Vol.4, No.11, 577-584 (2013) Agricultural Sciences
http://dx.doi.org/10.4236/as.2013.411078
Microclimate modification using eco-friendly nets
and floating row covers improves tomato
(Lycopersicon esculentum) yield and quality for
small holder farmers in East Africa
Mwanarusi Saidi1, Elisha O. Gogo1, Francis M. Itulya1, Thibaud Martin2,3, Mathieu Ngouajio4*
1Department of Crops, Horticulture and Soils, Egerton University, Egerton, Kenya;
2CIRAD UR Hortsys, Avenue Agropolis, Montpellier, France
3Icipe, Plant Health Department, Nairobi, Kenya
4Department of Horticulture, Michigan State University, East Lansing, USA;
*Corresponding Author:
Received 19 May 2013; revised 21 June 2013; accepted 15 July 2013
Copyright © 2013 Mwanarusi Saidi et al. This 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.
ABSTRACT
Tomato (Lycopersicon esculentum) is one of the
import ant veget ables in supplyi ng vit amins, min-
erals and fiber to human diets worldwide. Its
successful production in the tropics is, ho wever,
constrained by environmental variations espe-
cially under open field conditions. Two trials
were conducted at the Horticulture Research
and Teaching Field, Egerton Univ ersity, Keny a to
evaluate the effects of agricultural nets (ag-
ronets) herein called eco-friendly nets (EFNs)
and floating row covers (FRCs) on microclimate
modification, yield, and quality of tomato. A ran-
domized complete block design with five repli-
cations was used. Tomato plants were grown
under fine mesh EFN (0.4-mm pore diameter)
cover, large mesh EFN (0.9-mm pore diameter)
cover or FRC. The EFN and FRC were main-
tained either permanently closed or opened
thrice a week from 9 am to 3 pm. Two open con-
trol treatments were used: unsprayed (untreated
control) or sprayed with chemicals (treated con-
trol). The use of EFN or FRC modified the micro-
climate with higher temperatures, lower diurnal
temperature ranges, and higher volumetric wa-
ter content recorded compared with the controls.
On the other hand, light quantity and photo-
synthetic active radiation were reduced by the
use of EFN and FRC compared with the controls.
The use of FRC and EFN resulted in more fruit
and higher percent in marketable yield com-
pared with open field production. Fruit quality at
harvest was also significantly improved by the
use of EFN and FRC. Fruits with higher total
soluble solids (TSS), lower titratable acidity (TA),
and higher sugar acid ratio were obtai ned in EFN
and FRC treatments compared with the controls.
Fruits harvested from EFN and FRC were also
firmer compared with control fruits. These find-
ings demonstrate the potential of EFN and FRC
in modifying microclimate conditions and im-
proving yields and quality of tomato under tropi-
cal field conditions.
Keywords: Lycopers icon escul entum; Solanum
lycopersicum; Microclimate Modification; Protected
Cropping; Tomato Yields; Tomato Quality
1. INTRODUCTION
Tomato is a popular and versatile food crop grown and
consumed all over the world [1]. The popularity of to-
mato among consumers has made it an important source
of vitamins, minerals, and fiber in the diets of many peo-
ple. Besides, tomato contains good amounts of lycopene,
an antioxidant which purportedly fights free radicals that
can interfere with normal cell growth and activity; thus
reducing cancer, heart diseases and premature aging [2].
Successful production of the crop in the tropics, however,
suffers from environmental variations, especially in the
open fields. This affects growth of the crop leading to
poor yield and quality [3-5].
Temperature and soil moisture have been documented

M. Saidi et al. / Agricultural Sciences 4 (20 13 ) 577-584
578
among the main environmental factors that to a large ex-
tent affect tomato growth [6]. Temperatures below 10˚C
or above 30˚C affect growth and development of tomato
leading to low yield and poor fruit quality. Tomato also
requires adequate soil moisture for its growth and devel-
opment. Too much or limited soil moisture similarly
leads to low yield and poor fruit quality. Although, to-
mato requires light for the process of photosynthesis, the
crop may still produce better yields under reduced light
conditions [7,8].
The use of EFNs and FRCs in protected cultivation
was tested in Africa [9,10] and Europe [11], respectively
and proved to be effective in microclimate modification.
