPK fertilizers (NPK). The application of V positively affected strawberry yield only in the first
year. In all three years of fruiting, the highest yield was measured for NPK treatment. In the first
year, fertilization had no effect on fruit quality, while in the second and third years, the application
of leachate led to a significantly higher concentration of total soluble solids, total anthocyanins,
antioxidant activity of the fruit, and a lower concentration of total acid. Strawberries are grown for a
two- or three-year production cycle, so the application of V and VL cannot maintain the yield level as
was with the application of mineral NPK fertilizers. The quality of strawberry fruit, however, can be
improved significantly.
Keywords: fertilizers; mineral composition; antioxidant activity
1. Introduction
Vermicomposting represents an ecologically acceptable technology for converting
organic waste into nutritious compost [
1
]. Vermicompost contains high concentrations of
nutrients in available forms that plants absorb readily [
2
]. At the same time, vermicom-
post application can be an effective means of improving soil fertility due to the positive
impact on microbiological activity and soil physical properties [
3
]. So far, vermicompost
application has shown a positive effect on the growth of various plant species such as
tomato [
4
], pepper [
5
], corn [
6
], strawberries [
7
], chickpeas [
8
], and many others. In ad-
dition to the solid phase, as the final product, the vermicomposting process produces
leachate which can be used as a liquid fertilizer because it contains a certain amount of
nutrients [9,10]
. Besides necessary nutrients, vermicompost leachates also aid in the de-
velopment of plants because they contain substances that control plant growth, such as
humic acids, auxins (
0.55–0.77 pmol mL−1
), gibberellins (552–656 pg mL
−1
), and cytokinins
(
30–340 fmol mL−1) [11,12]
, which control a variety of processes related to plant growth
and yield, including the absorption of macro- and micronutrients. Additionally, according
to several authors, the application of vermicompost improves the fruit’s nutritional quali-
ties [
6
,
13
,
14
]. Other studies support the positive effects of the application of vermicompost
leachates on the increased resistance to salt stress of white stonecrop (Sedum album) and
pomegranate (Punica granatum) seedlings [
15
,
16
] as well as the increased growth of Chinese
cabbage (Brassica pekinensis) and tomato (Lycopersicon esculentum) [10,17].
The strawberry (Fragaria ananassa Dush.) is a hugely popular and economically im-
portant fruit species in many countries, including Serbia. In 2020, the value of strawberry
Horticulturae 2023,9, 337. https://doi.org/10.3390/horticulturae9030337 https://www.mdpi.com/journal/horticulturae
Horticulturae 2023,9, 337 2 of 12
output globally was USD 14 billion [
18
]. The strawberry is a cosmopolitan plant that
can be grown on different soil types and altitudes. All over the world, the area under
strawberry cultivation has increased significantly in the last decade, mainly due to the
increased demand [
19
]. Strawberry fruits are a great source of nutrients, and several bioac-
tive substances that may be beneficial to human health. Strawberry fruits may contain
antioxidant, anticancer, anti-inflammatory, and antineurodegenerative biological activities
because of their high polyphenol content, particularly anthocyanins [
20
]. These proper-
ties of strawberry fruits can be greatly influenced by agronomical practices, especially
fertilization [21].
The objective of this research was to compare and quantify the impact of vermicompost
and vermicompost leachate application on the yield and quality of strawberries concerning
the mineral NPK fertilization during a 3-year production cycle.
2. Materials and Methods
2.1. Experimental Site
The field experiment was conducted during 2009–2012 at a location near Novi Sad,
Serbia: (45
◦
20
0
24.44
00
N, 19
◦
50
0
22.32
00
E). The experiment was conducted on clay loam
soil classified as Phaeozem (the dominant soil type in northern Serbia). The soil was
slightly alkaline (7.92 pH in H
2
O) with a low content of calcium carbonate (0.83%) and
organic matter (2.05%). The content of available phosphorus was low (24.9 mg kg
−1
P),
while the content of available potassium was at an optimal level (179 mg kg
−1
K). The
concentrations of the available form of microelements were as follows: 2.06 mg kg
−1
DTPA-Fe; 18.56 mg kg−1DTPA-Mn; 0.89 mg kg−1DTPA-Cu; 1.26 mg kg−1DTPA-Zn.
The experimental plot was equipped with a drip irrigation system with water from
an artesian well. Irrigation was carried out every year from April to September when
the irrigation system was automatically switched on to keep the soil moisture tension
within the range of 15 to 25 kPa. A tensiometer was used to monitor soil moisture 15 cm
below the surface in the space between two strawberry plants. The chemical properties
of irrigation water were as follows: dry residue 431 mg L
−1
; pH 7.31; EC 0.71 dS m
−1
;
HCO3−6.83 meq L−1
; Cl
−
3.46 meq L
−1
; SO
4−2
2.03 meq L
−1
; Ca
2+
2.11 meq L
−1
; Mg
2+
3.02 meq L
−1
; Na
+
3.98 meq L
−1
; K
+
0.07 meq L
−1
; Fe 1.1 mg L
−1
; Mn 0.11 mg L
−1
;
Cu < 0.01 mg L−1; Zn 0.026 mg L−1.
