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Men Sarom, Buntong Borarin, Hing Thida, Ly Tyneth and Ou Wenjun
Phnom Penh, Cambodia
June 2014
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EXECUTIVE SUMMARY
Cassava has become the second largest crop production in Cambodia and contributes substantially to the
country economy after rice. The expansion of cassava from a homestead crop to a commercial crop, and
to the second largest crop production in the country raised many concerns especially in its relation to
deforestation and about its impacts to the environment, particularly to soil structure and its nutrients. On
the other hand cassava processing produces large amount of wastes including solid and liquid which are
high in organic matter constituents and cyanide. If not properly managed, liquid (water) waste has the
potential to pollute ground water or lakes, rivers or streams into which it flows. Furthermore, cassava
processing wastes can also produce unpleasant smells and unattractive pictures.
The main objectives of this study are therefore to (i) assess to what degree cassava plantation has caused
soil erosion and the depletion of soil nutrients and soil organic matter (organic carbon), and identify
practical mitigation measures that can be adopted by small-scale farmers to sustain their cassava
production, (ii) document and quantify the recent expansion of areas under cassava cultivation relative
to other previous and current land uses including other cash crops, forest, and deforested areas. This
relates to concerns about the possible causal links between cassava production and deforestation, and
(iii) identify the current practices of different scale cassava processing plants in term of waste
management, assess the potential risks from this waste management on the environment and especially
on water resources, and identify the current proper waste management applied by the processors as well
as the technologies which are either presently available or under development for waste treatment and
management.
The study was conducted in two provinces, Kampong Cham and Pailin, using both quantitative and
qualitative approaches. In Kampong Cham, based on cassava planted areas, three districts, namely
Dambe, Memot and Tbaung Khmom were selected for the study, whereas in Pailin the study was
conducted in the districts of Pailin and Sala Krao. This study included individual surveys with cassava
farmers and processors; testing on soil nutrient content (NPK), pH and soil organic matter (SOM) and
on water quality through identifying pH, Total Dissolved Solids (TDS) and Total Organic Carbon
(TOC) in water sources close to the cassava processing plants.
Results from this study show that the majority of cassava farmers have less than 10 hectares of land
available for crop cultivation. The production can be found in two ecosystems: on flat and sloping land.
About half of the cassava growing is found on sloping land at the north west region of the country
including Pailin. The current practice by farmers on land preparation is regarded as inappropriate that
make cassava fields particularly the sloping land very susceptible to soil erosion especially if it is
associated with heavy rainfall. Adoption of new improved practices is needed to avoid soil erosion.
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There are no differences in soil nutrients as well as the level of pH, soil humidity and organic matter in
the areas under cultivation of cassava and those areas under the cultivation of other crops and wild
habitats. Despite the widespread belief that cassava takes excessive amount of nutrients from the soil
and can lead to soil nutrient depletion and soil erosion, this finding suggests that cassava has a similar
nutrient withdrawal from the soil as other crops. Reports by many authors also support the finding.
The expansion of cassava production probably resulted from changing the cropping system prioritized
by farmers based on market demand and crop productivity output rather than by claiming new forest
land as previously believed. In Kampong Cham, only about 10% of the interviewed farmers reported the
conversion of forest land to cassava plantation and no farmers in Pailin reported to have converted
forest land to cassava plantation. It is suspected that forest had been earlier cleared for commercial
purpose and/or for the production of other crops such as maize before it has been transferred to cassava.
Nevertheless, as forest data is not available or very difficult to be obtained a conclusive remark about
the effect of cassava production on deforestation cannot be drawn. It is suggested that this subject
should be further analysed in order to provide a clear picture on the relationship between cassava
expansion and deforestation.
There are three types of cassava processing plants in Cambodia: dried chip, dried starch and wet starch
processing. Cassava processing produces big quantity of solid and liquid wastes that can have negative
impact to the environment and human health. Through their strong and unpleasant smell, wastewater
and solid wastes can cause a hostile environment for farming communities living nearby. The analysis
of water samples collected from the water courses nearby the processing plants indicated that the levels
of Total Dissolved Solids (TDS) and Total Organic Carbon (TOC) are much higher than the standard
value for household consumption. In addition, the aesthetic and beauty of the environment is also
substantially affected by cassava processing if they are not properly managed. Unless these wastes are
treated properly and well protected from leaking to the water stream in the areas, the use of water
originated from those areas for drinking and/or cooking should be avoided.
More than 50 per cent of cassava processing managers recognize the problems arising from their
processing wastes and for that reason most of the processing plants have already set up their own waste
management structure. However, it appears that since most of the structures do not follow technical
specifications, they are prone to flooding during the rainy season and current waste processing
procedures produce a strong and unpleasant smell for the nearby villages. During flooding, wastewater
that is contained in each pond is often discharged freely into rice fields or other open water sources in
the area.
It is recognized that newly developed waste management technologies are available in the country, but
they are more suitable for larger scale rather than for small and medium cassava processing plants
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which are still struggling to keep their business going. Limited access to those new technologies, lack of
relevant information on newly developed waste management technology and lack of confidence of
processing managers on developed technologies are considered the main barrier for developing eco-
friendly cassava processing industry in the country.
To overcome those constraints, technical support from relevant departments and institutions, and an
appropriate enforcement of existing national codes of conducts on waste management are necessary.
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TABLE OF CONTENTS
Executive Summary ……………………………………………………………………….. 2
Acronyms and Abbreviation ……………………………………………………………… 6
Introduction ………………………………………………………………………………... 7
Methodology ………………………………………………………………………………. 9
Results and Discussions …………………………………………………………………… 11
1. Assessing degree of soil erosion and the depletion of soil nutrients and soil organic
matter (organic carbon), and identification practical mitigation measures that can
be adopted by small-scale farmers to sustain their cassava production
11
• General situation of cassava production and its trend ………………………… 11
• Composition of soil nutrients and soil organic matters in soil planted to
cassava and other crops ………………………………………………………. 17
2. Expansion of areas under cassava cultivation relative to other previous and current
land uses including other cash crops, forest, and deforested areas ………. 23
3. Current practices of different scale cassava processing plants in term of waste
management. ……………………………………………………………………… 25
• General situation of cassava processing plants and their waste management 25
• Cassava dries chip processing ………………………………………………... 26
• Cassava dried starch processing …………………..………………………….. 27
• Cassava wet starch processing ……………………………………………….. 30
• Impact of cassava processing wastes on environment ………………………. 31
• Awareness of cassava processors on waste management and their constraints
in adopting new management ………………………………………………… 36
Conclusion ………………………………………………………………………………… 38
Recommendations…………………………………………………………………………. 40
Mitigation measures to sustain the country cassava production ……………………… 40
Sustainable utilization and management of cassava processing wastes………………. 43
References ………………………………………………………………………………… 44
Appendices ………………………………………………………………………………… 46
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ACRONYMS AND ABBREVIATIONS
CARDI Cambodian Agricultural Research and Development Institute
CIAT International Centre for Tropical Agriculture
GDA General Directorate for Agriculture
K Potassium
KCl Potassium chloride
MAFF Ministry of Agriculture, Forestry and Fisheries
MOE Ministry of Environment
MofCOM Ministry of Commerce of China
N Nitrogen
NGO Non-Governmental Organization
NPK Nitrogen, Phosphorus and Potassium
OM Organic matter
P Phosphorus
PDA Provincial Department of Agriculture
RUA Royal University of Agriculture
SOM Soil organic matter
TDS Total Dissolved Solids
TOC Total Organic Carbon
UNDP United Nations for Development Programmes
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INTRODUCTION
Cassava (Manihot esculenta Crantz) is the second largest crop production in Cambodia after rice. It is
grown mainly by smallholder farmers for food to supplement the rice diet, for animal feed and for
extraction of starch from its roots. At the recent years there has also been major interest in the use of
cassava as a raw material for the production of ethanol.