EFNs were also used in Kenya to improve tomato and
cabbage (Brassica oleracea var. capitata) transplant pro-
duction [12,13]. As a result of microclimate improve-
ment, EFNs and FRCs have been reported to signifi-
cantly alter air temperature and soil moisture which in-
fluence plant growth through changes in leaf characteris-
tics, biomass accumulation, and relative growth rate
leading to better yield and crop quality [14]. The present
study aimed at investigating the effects of EFNs and
FRCs on microclimate improvement, yield, and quality
of tomato under tropical field conditions.
2. MATERIALS AND METHODS
2.1. Experimental Site
The study was conducted at the Horticulture Research
and Teaching Field, Egerton University, Njoro, Kenya in
two seasons (May to Oct. 2011 and Oct. 2011 to Mar.
2012). The field lies at latitude of 0˚23ʹ S and longitude
35˚35ʹ E in the Lower Highland III Agro Ecological
Zone (LH3) at an altitude of ~2238 m above sea level.
The average maximum and minimum temperatures range
from 19 to 22˚C and 5 to 8˚C, respectively, with a mean
total annual rainfall of 1200 to 1400 mm. Soils are pre-
dominantly andosols with a pH of 6.0 to 6.5 [15].
2.2. Planting Material, Experimental Design,
and Treatments
“Rio Grande” tomato transplants were used as the
planting material in the study. Seedlings used were
started under an eco-friendly net (0.4-mm pore diameter)
covered nursery to ensure that they were of superior
quality and virus free. The experiment was laid in a ran-
domized complete block design (RCBD) with five repli-
cations and 8 treatments as follows: 1) open unsprayed
(untreated control), 2) open sprayed with synthetic insec-
ticides (treated control), 3) FRC maintained permanently
covered, 4) fine mesh (0.4-mm pore diameter) EFN
maintained permanently covered, v) large mesh (0.9-mm
pore diameter) EFN maintained permanently covered, 5)
FRC opened three times a week from 9:00 am to 3:00 pm,
6) fine mesh (0.4-mm pore diameter) EFN opened three
times a week from 9:00 am to 3:00 pm, and 7) large
mesh (0.9-mm pore diameter) EFN opened three times a
week from 9:00 am to 3:00 pm. Row covers used were
manufactured by Agribon, Mooreville, NC while the
EFN were manufacture by A to Z Textile Mills, Arusha,
Tanzania. Each block measured 71 × 1 m separated by a
1-m buffer. Within each block, individual experimental
units measured 1 × 8 m separated by a 0.5-m buffer. In
every plot, three posts 1.2-m long were placed 4-m apart
along the 8-m bed to serve as the support system for the
cover and the crop. These were grounded to 20-cm depth
to ensure that they were firm enough to provide the
needed support. Binding wire was then pinned at 30-cm
interval from the ground to the top of the posts to com-
plete the crop support system. Additionally, for the cov-
ered treatments, ordinary mild steel (R6) 1 m long pieces
were mounted on top of each post, fastened using U-nail
and bent to provide a tunnel shape top for dressing the
covers. Covers used on each experimental unit measured
3-m wide and 11-m long.
2.3. Land Preparation and Maintenance
Practices
The field was ploughed to ~20-cm depth and later har-
rowed to a fine tilth using disc plough and harrow, re-
spectively. Transplanting holes were manually dug using
hand hoes and diammonium phosphate (18% N, 46%
P2O5) applied at 10 g per hole and thoroughly mixed with
the soil prior to transplanting. Four weeks old tomato
seedlings were transplanted in one row 8-m long at 50-
cm spacing within the row [1] giving 16 tomato plants
per experimental unit. Before covering the plots with
EFN or FRC, all plots received a blanket spray of insec-
ticide (alpha-cypermethrin 10% EC) at the rate of 25
ml/20 l of water provided by Meya Agricultural Traders,
Nakuru, Kenya to take care of pests during the trans-
planting process. Thereafter, standard good agricultural
practices including fertilizer application, watering, weed-
ing and training were done uniformly on all experimental
units on need basis.
2.4. Data Collection
Data for all variables measured were collected from
the middle 14 plants in all the experimental units.