The average air temperature and precipitation data in the study years were obtained
from on-site meteorological stations and are presented in Figure 1.
Horticulturae 2023, 9, x FOR PEER REVIEW 3 of 13
Figure 1. Average air temperature and total monthly precipitation for hydrological years
(2010–2012).
2.2. Experiment Design
The experiment included five treatments arranged as completely randomized block
designs in four replications. Each individual trial plot consisted of 10 strawberry plants of
the June-bearing cultivar Senga Sengana, and the experiment consisted of a total of 20
plots. The experiment was set up on a plot where mineral fertilizers had not been applied
for the past 3 years, and the crop that preceded the planting of strawberries was winter
wheat. After the wheat harvest in mid-July 2009, the harvest residues were removed from
the plot, and the soil was plowed and prepared for planting strawberry seedlings.
A week before strawberry planting, raised beds 15 cm high and 80 cm wide were
formed with two drip irrigation hoses with a dropper capacity of 2 dm−3 h−1. After that, 50
µm thick and 1.3 m wide black polyethylene perforated foil (10 plants per m2) was
stretched over the raised beds. Strawberry planting was performed manually on 23 July
2009. During the entire period of the experiment, fungicides were applied every year to
prevent the most prevalent strawberry diseases: common leaf spot (Mycosphaerella
fragariae) and fruit rot (Botrytis cinerea).
The experiment consisted of five fertilization treatments:
1. Control treatment—no fertilization (Ø).
2. Preplant application of vermicompost in the amount which adds 170 kg N ha−1 (V) to
the soil.
3. Preplant application of vermicompost (170 kg N ha−1) and foliar application of ver-
micompost leachate during vegetation (four times during April–May and three
times in 15-day intervals during July–August (seven sprays per year in total) (VL)).
4. Foliar application and fertigation with vermicompost leachate (four times during
April–May and three times in 15-day intervals during July–August (seven sprays
per year in total) (L)).
5. Standard fertilization with mineral fertilizers (NPK). A total of 60 kg N ha−1, 30 kg
P2O5 ha−1, and 80 kg K2O ha−1 were applied each year as ammonium nitrate, super-
phosphate, and potassium nitrate, respectively.
In treatments 2 and 3 (V and VL), the vermicompost was incorporated into the sur-
face soil layer (0–30 cm) 1 week before strawberry planting (23 July 2009). At the same
time, in treatment 5 (NPK treatment), 300 kg ha−1 of compound mineral fertilizer 8:16:24
and 100 kg of ammonium nitrate were applied. Additionally, in this treatment, as a
standard fertilization practice, mineral NPK fertilizers were applied through a drip irri-
-10
-5
0
5
10
15
20
25
30
Average air temperatures( C)
Months/Years
Average air temperatures
Long term average
2010 20112012
0
40
80
120
160
200
Precipitation (mm)
Months/ Years
Monthly precipitation (mm)
Long term average
2010 2011 2012
Figure 1.
Average air temperature and total monthly precipitation for hydrological years (2010–2012).
Horticulturae 2023,9, 337 3 of 12
2.2. Experiment Design
The experiment included five treatments arranged as completely randomized block
designs in four replications. Each individual trial plot consisted of 10 strawberry plants of
the June-bearing cultivar Senga Sengana, and the experiment consisted of a total of
20 plots
.
The experiment was set up on a plot where mineral fertilizers had not been applied for the
past 3 years, and the crop that preceded the planting of strawberries was winter wheat.
After the wheat harvest in mid-July 2009, the harvest residues were removed from the plot,
and the soil was plowed and prepared for planting strawberry seedlings.
A week before strawberry planting, raised beds 15 cm high and 80 cm wide were
formed with two drip irrigation hoses with a dropper capacity of 2 dm
−3
h
−1
. After that,
50
µ
m thick and 1.3 m wide black polyethylene perforated foil (10 plants per m
2
) was
stretched over the raised beds. Strawberry planting was performed manually on 23 July
2009. During the entire period of the experiment, fungicides were applied every year to
prevent the most prevalent strawberry diseases: common leaf spot (Mycosphaerella fragariae)
and fruit rot (Botrytis cinerea).
The experiment consisted of five fertilization treatments:
1. Control treatment—no fertilization (Ø).
2.
Preplant application of vermicompost in the amount which adds 170 kg N ha
−1
(V) to
the soil.
3.
Preplant application of vermicompost (170 kg N ha
−1
) and foliar application of ver-
micompost leachate during vegetation (four times during April–May and
three times
in 15-day intervals during July–August (seven sprays per year in total) (VL)).
4.
Foliar application and fertigation with vermicompost leachate (four times during
April–May and three times in 15-day intervals during July–August (seven sprays per
year in total) (L)).
5.
Standard fertilization with mineral fertilizers (NPK). A total of 60 kg N ha
−1
,
30 kg P2O5ha−1
, and 80 kg K
2
O ha
−1
were applied each year as ammonium nitrate,
superphosphate, and potassium nitrate, respectively.
