IJERD – International Journal of Environmental and Rural Development (2023) 14-1

Research article
erd

On-farm Effects of Subsurface Drainage System on Chinese
Cabbage (Brassica pekinensis L. Rupr.) Production in Rainy
Season at Svay Rieng Province, Cambodia
TITHYA KANG*
Svay Rieng University, Svay Rieng, Cambodia
Email: kang_tithya@mail.sru.edu.kh

SARAVUTH TUM
Svay Rieng University, Svay Rieng, Cambodia

VANCHEY ROS
Svay Rieng University, Svay Rieng, Cambodia

NIMUL CHUN
Svay Rieng University, Svay Rieng, Cambodia

CHHUN HONG
Svay Rieng University, Svay Rieng, Cambodia

BORARIN BUNTONGRoyal University of Agriculture, Phnom Penh, Cambodia

KIMCHHIN SOKRoyal University of Agriculture, Phnom Penh, Cambodia

SIRANET ROEURN
Royal University of Agriculture, Phnom Penh, Cambodia

SOPHOANRITH RO
Royal University of Agriculture, Phnom Penh, Cambodia
Received 4 February 2023

Accepted 20 May 2023(*Corresponding Author)

Abstract Vegetable production in Cambodia is unstable during the rainy season due tosaturated soil conditions, leaving the comparative market advantage to neighboring Vietnam
and Thailand. One potential solution that has been proposed is the introduction of a Subsurface
Drainage (SD) system, as elucidated in our previous studies. In the current study, SD systems
was installed on plots of Chinese cabbage in Svay Chrum District, Svay Rieng Province, todetermine their potential in increasing the production period and productivity during the rainyseason. The treatments consisted of three SD systems within three growing conditions (GC)
including open-field, plastic house, and net house including five replications with a total of 45
plots. The results of the experiment showed positive improvement in terms of growth and yieldof Chinese cabbage at a rate of 15% and 22% for SD2 and SD3 systems respectively; and 58%
and 66% for net house and plastic house conditions, respectively. The extension of the
production period from intermittent to year-round is of great benefit to vegetable producers,
and will lead to improved market connections and better production margins, stabilizing
income generation. However, the analysis still excluded the cost-effectiveness and efficiencyof the experiment due to the absence of detailed data on expenditures, including the cost ofdrainage pipes, construction of the net and plastic houses, and water consumption.
Keywords on-farm, subsurface drainage (SD), Chinese cabbage, rainy seasonⒸ ISERD

