ARID ZONE JOURNAL OF ENGINEERING, TECHNOLOGY & ENVIRONMENT
AZOJETE March 2020. Vol. 16(1):28-36

Published by the Faculty of Engineering, University of Maiduguri, Maiduguri, Nigeria.
Print ISSN: 1596-2490, Electronic ISSN: 2545-5818

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Corresponding author’s e-mail address: mo.omobowale@ui.edu.ng 28

28

ORIGINAL RESEARCH ARTICLE

EVALUATION OF A LOW-COST GREENHOUSE FOR CONTROLLED ENVIRONMENT
CULTIVATION OF SWEET PEPPER

M. O. Omobowale
(Department of Agricultural and Environmental Engineering
Faculty of Technology, University of Ibadan, Ibadan, Nigeria)

* Corresponding author’s email address: mo.omobowale@ui.edu.ng

1.0 Introduction
Climate change as well as continuous increase in population has necessitated the need for
highly productive agriculture (Lutz, 2017). Climate change is one of the most serious
environmental and human threats undermining the achievement of agricultural production in
almost every part of the world. It is a real threat to lives and livelihoods as well as to the
environment (Stephenson et al., 2010). If food security will be attained, technologies that
minimize external threats to crops and increase crop production are needed. One major way of
providing efficient agriculture while preserving the quality of the environment is through

ARTICLE INFORMATION ABSTRACT
Sustainable agriculture is critical towards paving a way for year-round
production and supply of food all year round. Cultivation of fruits and
vegetables are vital due to high demand and nutritional values it provides
to consumers. The rising global population especially in developing
countries require other alternatives for sustainable crop production.
Cultivation in controlled environments using functional and durable
greenhouse structures presents an option. A low-cost greenhouse was
designed and constructed in Ibadan, Nigeria using locally available
materials was evaluated. Afrormosia wood was used in constructing the
frame while polyethylene of 2.5 mm thickness was used as sheathing
material for the walls. The floor which covered an area of 24 m2 was made
of porous concrete of batching mixture 1:4 (cement to gravel) while the
wall was 4 m high. Ventilation was passive with a vent area equal to 25%
of total surface area; made up of 20% at the wall area and 5% as the roof
vent. The roof was pitched at a 18° slope to allow easy drainage of rain
water. Sweet pepper (Capsicum annuum, Cabernet) seeds procured
Burpee Seeds USA were cultivated with the aid of planting pots within the
greenhouse in comparison with those planted in the open field for a
duration of eight weeks. Evaluation was based on crop growth and yield
parameters correlated with solar radiation, temperature and relative
humidity in the greenhouse and ambient environments, respectively
using randomized complete block design. Data were subjected to
descriptive and correlation analysis. Peak temperature and RH were
31.1°C and 91.1% respectively within the greenhouse in comparison with
29.7°C and 89.7% respectively outside. Peak solar radiation was 413.4
W/m2 in the greenhouse compared to 690.3 W/m2 in the ambient.
Growth parameters showed that the crops in the greenhouse performed
optimally when compared with plants in the open field with a yield of
18.1 t/ha in the greenhouse compared with no-yield recorded in the open
field. Utilization of greenhouses in crop cultivation can help to mitigate
the problem of food shortage.

© 2020 Faculty of Engineering, University of Maiduguri, Nigeria. All rights reserved.

Submitted 11 February, 2019
Revised 20 April, 2019
Accepted 25 April, 2019

Keywords:
Microclimate
Greenhouse
Temperature
Relative Humidity
Sweet pepper.

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greenhouse cultivation. Greenhouse allows for the manipulation of essential variables such as
temperature and relative humidity to achieve optimal crop production.