Traditionally cassava production in Cambodia was only a farmstead crop production that is grown
mainly on the farmer backyard. However, the situation changed. For the last 10 year cassava production
area in Cambodia expanded exponentially from less than 30 thousand hectares in 2004 to more than 400
thousand hectares in 2013 (MAFF, 2005-2013). Cassava is cultivated in almost all provinces in the
country, but major production is found in Kampong Cham, Battambang, Pailin, Kratie, and Kampong
Thom where cassava production areas range from 20 thousand hectares in Pailin to almost 70 thousand
hectares in Kampong Cham (MAFF, 2013).
The expansion of cassava from a homestead crop to a commercial crop, and to the second largest crop
production in the country raised many concerns especially in its relation to deforestation. It was reported
that in 1960 Cambodia's forests covered 73% of the total land area of the country. This forest coverage
decreased dramatically to 58 per cent in 1999 with the annual deforestation rate between 1993-97
estimated at 140,000-175,000 ha (MOE, 2002). It is believed that the reduction has been attributed
mainly to commercial logging and agricultural encroachment.
There are contradicted reports about the impacts of cassava growing to the environment, particularly on
soil structure and its nutrients. It is widely believed that, cassava is known to cause serious soil
degradation due to excessive uptake of nutrients leading to soil nutrient depletion, or by causing serious
soil erosion when grown on slopes.
In contrary, research has shown that cassava extracts less nutrients from the soil than most other food
crops (Howeler, 1991; Charoenrath et al., 2012) that makes cassava to be grown in areas with low soil
fertility where other crops cannot be grown productively. However as it is true for all crops when
cassava is grown continuously on the same land without inputs of manure or fertilizers, soil nutrients
will eventually be depleted and productivity will decline (Howeler, 1991; Charoenrath et al, 2012). This
is undeniable as even without growing any crop, the soil fertility will naturally decline by nutrient
leaching and erosion, particularly in the case of sandy soil texture. Finding has suggested that, soils
planted to cassava are particularly susceptible to erosion during the initial stage of the crop before the
canopy closes and rain impacts directly on the soil (Putthacharoen et al., 1998). To alleviate the
problem, in some areas bush-fallow rotations are used to maintain availability of soil nutrients for the
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next crop, but where such rotations are not possible, farmer apply animal or green manures, or chemical
fertilizers to maintain yields.
Cassava processing produces large amount of wastes including solid and liquid which are high in
organic matter constituents and cyanide. Solid wastes are mainly derived from cassava chip processing,
if properly managed, can be utilized in many ways in crop and animal productions. Liquid (water) waste
on the other hand has the potential to pollute ground water or lakes, rivers or streams into which it
flows. Cassava processing can also produce unpleasant smell and unattractive pictures. Due to all these
problems, cassava processing has always been regarded with a reputation of a major environment
pollutant.
However, there has been little reported study on extents of environmental concerns caused by both
cassava production and processing, and how to alleviate the problem to an acceptable level. The main
objectives of this study are therefore:
a) Assessing to what degree cassava plantation has caused soil erosion and the depletion of soil
nutrients and soil organic matter (organic carbon), and identifying practical mitigation measures
that can be adopted by small-scale farmers to sustain their cassava production.
b) Documenting and quantifying the recent expansion of areas under cassava cultivation relative to
other previous and current land uses including other cash crops, forest, and deforested areas.
This relates to concerns about the possible causal links between cassava production and
deforestation, the value and efficacy of utilizing cleared land for cassava cultivation, and the
wider issue of agricultural zonation.
c) Identifying the current practices of different scale cassava processing plants in term of waste
management, assessing the potential risks from this waste management on the environment and
especially on water resources, and identifying the current proper waste management applied by
the processors as well as the technologies which are either presently available or under
development for waste treatment and management.
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METHODOLOGY
Within the framework of the Cambodia-China-UNDP South-South Cooperation on Cassava Project
funded by the Chinese Ministry of Commerce (MofCOM), managed by UNDP Cambodia and the
Cambodian Ministry of Agriculture, Forestry and Fisheries, a study on environmental impact
assessment was carried out by a team from the Royal University of Agriculture. The study was
conducted in two provinces of Kampong Cham (Tbaung Khmom) and Pailin using both quantitative and
qualitative approaches. In Kampong Cham, based on cassava planted areas, three districts of Dambe,
Memot and Tbaung Khmom were selected for the study, whereas in Pailin the study was conducted in
the districts of Pailin and Sala Krao (Appendix 2). This study included surveys with cassava farmers and
processors, and testing on soil nutrient content (NPK), pH and soil organic matter (SOM) and on water
quality through identifying pH, Total Dissolved Solids (TDS) and Total Organic Carbon (TOC) in water
sources closed to the cassava processing plants.
1. Survey- there were two types of surveys: (1) cassava production history and practices in selected
location, and (2) waste management practiced by different level of cassava processors (small,
medium and large). For the first type of survey, 20 cassava farmers in each district were selected
for interviewing. That is 100 farmers in total selected for interviewing in the study
(Questionnaires attached: Appendix 2). This survey focused on:
- History of cassava production in the region: when and why
- Production practices: how to grow, application of fertilizer and pesticides, experience and
management of soil erosion, physically, mode of harvesting, and trend of cassava production
in the study areas.
For the waste management survey, a total of 41 cassava processors were selected for the study
(Questionnaires attached: Appendix 3). The focus of this survey was:
- Identification of different types of wastes produced by different levels of cassava processors
- Assessment of the processors’ understanding about the hazards of the wastes to human
health and surrounding environment including water sources in the surrounding areas, and
their waste management
2. Soil test- horizontal analysis of soil nutrient, pH and SOM were analyzed. Soil samples from the
areas under cultivation of cassava of not less than 3 years were taken for laboratory testing. The
same procedure was applied for those areas in close proximity with cassava plantation but
planted to other crops (cassava never planted in that area for at least 5 years), and also those
areas where forest or natural habitats are present. Sampling was conducted in two horizontal
layers- the topsoil (0-20cm) and at 30 to 50 cm depth. A total of 120 testing samples were taken
for laboratory testing on the availability of total nitrogen (N), phosphorus (P), and potassium
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(K), pH and the availability of soil organic matter (SOM). Sampling was taken from 3 cassava
growing districts in Kampong Cham (Dambe, Memot and Tbaung Khmom), and two districts in
Pailin. Five composite samplings in any location were mixed to constitute one testing sample.
3. Water quality test – 70 Samples of water sources (open well, deep well, pond or river) located in
close proximity to cassava processing plants were collected and sent to laboratory for testing on
pH, total dissolved solids (TDS) and the amount of total organic carbon (TOC) in the water.
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RESULTS AND DISCUSSIONS
1. Assessing degree of soil erosion and the depletion of soil nutrients and soil organic matter
(organic carbon), and identification practical mitigation measures that can be adopted by
small-scale farmers to sustain their cassava production.
1.1 General situation of cassava production and its trend in Kampong Cham and Pailin
There were 100 cassava farmers randomly selected for this study. Amongst them 60 farmers are
from Kampong Cham and, 40 farmers are from Pailin. More than half of the farmer interviewees were
male, about 40 per cent have never attended any school about the same percentage have attended
primary classes and only 16-17 percent have high school degree (Table 1).
