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Research Article
Contribution of Superabsorbent Polymers to Growth and Yield of
African Leafy Vegetables
Dorcas Ndunge Benard , J. P. O. Obiero , and D. O. Mbuge
Department of Environmental and Biosystems Engineering, University of Nairobi, P.O. Box 30197-00100, G.P.O, Nairobi, Kenya
Correspondence should be addressed to Dorcas Ndunge Benard; bndunge@uonbi.ac.ke
Received 15 February 2022; Revised 16 June 2022; Accepted 29 July 2022; Published 25 August 2022
Academic Editor: Othmane Merah
Copyright ©2022 Dorcas Ndunge Benard et al. is is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is
properly cited.
Superabsorbent polymers (SAPs) have been used as water-saving materials for limited irrigation water resources in arid and semi-
arid areas. e purpose of this study was to optimize SAP application dosage and irrigation intervals on the growth of African leafy
vegetables (ALVs) under greenhouse conditions. A factorial experiment was conducted under greenhouse conditions to de-
termine the optimal SAP application, dosage, and irrigation intervals for the growth and production of African leafy vegetables.
Two species of African leafy vegetables were studied: cowpea (Vigna unguiculata) and African nightshade (Solanum scabrum). e
experiment was performed in a randomized complete block design comprising 25 treatments: a factorial combination of five
superabsorbent polymer application doses (0 g, 0.5 g, 1 g, 1.5 g, and 2 g) SAP/Kg of soil substrate and five irrigation intervals (3
days, 4 days, 5 days, 6 days, and 7 days) with three replications. Statistical analysis of the results showed that the use of SAP in
irrigation can significantly promote the growth and yield of African leafy vegetables. SAP, irrigation, and their interactions
significantly affected (P<0.005) the plant height, stem diameter, leaf area, number of mature leaves/plant, and dry weight of leafy
vegetables. Treatment with SAP showed higher growth parameters and yield of vegetables compared to the treatments. Treatment
with 1 g SAP/kg of soil substrate and 5-day irrigation interval recorded the highest plant growth and yield, with 24%, 11.7%, 11.1%,
and 85.9% increase in cowpea plant height, leaf area, number of mature leaves, and dry weight/plant, respectively. e treatment
with 1 g SAP/kg of soil substrate and 5-day irrigation interval was observed as the best for the optimal production of African leafy
vegetables under greenhouse conditions. Hence, SAP could be a good strategy for food production within arid and semi-arid lands
where water resources are scarce.
1. Introduction
Water scarcity has been a global crisis over the years due to
the decline of annual rainfall levels and overexploitation of
renewable water resources [1]. Effects of climate change
coupled with the increasing water demand from the rapidly
growing population have escalated the water scarcity im-
pacts experienced all over the world. Irrigated agriculture
has been one of the coping strategies towards food security.
However, the water available for irrigation is limited and
therefore inadequate to meet the irrigation needs for crop
growth, especially within arid and semi-arid areas. Super-
absorbent polymers (SAP) have been used to conserve the
available irrigation water resources in arid and semi-arid
areas worldwide [2].
Superabsorbent polymers are cross-linked hydrophilic
networks that can absorb and retain 1000 times more water
than their original size and weight [3–5]. SAPs are synthetic
macromolecular materials that have high affinity and ac-
cumulation of water up to 100% of their own weight through
osmosis process [6]. Superabsorbent polymers can store a lot
of water in the hydrophilic networks owing to their high
swelling capacity [5]. Most SAPs are commonly produced
from acrylic acid, its salts, and acrylamide through solution
or inverse suspension polymerization processes. ey are
mostly made from the polymerization of acrylic acid blended
with sodium hydroxide in the presence of an initiator to form
a poly-acrylic acid and sodium salt, which is also referred to
as cross-linked sodium polyacrylate [7]. SAPs are classified
into two main categories, synthetic like petrochemical-based
Hindawi
Advances in Agriculture
Volume 2022, Article ID 8020938, 8 pages
https://doi.org/10.1155/2022/8020938
and natural—including polysaccharide and polypeptide-
based SAPs, and come in different forms including granules,
balls, and beads with varying sizes varying from coarse
powder to marbles [8]. For this research, polysaccharide-
based SAP granules were used.