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INTRODUCTION
Agriculture is an important mainstay of the Cambodian economy to lift many people out of poverty.
In 2021, the share of agriculture in Cambodia's gross domestic product (GDP) was 22.85%, including
the contributions of fishery at approximately 5.5%, livestock at 2.6%, forestry at 1.6%, and crops atabout 13% (MAFF, 2021). Although the major occupation of the Cambodians is agriculture, thecountry is a net agricultural importer, giving vegetable imports worth approximately USD 200
million annually (Thira et al., 2020). The heavy reliance of the country on neighboring countries'
vegetables is associated with the highly seasonal productions of Cambodian producers lasting foraround only three months from late December to late March. The period is appropriate for vegetableproduction as the weather is relatively mild and dry (Wandschneider et al., 2019). Moreover, rice
farmers are free from rice production and some of them opt to produce vegetables for additional
income, causing the volume of vegetables to reach a peak while the price falls to the lowest one (IRL,
2007). After the period, water becomes scarce and the soil becomes too dry whereas the wet season
faces the problem of too much rainfall, causing waterlogging, high pests, and diseases(Wandschneider et al., 2019). The discontinuous supply of vegetables at stable volume has caused
the vegetable value chain to break and loss of competitiveness to the neighboring countries, namely
Vietnam and Thailand. It is reported that local capacity for vegetable production could supply
approximately 45% of the market demand and 70% is in the peak period of the production in dry
season (CPS, 2019). A wide variety of vegetables was cultivated across the country, including leafy,
stem, and fruit-bearing, root, bulb, tuberous, leguminous green vegetables, etc. Fruit-bearing
vegetables were planted on 35,000 ha; leafy and stem vegetables on almost 6,000 ha. Vegetables are
increasingly recognized as essential for food and nutritional security. Vegetable production is a key
component of farm diversification strategies to provide a promising economic opportunity for
reducing rural poverty and unemployment in developing countries (Pepijn et al., 2018). Chinese
cabbage (Brassica pekinensis L. Rupr.) is annually grown as a salad crop. It is indigenous to China
and eastern Asia, where it has been in cultivation since the fifth century. Two more or less distinct
species of Chinese cabbage are grown. The leaves are long, dark green, and oblong or oval, and they
do not form a solid head. It is also called Chinese mustard (Kalloo et al., 1993). Chinese cabbage(Brassica pekinensis L. Rupr.) is a popular leafy vegetable of Cambodian farmers and consumers
among many kinds of vegetables for their daily food security and income generation (Um Raingsey,2015). The drainage system provides substantial benefits to agricultural production which could
contribute to (i) increasing farm income, (ii) intensification and diversification of cropping; and (iii)
generation of employment (Datta et al., 2004). Proper management of irrigation practices could
provide various benefits to crop production such as extended crop season, increased yield, andimproved aeration of the root zone. However, the development of drainage systems has been lagging
far behind the development of irrigation, leaving agriculture at a high risk of losing productive lands
due to waterlogging and salinization (Abdel, 2000). There is no exception for Cambodia where theintroduction of Subsurface irrigation systems has been very limited and hardly found at any
Cambodian farm. Unstable quantity on the supply side has been one of the reasons behind the lossof production competitiveness to the neighboring countries including Vietnam and Thailand. The
experience from the collaboration between Svay Rieng University with Svay Rieng Agricultural
Cooperatives shows that vegetable producers are facing severe issues of waterlogging during the wet
season causing their production to be least productive and delayed (Hong et al., 2021). Therefore,
the introduction of the SD system is essential to study in determining its potential contribution tovegetable production during the rainy season which could also be essential for other vegetableproducers across the country. The on-farm experiment was conducted with farmers in Svay Chrum
District, Svay Rieng Province to solve the problem of unproductive soil due to high water content(saturation) by the installation of a subsurface drainage with plastic house and net house. Draining
water from the production area under plastic houses and net houses would help farmers solve theproblem of highly saturated soil and continue their production during the wet season. The system
will be of great benefit to vegetable producers in terms of a production period that can be extended
from intermittent to year-round. This will lead to a better market connection and production marginwhich is stable in income generation.
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OBJECTIVE
The overall objective of the research is to determine the appropriateness, potential, and suitability ofthe subsurface drainage under different growing conditions with Chinese cabbage as per field
application of vegetable producers in increasing the period and productivity during the rainy season.
MATERIALS AND METHODS
Experimental Site
The experiment was conducted in Svay Chrum District, Svay Rieng Province, Cambodia (Fig. 1)
with fifteen farmers’ fields of vegetable producers who are members of Svay Rieng Agricultural
Cooperatives (SAC). The experiment was carried out from August to November 2022. The soil
characteristics of the experimental fields are located on the saturated soil of abandoned paddy fields
with soil pH of around 5.5 of the loamy soil (averagely, clay: 17.5%, silt: 39.4%, and sand: 41.4%).
The rainy seasonal precipitation ranges from 142.4 mm to 248.9 mm, while the temperature ranges
from 27.9oC to 29.8oC, and the humidity ranges from 80% to 92.5% (Table 1).