Table 1 Distribution of famers on gender and educational background
Kampong Cham Pailin
Respondent % Respondent %
Educational background
• Never attended 25 42 15 38
• Primary 25 42 18 45
• Secondary 10 16 7 17
• University 0 0 0 0
Gender of interviewee
• Male 33 55 25 62
• Female 27 45 15 38
More than 50 per cent of cassava plantation in Kampong Cham is cultivated on flat land and only 42 per
cent on sloping land. In Pailin, the situation is contrarily different from Kampong Cham, where 90 per
cent of cassava production is practiced on sloping areas (Table 3). Results of this study indicated
however that, in both Kampong Cham and Pailin, cassava is predominantly cultivated in the areas where
the slope is less than 30 degree and only in few isolated occasions where it is practiced in the area which
is steeper than 45 degree (Table 3).
This study also shown that, despite the production of cassava from 42 per cent to 90 per cent is
practiced on sloping land (Table 3), most farmers do plough the land up-down the slope (Table 4).
Result indicates that we have less than 36 per cent of farmers who prepare the land by contour and up to
80 per cent of farmers do prepare the land up and down the slope (Table 4). This latter practice can have
a very negative impact to the soil as it makes the land very susceptible to soil erosion especially if it is
associated with heavy rainfall. According to Howeler (2012) soil erosion is a function of rainfall, soil
structure, length and gradient of the slope, crop and management factors. Therefore this poor crop
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management could accelerate soil erosion in the area if this disturbing situation is not corrected on time.
Results from the survey have indicated that 16 farmers (17 per cent) in Kompong Cham and 10 farmers
(22 per cent) in Pailin reported of the problem they have come across with soil erosion on their cassava
plantation (Table 8).
Due to time limitations, quantifying soil erosion was difficult, but there are reports from many research
studies in the region that confirm a strong association between cassava productions in sloping land on
soil erosion (Howeler, 1991; Tongglum et al.; 1998, Vongkasem et al., 2000; Putthacharoen et al.
,1998; Suyamto and Howeler, 2004; Nguyen Dinh Kiem, 1989). According to Nguyen Dinh Kiem
(1989) cassava cultivation as monoculture gave a level of erosion of 145.1 t/ha/year that is significantly
higher than planting tea (33.3 t/ha/year), pine forest (28.7t/ha/year) and natural grass (12 t/ha/year).
Despite the quantity of the soil erosion being rather lower in their study, Suyamto and Howeler (2004)
reported that farmers practice (up-and-down ridging) produce a high level of erosion (11.81 t/ha) in
comparison with other cultural practice in cassava-based cropping systems in Indonesia.
Table 3 Topography of the areas planted to cassava
Topography Kampong Cham Pailin
Correspondent Share (%) Correspondent Share (%)
Flat 35 58 4 10
Slope 25 42 36 90
• Gentle slope (< 150) 10 40 20 55
• Medium (150-300) 8 32 10 28
• Steep (300-450) 5 20 2 6
• Very steep (>450) 2 8 4 11
Table 4 Land preparation practices by cassava farmers where the crop is planted in sloppy land.
Kampong Cham Pailin
Respondent Frequency (%) Respondent Frequency (%)
Plowing by contour 9 36 6 17
Plowing up and down of
the slop
16 64 30 83
Total 25 100 36 100
The majority of farmers in both provinces have less than 10 ha of land for cassava plantation (Table 5).
In Kampong Cham, famers do plant the crop directly without raising a bed but it is contrary to Pailin
where raising bed for cassava production is most common (Table 6). Differences in this practice are
probably influenced by differences in weather conditions of the two provinces where the study is taken.
Based on weather data over many years, it is obvious that rainfall in Kampong Cham is between 1200 to
1400 mm, which is less than the average rainfall in Pailin where it can range from 1600 to 1800 mm. In
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the area where rainfall is high, the construction of a bed is important in order to protect the crop from
flooding especially at the early stages of plant growth. This study also indicates a (possible) relationship
between rainfall pattern and planting method which can be horizontally (180 degree) or vertically (45-
90 degree). Result from this study has shown that most farmers in Kampong Cham prefer to plant the
crop horizontally (180 degree), whereas in Pailin, where the average rainfall in high, vertical planting is
more common (Table 6).
Table 5 Size of cassava plantation and percentage of farmer holding from 60 respondents in Kampong
Cham and 40 in Pailin.
Size of cassava plantation Frequency (%)
Kampong Cham Pailin
Less than 5 ha 62 45
Less than 10 ha 99 83
Less than 20 ha - 98
Less than 50 ha - 100
Less than 100 ha -
Less than 300 ha 100
Table 6 Cassava production practices.
Kampong Cham Pailin
Respondent Frequency (%) Respondent Frequency (%)
Raised bed 12 20 39 98
No bed 48 80 1 2
Planting vertical (900) 4 7 34 85
Planting horizontal (1800) 56 93 6 15
Spacing 50 x 150 cm 27 45 9 23
Spacing 100 x 100 cm 17 28 1 2
Spacing (others specify: 80x 80
cm,80x 100cm, 70x 70 cm 16 27 30 75
For the last 5 years, cassava productions trends in both provinces have indicated a declining yield (Table
7). In Kampong Cham yield declined from as high as 30.5 tons in a hectare before 2010 to less than 20
tons in 2013 (38 per cent decline). In Pailin, the situation is very similar: cassava root yield continuously
dropped from about 50 tons before 2010 to less than 30 tons of root yield in 2013 (42 per cent decline).
Causes for yield decline are presented in Table 8. Based on results presented in Table 8, it clearly
suggests that in Kampong Cham, where more than 50 per cent of the production is on flat land (Table
3), the main reasons for yield decline include weed problems, soil fertility decline and erosion, damages
caused by pests and diseases, the use of poor planting materials and heavy rainfall. In Pailin, where
more than 90 per cent of the production is on sloping land, excessive rain, erosion and declining soil
fertility and, poor planting materials are blamed for yield decline (Table 8).
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Table 7 Cassava Root yield (T/ha) for the last 5 years of cassava plantation.
Year Kampong Cham Pailin
Yield (T/ha) Standard
Deviation
Yield (T/ha) Standard
Deviation
2013 18.9 7.8 29.5 9.0
2012 25.8 27.9 36.4 12.0
2011 24.6 8.1 38.0 18.7
2010 27.2 9.0 42.0 18.7
Before 2010 30.5 10.9 50.6 21.1
Table 8 Reasons for yield decline in cassava production
Reasons Kampong Cham Pailin
Respondent % Respondent %
1 Weed problems 14 15 4 9
2 Soil erosion and soil
fertility declines
16 17 10 22
3 Insects and diseases 23 24 2 4
4 Stem and tuber of cassava
are destroys
3 3 4 9
5 Hot weather and too
much rains
12 13 11 24
6 Poor planting materials 11 12 5 11
7 No respond 15 16 9 20 Note: Respondent can provide more than one answers.
The majority of surveyed farmers (65-95 per cent) in both provinces have indicated that they never use
fertilizer in their cassava production (Table 10). It is understandable that upland soils in both provinces
where cassava is cultivated, classified as Kampong Siem, O’Riang Eu and Labansiek soil group which
are considered rich in soil nutrients (CARDI, 2009; CARDI, 2011; Bell et all, 2007; Seng vang et al.,
2007). Nevertheless, due to lack of nutrient replacement especially in the case where cassava is
continuously cultivated in the same area for many years, soil fertility certainly decline and consequently
lower cassava root yield. Therefore reduction in yield for the last 5 years (Table 8) could have resulted
from overexploitation of land resources where substantial quantities of nutrients are taken from the
field. This finding is supported by earlier studies. According to Howeler (2012), continuously planting
crops without fertilizer resulted in yield decline in all crops as nutrients are removed from the field in all
plant parts. As noted by Nguyen Tu Siem (1992), continuous cropping of upland rice and cassava
without fertilizer resulted in zero yield in the fourth crop cycle for upland rice, while cassava still
produced about 40 per cent of its first year yield.