Controlled environment agriculture (CEA) is the alteration of the environmental conditions to
achieve a desired conducive environment for crop and animal production. Cultivation of crops
in greenhouses can be independent of environmental conditions, thereby boosting the
possibilities of multiple harvest as compared to the seasonal open field agriculture. Controlled
environment agriculture is a technology-based approach toward food production Albright
(1990) with the aim of providing a protected environment for crop growth while maintaining
optimal growing conditions throughout all developmental stages. Forms of controlled
environment agriculture include hydroponics, aeroponics, aquaculture and aquaponics. The
benefits of controlled environment are numerous and far reaching and include, high volume of
local food production in urban and exurban environments on a year-round basis, optimal
growth conditions that eliminate the need for chemical fertilizers and harmful pesticides,
controlled nature of food production significantly reduces water use and protects water quality.
Generally, greenhouses are defined as structures used to control environmental conditions for
different crop cultivations (Mijinyawa and Osiade, 2011). Although, climatic conditions affect
crop production in the open field, the effects are limited in a controlled environment facility
because greenhouses are built to provide a conducive environment irrespective of climatic
conditions (Jones and Harrison, 2004; Gorjian et al., 2011). It has also been reported that the
application of greenhouse technology is economical on the long run in planting different crops,
both in small and large-scale production (Cook and Calvin, 2005).

Interestingly, within a greenhouse, structural, mechanical, nutritional, and micro-climatic
conditions are optimized to achieve the desirable crop growth (Connellan, 2002, Shamshiri et al.,
2018). Geometry, dimensions, and roof characteristics; reduction of solar intensity using shades
and vents; forced air circulation and evaporative cooling are manipulated to achieve optimal air
temperature, relative humidity and illumination (Ponjican et al., 2011). These factors are vital in
achieving productive and sustainable crop cultivation in a greenhouse. Ali et al. (2012) reported
that the production of horticultural crop provides more job opportunities per hectare of
production in comparison to cereal crop. A good perspective of increased employment
opportunities can be observed from the gradual shift of cereal production to high value
horticultural crops such as tomatoes in some parts of the world (Rao et al., 2003, Ibeawuchi et
al., 2015).

Babatola (2004) highlighted some challenges facing the agricultural sector such as poor
extension services, land tenure, limited planting materials, low technology application, and
limited postharvest facility. Crop cultivation in greenhouses is a viable option towards increasing
crop production. Modern and conventional greenhouses are expensive to set up. The
development of greenhouses from locally available materials will be a welcome development.
This paper provides details of the design, construction, and evaluation of a low-cost greenhouse
for cultivation of sweet pepper.

2. Methodology
2.1 Design
The design considerations were based on possible external and internal loads on the structure,
materials of construction, durability, rigidity, and microclimatic conditions. The construction site
is a swampy reclaimed soil with laterite. The site is water-logged in the rainy season with high

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Omobowale: Evaluation of a Low-Cost Greenhouse for Controlled Environment Cultivation of Sweet Pepper. AZOJETE,
16(1):28-36. ISSN 1596-2490; e-ISSN 2545-5818, www.azojete.com.ng

Corresponding author’s e-mail address: mo.omobowale@ui.edu.ng 30

water-table. Moreover, the unproductive nature of the area made the location a good ground
for greenhouse evaluation. Adequate natural ventilation was provided with a vent of about 25%
of the wall area.

Afrormosia lumber (known locally as Ayin wood) material was used in the construction of the
greenhouse frame due to its durability, hardness, workability, and ready availability. The
following parameters were utilized in the design of the greenhouse according to Mijinyawa
(2012), based on green grade moisture content of 40%; permissible bending stress parallel to
grain (11.2 N/mm2), permissible shear stress (1.4 N/mm2), compression parallel to grain (9.0
N/mm2), modulus of elasticity, E (13,200 N/mm2) and density (650 kg/m3). All structural
components which made up the frame (purlins, rafters, beams, and columns) were designed
using standard procedures. Wind load was calculated from the expression q = 0.0127 × V2 × k
(where q = velocity pressure in N/m2, V = wind velocity in m/s and k is a constant relating to the
height of the building in m, FAO, 2011). Some of the other design parameters adopted are
given in Table 1.