Fig. 1 The experimental location in Svay Chrum District, Svay Rieng, Cambodia
Table 1 Monthly rainfall, temperature and humidity during growing season in 2021-2022
Month
Aug
Sept
Oct
Nov
Total

Rainfall (mm)
2021
2022
218.8
174.3
255.5
238.5
254.2
248.9
248.4
142.4
976.9
804.1

Temperature (oC)
2021
2022
30.0
29.4
29.3
29.8
28.8
27.9
29.0
29.0
117.0
116.0

Humidity (%)
2021
2022
91.0
87.5
96.0
85.0
92.5
92.5
86.0
85.0
365.5
350.0

Experimental Design
The factorial design is used, containing fifteen farmers’ fields with five replications and nine
combined treatments including three SD systems and three GCs. The same design of the Subsurface
drainage (SD) systems (SD1 = No Subsurface drainage pipe, SD2 = 2 rows Subsurface drainage pipe
per bed, SD3 = 3 rows Subsurface drainage pipe per bed) were applied under the different Growing
Conditions (GC) of open field (OP), net house (NH), and plastic house (PH). One farmer’s field wasused as one GC, and three SD systems were allocated. The pipes were sawed in a row at every 2 cm
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with 1/3 dept of pipe size to make holes for water inlets to drain through outlets to the nearby canal.
The total land area for each farmer’s field was 5 m x 15 m =75 m2. The net house was fully coveredby a 150-mesh net, and the plastic house was surrounded covered by a 150-mesh net with 300 UVplastic covering on top of the roof.

Fig. 2 Illustration of the experimental design for each farmer’s field
Agronomic Practices
The Chinese cabbage seedlings were grown on the raised bed with the PVC pipe being buried
underneath (sawed side goes to the ground) at a depth of 20 cm under the root zone. Mechanicalmethods were used for pest management. The weeding was controlled every week till the harvestingby hand. During the experiment, the diseases were not observed. The insects were normally bothered
during the experiment, even in the net house or plastic house condition. The chemical methods ofcrop protection were used by spraying natural pesticides and by hand picking. For the irrigation, theplants were irrigated from pumped water sources by hand spraying with 20 liter-bucket. In case there
was not enough or no rain, the water was applied at field capacity. Some agronomic traits such as
root length, stem height, leaf area, and stem density (survived stem: is the total stem which is still
alive both useful and useless stems at the harvesting date, useful stem: is the good stem which canbe consumed, loss stem: is the died stem which cannot be survived at the harvesting day, damage
stem: is the total of useless stems and died stems), and weight (estimated max yield: is the average
weight of complete useful stems with 100% density at the harvesting date, useful yield: is the weightof good or consumable stems, loss yield: is the estimated weight of died stems which cannot be
survived at the harvesting day, damage yield: is the estimated weight of useless and died stems) of
the cabbages were collected. The collected data was analyzed as a factorial design using Statistix 8
program for the analysis of variance (ANOVA) and Minitab 20.4 for LSD mean comparison at pvalue p<0.01, p<0.05. Before the analysis, the data were normalized to exclude the covariance being
observed from the differentiation among farmer's plots.
RESULTS AND DISCUSSION
Effects on Agronomic Traits
To compare vegetative effects on the Chinese cabbage growth, the four key parameters were
measured from the experiment including root length, stem height, leaf area, and leaf number. The
result of the experiment is summarized in Tables 2-5.

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Table 2 A root length change of Chinese cabbage
Treatment (Tr)At planting day

Root length (cm)At harvesting day

Increase

2.43
2.51
2.42

9.39c
10.14b
11.30a

6.97c
7.62b
8.88a

2.47
2.45
2.43
6
ns
ns
ns

8.99c
10.21b
11.63a
18
**
**
ns

6.52c
7.76b
9.19a
18
**
**
ns

Growing condition (GC)Open field (OF)Net house (NH)
Plastic house (PH)
Subsurface drainage (SD)
SD1
SD2
SD3
CV (%)
Sig. (GC)
Sig. (SD)Sig. (GC X SD)