While there is no formal research on the links between pests and diseases and cassava production,
results from this study confirm their presence and the damage that they can cause to cassava crop yields
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(Tables 8 & 14). All farmers in both provinces ought to apply pesticides, in order to save their cassava
crop from being damaged by pests and diseases (Table 10). The use of pesticides on cassava production
especially if it is not under technical recommendation brings another negative impact to the
environment and human health. It is important therefore that this practice should be properly checked
and interventions should be promptly organized. There are other ways of managing crop damage by
pests and diseases. For instant, uses of resistant varieties, healthy planting materials and natural
biological agents are considered the other effective measures against pests and diseases but unlike the
use of chemical pesticides, these latter measures have no negative impact to the environment and human
wellbeing and also feasible or economic option for low-income farmers (Howeler, 2014, CARDI, 2012).
.
Table 10 Fertilizer and pesticides uses in cassava production.
Kampong Cham Pailin
Respondent % Respondent %
Fertilizer application
• Use 21 35 2 5
• Never use 39 65 38 95
Pesticides application
• Use 47 78 39 98
• Never use 13 22 1 1
With only 2 isolated cases in Pailin, cassava is manually harvested and the harvested roots are sold
directly to the traders without prior cleaned by any type of water (Tables 11 and 12). More than 99 per
cent of cassava roots sold is in the form of fresh roots with only 1-2 per cent is in the form of dried chip
(Table 12). Minimal involvement of machine harvester in cassava production plus no use of water to
clean the harvested roots is a positive sign in soil conservation strategy. Generally it is believed that the
combination of these two management practices, machine harvester and water cleaning can cause
serious soil erosion at the harvesting time.
Table 11 Harvesting in cassava production.
Kampong Cham Pailin
Respondent % Respondent %
Harvesting
• Machine harvester 0 0 2 5
• By hand 60 100 38 95
Cleaning
• Yes 0 0 0 0
• No 60 100 40 100
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Table 12 Sale of cassava products
Kampong Cham Pailin
Quantity (Ton) % Quantity (Ton) %
Year 2012
• Fresh roots 1467.5 99 8450.0 >99
• Dried chip 19.5 1 38.5 <1
Year 2013
• Fresh roots 1461.0 99 8294.3 96
• Dried chip 10.0 1 341.7 4
Note: Figures presented in this table are sum from all participated farmers in the survey.
Table 13 Cassava contribution to the household economy
Year Kampong Cham (%) Pailin (%)
Cassava Rice Others Cassava Rice Others
2013 70 15 15 76 0 24
2012 71 15 14 76 0 24
2011 74 14 12 70 0 30
2010 76 13 11 66 0 34
Before 2010 79 11 10 55 0 45
Cassava production in both provinces is facing insecurity unless all the constraints raised by famers are
solved (Table 14). In both provinces, Kampong Cham and Pailin, more than 60-70 percent of farmers
considered yield decline which is due to pests and diseases damage, and damage caused by drought and
flood, as the main constraints in their cassava production. Availability of labor is also raised by farmers
in both provinces, but it appeared that the problem is more serious in Pailin (35 per cent) then in
Kampong Cham (8 per cent). It is true that labor availability is becoming a major issue in all crop
production systems, including cassava, and this can be more critical if the production is to be expanded.
As Cambodia is solely dependent on international market for cassava products, any fluctuation in
cassava demand in the international market, particularly Chinese market, can have strong influence to
the local market. This situation cannot be avoided unless direct trade deal with Chinese counterpart is
to be made and along with that cassava wet starch processing is to be expanded and its production is met
the required standard. If the situation cannot be solved the move to more profitable crops such as rubber
and black pepper cannot be excluded. This speculation can be confirmed in the Table 15 where about 40
per cent of famers in Kampong Cham are ready to move to other cropping system as due to the
constraints they are facing (Table 14) and only 32 per cent will stay in the cassava business. There is a
reversed trend in Pailin, where more than 67 percent of farmers in Pailin still prefer to stay with cassava
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regardless of the problems they are facing and only 3 per cent said they want to stop growing this crop
(Table 15).
Yield declines which are more likely resulted by pest damages and soil fertility decline, can be
overcome by technical support of field experts providing that there is such a program available.
Table 14 Constraints in cassava production
Kampong Cham Pailin
Respondent Percentage Respondent Percentage
1 Availability of labor 4 8 14 35
2 Low price 7 14 0 0
3
Yield declined (Pest problems,
drought and too wet) 38 78 26 65
Table 15 Future plan
Kampong Cham Pailin
Respondent % Respondent %
1 Stop growing cassava 24 40 1 3
2 Grow more cassava 19 32 27 67
3 Not sure 15 25 8 20
4 Any other reasons 2 3 4 10
1.2 Composition of soil nutrients and soil organic matters in soils planted to cassava and other crops
Soil samples from the areas under cultivation of cassava of not less than 3 years were taken for
laboratory testing. The same procedure was applied for those areas planted to other cash crops located
in close proximity to cassava plantation but has never been planted to cassava, and those areas where
forest or natural habitats are present. Sampling was conducted in two horizontal layers- the topsoil (0-
20cm) and the sub-soil at 30 to 50 cm depth. From each layer, a total of 60 testing samples were taken
for laboratory testing. From these 60 samples, 20 are from cassava production plot, 20 from cash crop
production areas and the remaining 20 from forest land. At each sample site five composite samplings
were mixed to constitute one testing sample. Analyses on the availability of totals nitrogen (N),
phosphorus (P), and potassium (K), pH and the availability of soil organic matter (SOM) was conducted
in a private Food and Chemical Services laboratory in Phnom Penh (Appendix 5). Results of laboratory
analysis are presented in Tables 16-19.
Results from soil profile study conducted in Kampong Cham and Pailin demonstrated that cassava
production in Cambodia is generally occupied in three major soil groups namely Kampong Siem,
O’Riang Eu and Labansiek (Bell et al, 2007; Seng et al., 2009). This finding is strongly supported by
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the earlier upland soil classification in Cambodia by the Cambodian Agricultural Research and
Development Institute (White et al., 1997; Seng et al., 2007). Details description of each soil types can
be found in Appendix 6.
Results from this study do not support the hypothesis that cassava production leads to the depletion of
soil nutrients. Based on soil nutrient analysis, when comparing soil nutrients of N, P and K between soil
samples, at both top-soil layer (0-20cm) and sub-soil layer (30-50cm), taken from cassava growing
areas and those samples taken from land areas under the production of other crops and wild habitat we
found no differences between them for either in Kampong Cham or Pailin. Similar situation is found if
we compare the level of pH, soil humidity and organic matter (OM).
In all cases, we have test statistics of t comparatively lower than its critical value, therefore we can
declare with confidence that the levels of soil nutrients in the areas under cultivation of cassava are no
statistically different from those under the cultivation of other crops or under wild habitats (Table 16-
18).
Results from the analysis of soil samples collected from cassava production areas are contradicted to
general believes of high nutrient leaching in cassava cultivation but they are consistent with results
obtained from other studies. Nevertheless, this finding suggests the following:
• It is an indication that cassava has a similar nutrient withdrawal from the soil as compared to the
other crops. Earlier report presented by Howeler (1991) and Charoenrath et al. (2012) confirm
this finding as they came to the conclusion that cassava extracts even less nutrients from the soil
than most other food crops, and for that reason cassava can be grown in areas with low soil
fertility where other crops cannot be grown productively. Nevertheless, there has no earlier
report study on soil nutrients comparison between land of natural habitat and land planted to
cassava. It is very difficult however to make a general conclusion on nutrient withdrawal from
the soil as natural habitat consists of a diversity of different plant species, ranging from grasses,
bushes and trees, within any location and that can vary greatly between locations.