SAPs have a wide range of applications including ag-
riculture, medicine, disposable diapers, feminine napkins,
and cosmetic due to their water absorption and retention
capacity [9]. In irrigation, superabsorbent polymers are used
as water-saving materials and soil conditioners that absorb
and retain water supply and release water slowly around the
root zone on demand. ey are used to reduce the loss of soil
water and increase crop yield [10]. SAPs are mostly used
within the arid and semi-arid areas of the world to control
water shortage issue [11].
SAPs enhance soil nutrient retention and water-holding
capacity, thus increasing irrigation water use efficiency [12–15].
Reference [16] concluded that the use of SAP in arid and semi-
arid regions can enhance soil properties and increases soil
water-holding capacity and soil water retention, thus im-
proving irrigation efficiency, increasing crop growth, and in-
creasing water productivity of the crop. Reference [17]
indicated that the use of SAP in light soils could increase its soil
water-holding capacity. Reference [1] concluded that using an
adequate amount of superabsorbent polymer increases the
yield of tomato in both deficit and full irrigation conditions.
Moreover, Ref. [9] indicated increased soil moisture retention
capacity and crop’s growth parameters with increased SAP
application, and the best results were as a result of the com-
bination of the highest SAP doses and the highest watering
capacity. Reference [18] reported that SAP and irrigation levels
have a significant effect on the available soil moisture, high
doses of SAP resulted in the highest water use efficiency, and
SAP application increased crop yields. With the recent massive
adoption of using SAP in irrigation, there is no clear data on the
right dosage for optimal growth and production of crops.
African leafy vegetables (ALVs) are known for their su-
perior nutritional value; they are rich in vitamins, minerals,
and trace elements. References [19, 20] stated that ALVs are
rich in numerous amounts of health-promoting compounds
that help in fighting against infectious diseases and mainte-
nance of good health. African nightshade leaves comprise 4.6 g
protein, 442 mg calcium, 12 mg iron, 8.8 mg vitamin A, and
131 mg vitamin C per 100 g of fresh weight. Cowpea contains
4.7 g protein, 152 mg calcium, 39 mg iron, 5.7 mg vitamin A,
and 57 mg vitamin C per 100 g of fresh weight [21]. However,
despite the known benefits of African leafy vegetables and the
increased campaigns towards their consumption, data on their
irrigation water requirements and irrigation scheduling are
still scanty or not available. is article focuses on the opti-
mization of superabsorbent polymers and irrigation intervals
on the growth and yield of African leafy vegetables (ALVs)
under greenhouse conditions.
2. Methods and Materials
2.1. Experimental Design. e study was conducted in a
greenhouse within Green Fingers Farm, located at latitude
1°21′29.1′′ south and longitude 38°01′16.7′′ east, in the years
2020 and 2021. e study was carried out as a factorial
experiment in a randomized complete block design (RCB)
comprising 25 treatments. e 25 treatments were a factorial
combination of five SAP application levels (0 g/pot (S
1
),
1.5 g/pot (S
2
), 3 g/pot (S
3
), 4.5 g/pot (S
4
), and 6.0 g/pot (S
5
)
concentrations of SAP) and five irrigation intervals (three
days (I
1
), four days (I
2
), five days (I
3
), six days (I
4
), and seven
days (I
5
)). Each treatment was done in three replicates, and
each replicate consisted of one pot. SAP used was poly-
saccharide-based SAP in form of granules. e African leafy
vegetables (ALVs) studied were cowpea (Vigna unguiculata)
and African nightshade (Solanum scabrum). Each pot
contained three (3) kilograms of soil substrate prepared by
mixing soil and chicken manure in the ratio of 3 :1, and SAP
granule doses according to the experimental design. Based
on the number of treatments and their corresponding
replicates, 150 planting pots were used for the experiment.
e drip irrigation method was used as the irrigation water
application technique for the project. e project’s experi-
mental design is presented in Table 1.