Table 3 Stem eight change of Chinese cabbage
Treatment (Tr)Growing condition (GC)Open field (OF)Net house (NH)
Plastic house (PH)
Subsurface drainage (SD)
SD1
SD2
SD3
CV (%)
Sig. (GC)
Sig. (SD)Sig. (GC X SD)

Stem height (cm)At planting day At 1st week At 2nd week At harvesting day Increase
9.09
9.13
9.05

14.74 c14.89 bc
16.12 a24.47c24.83bc
26.03a26.44c27.19b30.09a17.35c18.07b
21.03a

9.17
9.03
9.07
2
ns
ns
ns

13.59 c15.73 b16.41 a5****
ns

24.00c25.21b
26.13a6****
Ns

26.60c27.83b
29.28a7****ns

17.44c18.80b
20.21a8****
ns

Table 4 Maximum leaf area change of Chinese cabbage
Treatment (Tr)Growing condition (GC)Open field (OF)Net house (NH)
Plastic house (PH)
Subsurface drainage (SD)
SD1
SD2
SD3
CV (%)
Sig. (GC)
Sig. (SD)Sig. (GC X SD)

Maximum leaf area (cm2/leaf)
At planting day At 1st week At 2nd week At harvesting day Increase
8.90
8.98
9.03

28.54c30.10b34.82a81.03c90.60b97.24a187.25c196.87b206.43a178.35c187.89b197.41a

8.88
9.04
8.98
3
ns
ns
ns

29.03c31.81ab32.63a16****
ns

85.07c90.91b92.88a21****
Ns

189.20c
197.87b203.48a
19
**
**
ns

180.32c188.84b194.50a
20
**
**
ns

Tables 2 to 4 show that the level of changes for root length, stem height, and leaf area at thedifferent growing stages of the Chinese cabbage are statistically different after the planting stages.
Growing conditions and Subsurface drainage systems could make a significant impact on the growthof cabbage with a p-value less than 0.01. Overall, the level of increase of growing condition in Plastic
House (PH) is observed to be better than Net House (NH) and Open Field (OF), while the level ofⒸ ISERD

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increase of SD3 is observed to be better than SD2 and SD1. Plastic House (PH) performed the best
as well as SD3, but the interaction of GC x SD was not significantly detected for root length, stemheight, and leaf area of the cabbage in all growth stages.
Table 5 Leaf number change of Chinese cabbage
Subsurface
drainage(SD)
SD1
Open Field (OF)
SD2
SD3
SD1
Net House (NH)
SD2
SD3
SD1
Plastic House (PH)SD2
SD3
CV (%)
Sig. (GC)
Sig. (SD)Sig. (GC X SD)

Growing conditions(GC)

At planting
day
2.99
2.97
2.97
2.98
2.99
2.99
2.98
2.97
2.99
1
ns
ns
ns

Number of leaves (leaf/stem)
At harvestingAt 1st week At 2nd week
day
3.63h
7.45e
10.06i
3.88g
8.59d
10.54h3.91fg8.40d10.80g
3.96ef8.75d
11.25f
4.03cd9.22c
12.55d
4.11ab
9.77ab
12.75c3.98de9.16c
12.15e4.10bc
9.69ab
12.96b
4.18a10.07a13.27a
2
9
5
**
**
**
**
**
**
**
*
**