• In the common sense, natural forest soils are better in physical, chemical and biological
properties than agricultural soils. It can be true for some but not all. In our case, due to the
expansion of commercial and agricultural activities in the regions, there is no dense forest
nearby therefore degraded forest lands which are as much as natural grass land where soil
nutrients are easily degraded especially if this forest situates on sloping land were used (Picture
plate 1). Occasional application of fertilizers, chemical and/or organic, and tillage when the land
is cultivated could be the other factors that can help maintain soil properties in the agricultural
land as compare to neglected degraded forest land. Result of this study may also provide, other
Page | 19
than just a comparison with cassava planted land, a general picture of nutrient values of
degraded forest land.
Picture Plate 1. Wild habitat and degraded forest lands where soil samples were taken.
Tables 16 & 18 clearly show that the average content of nitrogen (N) in the soil surface of samples
taken from the three types of soils planted to cassava, to other crops and to forest are consistently
similar among them as well as between the provinces. In Kampong Cham the level of N ranges 1.29,
1.35 & 1.27 g/Kg dry weight for cassava planted soil, for other crops cultivation and for forest soil,
respectively. In Pailin, they are at a similar range of 1.32, 1.65 & 1.35 g/Kg dry weight, respectively.
There is also similarity (no significant difference) between the level of phosphorous (P) in any particular
province, but its level appears higher in Kampong Cham soils than in Pailin as it ranges of 0.44, 0.48,
0.34 vs 0.14, 0.13, 0.06 g/Kg dry weight respectively. This result may indicate that Kampong Cham
soils are rich in P as compared to Pailin. It is in a reversed situation for the level of potassium (K) as it
contains higher in Pailin than in Kampong Cham soils. There are also differences in pH and OM in both
provinces. According to this study, soil in Kampong Cham is more acidic (pH is around 5), whereas in
Pailin it is close to neutral (pH is around 6.30). Pailin Soil is also likely to have more organic matter
(OM) than in Kampong Cham soils (Table 20).
Results also indicate that at the sub-soil layer (30-50cm), there is lower in the content of N and poorer
OM as compared to the surface layer. There is no difference however between the levels of P, K and
soil humidity (Table 20).
Page | 20
Table 16 Nutrient contents of soils under cassava, other crop productions and forest habitat in Kampong
Cham
N (g/Kg DW) P (g/Kg DW) K (g/Kg DW)
Cassava Crops Forest Cassava Crops Forest Cassava Crops Forest
Top Soil (0-20cm)
Min 0.36 1.09 0.52 0.04 0.05 0.03 0.14 0.17 0.15
Max 3.47 1.96 3.93 1.44 1.16 1.37 0.95 0.29 0.38
Mean 1.29 1.35 1.27 0.44 0.48 0.34 0.31 0.20 0.24
Standard deviation 0.70 0.35 0.91 0.41 0.45 0.41 0.24 0.05 0.07
t-test (cassava vs crops) 0.80 0.86 0.10
Level of significance ns ns ns
t-test (cassava vs forest) 0.95 0.53 0.27
Level of significance ns ns ns
Sub Soil (30-50cm)
Min 0.36 0.34 0.32 0.04 0.05 0.03 0.14 0.14 0.14
Max 1.82 0.97 1.14 0.62 0.59 0.72 0.82 0.32 0.42
Mean 0.76 0.72 0.64 0.23 0.35 0.23 0.22 0.20 0.21
Standard deviation 0.36 0.25 0.23 0.19 0.22 0.22 0.16 0.07 0.08
t-test (cassava vs crops) 0.80 0.33 0.58
Level of significance ns ns ns
t-test (cassava vs forest) 0.28 0.91 0.72
Level of significance ns ns ns
Table 17 Soil pH, humidity and organic matter (OM) of soils under cassava, other crop productions and
forest habitat in Kampong Cham
pH Soil humidity (g/100g) OM (g/100g DW)
Cassava Crops Forest Cassava Crops Forest Cassava Crops Forest
Top Soil (0-20cm)
Min 3.93 4.40 4.16 2.99 9.36 3.06 1.26 2.40 1.39
Max 6.26 5.70 6.50 17.70 17.20 19.20 5.02 4.22 5.29
Mean 5.16 5.04 5.08 8.02 12.69 9.48 3.07 3.45 2.91
Standard deviation 0.64 0.60 0.72 4.58 3.34 5.91 0.97 0.76 1.18
t-test (cassava vs crops) 0.73 0.47 0.71
Level of significance ns ns ns
t-test (cassava vs forest) 0.72 0.03 0.38
Level of significance ns ns ns
Sub Soil (30-50cm)
Min 4.16 4.30 3.93 6.81 10.70 6.13 0.87 0.83 0.67
Max 6.33 5.53 6.90 18.50 19.10 21.50 4.37 4.38 4.51
Mean 4.99 4.84 4.68 13.28 15.34 12.97 2.38 2.94 2.54
Standard deviation 0.74 0.49 0.79 3.98 3.73 5.33 1.11 1.37 1.41
t-test (cassava vs crops) 0.58 0.32 0.43
Level of significance ns ns ns
t-test (cassava vs forest) 0.27 0.86 0.73
Level of significance ns ns ns
Page | 21
Table 18 Nutrient contents of soils under cassava, other crop productions and forest habitat in Pailin
N (g/Kg DW) P (g/Kg DW) K (g/Kg DW)
Cassava Crops Forest Cassava Crops Forest Cassava Crops Forest
Top Soil (0-20cm)
Min 0.67 0.77 0.82 0.03 0.04 0.05 0.28 0.57 0.66
Max 1.89 3.11 1.88 0.27 0.28 0.06 0.99 2.28 1.41
Mean 1.32 1.65 1.35 0.14 0.13 0.06 0.55 1.20 1.04
Standard deviation 0.43 0.66 0.75 0.06 0.09 0.01 0.21 0.61 0.53
t-test (cassava vs crops) 0.20 0.58 0.01
Level of significance ns ns ns
t-test (cassava vs
forest)
0.96 0.00 0.41
Level of significance ns ns ns
Sub Soil (30-50cm)
Min 0.40 0.42 0.36 0.04 0.07 0.18 0.17 0.15 0.26
Max 1.76 1.51 1.19 0.39 0.21 0.24 0.93 1.19 1.24
Mean 0.86 0.95 0.78 0.13 0.12 0.21 0.41 0.55 0.75
Standard deviation 0.37 0.36 0.59 0.10 0.05 0.04 0.20 0.32 0.69
t-test (cassava vs crops) 0.59 0.80 0.25
Level of significance ns ns ns
t-test (cassava vs
forest)
0.87 0.12 0.61
Level of significance ns ns ns
Table 19 Soil pH, humidity and organic matter (OM) of soils under cassava, other crop productions and
forest habitat in Pailin
pH Soil humidity (g/100g) OM (g/100g DW)
Cassava Crops Forest Cassava Crops Forest Cassava Crops Forest
Top Soil (0-20cm)
Min 5.70 5.96 6.36 2.48 1.67 5.30 3.03 3.67 3.64
Max 7.06 7.36 6.63 17.50 15.40 6.33 7.56 6.15 6.53
Mean 6.33 6.55 6.50 8.67 8.38 5.82 4.44 4.84 5.09
Standard deviation 0.46 0.46 0.19 4.50 3.61 0.73 1.13 0.96 2.04
t-test (cassava vs crops) 0.29 0.87 0.38
Level of significance ns ns ns
t-test (cassava vs forest) 0.45 0.06 0.73
Level of significance ns ns ns
Sub Soil (30-50cm)
Min 5.66 5.06 6.03 9.49 7.30 7.01 2.87 3.02 2.49
Max 6.96 6.90 7.63 19.20 23.00 13.70 5.10 4.97 5.20
Mean 6.33 6.30 6.83 14.22 14.46 10.36 3.94 3.87 3.85
Standard deviation 0.41 0.52 1.13 3.45 5.25 4.73 0.74 0.75 1.92
t-test (cassava vs crops) 0.89 0.90 0.83
Level of significance ns ns ns
t-test (cassava vs forest) 0.64 0.44 0.96
Level of significance ns ns ns
Page | 22
Table 20 Average soil nutrients and Soil pH, humidity and organic matter (OM) for both provinces
Nitrogen (g/Kg DW)
Phosphorous (g/Kg DW)
Potassium (g/Kg DW)
pH Humidity (g/100g)
OM (g/100g DW)
KC Pailin KC Pailin KC Pailin KC Pailin KC Pailin KC Pailin
Surface layer
• Cassava 1.29 1.32 0.44 0.14 0.31 0.55 5.16 6.33 8.02 8.67 3.07 4.44
• Other crops 1.35 1.65 0.48 0.13 0.20 1.20 5.04 6.55 12.69 8.38 3.45 4.84
• Forest 1.27 1.35 0.34 0.06 0.24 1.04 5.08 6.50 9.48 5.82 2.91 5.09
Average 1.30 1.44 0.42 0.11 0.25 0.93 5.09 6.46 10.06 7.62 3.14 4.79
Sub-soil
• Cassava 0.76 0.86 0.23 0.13 0.22 0.41 4.99 6.33 13.28 14.22 2.38 3.94
• Other crops 0.72 0.95 0.35 0.12 0.20 0.55 4.84 6.30 15.34 14.46 2.94 3.87
• Forest 0.64 0.78 0.23 0.21 0.21 0.75 4.68 6.83 12.97 10.36 2.54 3.85
Average 0.71 0.86 0.27 0.15 0.21 0.57 4.84 6.49 13.86 13.01 2.62 3.89
KC : Kampong Cham,
Page | 23
2. Expansion of areas under cassava cultivation relative to other previous and current land
uses including other cash crops, forest, and deforested areas.