Table 1: Design parameter and values of the greenhouse structure
S/N Parameters Values
1 Greenhouse dead-load, w 15.9 N/m
2 Wind load, q 4.24 N/m2
3 Polythene covering density (low range) 0.925 kg/cm3
4 Polythene thickness covering 2 mm
5 Slope angle of roof 18°
6 Bending and allowable stress of purlin 0.56 N/mm2; 11.20 N/mm2
7 Maximum bending moments for beam 43.1 Nm;
8 Greenhouse floor area 24 m2
9 Total roof vent area 2.16 m2
10 Length of greenhouse 6 m

2.2 Construction
The frame of the greenhouse was constructed using 100 by 100 mm wooden columns, installed
400mm into the foundation slab. The floor was constructed using concrete grade C20 (mixing
ratio 1:3:5) as recommended by FAO, (2011) and a black coloured plastic film was incorporated
as the damp-proof course (DPC) level as in Figure 1. The floor had a gentle slope of about 5° to
allow efficient water drainage. A transparent plastic sheet (polyethylene) of 2 mm thickness was
used as the covering material (Figure 2). It was selected because it is cheap, readily available,
has good light transmittance and easy to use. This was achieved through the provision of top
and side vents across the length of the greenhouse. The side vents were 1 by 6m while the tope
vents were 0.2 by 6m in dimension, to allow cool air to flow through the side vents driving warm
air out through the roof vents.

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Figure 1: The Greenhouse floor at the DPC
level

Figure 2: Greenhouse Covering the greenhouse

2.3 Evaluation
Temperature and relative humidity profiles were monitored in the greenhouse after which an
evaluation was carried out by cultivating sweet pepper (Capsicum annuum, Cabernet). The seeds
were obtained from Burpee Seed Company, USA and raised in the nursery for four weeks. The
seedlings were thereafter transplanted from the nursery to the greenhouse on the 10th of
September 2016 into 33 plastic pots with a volume of 10 liters each (Figure 3). Sandy-loam soil
was obtained, and thoroughly mixed and foreign materials removed. The mixed soil was then
filled into the plastic pots and watered to set before transplanting. Nitrogen-Phosphorus-
Potassium (NPK) fertilizer (15:15:15) was applied on the soil; the first application was performed
two weeks after transplanting while the second application was performed three weeks later.
The transplanted seedlings were adequately watered and monitored for any development. The
control experiment was set up in an open field beside the greenhouse and the pepper seedlings
were transplanted and monitored. Crop performance (plant height, number of leaves, leaf area
index and yield) were measured and recorded.
Plant height was measured from the base of the soil to the collar of the uppermost leaf using a
ruler. Five plants per row were sampled for crop performance parameters on a weekly basis.
These were also measured for the control experiment. The leaf area was traced out on graph
paper to measure area. From this measurement, this surface area and leaf area index were
estimated by the formula:

Leaf Area index (LAI) =
SA
LA (1)

where: LA is the Leaf Area and SA is the Soil surface area covered by the plant.
Temperature and relative humidity data loggers (Lascar EL-USB 2 model, Lascar Electronics, USA)
were placed inside and outside the greenhouse to record both ambient and greenhouse
conditions. The data loggers were set to read at every one-hour interval. A light meter (Solar
Power Meter SM-206) was also used to record the light intensity entering the greenhouse daily
while a digital weighing scale (Accuris Instruments W3300 with a capacity of 10 kg, 1 decimal
place) was used to measure the weights of the harvested pepper. Data collected were subjected
to correlation and descriptive statistics.

3. Results and Discussion
3.1 Temperature and Relative Humidity Trends
Ambient and greenhouse temperature trends during the two-month evaluation period are
shown in Figure 3. The greenhouse had a peak temperature of 31.1°C while that of the ambient

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Omobowale: Evaluation of a Low-Cost Greenhouse for Controlled Environment Cultivation of Sweet Pepper. AZOJETE,
16(1):28-36. ISSN 1596-2490; e-ISSN 2545-5818, www.azojete.com.ng

Corresponding author’s e-mail address: mo.omobowale@ui.edu.ng 32

temperature was 29.7°C. Expectedly, greenhouse temperatures were higher than that of the
ambient as radiant energy from the sun heats up the structure and part of the heat is trapped
within. The temperature ranged between 26.5 to 31.1°C in the greenhouse throughout the
entire growing period. This is considered suitable for sweet pepper production, which is known
to perform well within maximum air temperature up to 35°C (Kittas et al., 2005). Similarly,
relative humidity (RH) data showed that the greenhouse had a peak RH of 91.1% while that of
the ambient RH was 80.4% (Figure 4). Moreover, RH within the greenhouse was consistently
higher than that of the ambient which can be attributed to the consistent application of water
within the structure to meet the crop water requirements of the plants (Omid and Shafei, 2005).