In treatments 2 and 3 (V and VL), the vermicompost was incorporated into the surface
soil layer (0–30 cm) 1 week before strawberry planting (23 July 2009). At the same time,
in treatment 5 (NPK treatment), 300 kg ha
−1
of compound mineral fertilizer 8:16:24 and
100 kg of ammonium nitrate were applied. Additionally, in this treatment, as a standard
fertilization practice, mineral NPK fertilizers were applied through a drip irrigation system
once a week from April to mid-September in all three growing seasons. The total applied
amounts of nitrogen, phosphorus, and potassium through different fertilization treatments,
as well as the time and method of fertilizer application, are shown in Table 1.
Table 1.
Total amounts of nitrogen, phosphorus, and potassium applied through different fertilization
treatments, time, and method of fertilizer application.
Fertilization
Treatments
Time and Method of Fertilizer Application
Before Planting (Year 2009) (Plowed) During Vegetation (Years 2009–12)
(Fertigation)
During Vegetation (Years 2009–12)
(Foliar Application)
N
(kg ha−1)
P2O5
(kg ha−1)
K2O
(kg ha−1)
N
(kg ha−1)
P2O5
(kg ha−1)
K2O
(kg ha−1)
N
(kg ha−1)
P2O5
(kg ha−1)
K2O
(kg ha−1)
Ø - - - - - - - - -
V 170 251 110 - - - - - -
V + L 170 251 110 - - - 2.5 4.47 6.3
L - - - 25 44.5 63 2.5 4.47 6.3
NPK 60 80 120 70 40 80 - - -
Ø, control; V, vermicompost; V + L, vermicompost + leachate; L, leachate; NPK, mineral fertilizer.
The application of mineral fertilizers was carried out under the same conditions during
the growing season when vermicompost leachate was applied, with two-thirds of the total
Horticulturae 2023,9, 337 4 of 12
amount of fertilizer applied in the first half of the growing season (before the strawberry
blossoms), while the rest was applied in the second half of the growing season during
August and September each year.
The vermicompost leachate used in this research was collected on the same farm
where the vermicompost was produced. The required amount of vermicompost leachate
used during the growing season was collected every year in the spring. Every year before
application, the samples of vermicompost leachate were analyzed, and the average values
of the chemical composition of three samples (for three years of application) are shown in
Table 2. During the growing season, vermicompost leachate was stored in a refrigerator at
a temperature of 4 ◦C.
Table 2. Chemical properties of organic fertilizers.
Chemical Properties Organic Fertilizers
Vermicompost Vermicompost
Leachate
Bulk density (g cm−3)- 1.05
Dry mater (g kg−1)754 12.6 ±0.64
pH 7.56 7.21 ±0.11
Total N (g kg−1)19.9 0.357 ±0.05
NO3-N (mg kg−1)450 306.2 ±47.2
NH4-N (mg kg−1)86.1 50.5 ±11.15
Organic C (g kg−1)274 17.5 ±1.94
C/N ratio 13.8 49.2 ±2.30
Total P (g kg−1)13.2 0.28 ±0.06
Water soluble P (mg kg−1)621 0.028 ±0.0006
Total K (g kg−1)10.5 0.75 ±0.14
Water soluble K (mg kg−1)798 0.075 ±0.22
Total Ca (g kg−1)18.6 0.102 ±0.02
Total Mg (g kg−1)6.50 0.074 ±0.015
Fe (mg kg−1)1054 96 ±13.05
Mn (mg kg−1)171 1.35 ±0.91
Cu (mg kg−1)8.90 2.5 ±0.86
Zn (mg kg−1)45.2 3.0 ±0.90
For fertigation, aqueous vermicompost extracts were prepared by diluting vermicom-
post leachate with tap water at a ratio of 1:2 (vol/vol). Before application, the solution was
filtered through filter paper and applied at the rate of 2 L m
−2
. Foliar application of vermi-
compost leachate at the rate of 0.1 L m
−2
(filtered undiluted solution) was performed with
a hand sprayer in all three growing seasons. Fertigation with vermicompost leachate was
performed at the same time as the foliar application. Prior to the application of vermicom-
post leachate, all the plots were irrigated for an hour before the leachate application. The
chemical compositions of applied vermicompost and vermicompost leachate are presented
in Table 2.
2.3. Measurements and Analytical Determination
The soil pH value was measured in a soil/water suspension (1:2.5 ratio, respectively)
with a Metrel MA 3657 pH meter. The calcium carbonate (CaCO
3
) content in the soil was
measured using a Scheibler calcimeter, a volumetric method. Soil organic matter (organic
C) was analyzed by a CHNS analyzer (Elementar Vario EL, GmbH, Hanau, Germany).
Horticulturae 2023,9, 337 5 of 12
Available-form phosphorus and potassium in the soil were analyzed after extraction with
an AL solution (0.1 mol L
−1
ammonium lactate and mol L
−1
acetic acid, pH 3.75) at a
soil-to-solution ratio of 1:20 (w/v) [
22
]. The concentration of available phosphorus was
measured spectrophotometrically, while the concentration of K was measured by flame
photometric technique. Plant-available fractions of Fe, Mn, Cu, and Zn in the soil samples
were measured after extraction with DTPA-TEA buffer (0.005 mol L
−1
DTPA + 0.01 mol L
−1
CaCl
2
+ 0.1 mol L
−1
TEA)) by an atomic absorption spectrometer (Shimadzu 6300, Kyoto,
Japan). The dry matter content in vermicompost was determined using the gravimetric
method by drying to a constant weight at 70 ◦C for 24 h.