Microclimate: WatchDog Plant Growth Station data
loggers (2475; Spectrum Technologies, Plainfield, IL)
were used to collect climatic data. Each Data logger was
screwed 0.5-m high on a wooden post at the center of
each treatment. Data were recorded and averaged weekly.
On weekly basis, the data were downloaded into the
computer and hard copies printed to ensure safety. Data
collected included; air temperature (˚C), diurnal tempera-

M. Saidi et al. / Agricultural Sciences 4 (20 13 ) 577-584 579
ture range (˚C), volumetric water content (%) using an
external sensor (WaterScoutTM SM 100), photosyn-
thetically active radiation (mmol·m−2·s−1), and daily light
integral (mol·d−1).
Yield: Fruit harvesting was piece meal on weekly ba-
sis over a period of four weeks. Physiologically mature
fruit at pink stage were harvested from the 14 middle
plants in each treatment. At each harvest, total and mar-
ketable fruit number and weight from each experimental
unit was taken and recorded. Percentage increase in
marketable yield was also computed using the yield of
the untreated control as the base.
Quality: Fruit quality variables measured in this study
were firmness, total soluble solids (TSS), titratable acid-
ity (TA) and sugar:acid ratio. Tomato fruit at red ripe
stage was used. Fruit firmness (KgF) was determined
using a hand held penetrometer (FT327; Shangai Preci-
sion and Scientific Instrument Co., Shangai, China). To-
tal soluble solids were determined using a hand held re-
fractometer (RHB; Shangai Precision and Scientific In-
strument Co., Shangai, China) as per the procedure de-
scribed by Tigchelaar [16]. Titratable acidity (TA) was
determined for the same fruit used to determine total
soluble solids using the coloured indicator method as
described by Turhan and Seniz [17]. Sugar acid ratio was
computed using the formula; Sugar:acid ratio = %Brix
value/Percentage acid [18].
2.5. Data Analysis
The Proc univariate procedure of SAS (version 9.1;
SAS Institute, Cary, NC) was used to check for normality
of the data before analysis. Data were then subjected to
analysis of variance (ANOVA) using the GLM at P ≤
0.05. Data for the two seasons were pooled together and
analyzed using the statistical model: Yij = μ + βi + αj + εij
where; Yij is the tomato response, μ is the overall mean,
βi is the ith blocking effect, αj is the effect due to the jth
treatment and εij is the random error term. Means for
significant treatments, at the F test, were separated using
Tukey’s honestly significant difference (THSD) test at P
≤ 0.05.
3. RESULTS
3.1. Temperature
Covering plants with FRC or EFN influenced tem-
perature within the vicinity of tomato plants. Throughout
the study, the highest temperatures were recorded under
FRC maintained permanently covered (Figure 1). Mean
temperature for this treatment for the two seasons was
23.5˚C. Among the other treatments, mean temperatures
were 23.0, 22.7, 21.7, 21.3, and 20.9˚C, under FRC
opened thrice a week, 0.4-mm EFN covered permanently,
0.4-mm EFN opened thrice a week, 0.9-mm EFN cov-
Figure 1. Effects of floating row covers and eco-friendly nets
on weekly temperature during tomato production. Values
shown are averaged across the two seasons (Season 1, May to
Oct. 2011 and Season 2, Oct. 2011 to Mar. 2012). Control was
where the crop was uncovered; permanent is where the FRC
or EFN were covered throughout except during crop mainte-
nance periods, and opened is where the FRC or EFN were
opened thrice a week from 9.00 am to 3.00 pm.
ered permanently, and 0.9-mm EFN opened thrice a
week, respectively compared with 19.4˚C for the control.
3.2. Diurnal Temperature Range
The use of FRC and EFN covers reduced the diurnal
temperature range throughout the study period (Figure
2). Averaged over the two growing seasons, FRC and
0.4-mm EFN maintained permanently covered gave the
lowest diurnal temperature ranges of 3.3˚C and 3.4˚C,
respectively compared with the control (5.8˚C). Among
the other treatments, diurnal temperature range was
lower under FRC opened thrice a week (3.7˚C), followed
by 0.4-mm net opened thrice a week (4.1˚C), then 0.9-
mm net covered permanently (4.2˚C) and highest under
0.9-mm EFN cover opened thrice a week (4.5˚C).