Note. S—SAP. I—irrigation frequency.
C
—Cowpea.
N
—African nightshade.
2.2. Soil Study. ree (3) soil samples were randomly col-
lected from three (3) different locations inside and outside
the greenhouse and from a depth of 0–20 cm and taken to
the lab for physical and chemical quality analysis. Soil
analysis was carried out for its classification, pF, saturated
hydraulic conductivity (Ksat), and chemical composition.
e soils were air-dried for 48 hrs, and crushed and sieved
through a 2-mm sieve before lab analysis. Potassium (K) and
sodium (Na) levels were determined by leachates using flame
photometer (Na and K), whereas calcium (Ca) and mag-
nesium (Mg) by atomic absorption spectrophotometer (Ca
and Mg). Electrical conductivity (EC) was done using a
conductivity bridge meter. e nitrogen (N) level in the soil
is measured by using the Kjeldahl method [22]. Phosphorus
(P) was extracted using the Olsen method, and the soil
texture was determined using the Bouyoucos hydrometer
method [23].
2.3. Crops’ Management. e pots were filled with equal
volumes of sandy clay loam soil substrate (3 kilograms)
prepared by mixing soil and chicken manure in the ratio of
3 : 1. SAP concentrations were applied to each pot accord-
ingly and mixed with the soil substrate properly and the pots
arranged in the greenhouse accordingly and appropriately
with a spacing of 40 cm along the rows. Planting for both
vegetables was performed by direct sowing in the prepared
pots. e drip irrigation method was used as the irrigation
water application technique for the study. Irrigation oper-
ation was carried out each day in different irrigation in-
tervals of 3, 4, 5, 6, and 7 days based on the experimental
design. Five seeds of cowpeas were planted per pot. Irri-
gation was applied uniformly to the treatments on the
planting date for the vegetables and varied thereafter
according to the irrigation interval treatments. inning was
performed 14 days after sowing to maintain three (3) plants
2Advances in Agriculture
per pot for cowpeas, whereas for African nightshade,
thinning was performed 30 days after sowing to maintain
four (4) plants per pot.
2.4. Data Collection. e key crops’ growth parameters
studied included the height of the plant, diameter of the
stem, number of mature leaves per plant, and mature leaf
area. Two plants per pot were randomly identified and
marked for monitoring. Measurements of the key crops’
growth parameters were carried out on the identified plants
once a week over the growth period. e plant height was
measured from the plant base to the apex using a tape
measure, whereas the diameter of the stem was measured at
the plant base using a Vernier caliper. e number of mature
leaves per plant was determined by physically counting the
leaves. e leaf area was determined by measuring the
longest point (length) and the broadest point (width) of the
leaf using tape measure [24]. Leaf area (A) was estimated
using the following equation:
AL�L×W, (1)
where A
L
is the leaf area (m
2
), Llength (m), and Wwidth
(m).
e number of leaves, size of the leaves, plant height, and
diameter were monitored once every seven days on each pot
for 5 weeks (starting at 5 weeks after planting for African
nightshade and at 2 weeks after planting for cowpeas).
Harvesting of African nightshade was performed at 13
weeks from planting by removing the whole plant from the
pots. Harvesting of cowpeas was performed in two states:
wet state and dry state. For the wet state, harvesting was
performed at 12 weeks from planting by removing the whole
plant from the pots, whereas the dry state (when the pods
and the entire plant were dry) harvesting was performed at
13 weeks from planting by plucking the dry pods. Weights in
the wet state for the entire plant, leaves, and pods were
measured after harvesting using a weighing scale.
e harvest was oven-dried at a temperature of 50°C in the
Food and Processing Laboratory in the Department of En-
vironmental and Biosystems Engineering, University of Nai-
robi. After drying, the weight in the dry state of the leaves and
pods was also measured using a weighing scale. e number of
pods per plant and seeds per plant were also counted.