Ground samples of vermicompost were analyzed for total C and N using an automated
CHNS analyzer (Elementar Vario EL, GmbH, Hanau, Germany).
The contents of K, Fe, Mn, Cu, and Zn in vermicompost and vermicompost leachate
were analyzed by the wet digestion method (mixture of HNO
3
:HCIO
4
), while the con-
centrations of these elements in the solution were determined by the method of atomic
absorption spectrophotometry (AAS, Shimadzu 6300). The concentration of P in vermi-
compost and leachate was measured by the spectrophotometric molybdovanadate method
after wet digestion with hydrochloric acid [
23
]. Mineral N in the vermicompost was ex-
tracted by
2 mol L−1
KCl (1:4, soil-to-solution ratio, weight basis) and determined by steam
distillation [24].
The strawberry yield was calculated by taking into account all harvested fruits. In
order to determine the average weight of the fruit, 30 strawberry fruits were randomly
selected from each repetition at the peak of the harvest period and weighed separately. The
quality parameters of strawberry fruit were determined from the same samples taken for
average weight.
The TMS-PRO texture analyzer (Food Technology Corporation—Sterling, VA, USA)
with a 5 mm diameter stainless steel probe was used for determining the strawberry fruit
firmness. The firmness of the fruit represents the mean value of the resistance force of
strawberry fruit from the equatorial side and is measured in newtons (N).
Strawberry fruit color was measured using the Konica Minolta CR-400 three-filter
colorimeter (Mississauga, ON, Canada). The measured color values of strawberry fruit
are based on the CIE L*a*b* color system (Commission Internationale de l’Éclairage or
International Commission on Illumination, CIE), where value L* represents the luminance
(illumination, lightness), and a* and b* represent the color. Based on the obtained readings
for the values of a* and b*, value C was calculated, which represents the chromaticity or
purity of the color, as well as the angle h
◦
, which defines the intensity of the red color
(0◦= purple red, 90◦= yellow, 180◦= bluish-green, 270◦= blue) [25].
Fruit slices, obtained from 30 whole berries in 4 replicates, were homogenized in a
blender and used to determine total soluble solids (TSS) and titratable acidity (TA).
The concentration of TSS (expressed in Brix
◦
) in the fresh mass of strawberry fruit was
measured by direct reading using a hand-held refractometer (Hunan Xiangxin instruments,
Changsha, China), whereas TA was measured on filtered strawberry juice by the titration
method with 0.1 M NaOH (the equivalence point was at pH 8.1). The volume of NaOH
solution used for titration was multiplied by the correction factor (0.64), and the results
were expressed as percentages.
The concentration of total anthocyanins in the fresh fruits of strawberries was deter-
mined by the pH differential method with two buffer systems as buffer solutions: potassium
chloride, pH 1 (0.025 mol L
−1
), and sodium acetate, pH 4.5 (0.4 mol L
−1
) [
26
]. The antho-
cyanin content in the fresh strawberry fruit mass was expressed in mg of pelargonidin-
3-glucoside equivalents per 100 g of fresh strawberry fruit. In the same samples, the
antioxidant activity of strawberry fruit was determined by the FRAP method (ferric re-
ducing antioxidant power) [
27
]. The total antioxidative capacity of strawberry fruit was
expressed in FRAP units, wherein one FRAP unit is equivalent to 100 µM Fe2+.
To determine the mineral composition, thirty whole berries randomly selected from
each replicate were mixed thoroughly and then dried at 80
◦
C for 72 h to the constant
Horticulturae 2023,9, 337 6 of 12
weight in a forced air oven. After that, the mineral composition was determined by the
method of wet digestion with nitric acid (HNO
3
) in a microwave oven at a temperature
of 200
◦
C and a pressure of 170 psi, while the concentrations of K, Ca, Mg, Fe, Mn, Cu,
and Zn in the obtained solution were measured by atomic absorption spectrophotometry
(Shimadzu 6300).
2.4. Statistics
All data obtained by measurements in the field experiment were subjected to analysis
of variance (ANOVA), and the significance of differences between treatment means was
assessed using Tukey’s test (probability level, p< 0.05). The statistical analyses were
performed using the STATISTICA 9.0 software (StatSoft Inc., Tulsa, OK, USA).
3. Results
3.1. Strawberry Yield
The preplant application of vermicompost (treatments V and V + L) and standard
fertilization with mineral fertilizers (NPK) had a positive effect on the total yield of straw-
berries in the first year of fruiting (Figure 2). In these treatments, the strawberry yield
ranged between 902 and 947 g plant
−1
and was significantly higher than the yield achieved
on the control (737 g plant
−1
) and L treatment (751 g plant
−1
) (Figure 2). However, in the
second and third years of fruiting, a significantly higher strawberry yield compared to
control was recorded only in the NPK treatment, whereas the residual effects of vermi-
compost application (V and V + L treatments) were not detected in the second and third
fruiting years of strawberries (Figure 2). In the first fruiting year, the number of flowers per
strawberry plant on the V, V + L, and NPK treatments was significantly higher compared
to control. On the other hand, in the second and third year of fruiting, only the plants in
the NPK treatment had a significantly higher number of flowers compared to the control
and other fertilization treatments. In all three fruiting years, the average fruit weight did
not differ significantly between treatments (Figure 2).