The national data on major crop production areas have indicated a substantial increase in cassava
plantation along with a marginal increase of maize (Table 21). As shown in this Table 21, from 2010 to
2013 there was a new claimed land for agricultural production of 477, 229 ha, from which rice
cultivation claimed more than 50 per cent, followed by cassava (48 %) and maize (7%). On the other
hands, there was a reduction in soybean and mungbean production. It is not clear, how this agricultural
land could be increased in this substantial figure, but as suggested by MOE (2002), this could be
attributed to the encroachment on forest land through deforestation activities.
However, this study has shown that only 10 per cent of cassava farmers in Kampong Cham admitted
that the land they currently use for cassava plantation had recently been converted from a forest land
(Table 22). This was not even the case in Pailin where no farmer has reported of claiming forest land for
cassava production. Result of this study suggests that the expansion of cassava production areas is likely
resulted from changing crop cultivation as prioritized by farmers rather than by transforming forest
areas into cassava land. About 95 per cent of respondents in Pailin specified that they decided to change
from maize to cassava production (Table 22) because of economic reason, i.e cassava produces high
yield and therefore they can get higher income by growing this crop (Table 23). Similarly in Kampong
Cham, where 43 per cent of farmers indicated of their decision to change from soybean to cassava
farmers (Table 22), 35 percent of them agreed that cassava can provide higher yield and more income
for their family (Table 23).
It is obvious that the expansion of cassava production in these areas probably resulted from changing
cropping system prioritized by farmers based on market demand and crop productivity output rather
than by claiming new forest land as previously believed. This result clearly contradicts to a general
belief that a dramatic expansion of cassava production from less than 30 thousand hectares in 2004 to
more than 400 thousand hectares in 2013 (MAFF, 2005-2013) was a direct link to deforestation. It could
be possible that forest had been earlier cleared for the production of other crops such as maize before it
has been transferred to cassava.
Forest data is not available at all levels, district, provincial and national, therefore it is not possible to
make a conclusive remark on the effect of cassava production on deforestation.
Page | 24
Table 21 Areas under crop production in 2010 and 2013 and rate of their increase1)
Cultivated area (ha) Rate of increase (2013-2010)
2010 2013 Hectare %
Rice 2,795,892 3,052,420 256,528 53.8
Maize 205,070 239,748 34,678 7.3
Cassava 190,525 421,375 230,850 48.4
Soybean 101,904 80,688 - 21,216 - 4.4
Mungbean 66,265 54,312 - 11,953 - 2.5
Vegetables 49,873 52,449 2,576 0.5
Others2) 106,690 92,456 - 14,234 - 3.0
Total cropping areas (ha) 3,516,219 3,993,448 477,229 100
1)After MAFF Annual Report 2011 and 2014. 2). Including peanut, sugar cane, sweet potato, sesame, jute and tobacco
Table 22 Crops grown in the areas where is now planted to cassava
Crops grown before
change to cassava Kampong Cham Pailin
Respondent Share (%) Respondent Share (%)
Forest 6 10 0 0
Rubber 2 3 0 0
Maize 1 2 38 95
Soybean 26 43 1 2.5
Others 25 42 1 2.5
Table 23 Reasons for changing to cassava
Reasons Kampong Cham Pailin
Respondent Share (%) Respondent Share (%)
1 Cassava provides high yield and high
income and market demand 21 35 16 40
2 Cassava is easy to grow 3 5 5 12
3 follow their neighbors 8 13 0 0
4 Soybean is low yielding and low price 11 18 1 3
5 Rice cannot grow well 6 10 0 0
6 Have many land 2 3 0 0
7 Maize is low yielding and low income 0 0 10 25
8 Like to change the crop for rotation 1 2 5 12
9 Others 7 12 3 8
10 Not responded 1 2 0 0
Page | 25
3. Current practices of different scale cassava processing plants in term of waste
management. Assessing the potential risks from cassava processing waste management on the
environment and especially on water resources, and identifying the current proper waste
management applied by the processors as well as the technologies which are either presently
available or under development for waste treatment and management
3.1 General situation of cassava processing plants and their waste management
A total of 41 cassava processors were selected for this study. There were 23 in Kampong Cham and 18
in Pailin (Table 24). Despite there is a classification of enterprise based on their investment capital and
number of employee (Table 25 ), in practice this classification cannot be applied in the purpose of this
study for cassava processing plants. Therefore due to lack of information to classify the scale of
cassava processing plants and their availability to join the study, selection of samples for interviews
were based mainly on cassava related products. Those are the production of cassava dried chips, dried
starch, wet starch and semi-final product of cassava known as Sagu and Saray. Thirty one samples were
collected from dried chip processors, 3 from dry starch, 1 from wet starch and 6 from sagu and saray
processors. There are 8 processing plants, 5 in Kampong Cham and 3 in Pailin, that produce dried
starch, but among them only 3 were selected to this study.
Table 24 Type and number of samples selected for waste management survey
Type of processing plant Samples selected
Kampong Cham Pailin Total
Dried chips processors 14 17 31
Dry starch processors 02 01 03
Wet starch processors 01 - 01
Sagu and Saray processors 6 - 6
Total 23 18 41
Table 25: Classification of enterprise of Ministry of Industry and Handicraft, SMEs
Scale Capital/properties of investment (not
include land) (USD)
Number of employee
(person)
Micro Enterprise < 50,000.00 Less than 10
Small enterprise 50,000.00-250,000.00 10-50
Medium enterprise 250,000.00-500,000.00 51-100
Large enterprise > 500,000.00 >100
Source: Department of SMEs, MIH, 2014 (presentation in Seminar on Green Industry)
Page | 26
Based on the above classification to cassava dried chips, dried starch, wet starch and semi-final product
of cassava known as Sagu and Saray, results from this study have clearly shown variation in their
production chains and their associated waste products.