3. Results and Discussions
3.1. Soil Analysis. e soils are classified as sandy clay loam
with neutral pH values ranging from 6.70 to 6.86 as pre-
sented in Table 2. is range of soil pH is recommended for
irrigation as it is considered to have the maximum avail-
ability of most macronutrients that are essential for plant
growth and yield [25]. e soils showed low total nitrogen
percentage of less than 0.2%. Chicken manure was added to
the soil to fix low nitrogen percentage. e addition of
chicken manure to the soil increases the level of nitrogen and
potassium nutrients [26]. Organic carbon is a measure of soil
organic matter and is very important in agricultural soils.
e recommended range for soil organic carbon percentage
is 2.5 to 4%. e soils showed low to moderate percentage of
organic carbon ranging from 1.3% to 1.5%. However, the
addition of chicken manure also increases the levels of
organic carbon in the soil. Phosphorous and potassium
contents were ranging from 75.2 to 82.8 ppm, and 0.2 to
0.38 cmol/kg soil, respectively. is is considered sufficient
for plant growth.
3.2. Statistical Analysis. Statistical analysis of variance
(ANOVA) of the results was performed at 95% confidence
interval using Microsoft Excel 2016. Two-way ANOVA with
three replications was used to assess the effect of superabsorbent
Table 1: Field layout of the experimental design.
IRRIGATION LEVELS
I1(3 days) I2 (4 days) I3 (5 days) I4 (6 days) I5 (7 days)
SAP
DOSAGE
LEVELS
S1
(0 g/Pot)
S2
(1.5 g/Pot)
S3
(3 g/Pot)
S4
(4.5 g/Pot)
S5
(6 g/Pot)
S1I1C
S1I1N
S2I1C
S2I1N
S3I1C
S3I1N
S4I1C
S4I1N
S5I1C
S5I1N
S1I2C
S1I2N
S2I2C
S2I2N
S3I2C
S3I2N
S4I2C
S4I2N
S5I2C
S5I2N
S1I4C
S1I4N
S2I4C
S2I4N
S3I4C
S3I4N
S4I4C
S4I4N
S5I4C
S5I4N
S1I5C
S1I5N
S2I5C
S2I5N
S3I5C
S3I5N
S4I5C
S4I5N
S5I5C
S5I5N
S1I3C
S1I3N
S2I3C
S2I3N
S3I3C
S3I3N
S4I3C
S4I3N
S5I3C
S5I3N
Key :
Cowpea Treatment
African nightshade Treatment
Note:
S - SAP
I - Irrigation Frequency
C - Cowpea
N - African nightshade
Advances in Agriculture 3
polymer (SAP) on growth parameters and yield of ALVs for
different SAP levels and irrigation frequencies. e statistical
analysis indicated that the effect of various levels of superab-
sorbent polymer and irrigation frequencies were significant for
African leafy vegetables’ plant height, stem diameter, leaf size,
number of leaves per plant, and yield.
3.3. Effect of Superabsorbent Polymers on ALVs’ Growth
Parameters
3.3.1. Cowpea. For cowpea, significant effects of superab-
sorbent polymers, irrigation, and their interactions
(P<0.05) on plant height, stem diameter, and number of
mature leaves are observed as shown in Table 3. However,
there were no significant effects (P>0.05) of superabsorbent
polymers and irrigation on leaf area. Irrigation frequency
had higher significant effects (P<0.05) on the vegetable’s
plant height, stem diameter, and number of mature leaves. A
significant interaction effect of the interaction of SAP and
irrigation interval on plant height and the number of mature
leaves was also observed.
High significant effect of SAP, irrigation, and their in-
teraction (P<0.05) on plant height, leaf area, and number of
mature leaves was recorded in the first 21 days from
emergence as presented in Table 4.
Under S
1
(no SAP) treatment, the highest cowpea plant
height, stem diameter, leaf area, and number of mature
leaves per plant were 53.6 cm, 2.5 cm, 0.94 cm
2
, and 9, re-
spectively, whereas for S
2
treatment, the highest plant height,
stem diameter, leaf area, and number of mature leaves per
plant were 57.9 cm, 2.4 cm, 0.98 cm
2
, and 10, respectively.