Horticulturae 2023, 9, x FOR PEER REVIEW 7 of 13
Figure 2. The total number of flowers (A), average strawberry fruit weight (B), and total yield of
strawberries (C). Ø, control; V, vermicompost; V + L, vermicompost + leachate; L, leachate; NPK,
mineral fertilizer. Different letters denote a significant difference at p < 0.05 for each year sepa-
rately.
3.2. Mineral Composition of Strawberry Fruit
The mineral composition of strawberry fruit over three years of fruiting is shown in
Table 3. In the first year of fruiting, in all four fertilization treatments, the concentration
of K in strawberry fruit was significantly higher compared to control. In the second and
third years of fruiting, a higher concentration of K compared to control was measured
only in treatments L and NPK. On the other hand, the application of vermicompost and
leachate did not lead to a significant increase in the concentration of the other elements.
In contrast, standard fertilization with NPK fertilizers led to increased concentrations of
K, Fe, Mn, Cu, and Zn in strawberry fruit in all three years of fruiting.
Table 3. Mineral composition of strawberry fruit.
2010 (First Fruiting Year)
Fertilization
K
g kg−1
Ca
g kg−1
Mg
g kg−1
Fe
mg kg−1
Mn
mg kg−1
Cu
mg kg−1
Zn
mg kg−1
Ø 1
1.11 c
125 a
102 a
3.98 b
3.72 b
0.39 a
0.80 c
V
1.26 b
120 a
102 a
5.13 ab
3.99 b
0.38 a
0.83 bc
V + L
1.27 b
117 a
96 a
5.75 ab
3.79 b
0.37 a
0.95 b
L
1.42 a
119 a
105 a
4.47 ab
3.95 b
0.38 a
0.74 c
NPK
1.37 ab
114 a
112 a
6.99 a
4.98 a
0.42 a
1.19 a
2011 (Second Fruiting Year)
Ø
1.32 c
149 a
125 a
6.60 b
5.82 b
0.70 b
1.21 b
V
1.34 bc
152 a
130 a
6.17 b
6.22 b
0.79 b
1.23 b
V + L
1.36 b
155 a
126 a
5.44 b
6.35 b
0.65 bc
1.21 b
a
a
a
a
a
a
a
a
a
a
a
a
a
a
a
6
8
10
12
14
16
18
20
Ø
V
V+L
L
NPK
Ø
V
V+L
L
NPK
Ø
V
V+L
L
NPK
Year: 2010
Year: 2011
Year: 2012
Fruit weight (g)
B
b
a
a
b
a
b
b
b
b
a
b
b
b
b
a
400
600
800
1000
1200
Ø
V
V+L
L
NPK
Ø
V
V+L
L
NPK
Ø
V
V+L
L
NPK
Year: 2010
Year: 2011
Year: 2012
Total yield (g plant−1)
C
b
a
a
b
a
b
b
b
b
a
c
bc
b
bc
a
60
80
100
120
140
160
Ø
V
V+L
L
NPK
Ø
V
V+L
L
NPK
Ø
V
V+L
L
NPK
Year: 2010
Year: 2011
Year: 2012
Number of flowers (plant−1)
A
Figure 2.
The total number of flowers (
A
), average strawberry fruit weight (
B
), and total yield of
strawberries (
C
). Ø, control; V, vermicompost; V + L, vermicompost + leachate; L, leachate; NPK,
mineral fertilizer. Different letters denote a significant difference at p< 0.05 for each year separately.
Horticulturae 2023,9, 337 7 of 12
3.2. Mineral Composition of Strawberry Fruit
The mineral composition of strawberry fruit over three years of fruiting is shown in
Table 3. In the first year of fruiting, in all four fertilization treatments, the concentration of
K in strawberry fruit was significantly higher compared to control. In the second and third
years of fruiting, a higher concentration of K compared to control was measured only in
treatments L and NPK. On the other hand, the application of vermicompost and leachate
did not lead to a significant increase in the concentration of the other elements. In contrast,
standard fertilization with NPK fertilizers led to increased concentrations of K, Fe, Mn, Cu,
and Zn in strawberry fruit in all three years of fruiting.
Table 3. Mineral composition of strawberry fruit.