Increase
7.07i
7.57h
7.83g
8.26f
9.55d
9.77c
9.18e
9.99b
10.28a5******

The finding (Table 5) shows that leaf numbers were not significant at planting. At the later stage,
the level of changes for the number of leaves at the different growing stages of the Chinese cabbage
were statistically different. All parameters of growing conditions (GC) and Subsurface drainage (SD)systems could make a significant impact on the growth of cabbage with a p-value less than 0.01. In
addition, the interaction of GC x SD was significant. Overall, the best performance of crop growth
was observed under plastic house conditions with Subsurface drainage systems type 2 (SD2) and 3(SD3).
Effects on Productivity
The Stem density, stem weight, and yield per hectare were measured and calculated from theexperiment to compare productivity effects. The results from the experiment are provided in Tables
6 and 7.
Table 6 Stem density on the harvesting day of Chinese cabbage
Growing conditions Subsurface(GC)drainage (SD)
SD1
Open field (OF)
SD2
SD3
SD1
Net house (NH)
SD2
SD3
SD1
Plastic house (PH)SD2
SD3
CV (%)
Sig. (GC)
Sig. (SD)Sig. (GC X SD)

Survived stem
9.57h
13.92g14.92f17.78e19.68d20.68c20.09cd
22.00b
23.32a4
ns
ns**Ⓒ ISERD

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Stem Density (stem/m2)
Useful stem
Loss stem
7.44g
15.43a8.16fg11.08b8.80f
10.08c16.16e7.22d
17.86d5.32e
19.23c
4.32f
18.29cd
4.91ef21.09b3.00g
22.36a
1.68h
4
4
**
**
**
**
**
**

Damage stem
17.56a16.84ab16.20b
8.84c
7.14d
5.77e
6.71de
3.91f
2.64g
4
**
**
**

IJERD – International Journal of Environmental and Rural Development (2023) 14-1

The result (Table 6) shows that the level of changes for the density of survived stem, useful
stem, loss stem, and damaged stem on the harvesting day of the Chinese cabbage are statisticallydifferent. All parameters under growing conditions and Subsurface drainage systems could make asignificant impact on the productivity of cabbage with a p-value less than 0.01. The interaction of
GC x SD was significant. In overall, the plastic house condition with Subsurface drainage system
type 3 was observed to be the best performance for survived stem and useful stem, while under plastic
house condition with Subsurface drainage system type 2 and net house condition with Subsurface
drainage system type 3 were observed to be better performance compared to Subsurface drainage
system type 1 in all growing conditions. In addition, open field condition with Subsurface drainage
system type 1 was observed to be the worst performance for loss stem and damage stem.
Table 7 Yield of Chinese cabbage
Growing
conditions(GC)
Open field(OF)
Net house(NH)
Plastic
house (PH)

Subsurface
drainage (SD) Estimated max yield
SD1
SD2
SD3
SD1
SD2
SD3
SD1
SD2
SD3

CV (%)
Sig. (GC)
Sig. (SD)Sig. (GC X SD)