3.3. Soil Moisture
The use of FRC and EFN maintained higher soil
moisture content (measured as volumetric water content)
throughout the study period (Figure 3). Averaged over
the two study seasons, FRC and 0.4-mm EFN used per-
manently maintained the highest soil moisture with
means of 33.7% and 33.3%, respectively. The lowest
mean soil moisture content (22.5%) was recorded under
the control treatment. Among the other treatments, mean
soil moisture content was 32.5%, 31.2%, 30.8%, and
30.0% for FRC opened thrice a week, 0.9-mm net cov-
ered permanently, 0.4-mm net opened thrice a week, and
0.9-mm net opened thrice a week, respectively.
3.4. Photosynthetically Active Radiation
Floating row covers (FRC) and EFN covering affected
photosynthetically active radiation (PAR). Generally
PAR reaching the crop was reduced by the use of FRC

M. Saidi et al. / Agricultural Sciences 4 (20 13 ) 577-584
580
Figure 2. Effects of floating row covers and eco-friendly nets
on diurnal temperature range during tomato production. Val-
ues shown are averaged across the two seasons (Season 1,
May to Oct. 2011 and Season 2, Oct. 2011 to Mar. 2012).
Control treatment was left uncovered; permanent is where the
FRC or EFN were covered throughout except during crop
maintenance periods and opened is where the FRC or EFN
were opened thrice a week from 9.00 am to 5.00 pm.
Figure 3. Effects of floating row covers and eco-friendly nets
on soil moisture content (volumetric water content) during
tomato production. Values shown are averaged across the two
seasons (Season 1, May to Oct. 2011 and Season 2, Oct. 2011
to Mar. 2012). Control treatment was left uncovered; perma-
nent is where the FRC or EFN were covered throughout ex-
cept during crop maintenance periods and opened is where the
FRC or EFN were opened thrice a week from 9.00 am to 5.00
pm.
and EFN (Figure 4). Tomato plants under the control
treatment registered higher PAR levels in all sampling
dates. The mean PAR received by control plants was
615.3 mmol·m−2·s−1 compared to 593.3, 592.6, 591.7,
590.8, 590.7, and 590.6 mmol·m−2·s−1 recorded under
0.9-mm EFN opened thrice a week, 0.4-mm EFN opened
thrice a week, 0.9-mm EFN covered permanently, FRC
used permanently, FRC opened thrice a week, and 0.4-
mm EFN covered permanently, respectively.
3.5. Light Quantity (Daily Light Integral)
Using FRC and EFN in tomato growing reduced the
light quantity that reached the crop (Figure 5). Control
plants received more light compared with plants under
FRC or EFN in all data collection days. Averaged over
the two seasons, control plants received 43.2 mol·d−1
compared with 35.7, 35.4, 35.1, 34.6, 34.5, and 34.2
mol·d −1 under 0.9-mm EFN opened thrice a week, 0.4-
Figure 4. Effects of floating row covers and ecofriendly nets
on photosynthetically active radiation during tomato produc-
tion. Values shown are averaged across the two seasons (Sea-
son 1, May to Oct. 2011 and Season 2, Oct. 2011 to Mar.
2012). Control treatment was left uncovered; permanent is
where the FRC or EFN were covered throughout except dur-
ing crop maintenance periods and opened is where the FRC or
EFN were opened thrice a week from 9.00 am to 5.00 pm.
Figure 5. Effects of floating row covers and eco-friendly nets
on light quantity during tomato production. Values shown are
averaged across the two season (Season 1, May to Oct. 2011
and Season 2, Oct. 2011 to Mar. 2012). Control treatment was
left uncovered; permanent is where the FRC or EFN were
covered throughout except during crop maintenance periods
and opened is where the FRC or EFN were opened thrice a
week from 9.00 am to 5.00 pm.
mm EFN opened thrice a week, 0.9-mm EFN covered
permanently, 0.4-mm EFN covered permanently, FRC
opened thrice a week, and FRC used permanently, re-
spectively.