2010 (First Fruiting Year)
Fertilization K
g kg−1
Ca
g kg−1
Mg
g kg−1
Fe
mg kg−1
Mn
mg kg−1
Cu
mg kg−1
Zn
mg kg−1
Ø11.11 c 125 a 102 a 3.98 b 3.72 b 0.39 a 0.80 c
V 1.26 b 120 a 102 a 5.13 ab 3.99 b 0.38 a 0.83 bc
V + L 1.27 b 117 a 96 a 5.75 ab 3.79 b 0.37 a 0.95 b
L 1.42 a 119 a 105 a 4.47 ab 3.95 b 0.38 a 0.74 c
NPK 1.37 ab 114 a 112 a 6.99 a 4.98 a 0.42 a 1.19 a
2011 (Second Fruiting Year)
Ø 1.32 c 149 a 125 a 6.60 b 5.82 b 0.70 b 1.21 b
V 1.34 bc 152 a 130 a 6.17 b 6.22 b 0.79 b 1.23 b
V + L 1.36 b 155 a 126 a 5.44 b 6.35 b 0.65 bc 1.21 b
L 1.60 a 135 a 129 a 6.35 b 6.06 b 0.52 c 1.25 b
NPK 1.53 ab 146 a 137 a 10.5 a 9.08 a 0.94 a 1.35 a
2012 (Third Fruiting Year)
Ø 1.56 b 171 a 148 ab 3.61 b 3.37 b 0.34 b 0.57 b
V 1.59 b 155 a 136 b 3.44 b 3.45 b 0.22 c 0.74 b
V + L 1.42 b 157 a 133 b 3.27 b 2.27 c 0.28 bc 0.75 b
L 1.92 a 154 a 143 ab 3.32 b 3.33 b 0.31 bc 0.66 b
NPK 1.86 a 152 a 157 a 6.90 a 5.25 a 0.51 a 1.02 a
Ø, control; V, vermicompost; V + L, vermicompost + leachate; L, leachate; NPK, mineral fertilizer. Different letters
denote a significant difference at p< 0.05 for each year separately.
3.3. Strawberry Color and Mechanical Properties
Fertilization treatments had a significant effect on fruit color parameters in all three
years of fruiting (Table 4). In the first 2 years of fruiting, the lowest values of h
◦
were
measured in treatment V. In addition to a more intense color, strawberry fruits in this
treatment were characterized by lower chromaticity (lower C values) compared to NPK
treatment and control. The application of NPK fertilizers had the opposite effect from the
application of leachate. Strawberry fruits in this treatment were characterized by lighter
(higher L values) and more chromatic colors (higher C values) but less redness (higher h
◦
values) compared to treatment L. The application of vermicompost (V and V + L treatments)
did not significantly affect the color of the strawberry fruit (Table 4).
Figure 3shows the parameters of strawberry fruit quality depending on the fertiliza-
tion treatment during the three years of fruiting. The application of vermicompost leachate
led to a higher TSS concentration and a higher TSS/TA ratio compared to control. Addi-
tionally, leachate application led to a significantly higher concentration of anthocyanins
and antioxidant activity of the fruit (FRAP) not only in the control but also in the NPK
treatment. On the other hand, the lowest firmness of strawberry fruit in all three years
was measured on the treatment where vermicompost leachate was applied (L treatment).
Strawberry fruit quality parameters in treatment V, in all three years of fruiting, did not
differ significantly compared to the control treatment without fertilization.
Horticulturae 2023,9, 337 8 of 12
Table 4. Strawberry fruit color parameters (L, lightness; C, chromaticity; h◦, intensity of red color).
2010
Fertilization L C h◦
Ø 29.6 a 35.5 a 27.7 ab
V 29.5 a 32.3 ab 29.4 ab
V + L 30.6 a 34.8 a 29.2 ab
L 28.9 a 30.9 b 26.8 b
NPK 30.7 a 35.4 a 29.9 a
2011
L C h◦
Ø 30.4 a 29.0 a 29.8 ab
V 29.7 ab 27.9 ab 32.8 a
V + L 30.6 a 28.4 a 31.0 ab
L 28.6 b 25.3 b 29.7 b
NPK 31.2 a 30.0 a 33.1 a
2012
L C h◦
Ø 33.3 ab 38.2 b 33.5 b
V 33.4 ab 37.1 bc 33.6 b
V + L 31.9 b 35.0 cd 34.5 b
L 32.3 b 33.4 d 33.7 b
NPK 34.7 a 41.5 a 37.3 a
Ø, control; V, vermicompost; V + L, vermicompost + leachate; L, leachate; NPK, mineral fertilizer. Different letters
denote a significant difference at p< 0.05 for each year separately.
Horticulturae 2023, 9, x FOR PEER REVIEW 9 of 13
cyanins and antioxidant activity of the fruit (FRAP) not only in the control but also in the
NPK treatment. On the other hand, the lowest firmness of strawberry fruit in all three
years was measured on the treatment where vermicompost leachate was applied (L
treatment). Strawberry fruit quality parameters in treatment V, in all three years of
fruiting, did not differ significantly compared to the control treatment without fertiliza-
tion.
Figure 3. The concentration of total soluble solids (TSS)(A), total acids (TA) (B) and the ratio be-
tween TSS and TA (C), anthocyanins (mg cyanidin-3-glucoside/100 g of fruit) (D), antioxidant ac-
tivity (FRAP units) (E), and the firmness of strawberry fruit (F). Ø, control; V, vermicompost; V + L,
vermicompost + leachate; L, leachate; NPK, mineral fertilizer. Different letters denote a significant
difference at p < 0.05 for each year separately.