Cassava dried chip processing
Dried chip, sun dried of fresh chopped cassava root, is processed in both provinces. Nevertheless, the
scale of its production in Pailin is relatively larger than in Kampong Cham province. In Pailin, the area
for dried chip production was constructed under big capital investment, whereas in Kampong Cham,
dried chip was produced mainly at family scale and only then directly supply to the local processing
plant or through cassava dealer. Based on the result of this study, it is suggested that for the production
of 463 Kg dried starch, it requires about 1 ton of fresh cassava root.
In both provinces for the production of dried chip, two methods of cassava chopping were observed, i.e
chopping by hand and by machine. Chopping by hand is commonly practiced in small scale processing
plants and can be found in both provinces, Kampong Cham and Pailin. However, chopping by machine
is found in few occasions only in Pailin (Fig.1).
Figure 1 Processing of cassava dried chip and its wastes
Collecting from
farmers
Domestic Processor
(Dry starch processing)
Fresh root of cassava
(1 ton)
Sun drying (7-14 days)
Storage in warehouse
Chopping by
hand
Export
(Thailand)
Chopping by
machine
Dry Chip (463 Kg)
Solid waste: peel,
debris, flour (9.18 Kg)
Odor of Water from
cassava pulp
Odor of Water when
raining
Air pollution (dust)
(Inside processing area)
Use for Fertilizer, as
wood, kept in field
Page | 27
Based on the results of this study, processing of dried chip has produced several forms of wastes.
Dusting commonly happens within the processing floor and creates air pollution which can be harmful
to both workers and the surrounding environment. Solid waste is another form of waste product
produced by dried chip processing. This solid waste can include the peel of cassava roots, root debris
and cassava flour left on the floor after the processing. It is reported that, for 1 ton of fresh root, there is
about 20 Kg of solid waste. Another form of pollution caused by dried chip processing is in the form of
an unpleasant smell that generally vapors after the rain (Table 26).
Table 26 Production of wastes produced at different stage of dried chip processing
Stage of operation Type of waste generated Average amount of waste/Level of
pollution
Peeling and chopping Peel, stem of cassava, and
other debris
20 Kg/Ton of fresh root cassava
Sun drying Smell 10 m (in normal condition)
Liquid waste from
physiological break down
-
Collecting and other
operation
Noise (if using machine) -
Dusty Depending on wind speed
Cassava dried starch processing
Dried starch is one of the main products produced from fresh cassava root. Cassava starch is used in
preparing several delicious foods. The fresh root to dried starch ratio is 1 to 0.25 which means that 1 ton
of fresh roots produces 250 Kg dried starch.
Out of 8 starch processing plants operated in the country, 3 were involved in this study. Among those, 2
are in Kampong Cham and the other one is in Pailin (Table 24). Results of this study have shown, not
only the production capacity of these dried starch factories that are different, they are also equipped with
different technologies and number of employees (Table 27). The TTY which is located in Kampong
Cham is the largest cassava processing plant. They do have the capacity to produce up to 10T dried
starch in one hour and in one day they can produce up to 200T dried starch. The others two, Sun Art in
Kampong Cham and Tay Meng in Pailin are similar in size of production but number of their employee
is big different (Table 27).
Table 27 Scale of processing factories of dried starch product
Name of
factory Location Capacity
Actual
production
Number of Staff
Full time Contract
TTY Kampong Cham 10 t/hour 200 t/day 70 176
Sun Art Kampong Cham (no info) 50 t/day 40 -
Tay Meng Pailin (no info) 45-60 t/day 13 -
Page | 28
As the daily production capacity of these three factories is different and so the technologies they are
applying, there are different types and quantity of wastes produced by any individual factory. The three
visited factories are equipped with different types of drying systems that use different sources of energy.
Heating system in Tay Meng factory used rice husk as energy source for heating, while black oil is used
in Sun Arth factory and, firewood is used in TTY. These heating sources produce different wastes such
as ashes from rice husk and firewood and, oil spillage from black oil. All the heating system produce
smoke, particularly if the source for heating is black oil.
For a normal operation, TTY factory requires a daily minimum of 800 tons fresh cassava roots.
However, its operation is strictly limited as the factory can be functioning for only during the cassava
harvesting season that lasts for three months between December, January and February. This situation
is also true for other factories. Shortage of supply or no supply of fresh cassava roots beyond this period
is the main reason.
The principle of dried starch processing in the three factories is quite similar especially at Sun Art and
Tay Meng factories, where extraction by using water for cleaning and dewatering and, drying by hot air
is used. In TTY, in addition to the principle used by other two factories, the factory has included in the
system a centrifuge device to extract cyanide compound from final product. The three factories however
use different heating device, a device that has a function to supply heat for drying cassava flour. The
heating source of energy used for the heating device is rice husk in Tay Meng, black oil in Sun Arth and
firewood in TTY. Illustration of a general dried starch processing is shown in the Figure 2.
In the process of producing dried starch, a big quantity of fresh roots and big amount of water are used.
Left over parts of the fresh root such as peel, some soil debris and used water for cleaning become both
solid and liquid wastes. These wastes are produced at different processing stages as indicates in Table
28. Despite there are many waste products derived from dried starch processing which can have strong
negative impact to the environment, especially if no proper management has been taken, most
respondents consider unpleasant smell produced by cassava dried starch processing is the major
disturbing waste as it can reach up to 500 meters in diameter. To minimize the problem, the current
practice applied by the processing plant is to pile the solid waste and then cover them with plastic sheet
(Picture 2). At the moment, this practice is likely to be a good innovative approach to halt the smell
from reaching neighboring farming communities, but for a long term solution a more feasible waste
management practice is needed.
Page | 29
Figure 2: Flow diagram of solid and water waste from dried cassava starch processing
Table 28 Types of wastes for dried starch processing
Unit Operation Waste Quantity of processing wastes
TTY Sun Art Tay Meng
Peeling, cleaning, grating Peel, soil
debris
5% of fresh
root
5% of fresh root 55 T in 4-5 days
production
Waste water (*) (no data) (No data)
Grinding, screening Pulp waste - (a) (+)
Filtration/centrifuge waste water (*) (Not data) (No data)
Starch
residue
- (a) (+)
Drying using hot air ash (No data) NA (no data)
Waste water treatment
plant
Smell 30 m 25m 4 m
Note: (*) all wastewater from dried starch processing = 42 m3/T dried starch, (+) solid waste from separation for starch = 85
T in 4-5 days production, (a).solid waste from separation for starch = 600 Kg per fresh roots
Fresh root of cassava
(1 ton)
Peeling, Washing
Grating
Grinding and Screening
Filtration/Centrifuge
Drying using hot air
Cyclone and cooling cyclone
Shifter and packaging
Dry cassava starch
Water
Burning of:
-Oil (for Tay Meng)
-Wood (for TTY)
-Rice husk(for Sun Art)
Water
Peel, soil debris
Pulp waste
Starch residue
Waste water
Waste water
Ash water
Page | 30
Picture plate 2 Solid waste is covered with plastic sheet to halt the smells from reaching to nearby
village
Cassava wet starch processing
Wet starch production is mainly for the production of sagu and saray. Due to the limitation of wet starch
processing plant in the country, only one factory of wet starch processing which is located in Sourng
district, Kampong Cham (Tbaung Khmom) province was used in this study. The factory is considered a
small scale processor, with the capacity of producing wet starch of 30 T of fresh root per day. The
operational flow of wet starch processing is shown in the Fig. 3.
