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European Journal of Applied Sciences – Vol. 12, No. 1
Publication Date: February 25, 2024
DOI:10.14738/aivp.121.16195
Tiwa, J. M. F., Lekeufack, M., Edzigui, M. L. T., Fowoung, D., Tanetsa, A. E. M., Djiomou, A. C., & Fonkou, T. (2024). Growth and
Yield Responses of Okra (Abelmoschus Esculentus) Grown on Soil Amended with Dewatered Domestic Sewage Sludge in the West
of Cameroon. European Journal of Applied Sciences, Vol - 12(1). 38-52.
Services for Science and Education – United Kingdom
Growth and Yield Responses of Okra (Abelmoschus Esculentus)
Grown on Soil Amended with Dewatered Domestic Sewage Sludge
in the West of Cameroon
Justine Mireille Fotsa Tiwa
Research Unit of Applied Botany, Department of Plant Biology, Faculty of
Science, University of Dschang, Cameroon, P.O. Box 67, Dschang, Cameroon
Martin Lekeufack
Research Unit of Applied Botany, Department of Plant Biology, Faculty of
Science, University of Dschang, Cameroon, P.O. Box 67, Dschang, Cameroon
Marcelle Léonce Tsimi Edzigui
Research Unit of Applied Botany, Department of Plant Biology, Faculty of
Science, University of Dschang, Cameroon, P.O. Box 67, Dschang, Cameroon
Diane Fowoung
Research Unit of Applied Botany, Department of Plant Biology, Faculty of
Science, University of Dschang, Cameroon, P.O. Box 67, Dschang, Cameroon
Amandine Elodie Manekeu Tanetsa
Research Unit of Applied Botany, Department of Plant Biology, Faculty of
Science, University of Dschang, Cameroon, P.O. Box 67, Dschang, Cameroon
Adrienne Chimi Djiomou
Research Unit of Applied Botany, Department of Plant Biology, Faculty of
Science, University of Dschang, Cameroon, P.O. Box 67, Dschang, Cameroon
Théophile Fonkou
Research Unit of Applied Botany, Department of Plant Biology, Faculty of
Science, University of Dschang, Cameroon, P.O. Box 67, Dschang, Cameroon
ABSTRACT
Sewage sludge can be good to remedy soil depletion problems by intensive cropping
and overcome fertilization costs in agriculture. This study aimed to assess the
influence of domestic sewage sludge on the growth and yield of Abelmoschus
esculentus in West of Cameroon. Sewage sludge from the digester of sewage
treatment plant in University of Dschang was dewatered on filter beds and ground
in a mill. It was applied to fields at rates of 10 t/ha (T1), 20 t/ha (T2) and 30 t/ha
(T3) to evaluate their effects on the growth and yield of okra (KIRIKOU F1 variety).
The experimental design was completely randomized bloc with three replicates.
Growth parameters including plant height, leaf number and leaf area and yield
parameters including flower buds’ number, flower number, total fruit number,
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Tiwa, J. M. F., Lekeufack, M., Edzigui, M. L. T., Fowoung, D., Tanetsa, A. E. M., Djiomou, A. C., & Fonkou, T. (2024). Growth and Yield Responses of
Okra (Abelmoschus Esculentus) Grown on Soil Amended with Dewatered Domestic Sewage Sludge in the West of Cameroon. European Journal of
Applied Sciences, Vol - 12(1). 38-52.
URL: http://dx.doi.org/10.14738/aivp.121.16195
mature fruit number, fruit diameter and weight were evaluated with time. Growth
parameters were collected from the fourth week after sowing at biweekly
frequency, while yield parameters were measured weekly from first flower buds’
formation until end of experiment. The highest plant height, leaf number and leaf
area were obtained on the T2 field. Yields in T1, T2 and T3 fields were statistically
similar with positive control T4 (0.25 t/ha of 12-14-19 NPK) but differed
significantly with the negative control T0 (no fertilizer) which was similar with
positive control. The best yield (0.588 t/ha) was achieved from fields fertilized with
T2. These results show that sewage sludge, a by-product of domestic sewage
treatment, can be used as fertilizer for okra production.