4. Discussion
The treatments where vermicompost was applied at the time of planting (treatments
V and V + L) and the treatment with a standard fertilization program with NPK fertilizers
led to a significant increase in strawberry yield in the first year of fruiting. In these
treatments, the yield of strawberries ranged between 813 and 829 g plant−1, respectively,
and was significantly higher than the control (693 g plant−1) and the treatment where
vermicompost leachate was applied (705 g plant−1) (Figure 2). Such results are in agree-
ment with the previous research by [25,28], who also reported the positive effect of the
preplant application of vermicompost on strawberry yield. However, in the second and
third years of fruiting, a significantly higher strawberry yield compared to control was
observed only in the NPK treatment, while the residual effects of vermicompost applica-
tion were not registered in the second and third years of fruiting (Figure 2).
In our study, vermicompost was applied prior to strawberry planting. Due to fa-
vorable conditions for mineralization (favorable temperatures for mineralization during
August), most of the nitrogen from vermicompost likely became available to the straw-
berry plants in the year of application. In this case, the release of nutrients and primarily
nitrogen from the vermicompost coincided with the period of flower differentiation. It is
a
a
a
a
a
b
b
ab
a
b
b
ab
ab
a
ab
4
5
6
7
8
9
Ø
V
V+L
L
NPK
Ø
V
V+L
L
NPK
Ø
V
V+L
L
NPK
Year: 2010
Year: 2011
Year: 2012
TSS (%)
A
ab
b
ab
b
a
ab
ab
ab
b
a
b
b
b
b
a
0.3
0.4
0.5
0.6
0.7
Ø
V
V+L
L
NPK
Ø
V
V+L
L
NPK
Ø
V
V+L
L
NPK
Year: 2010
Year: 2011
Year: 2012
TA (%)
B
b
ab
b
a
b
c
c
bc
a
c
b
a
ab
a
b
10
12
14
16
18
20
22
Ø
V
V+L
L
NPK
Ø
V
V+L
L
NPK
Ø
V
V+L
L
NPK
Year: 2010
Year: 2011
Year: 2012
Ratio TSS/TA
C
b
b
ab
a
a
b
b
a
a
b
b
b
ab
a
b
30
40
50
60
70
80
90
Ø
V
V+L
L
NPK
Ø
V
V+L
L
NPK
Ø
V
V+L
L
NPK
Year: 2010
Year: 2011
Year: 2012
Anthocyanins
D
a
a
a
a
a
ab
ab
a
a
b
b
ab
a
a
b
20
30
40
50
60
70
80
90
100
Ø
V
V+L
L
NPK
Ø
V
V+L
L
NPK
Ø
V
V+L
L
NPK
Year: 2010
Year: 2011
Year: 2012
FRAP
E
a
ab
ab
b
ab
ab
a
a
b
а
a
a
a
a
a
0.6
0.8
1
1.2
1.4
1.6
1.8
2
Ø
V
V+L
L
NPK
Ø
V
V+L
L
NPK
Ø
V
V+L
L
NPK
Year: 2010
Year: 2011
Year: 2012
Firmness (N)
F
Figure 3.
The concentration of total soluble solids (TSS) (
A
), total acids (TA) (
B
) and the ratio between
TSS and TA (
C
), anthocyanins (mg cyanidin-3-glucoside/100 g of fruit) (
D
), antioxidant activity
(FRAP units) (
E
), and the firmness of strawberry fruit (
F
). Ø, control; V, vermicompost; V + L,
vermicompost + leachate; L, leachate; NPK, mineral fertilizer. Different letters denote a significant
difference at p< 0.05 for each year separately.
Horticulturae 2023,9, 337 9 of 12
4. Discussion
The treatments where vermicompost was applied at the time of planting (treatments V
and V + L) and the treatment with a standard fertilization program with NPK fertilizers led
to a significant increase in strawberry yield in the first year of fruiting. In these treatments,
the yield of strawberries ranged between 813 and 829 g plant
−1
, respectively, and was
significantly higher than the control (693 g plant
−1
) and the treatment where vermicompost
leachate was applied (705 g plant
−1
) (Figure 2). Such results are in agreement with the
previous research by [
25
,
28
], who also reported the positive effect of the preplant application
of vermicompost on strawberry yield. However, in the second and third years of fruiting, a
significantly higher strawberry yield compared to control was observed only in the NPK
treatment, while the residual effects of vermicompost application were not registered in the
second and third years of fruiting (Figure 2).
In our study, vermicompost was applied prior to strawberry planting. Due to favorable
conditions for mineralization (favorable temperatures for mineralization during August),
most of the nitrogen from vermicompost likely became available to the strawberry plants
in the year of application. In this case, the release of nutrients and primarily nitrogen from
the vermicompost coincided with the period of flower differentiation. It is possible that
the plants formed a higher reserve of N, leading to more flowers per plant in the first year
of fruiting (Figure 2), which in turn led to an increase in yield due to a higher number of
fruits per strawberry plant [29,30].
The application of vermicompost leachate in our study did not increase strawberry
yield, which is in contrast to the studies of [
31
,
32
], who reported the positive effect of
foliar application (seven times during vegetation) of compost extract on strawberry yield.
The reason for the absence of a positive influence of vermicompost leachate on the yield
of strawberries in our study may be the relatively high fertility of the soil on which the
experiment was conducted, and the relatively low nitrogen content in vermicompost
leachate (Table 2).
The application of vermicompost significantly increased the concentration of K and
Zn in strawberry fruit only in the first year of fruiting, while the fertigation and foliar
application of vermicompost leachate (L treatment) significantly increased the concentration
of K compared to control during all three years of fruiting.