Under S
3
treatment, the highest plant height, stem diameter,
leaf area, and number of mature leaves per plant were
66.7 cm, 2.5 cm, 1.05 cm
2
, and 10, respectively. For S
4
treatment, the highest plant height, stem diameter, leaf area,
and number of mature leaves per plant were 57.3 cm, 2.5 cm,
0.99 cm
2
, and 10, respectively, and for S
5
treatment, the
highest plant height, stem diameter, leaf area, and number of
mature leaves per plant were 52.2 cm, 2.5 cm, 0.89 cm
2
, and
10, respectively. e highest cowpea plant height, plant stem
diameter, and leaf area were recorded under treatment S
3
I
3
(3 g of SAP per pot and 5-day irrigation interval) as pre-
sented in Figure 1. e lowest cowpea plant height, plant
stem diameter, leaf area, and number of mature leaves per
plant were recorded under treatment S
1
I
1
. e difference
between all treatments with SAP and the treatments without
SAP is significant. Treatments with varying doses of SAP
recorded higher growth parameters compared to the
treatments without SAP. is means that superabsorbent
polymers promote crop growth and development as dis-
cussed in Ref. [27]. For optimal crop production, SAP
application dosage should be up to an optimal level. Ex-
cessive superabsorbent polymer application dosage can lead
to soil water logging, hence stunted growth and low yields.
3.3.2. African Nightshade. ere were no significant effects
of SAP, irrigation, and the interaction of SAP and irrigation
(P>0.05) on plant height. Irrigation showed high signifi-
cance (P<0.05) on stem diameter, leaf area, and number of
mature leaves per plant as presented in Table 5. However,
like cowpea, high significant effects of SAP, irrigation, and
their interaction (P<0.05) on plant height, leaf area, stem
diameter, and number of mature leaves were recorded in the
first 21 days from emergence.
Significant difference between all treatments with SAP
and the treatments without SAP was recorded for African
nightshade growth. e highest plant height, stem diameter,
leaf area, and number of mature leaves per plant were
recorded under Treatment S
3
I
3
(3g of SAP per pot and 5-day
irrigation interval) as 51 cm, 2.7 cm, 1.92 cm
2
, and 16, re-
spectively. e lowest were recorded under S
1
I
1
treatment as
34.6 cm, 2.4 cm, 1.52 cm
2
, and 10, respectively, as shown in
Figure 2.
e results showed that an interaction of SAP appli-
cation and irrigation can promote the growth of vegetables.
is agreed with the study of Ref. [15], which indicated that
the application of SAP increases plant height, leaf area
index, and dry matter. In all irrigation intervals, the ap-
plication of SAP enhanced plant vegetative growth pa-
rameters including height, stem diameter, leaf area, and
number of mature leaves per plant. SAPs enhance the
water- and nutrient-holding capacity of soil lending them
continuously available at the root zone for optimal ab-
sorption by plants, hence better plant performance. Su-
perabsorbent polymers increase plant height [28], as
indicated in the results of this research.
3.4. Effect of Superabsorbent Polymers on the Yield of ALVs.
Reference [2] indicated that dry matter is a vital measure of
crop growth and yield. Dry matter yield is an important
indicator of fertilizer efficiency [29]. Dry weight of leaves
and pods of the African leafy vegetables was considered in
yield determination.
3.4.1. Cowpea. SAP, irrigation, and their interactions
demonstrated significant effects (P<0.05) on the dry weight
of cowpea as presented in Table 6. Irrigation showed a
significant effect on the number of pods per plant. However,
there was no significant effect on the number of seeds per
pod. e highest dry matter yield for cowpea was recorded
under treatment S
3
I
3
as 171 g/plant, whereas the lowest yield
Table 2: Physico-chemical properties of soil.