Keywords: Abelmoscus esculentus, Sewage sludge, Fertilization, Yield, West of Cameroon.
INTRODUCTION
Urbanization and galloping demography are inevitably accompanied by a growing production
of solid and liquid wastes by human, industrial or domestic activities. In developing countries,
liquide waste is most often discharged into receiving environments untreated [1]. As water
resources are not inexhaustible, their degradation through the discharge of polluted water can
not only seriously damage the environment, but also lead to risks of clean water shortage [2].
It is therefore essential to limit pollution discharges into the natural environment by treating
all domestic, agricultural and industrial effluents (Alighardashi, 2007). The treatment of
domestic sewage generates, on one hand, liquid effluent of suitable quality that can be
discharged into surface waters with minimal impact on the environment or public health, and
on the other hand, residues such as sludge considered as waste [4]. Whatever the treatment
system adopted, sewage treatment is accompanied by the production of significant quantities
of sludge, which must be disposed of. Some ways of disposing this sludge include landfilling and
incineration with little or no added value, as well as energy recovery through biogas
production, for example, source of heat and electricity, and biological or agricultural recovery
through the production of fertilizer and compost. The latter are green technologies that
transform sludge into high value-added products while minimizing pollution risks of the
environment [5]. Sludge from domestic sewage treatment is rich in organic matter and has high
levels of mineral elements essential for improving soil quality and plants yield (Albrecht, 2007;
Mulaji, 2011; Hannachi et al., 2014). Abelmoschus esculentus (okra) is a non-nitrogen-fixing
annual plant with nutritional and medicinal virtues that are of great interest worldwide [9]. It
adapts to different soil types and is cultivated for its fruits, leaves, stem, roots, inflorescence
and seeds [10]. Cameroon is considered the 8th largest producer of okra, with an annual output
of 100,025 tonnes. The regions with the highest production and marketing potential are the Far
North, Centre and West regions, with 3.7 t/ha, 1.9 t/ha and 1.1 t/ha respectively [11]. On
average in 2009 and 2010 in Cameroon, okra production was 2.53 t/ha and 2.52 t/ha
respectively [12]. Despite okra's multiple uses, its proven nutritional value, its financial value
and the renewed interest in vegetable crops, okra cultivation in several tropical countries faces
multiple constraints that negatively affect its production (Sawadogo et al., 2006; Gnago et al.,
2011; Medagam et al., 2012). In Cameroon, the quantities of okra produced and available on the
markets are still very low compared with the ever-increasing demand [16]. The main causes of
this insufficient supply are, among others, the reduction in cultivated areas in favor of
construction, urbanization associated with population growth and, above all, the declining
fertility of cultivated soils [16]. Nitrogen, phosphorus and potassium are naturally present in
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European Journal of Applied Sciences (EJAS) Vol. 12, Issue 1, February-2024
soils, but exogenous inputs may be necessary to achieve the desired crop yields. Additional
inputs are generally provided by synthetic fertilizers. The valorization of sewage sludge could
be an alternative to remedy the problems of soil depletion by intensive cropping on the one
hand, and to limit fertilization costs on the other [4]. As sewage sludge is fairly widely available,
its fertilizing effects compared with those of synthetic fertilizers could be an asset for its
integration into local authority sanitation programs. The aim of the present study is to valorize
domestic sewage sludge in urban agriculture, particularly in market gardening.
MATERIALS AND METHODS
Study Site
The study was conducted in the plot dedicated to agricultural practices on the campus of the
University of Dschang, near the sewage treatment plant. Dschang is located between latitude
5°25' and 5°30' North, and longitude 10°0' and 10°5' East (Figure 1) and at average altitude of
1400 m above sea level. It has an equatorial climate characterized by an average annual
temperature of 20.1°C with thermal amplitude of 2.2°C, rainfall of 1911 mm, a short dry season
(November to February) and a long rainy season (March to October) [17].