Total Fruit Yield: Growing tomato under EFN or
FRC significantly increased tomato yield (Tab le 1). The
use of FRC maintained permanently covered resulted in
the highest total fruit number with the lowest fruit num-
ber obtained in the treated control and the 0.9-mm EFN
maintained permanently covered. Among the other treat-
ments, more fruits were harvested from plants under the
FRC opened thrice a week followed by the untreated
control, 0.4-mm EFN maintained permanently, 0.4-mm
EFN opened thrice a week, and 0.9-mm EFN opened
thrice a week treatment in descending order. In terms of
total fruit fresh weight, FRC maintained permanently
covered had the highest yield while the untreated control
gave the lowest yield (Table 2). Superiority in total fresh
fruit weight among the other treatments followed the
order; treated control, 0.9-mm EFN opened thrice a week,
0.9-mm EFN maintained permanently, 0.4-mm EFN

M. Saidi et al. / Agricultural Sciences 4 (20 13 ) 577-584 581
Table 1. Effects of floating row covers (FRC) and eco-friendly
nets (EFN) on tomato yield (no./m2) during production. The
values shown are averaged across the two seasons, May to Oct.
2011 and Oct. 2011 to Mar. 2012.
Tr eatm ent+ Total fruit
(no./m2)
Marketable
fruit
(no./m2)
Increase in
marketable fruit
number (%)***
Untreated control 41.2 bc** 31.8 e 0
Treated control 38.8 e 35.4 d 11.3
FRC permanent 43.0 a 42.0 a 32.1
0.4-mm EFN permanent 40.6 c 39.0 b 22.6
0.9-mm EFN permanent 38.8 e 35.8 cd 12.6
FRC opened 42.6 ab 40.0 b 25.8
0.4-mm EFN opened 40.4 cd 36.8 c 15.7
0.9-mm EFN opened 39.0 de 34.8 d 9.4
*Untreated control had no pesticide applied, treated control was sprayed
with pesticides, permanent is where the FRC or EFN were covered through-
out except during crop maintenance periods and opened is where the FRC or
EFN were opened thrice a week from 9.00 am to 3.00 pm. **Means followed
by the same letter within a column and a parameter are not significantly
different according to Tukey’s honestly significant difference (THSD) at P ≤
0.05. ***Percent increase in marketable yield = x-untreated control/untreated
control ×100, where x is marketable yield for the given treatment.
Table 2. Effects of floating row covers (FRC) and eco-friendly
nets (EFN) on tomato yield (Kg/m2) during production. The
values shown are averaged across the two seasons, May to Oct.
2011 and Oct. 2011 to Mar. 2012.
Tr eatm ent* Total fruit
(Kg/m2)
Marketable
fruit
(Kg/m2)
Increase in
marketable fruit
weight (%)***
Untreated control 3.8 g** 3.0 f 0.0
Treated control 4.4 f 4.0 e 33.3
FRC permanent 7.6 a 7.4 a 146.7
0.4-mm EFN permanent 6.2 c 6.0 c 100.0
0.9-mm EFN permanent 5.2 ed 4.8 d 60.0
FRC opened 6.8 b 6.4 b 113.3
0.4-mm EFN opened 6.0 d 4.8 d 60.0
0.9-mm EFN opened 4.8 ef 4.2 e 40.0
*Untreated control had no pesticide applied, treated control was sprayed
with pesticides, permanent is where the FRC or EFN were covered through-
out except during crop maintenance periods and opened is where the FRC or
EFN were opened thrice a week from 9.00 am to 3.00 pm. **Means followed
by the same letter within a column and a parameter are not significantly
different according to Tukey’s honestly significant difference (THSD) at P ≤
0.05. ***Percent increase in marketable yield = x-untreated control/untreated
control ×100, where x is marketable yield from the treatment.
opened thrice a week, 0.4-mm EFN maintained perma-
nently and FRC opened thrice a week.
Marketable Yield: The number of marketable fruit
was also influenced by the use of EFN and FRC covers.
Growing tomato under FRC maintained permanently
covered yielded the highest number of marketable fruit
(Table 1). The lowest number of marketable fruit was, on
the other hand, obtained from the untreated control.