Site pH (H
2
O) %N%O.C. K (cmol/kg) P (ppm) EC (ds/m) Bulk density (g/cm
3
) Porosity K
Sat
(cm/hr)
1 6.86 0.09 1.31 0.38 75.2 0.14 1.40 47.3 3.82
2 6.70 0.16 1.50 0.20 80.5 0.18 1.43 46.1 3.47
3 6.78 0.12 1.40 0.26 82.8 0.14 1.46 45.0 3.15
4Advances in Agriculture
0
2
4
6
8
10
12
14
16
18
S1 S2 S3 S4 S5
SAP LEVELS
Plant Height × 10² [mm]
Stem Diameter × 10 [mm]
Leaf Area × 10 [mm²]
No. of Mature Leaves/Plant [-]
Yield/Pot × 10 [g]
y =-1.3231x2 + 9.1486x
Figure 1: Effect of SAP on the growth and yield of cowpea.
Table 3: ANOVA for dependent variables and their interaction with cowpea plant at 95% confidence level.
Source of variation P-values at 95% confidence level
Plant height Stem diameter Leaf area (ns) No. of mature leaves/plant
SAP 0.145
ns
0.428
ns
0.455 0.275
ns
Irrigation 0.001∗<0.001∗0.083 <0.001∗
SAP ×irrigation <0.001∗0.5457
ns
0.314 0.001∗
∗Represents significance at 0.05 confidence level.
ns
represents nonsignificance.
Table 4: Variation of ANOVA over 32 days of cowpea plant from emergence.
No. of days from emergence Source of variation P-values at 95% confidence level
Plant height Stem diameter Leaf area No. of mature leaves/plant
14 days
SAP <0.001∗0.056
ns
<0.001∗0.004∗
Irrigation <0.001∗0.085
ns
<0.001∗<0.001∗
SAP ×Irrigation 0.007∗0.542
ns
0.061
ns
<0.001∗
21 days
SAP 0.010∗<0.001∗0.279
ns
0.059
ns
Irrigation 0.008∗0.164
ns
0.304
ns
0.002∗
SAP ×Irrigation 0.388
ns
0.115
ns
0.307
ns
0.070
ns
28 days
SAP 0.857
ns
0.064
ns
0.084
ns
0.421
ns
Irrigation 0.020∗0.008∗0.078
ns
<0.001∗
SAP ×Irrigation 0.091
ns
0.321
ns
0.149
ns
0.042∗
35 days
SAP 0.199
ns
0.987
ns
0.429
ns
0.141
ns
Irrigation 0.065
ns
<0.001∗0.025∗<0.001∗
SAP ×Irrigation 0.005∗0.522
ns
0.085
ns
<0.001∗
32 days
SAP 0.066
ns
0.779
ns
0.704
ns
0.176
ns
Irrigation <0.001∗<0.001∗0.323
ns
<0.001∗
SAP ×Irrigation <0.001∗0.336
ns
0.698
ns
0.028∗
∗Represents significance at 0.05 confidence level.
ns
represents nonsignificance.
Advances in Agriculture 5
was recorded as 92 g/plant under treatment S
1
I
1
as presented
in Figure 1. e difference between the treatments with SAP
dosage and those without was significant.
3.4.2. African Nightshade. Significant effects of SAP doses
(P<0.05) on African nightshade yield were observed. Irri-
gation and the interaction of SAP and irrigation showed no
significant effects on the yield as presented in Table 7. e
greatest effect on African nightshade yield was demonstrated
in treatment with S
3
I
3
(3 g of SAP per pot and 5-day irrigation
interval). e highest dry weight of African nightshade leaves
was recorded under treatment S
3
I
3
as presented in Figure 2.
e interaction of superabsorbent polymers and irri-
gation showed a significant effect on the yield of African
leafy vegetables as indicated in similar studies [2, 30, 31].
An overall ANOVA indicated that the use of super-
absorbent polymers in irrigation significantly affected
plant height, stem diameter, leaf area, number of mature
leaves per plant, and dry matter yield. Superabsorbent
polymers absorb and retain irrigation water for longer
periods and release it to the crop roots when needed, thus
reducing the effects of water deficit in crops [17, 27, 32].