Figure 1: Location of study site
Experimental Setup
The field experiment was carried out using a completely randomized block design covering an
area of 70 m2. This set-up consisted of three blocks representing three replicates. Each block
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Tiwa, J. M. F., Lekeufack, M., Edzigui, M. L. T., Fowoung, D., Tanetsa, A. E. M., Djiomou, A. C., & Fonkou, T. (2024). Growth and Yield Responses of
Okra (Abelmoschus Esculentus) Grown on Soil Amended with Dewatered Domestic Sewage Sludge in the West of Cameroon. European Journal of
Applied Sciences, Vol - 12(1). 38-52.
URL: http://dx.doi.org/10.14738/aivp.121.16195
was subdivided into five plots, each measuring 3 m x 1 m (Table I), with distances of 0.5 m
between blocks and 0.5 m between plots.
Table I: Schematic diagram of the experimental set-up used in the field
BLOCK A BLOCK B BLOCK C
T0: with no fertilizer (negative
control)
T1: 10 t/ha of sludge T4: 0,25 t/ha of 12-14-19 NPK
(positive control)
T2: 20 t/ha of sludge T3: 30 t/ha of sludge T2: 20 t/ha of sludge
T3: 30 t/ha of sludge T4: 0,25 t/ha of 12-14-19 NPK
(positive control)
T0: with no fertilizer (negative
control)
T1: 10 t/ha of sludge T2: 20 t/ha of sludge T3: 30 t/ha of sludge
T4: 0,25 t/ha of NPK 12-14-19
NPK (positive control)
T0: with no fertilizer (negative
control)
T1: 10 t/ha of sludge
Sowing and Plot Maintenance
The experimental field was subdivided into plots, each comprising 5 pockets. Sowing then
followed two weeks after sludge spreading. Okra seeds of the KIRIKOU F1 variety were
purchased from SEMAGRI seeds enterprise. This is an early, short hybrid variety that matures
between 55 and 60 days after sowing, with fleshy, very mucilaginous, medium-green fruits.
Three seeds were placed in each pot with a spacing of 50 cm between the pots. After emergence,
the seedlings were thinned to one plant per pocket. Weeds were controlled by weeding with a
hoe.
Evaluation of the Influence of Amendments on Okra Growth
This evaluation was carried out by measuring morphometric plants growth parameters from
the 4th week after sowing (WAS) with a biweekly frequency. Plant height was measured from
the ground level to the tip of longest leaf of the crown of the main stem; the leaf number per
plant was determined by counting; leaf area was calculated from the length and width of all
leaves per plant, using the following formula from Raunkiaer (1934) [18].
Leaf area =
2
3
LW (1)
Where L = leaf length and W = leaf width.
Evaluation of the Influence of Amendments on Okra Flowering and Yield
This evaluation was carried out every week from the formation of the first flower buds to the
end of the experiment. The number of flower buds, number of flowers on each plant, total
number of fruits and number of mature fruits (edible fruits harvested per plant not more than
seven days after flowering) were counted. Similarly, the diameter of mature fruits was
measured using a caliper square, and their weight using an electronic balance. These weights
were used to calculate yield according to the following formula [19]:
Yield (t/ha) =
M
SOP
(2)
Where: M = fruit mass (t) and SOP = surface area cultivated (ha).
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European Journal of Applied Sciences (EJAS) Vol. 12, Issue 1, February-2024
Statistical Analysis
Shapiro Will's homogeneity test was used to assess the distribution of mean values of okra
growth and yield parameters between treatments. When these averages were normally
distributed between treatments, the one-factor analysis of variance test was used to compare
the means and when they were different, the Duncan’s multiple range test was used to separate
them. On the other hand, when the distribution was abnormal, the comparison was made
possible by the non-parametric Kruskal Wallis (H) test.