Among the other treatments, the FRC opened thrice a
week and the 0.4-mm EFN maintained permanently cov-
ered yielded more marketable fruit numbers followed by
the 0.4-mm EFN opened thrice a week, then 0.9-mm
EFN maintained permanently covered, with lower num-
bers of marketable fruit recorded for the treated control
and 0.9-mm EFN opened thrice a week treatments. The
trend was similar for marketable fresh fruit weight (Ta-
ble 2). The highest marketable fruit fresh weight was
obtained from the FRC maintained permanently covered.
Among the other treatments, marketable fresh fruit
weight was higher under FRC opened thrice a week fol-
lowed by 0.4-mm EFN maintained permanently, 0.4-mm
EFN opened thrice a week, 0.9-mm EFN covered per-
manently, 0.9-mm EFN opened thrice a week, and the
treated control in a decreasing order. A similar trend was
also observed for marketable fresh fruit weight.
Percent Marketable Fruit Gain: Using the market-
able fruit yield for the untreated control as the denomi-
nator in the equation, the use of EFN and FRC influ-
enced the percent marketable yield gain. FRC maintained
permanently covered registered the highest percent in-
crease in marketable fruit number (Table 1). Among the
other treatments, increase in marketable yields followed
the descending order of FRC opened thrice a week, 0.4-
mm EFN used permanently, 0.4-mm EFN opened thrice
a week, 0.9-mm EFN used permanently, treated control
and 0.9-mm EFN opened thrice a week. A similar trend
was observed with the percent increase in marketable
fresh fruit weight (Table 2).
3.6. Quality
Fruit Firmness: The use of EFN and FRC in tomato
growing significantly influenced tomato fruit quality
(Table 3). Growing tomato under FRC permanently cov-
ered yielded firmer fruit compared with all the other
treatments. The least firm fruit were obtained in the con-
trol treatments. Among the other treatments, fruit were
more firm from the 0.4-mm EFN covered permanently
and FRC opened thrice a week followed by 0.9-mm EFN
covered permanently, 0.4-mm EFN opened thrice a week,
and lowest in the 0.9-mm EFN opened thrice a week
although the difference was not statistically significant
(P ≤ 0.05).
Total Soluble Solids: Total soluble solids (TSS) of
tomato fruit was significantly influenced by the use of
EFN and FRC (Ta bl e 3 ). Fruit grown under FRC main-
tained permanently covered had the highest TSS while
those produced in the open had the lowest TSS. Among
fruit grown under the other treatments, TSS was higher
in fruit grown under FRC opened thrice a week and 0.4-
mm EFN maintained permanently covered treatments

M. Saidi et al. / Agricultural Sciences 4 (20 13 ) 577-584
582
Table 3. Effects of floating row covers (FRC) and eco-friendly
nets (EFN) on tomato fruit quality at harvest. The values shown
are averaged across the two seasons, May to Oct. 2011 and Oct.
2011 to Mar. 2012.
Tr eatm ent* Firmness
(KgF)
TSS
(%)
TA
(%)
Sugar acid
ratio
Untreated control 3.2 d** 2.9 d 4.1 a 0.7 d
Treated control 3.3 d 3.1 d 4.0 a 0.8 d
FRC permanent 5.9 a 6.0 a 3.3 b 1.8 a
0.4-mm EFN permanent 5.5 b 5.8 b 3.4 b 1.7 b
0.9-mm EFN permanent 5.2 c 5.3 c 3.6 b 1.5 c
FRC opened 5.5 b 5.7 b 3.5 b 1.7 b
0.4-mm EFN opened 5.2 c 5.3 c 3.5 b 1.5 c
0.9-mm EFN opened 5.1 c 5.2 c 3.6 b 1.5 c
*Untreated control had no pesticide applied, treated control was sprayed
with pesticides, permanent is where the FRC or EFN were covered through-
out except during crop maintenance periods and opened is where the FRC or
EFN were opened thrice a week from 9.00 am to 3.00 pm. **Means followed
by the same letter within a column and a parameter are not significantly
different according to Tukey’s honestly significant difference (THSD) at P ≤
0.05.
followed by 0.4-mm EFN opened thrice a week, then
0.9-mm EFN covered permanently, and least under 0.9-
mm net opened thrice a week.