On the other hand, in the NPK treatment, where fertilization was performed during
all three years of fruiting, the concentrations of K, Fe, Mn, and Zn in strawberry fruit were
significantly higher compared to control. These results are consistent with the research
of [
33
,
34
], who also reported the positive influence of fertilization with macroelements,
primarily nitrogen, on the uptake of microelements.
The concentration of TSS in strawberry fruit, in all three years of fruiting, had values
that ranged from 6.01% to 8.47%. In the first year, no significant differences were registered
between treatments regarding TSS concentration in strawberry fruit, despite a significant
difference in yield between treatments. In the first year of fruiting, significantly more
precipitation was measured not only compared to the second and third years of fruiting but
also compared to the long-term average (Figure 1). Heavy precipitation, combined with
cloudy weather, may be the reason why the concentration of TSS in strawberry fruit did not
differ significantly between treatments. Ref. [
35
] also reported the enormous influence of
weather conditions during strawberry harvest on the concentration of TSS and the chemical
composition of strawberry fruit in general. In the second and third years of fruiting, the
highest TSS concentration was measured on treatment L, which led to a significantly higher
TSS/TA ratio compared to other treatments.
The authors of [
31
] also reported a higher TSS concentration and lower TA values in
strawberry fruit compared to the control treatment due to the application of vermicompost
leachate. According to [
36
], the foliar application of a vermicompost extract led to an
increase or decrease in fruit firmness depending on the tomato variety, while in all varieties,
it led to a decrease in the concentration of ascorbic acid. On the other hand, the highest TA
was measured in the fruits on NPK treatment. The increased acidity of strawberry fruit
Horticulturae 2023,9, 337 10 of 12
may be a consequence of the higher amount of N applied on this treatment (compared to
other treatments), which could lead to higher fruit acidity and a lower TSS/TA ratio [
21
,
37
].
The highest anthocyanin concentration and antioxidant activity of the fruit (FRAP
values) were measured on the treatment where vermicompost leachate was applied. The
vermicompost leachate used in our study had a relatively high K concentration (Table 2),
which may have affected the anthocyanin concentration in strawberry fruit [
38
]. Addition-
ally, vermicompost leachate contains phytohormones [
11
,
12
], which could have a significant
role in increasing the concentration of anthocyanins in strawberry fruit, especially gibberel-
lic acid [39].
The higher concentration of anthocyanins due to the application of vermicompost
leachate resulted in a change in the color of strawberry fruit [
40
], so the fruits had a more
intense red color (lower values of h
◦
) and a darker and less chromatic color compared to
the treatment with NPK fertilizers, and in some years, compared to the control as well.
Additionally, the higher concentrations of TSS and anthocyanins and the darker fruit
color all indicate a higher degree of fruit maturity, which explains why the fruits had the
lowest fruit firmness after the application of vermicompost leachate [41].
The influence of fertilization treatment on certain parameters of strawberry quality
differed between the years of fruiting, which indicates the existence of interactions between
external factors (temperature, precipitation, etc.) and applied fertilizers [37].
5. Conclusions
The results showed that the preplant application of vermicompost applied in a rela-
tively small dose (equivalent to 170 kg N/ha) had a positive effect on the yield, which in
the first year of fruiting was comparable to the yield obtained in the treatment with the
standard application of NPK fertilizers. On the other hand, in the second and third years
of fruiting, the yield on this treatment was at the level of the control treatment (without
fertilization) and significantly lower compared to the treatment with standard fertilization
with NPK fertilizers.
The application of vermicompost leachate by fertigation and foliar application did
not affect strawberry yield but had a positive effect on strawberry fruit quality parameters
such as total soluble solids, total anthocyanins, and antioxidant activity of strawberry fruit.
If strawberries are grown for 2 or 3 years in the same place, the preplant application of ver-
micompost and vermicompost leachate application during vegetation cannot maintain the
yield level as with the application of mineral NPK fertilizers, but the quality of strawberry
fruit can be improved significantly.
Recycling of organic wastes is becoming increasingly important as the need to protect
natural resources grows, and vermicomposting as a technology can certainly make a
significant contribution. Further research should provide answers to the economic aspects
of the application of vermicompost and vermicompost leachate in strawberry production as
well as answers to the eventual contamination of strawberry fruit with harmful substances
that can be found in organic fertilizers.
Author Contributions:
Conceptualization, R. ˇ
C., M.S.M. and K.P.; methodology, R.ˇ
C., B.M.P., M.T.R.
and N.M.; software, M.D.L.; validation, R. ˇ
C. and N.M.; writing—original draft preparation, R. ˇ
C. and
K.P.; writing—review and editing, D.K. and M.D.L.; supervision, M.S.M.; funding acquisition, M.S.M.
All authors have read and agreed to the published version of the manuscript.
Funding:
This work was supported by the Ministry of Science, Technological Development and
Innovation of the Republic of Serbia (no. 451-03-47/2023-01/200117).
Data Availability Statement: Not applicable.
Conflicts of Interest: The authors declare no conflict of interest.
Horticulturae 2023,9, 337 11 of 12
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