Total yield (ton/ha)
Useful yield

Loss yield

Damage yield

9.53g
10.58fg
11.58f21.57e25.65d28.40c26.70d31.97b
34.51a3******

19.77a14.37b
13.27b
9.63c
7.64d
6.38d
7.17d
4.55e
2.59f
3
**
**
**

22.50a21.84a21.32a11.79b
10.25c
8.52d
9.79cd
5.92e
4.07f
3
**
**
**

32.03i32.42h
32.90g33.36f35.90e36.92d36.49c37.90b38.58a1******

The result (Table 7) shows that the level of changes for the estimated maximum yield, usefulyield, loss yield, and damage yield of the Chinese cabbage are statistically different. All parameters
under growing conditions and Subsurface drainage systems could make a significant impact on the
productivity of cabbage with a p-value less than 0.01. The interaction of GC x SD graduallydeveloped and became significant. In overall, the plastic house condition with Subsurface drainage
system type 3 was observed to be the best performance for estimated maximum yield and usefulyield, while under plastic house condition with Subsurface drainage system type 2 and net housecondition with Subsurface drainage system type 3 were observed to be better performance comparedto Subsurface drainage system type 1 in all growing conditions. In addition, open field condition with
Subsurface drainage system type 1 was observed to be the worst performance for loss yield anddamage yield.
Discussion
The result of the experiment indicated high productive benefits for the Chinese cabbage in terms ofyield at a rate of 15% and 22% for SD2 and SD3 systems respectively; and 58% and 66% for net
house and plastic house conditions respectively. In comparison to the previous assignment conductedat the same location during the dry season, the increase is 26% to 34%, respectively (Hong et al.,2021). The yield from the experiment was slightly better than the one being conducted during thedry season at the Royal University of Agriculture with a yield of 28 tons/ha (Teb Kimheng, 2015).
This would be more precise with the full-control condition of experimentation which would bepossible in generalizing the actual condition of the country. In addition, a ﬁeld experiment was
conducted in paddy ﬁelds during the rainy seasons (October to May) from 2011 to 2015 to evaluate
a suitable drainage system for improving the grain yield of lowland paddy soil. The saturated
hydraulic conductivity of the soil in all treatments increased, which resulted in improved soil
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properties, water movement, and drain discharge rates (Mehdi et al., 2016). The results of theexperiment were quite better in comparison to the installation of a subsurface drainage system
resulting in an improvement of paddy yield by 13.27% and an increase in soil organic carbon content.
However, it was the first year after the installation of the subsurface drainage; the yield could be
expected to improve considerably during the succeeding seasons with appropriate and better
cropping and irrigation management practices (Sahana et al., 2023). The increase was due toimprovement in soil physical properties viz., infiltration rate, porosity, and chemical properties (lowpH, EC, ESP) and improved nutrient availability in the drained field. Similarly, Abdel-Dayem, andRitzema (1990) reported an increased yield of many crops to a tune of 10% for rice, 48% for berseem,
75% for maize, and more than 130% for wheat under a subsurface drainage system. The increase
was because of decreased soil salinity, and improved air and water condition in crop root zones. The
poor yield of maize in the undrained field due to poor soil physicochemical properties viz., shallow
water table depth, high pH, EC, and ESP (Stieger and Feller, 1994; Samad et al., 2001 and Zhang etal., 2015), which limits the growth and development of crops in waterlogged saline-alkali soil
(Arumugam et al., 2019). In addition, the enormous increase would result in reducing of water stressand strong drops of rain under the plastic house protection during the rainy season. This would bringenormous economic benefits for farmers. It is reported that the consumption of vegetables in
Cambodia is approximately 1,062 million tons per year (SAAMBAT Project, 2020). This would
translate into approximately contribution of 79,650-116,820 tons with the application of Subsurface
drainage and approximately contribution of 307,980-350,460 tons with the application of growing
condition (Net house and Plastic House) for the wet season production (June to December) for
Cambodia with the application of the drainage under the net house or plastic house condition at the
maximum scenario. There is still another concern regarding the cost of the drainage pipe and growing
structures, which was included in the production. A more detailed analysis of the cost and benefit of
the product will be included in future research assignments to make the drainage system and net orplastic house growing condition more determined and applicable for the rainy season.
CONCLUSION
The growth of the Chinese cabbage within the Subsurface drainage (SD2 and SD3) systems andgrowing conditions (NH and PH) performed better under both saturated and drought conditions. At
the time of rain, the cabbage could continue its growth with less effect, while during the time ofdrought, cabbage could maintain its yield, possibly because of good aeration of the soil and less soil
compaction after a strong drop of rain. The analysis still excluded the cost-effectiveness andefficiency of the experiment due to the absence of detailed expenditures on drainage pipe,
construction of the net and plastic house, and water consumption is also excluded. Anyway, future
research should be conducting a detailed analysis of the loss of other nutrients in soils, water
consumption, and possible economic loss as a result of drainage systems and conduct a detailed
analysis of the economic benefits of drainage systems with actual price estimation.
ACKNOWLEDGEMENTS
The authors would like to acknowledge the sub-research project “Effects of Drainage System andGreen House on the Productivity of Vegetable Production” funded by “Higher Education
Improvement Project (HEIP)” through Svay Rieng University, Cambodia.
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