Treatment with superabsorbent polymers showed higher
growth parameters and yield of both vegetables compared
to the treatments. Treatment S
3
I
3
(3 g of superabsorbent
polymer per 3 kilograms of soil substrate and 5-day ir-
rigation interval) recorded the highest plant growth and
yield compared to all other treatments. For instance, S
3
I
3
treatment in cowpea recorded 24%, 11.7%, 11.1%, and
85.9% increase in plant height, leaf area, number of
mature leaves, and dry weight per plant in comparison
with no SAP and 3-day irrigation interval treatment (S
1
I
1
).
Treatment S
3
I
3
was observed as the best for optimal
production of African leafy vegetables under greenhouse
conditions.
Table 6: ANOVA for dependent variables and their interaction on cowpea plant yield at 95% confidence level.
Source of variation P-values at 95% confidence level
Dry weight No. of pods/plant No. of seeds/pod (ns)
SAP 0.013∗0.991
ns
0.330
Irrigation 0.009∗0.007∗0.118
SAP ×irrigation 0.002∗0.154
ns
0.499
∗Represents significance at 0.05 confidence level.
ns
represents nonsignificance.
y = -0.705x2+ 5.0249x -3.8491
0
2
4
6
8
10
12
14
16
18
20
S1 S2 S3 S4 S5
SAP LEVELS
Plant Height × 10² [mm]
Stem Diameter × 10 [mm]
Leaf Area × 10 [mm²]
No. of Mature Leaves/Plant [-]
Yield/Pot × 10 [g]
Poly. (Yield/Pot × 10 [g])
Figure 2: Effect of SAP on African nightshade growth and yield.
Table 5: ANOVA for dependent variables and their interaction with African nightshade plant at 95% confidence level.
Source of variation P-values at 95% confidence level
Plant height (ns) Stem diameter Leaf area No. of mature leaves/plant
SAP 0.094 0.280
ns
0.118
ns
0.068
ns
Irrigation 0.086 0.004∗0.011∗0.012∗
SAP ×irrigation 0.621 0.389
ns
0.777
ns
0.046
ns
∗Represents significance at 0.05 confidence level.
ns
represents nonsignificance.
6Advances in Agriculture
4. Conclusions and Recommendations
Use of superabsorbent polymers in irrigation significantly
promotes the growth and yield of African leafy vegetables.
Incorporation of superabsorbent polymers in soil substrate
increases plant height, plant stem diameter, leaf area, and dry
biomass of leafy vegetables. Treatment with superabsorbent
polymers showed higher growth parameters and yield of
both vegetables as compared to the treatments.
Although different superabsorbent polymer doses
showed an increase in the growth of African leafy vegetables,
treatment S
3
I
3
(1g SAP/kg of soil substrate and 5-day ir-
rigation interval) showed better plant performance than all
other treatments. Treatment S
3
I
3
was observed as the best for
optimal production of African leafy vegetables under
greenhouse conditions. Hence, superabsorbent polymers
could be a good strategy for food production within arid and
semi-arid lands where water resources are scarce.
Further studies on superabsorbent polymers’ longevity
in the soil and their effects on the growth and production of
crops after repeated use on the same soil substrate should be
carried out.
Data Availability
e data used to support the findings of this study are
available from the corresponding author upon request.
Conflicts of Interest
e authors declare that they have no conflicts of interest or
personal relationships that could have appeared to influence
the work reported in this article.
Acknowledgments
is work was funded by the National Drought Management
Authority (NDMA) of Kenya (grant number NDMA/EDE
DRMC/006/2019-2020). e authors would like to ac-
knowledge and thank the National Drought Management
Authority (NDMA) of Kenya for funding the research, and
Elizabeth Kyalo of Green Fingers Farm for the use of her
farm for this research. e authors thank Joseph Musyoki,
Victor Munyau, and Bonface Muliro for their technical
support.
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