Figure 3: Mean daily temperature trends in the greenhouse and ambient environment

Figure 4: Daily relative humidity trends in the greenhouse and ambient environment

3.2 Solar Radiation
The peak solar radiation within the greenhouse was 413.4 W/m2 while that of the ambient was
690.3 W/m2. Ambient solar radiation was consistently higher than that of the greenhouse is due
to the direct radiation from the sun, unlike the greenhouse where part of the solar radiation is
diffused as it passes through the covering material (polythene). The relatively low-cost covering
material was however suitable as it allowed sufficient solar radiation needed for photosynthesis
into the greenhouse (Figure 5).

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Figure 5: Daily solar radiation trends in the greenhouse and ambient environment

3.3 Crop Performance
Sweet pepper planted in the greenhouse performed better throughout the period of evaluation
compared to the open field crops. Comparison between mean plant height, number of leaves
and leaf area of crops in greenhouse and open field at the end of the evaluation were 200.0 ±
17.6 and 89.5 ± 18.3 mm, 30.7 ± 7.87 and 10.8 ± 2.58 and 28.0 ± 8.67 and 7.4 ± 2.12 mm2
respectively (Figures 6-8). Similar results were reported by Priya et al. (2002) in sweet pepper.
Moreover, within the greenhouse, mean stem diameter, leaf girth, root depth and shoot height
were 4.21 ± 0.57 mm, 61.7 ± 18.29 mm, 126.1 ± 37.14 mm and 182.0 ± 48.32 mm respectively
(Figure 9). A total mass of 1,874.5g of sweet pepper fruit was harvested from the greenhouse,
equivalent to 18.1 t/ha when the soil surface area in the greenhouse is considered. Typical yields
of sweet pepper ranges between 10 to 30 t/ha (Stoffella et al.,1995; Alsadon et al., 2013;
Dagnoko et al., 2013). In contrast, the open field crops yielded no fruits in addition to the fact
that the crops were stunted (Figure 10). These results agree with the findings of Papadopoulos
and Ormrod (1991).

Number of weeks after transplanting

2WAT 3WAT 4WAT 5WAT 6WAT  7WAT 8WAT

Pl
an
t H
eig
ht
 (c
m
)

0

5

10

15

20

25

Greenhouse
Open Field

Number of weeks after transplanting

1WAT 2WAT 3WAT 4WAT 5WAT 6WAT 7WAT

N
o 
of
 L
ea
ve
s

0

5

10

15

20

25

30

35

Greenhouse
Open Field

Figure 6: Mean plant height under green house
and open field cultivation

Figure 7: Mean leaf count under green
house and open field cultivation

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Omobowale: Evaluation of a Low-Cost Greenhouse for Controlled Environment Cultivation of Sweet Pepper. AZOJETE,
16(1):28-36. ISSN 1596-2490; e-ISSN 2545-5818, www.azojete.com.ng

Corresponding author’s e-mail address: mo.omobowale@ui.edu.ng 34

Figure 8: Mean leaf area under green house
and open field cultivation

Figure 9: Crop Parameters within the Greenhouse

Figure 10: Greenhouse and open field sweet pepper 7 weeks after transplanting

4. Conclusion
This study evaluated the performance of sweet pepper grown in a low-cost greenhouse in
comparison with field growth conditions in an agriculturally unproductive soil. The greenhouse
crops showed increased plant height, number of leaves and leaf area index, which translated
into increased yield. Observations confirmed that in the greenhouse, there is reliability of yield
which shows the possibility of year-round production in an unproductive environment. The high
performance observed in crops grown in the greenhouse is attributed to improved leaf
physiology (i.e. increased number of stomata) and adequate photosynthesis. Moreover, the
micro-climate within the greenhouse was adequate for the crops to survive. However, due to
the nature of the soil in the open field experimented, crop performance was extremely poor.
This study recommends further work to evaluate performance using other crops across different
seasons of the year with different water application regimes. Performance under ventilated
conditions should also be considered. Advocacy to farmers living close to poor agricultural or
degraded soils on the potentials of low-cost greenhouses should also be intensified.

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