RESULTS AND DISCUSSION
Effect of Sewage Sludge Amendment on Okra Growth
The growth trends of okra plants grown with various doses of sewage sludge are presented in
figure 2. The application of sewage sludge at doses of 10 t/ha (T1), 20 t/ha (T2) and 30 t/ha
(T3) resulted in average plant height of 51.73±4.8 cm, 53.80±5.2 cm and 51.54±4.5 cm
respectively all higher than those of the negative control T0 (no fertilizer) and the positive
control T4 (0.25 t/ha NPK (12-14-19)) which were 38.00 ± 5.1 and 45.42 ± 4.9 cm respectively.
Figure 2: Variation of okra plant height with different doses of treated sludge with time: T1 (10
t/ha); T2 (20 t/ha); T3 (30 t/ha); T0 (negative control) and T4 (positive control)
The evolution of the number of leaves on okra plants grown with the different treated sludge
doses and the controls are depicted on figure 3. Generally, there was an increase in leaf number
per plant over time with the different doses of treated sludge. However, after the 7th week of
plant growth, a decrease in leaf number was observed, due to leaf fall in all plants in general
(figure 3). At this time, the treatment T2 (20 t/ha) obtained higher average leaf number
(21±2.1) than the positive control T4 (0.25 t/ha NPK (12-14-19)) which was 20±1.9 leaves.
Senescence was observed from week 9 onwards in all treatments as the number of healthy
0
10
20
30
40
50
60
70
S2 S4 S5 S6 S7 S8 S9 S10
Plant height (cm)
Time (weeks)
T0 T1 T2 T3 T4
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Tiwa, J. M. F., Lekeufack, M., Edzigui, M. L. T., Fowoung, D., Tanetsa, A. E. M., Djiomou, A. C., & Fonkou, T. (2024). Growth and Yield Responses of
Okra (Abelmoschus Esculentus) Grown on Soil Amended with Dewatered Domestic Sewage Sludge in the West of Cameroon. European Journal of
Applied Sciences, Vol - 12(1). 38-52.
URL: http://dx.doi.org/10.14738/aivp.121.16195
positive control T4 (0.25 t/ha NPK (12-14-19)) with 10.67 ± 2.31 flower buds. However, after
the 8th WAS, a sharp drop in the number of flower buds was observed for all the treatments and
no flower buds were observed at 10th WAS. In fact, all flower buds had turned into flowers then
fruits by this time.
Figure 5: Variation of average flower buds per plant (a) and flowers per plant (b) of the okra
plants grown with different doses of treated sewage sludge with time
The variation in the average number of flowers on okra plants grown at various doses of
dewatered sludge with time are presented on figure 5b. The doses of 10 t/ha (T1), 20 t/ha (T2)
and 30 t/ha (T3) revealed a zigzag pattern of evolution of flower number per plant through the
flowering period of the okra plants. In fact, as new flowers bloomed, the old ones developed
into fruits, probably at different speeds. At the 8th WAS, the different okra plants treated with
dewatered sewage sludge had average number of flowers per plant higher than those the
negative control (T0) and positive control (T4). Treatment 20 t/ha (T2) produced a higher
average number of flowers on okra plants than the positive control T4 (0.25 t/ha NPK (12-14-
19)), i.e., 13 ± 0.6 / 10 ± 0.0 flowers per plant respectively.
The variation in average yield parameters of okra (A. esculentus) grown with the different doses
of treated sewage sludge are presented in figure 6. The okra plants grown with T1, T2 and T3
as well as the positive (T4) controls began to produce fruits at the 6th WAS (figure 6a). The
different sludge treatments produced more fruits than the positive and negative controls. The
highest number of fruits were produced with T2 (62 ± 3.79 fruits) followed by T3 (53 ± 12.74
fruits) while T1 had the least (50 ± 20.66 fruits).
All the treatments obtained mature okra fruits at the 7th WAS (figure 6b). At 10th WAS which
marked the end of the experiment, the treatments T2 and T3 remained the best in mature fruits
production with respect to the rest of the treatments including the positive control.