Titratable Acidity: The use of EFN and FRC signifi-
cantly influenced tomato fruit TA (Tabl e 3 ). The control
treatments yielded fruit with the highest TA while the
fruit harvested from FRC maintained permanently cov-
ered had the lowest TA. The titratable acidity of fruit
grown under the other treatments was not statistically
different (P ≤ 0.05).
Sugar Acid Ratio: Sugar acid ratio (TSS:TA) was sig-
nificantly influenced by the use of FRC and EFN covers
(Table 3). Fruit harvested from the control treatments
had the lowest TSS:TA while fruit grown under FRC
maintained permanently covered had the highest TSS:TA.
Among other treatments, fruit from the 0.4-mm EFN
maintained permanently covered and FRC opened thrice
a week had higher TSS: TA followed by 0.4-mm EFN
opened thrice a week, then 0.9-mm EFN maintained per-
manently covered and lowest in 0.9-mm EFN opened
thrice a week treatment although the difference in sugar
acid ratio among these treatments were not significant (P
≤ 0.05).
4. Discussion
Using FRC or EFN in the current study effectively
modified the microclimate around the growing tomato
plants. Mean daily temperature increased with the use of
FRC and EFN covers compared with the control. In ad-
dition to increasing mean daily temperature, FRC and
EFN reduced the diurnal temperature range of the imme-
diate crop environment. Mitigating diurnal temperature
fluctuations may be beneficial for the crop. Under the
covered plots, air temperature increase also tended to
increase with a decrease in cover pore diameter. As ex-
pected, a reverse trend was observed with diurnal tem-
perature range, which tended to decrease with decrease
in cover pore diameter. Thus, using covers with smaller
pore diameter resulted in a higher temperature and lower
diurnal temperature range and vice versa. Generally, air
temperature also remained consistently higher in treat-
ments with covers maintained permanently covered com-
pared with when the covers were opened thrice a week
due to a reduction of the cover effect during the periods
when the covers are open. A reverse trend was observed
with diurnal temperature range, which tended to be lower
in treatments with covers maintained permanently cov-
ered compared with when the covers were opened thrice
a week. The use of netting and any other type of covering
has been shown to restrict air movement around the
growing crop resulting in higher temperature and lower
diurnal temperature range [19,20]. Opening of nets dur-
ing the growing period of plant has been shown to en-
hance air movement within the vicinity of the crop,
leading to lower air temperatures under opened nets [21].
In a study with mesh of different sizes, Antignus et al.
[22] showed that smaller mesh size nets resulted in
higher air temperatures than large mesh size nets. In the
current study, the higher temperatures and lower diurnal
temperature range recorded for covered tomato plots
compared with uncovered plots; finer mesh covers com-
pared with larger mesh covers as well as under perma-
nent cover compared with covers opened thrice a week
could therefore be attributed to the differences in the
levels of restriction in air movement around the growing
tomato crop amongst the different treatments leading to a
differential effect in temperature dynamics.
Soil moisture content was also higher in all covered
compared with uncovered plots. Permanent use of FRC
and EFN also tended to maintain higher soil moisture
levels than when covers were opened thrice a week. Gen-
erally, soil moisture content was also higher under
smaller pore diameter covers than under larger pore di-
ameter covers during the study. Covering crops reduce
instantaneous solar radiation through shading [23] re-
sulting to lower evaporation from the ground, thus main-
taining higher soil moisture contents [24]. This argument
lends support to the higher moisture levels observed un-
der covered plots in the current study. Majumdar [19]
similarly reported higher soil moisture under net covered
plots compared with uncovered plots.
Contrary to temperature and moisture levels, PAR and
light quantities that reached the tomato crop were low-
ered by the use of EFN and FRC. A higher reduction in
PAR and light quantity was also noted in treatments

M. Saidi et al. / Agricultural Sciences 4 (20 13 ) 577-584 583
where EFN and FRC were maintained permanently cov-
ered and with decreasing cover pore diameter. Covers
block light as well as reduce the light quality [22]. The
reduction in PAR and light quantity under FRC and EFN
observed in the current study could, therefore, be attrib-
uted to the light blocking properties of the materials used
with more light being blocked when covers of smaller
pore diameter were used or when the covers were main-
tained permanently. Although the use of EFN and FRC
lowered PAR reaching the crop, the quantity of light re-
ceived by the crop still remained within acceptable range
and did not have major impact on the plants.
Following the microclimate modification registered
under FRC and EFN treatments, improved tomato yield
was also recorded in most of the covered plots. Yield also
tended to increase with a decrease in cover pore diameter.
Permanently covered tomato also yielded more market-
able fruit, higher fruit weight, and higher percent in-
crease in marketable yield compared with when covers
were opened thrice a week. Covers have been reported to
modify internal temperature, soil moisture and diurnal
temperature range inside protected culture [25] which
tends to favor physiological processes of plants leading
to better growth and development, and subsequently
higher yields [6]. In the current study, higher air tem-
perature and soil moisture and lower diurnal temperature
range was noted under covered compared with control
treatments which could have favored better physiological
plant development under our climatic conditions. Better
physiological development translates to higher photo-
synthetic activities [26]. When photosynthesis is en-
hanced, more food is manufactured and translocated to
sinks which could probably have favored the growth and
development of tomato plants leading to higher fruit
yield. Weerakkody et al. [27] also obtained more tomato
fruits, higher marketable yield and better fruit quality in
protected tomato than in unprotected tomato.
In addition to tomato yields, the use of FRC and EFN
also yielded better quality tomato fruit. Fruit harvested
from FRC and EFN covered treatments were firmer with
higher TSS, and TSS:TA but lower TA compared with
control fruit. When tomato plants are grown under covers,
their quality tends to be enhanced [23]. Findings of our
study lend support to this argument. Fruit obtained from
permanent covers tended to be of better quality than
those from covers opened thrice a week. Fruit quality
also tended to increase with decreasing cover pore di-
ameter. Temperature and water are among the preharvest
factors affecting quality of fruits. Weerakkody et al., and
Borthwick [7,27] reported that temperature and water
play an important role in quality development in fruits.
Water and temperature have been reported to play a ma-
jor role in photosynthesis, cell wall development, cell
membrane integrity and ripening process of fruits [6,25].
Modified internal temperature and high soil moisture
under covers in the current study may have led to better
photosynthetic activities and cell wall development lead-
ing to higher TSS, lower TA, higher sugar acid ratio and
firm fruits under the covered treatments. Such fruit with
higher TSS, lower TA, higher sugar acid ratio and firm
are good indicators for fresh market consumption both in
cooking and as salad.
Results of the present study demonstrate the potential
of EFN and FRC as viable strategies for improving mi-
croclimate around tomato plants and improving tomato
yields and quality. Besides, the use of these technologies
also stands to reduction on the use of pesticides during
tomato production due to the physical and visual barrier
they create around the crop for insects. All these could
lead to healthier fruits as well as contributing to envi-
ronmental quality. While the findings of this study pro-
vide a good foundation to understanding the influence of
EFN and FRC in microclimate modification and tomato
performance, further testing of the technologies using a
wider range of mesh sizes and colours, different tomato
varieties and in different tomato growing agro ecological
zones would be beneficial. A full economic analysis fac-
toring in the cost of purchase, installation and manage-
ment of EFN and FRC will also be of benefit to the
growers.
5. ACKNOWLEDGEMENTS
This study was made possible by the generous support of the Ameri-
can people through the U.S. Agency for International Development
(USAID) under Award No. EPP-A-00-09-00004. Additional financial
support was provided by Michigan State University and the Centre de
coopération internationale en recherche agronomique pour le develop-
pement (Cirad). The contents are the responsibility of Horticulture
Collaborative Research Support Program (HortCRSP) project Bio-
NetAgro investigators and do not necessarily reflect the views of
USAID or the U.S. Government. We acknowledge our project partners,
the Egerton University, the Kenya Agricultural Research Institute
(KARI) and the International Centre of Insect Physiology and Ecology
(ICIPE) in Kenya; A to Z Textile Mills in Tanzania; University of
Abomey Calavi, Institut National des Recherches Agricoles du Bénin
(INRAB), and Association des Personnes Rénovatrices des Technolo-
gies Traditionnelles (APPRETECTRA) in Benin for their support.
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