Figure 3: Flow diagram of wet starch processing and associated wastes
Fresh root of cassava
(1 ton)
Cleaning, grating, washing
Grinding
Filtrating for starch solution
Wet starch (600 kg)
Water
Water
Peel, soil debris
waste(50 Kg)
Waste water-1
Pot-
1
Pot-
1
Pot-
1
Pot-
1 Waste water-2
Pulp waste � sell
Washing and Dewatering of for wet starch
Lin
e-1
Lin
e-2
----
Lin
e-21
Water
Waste water-3
Water treat Pond-2
Water treat Pond-1
Collecting for solid
Remaining pulp
waste � sell
Page | 31
In the process of wet starch production, several forms of wastes are also produced. These include waste
water, solid waste, and oil spillage (Table 29). Due to their strong and unpleasant smells, solid and
water wastes are considered to have a negative impact on the health and daily lives of people in the area.
As the factory is located close to the village, farmers frequently complain about unpleasant smells
coming from the factory, and especially during the transportation of solid waste through the village.
Moreover, the waste water resulting from wet starch processing can have strong impact to the
populations of fishes and other aquacultures in the areas and can substantially decrease their
populations. In addition, in high concentration waste water can also reduce rice yield if not properly
managed. There were cases where the factory waste water leaked or discharged to farmer’s fields that
destroyed their rice crop and all living aquacultures.
Table 29 Types of waste from wet starch processing
Unit Operation Type of waste Amount of waste
Cleaning, grating, washing Peel, soil debris 50 Kg
Wastewater (1)
Grinding -
Filtrating for starch solution Pulp (cannot estimate)
Wastewater (1)
Washing and Dewatering of wet starch
Waste water (1)
Remaining solid waste starch (cannot estimate)
-outside operation using machine
-Machine operation
Dust 10 Kg/ T fresh
water treatment plant Odor 150 m
Note: (1) waste water cannot be estimated by the processor. The total water for using is 18 times pumping from ground water
per day, using 60 cm diameter pipe.
3.2 Impact of cassava processing wastes on environment
It is known that cassava processing produces a big quantity of wastes that can have negative impact to
the environment and human health (Table 30). Through their strong and unpleasant smell these cassava
processing wastes cause a hostile environment for farming communities living nearby. In addition if
they are not properly managed, the aesthetic and beauty of the environment is also substantially affected
(Picture plate 3).
One of the major threats to the environment by starch processing industry is the content of hydrocyanic
acid and the unbroken down cyanogenic glycoside - linamarin and lotaustralin which produces toxic
Page | 32
and acidic effect in their processing wastes (Okunade and Adekalu, 2013). If these products are not
properly treated, they constitute potent toxicant to the soil, soil organisms, water and plants. During the
process of cassava processing (dried chip, dried starch, and wet starch), it resulted particularly in large
volume of wastewater and solid waste. The quality and quantity of this waste vary greatly due to plant
age, varieties, time after harvesting, kind of industrial equipment used in processing and its adjustment
(Oliveira et al., 2001).
Table 30 Types of wastes produced by cassava processing
Type of waste Cassava processing Produce
odor
Potential impact to
human health and
environment
(Scale of 0-3)1)
Dried
chip
Dried
starch
Wet
starch
Sagu
Solid waste
• Peel Yes Yes Yes No Yes 1
• Stem debris Yes Yes Yes No Yes 1
• Soil debris Yes Yes Yes No No 0
• Flour/Flake Yes Yes Yes Yes Yes 2
• Pulp Waste No No Yes No Yes 1
Liquid waste
• Wastewater No Yes Yes No Yes 3
1). Scale: 0: no impact, 3: with strongest negative impact,
Picture plate 3. Esthetic and beauty of the environment is substantially affected by cassava processing
wastes
Cassava processing generates two types of liquid waste, the first one is produced by washing and
peeling of cassava roots that generally contains a large amount of inert material and, the second one is
produced by draining starch sedimentation tank (Table 3.7).
Page | 33
Wastewater from cassava processing is odorous with unpleasant smell. Due to its high microbial
content, it is subject to a relatively rapid breakdown. This wastewater is normally rich in cyanogens
content therefore it causes a general concern of their possible effect on health and the environment.
However, even with such possible harmful effect, this water can be discharged directly by the factory
onto soils and nearby rivers and streams. It is therefore presenting a strong risk for the environment
through reducing quality of the stream and makes its water less suitable for other downstream users.
Polluted water can cause unpleasant odours and flies infested environment and eventually affect the
health of the inhabitants adversely. This study has observed that wastes from cassava processing and
waste disposal into nearby stream/pond have created severe environmental complications like murky
colour of the stream water, unpleasant odour, and fly nuisance.
To evaluate the environmental impact by cassava processing plants, water sources (open well, deep
well, pond or river) located in close proximity to studied cassava processing plants were collected for
laboratory analysis on the concentration of Total Organic Carbon (TOC) and other parameter related to
the quality of wastewater such as Total Dissolved Solids (TDS) and pH. A total of 56 water samples
were collected from water sources nearby cassava processing areas such as dried chip processing, dried
starch processing plant, and sagu production. In addition samples from wastewater pond that can be
discharged to nearby fields were also taken. Additionally for comparison purpose, another 6 water
samples from Mekong River, from tap water and from bottled drinking water were also collected and
analyzed.
Results of water quality analysis in relation to domestic purposes are presented in Table 31. According
to a general recommended standard for domestic uses, pH of the water should be between 6.00 and 9.00,
and the level of TDS should be between 500-2000mg/L. As there is no available standard for Total
Organic Carbon (TOC), the level of TOC in the samples collected from Mekong River and city tape
water which is at the maximum level of 78mg/L is used as a working standard.
Based on results presented in Table 31, it is clearly demonstrated that water samples collected from
water sources near the cassava processing is either slightly acidic or highly alkaline. In Kampong Cham,
the minimum pH of the samples ranges from 5.7 to 8.8, whereas in Pailin, it ranges from 7.20 to 9.50
(Table 31). Reason for a different effect of cassava processing and its waste into the water sources is not
clear. In addition to the pH level, the quality of water in the surrounding areas is also determined by the
level of TDS. The level of TDS is related to the aesthetic behavior of the water therefore higher TDS
represent a poorer look of the water. Result of the analysis has indicated that only water samples from
Kampong Cham has got maximum level higher than the recommended upper threshold for edible use of
2000mg/L. Therefore water in these areas is not recommended to take either for direct drinking or for
cooking. Similarly in Pailin, despite it is lower than in Kampong Cham, the maximum threshold of
Page | 34
TDS is also very high (> 1000mg/L) as compared to this level at the Mekong river (Table 32), therefore
along with its high pH (a maximum up to 9.50), it should be restricted taking this water for any
household consumption especially for cooking or for drinking.
To increase public health the United States of America has funded a program, name the CALFED
Drinking Water quality to reach a challenging goal of an average concentration of TOC of 3mg/L in
their supplied tape water (CALFED). In our situation (see Table 32), the level of TOC concentration in
the city tape water is still significantly high (68 mg/L) as compared to bottled drinking water (19.5
mg/L).
However, this level is so variable and very high for the water collected from water streams at the
cassava processing areas. There is a strong variation between water samples collected for TOC analysis
at different locations in both Kampong Cham and Pailin (Table 31). In both water layers, the surface
water and the bottom layer, the level of TOC is relatively similar. The level of TOC ranges from 19.5 to
156mg/L with an average of 58.5 and standard variation (SD) of 39 mg/L in Pailin, whereas in
Kampong Cham it ranges from 19.5 to 819mg/L (surface) and 799mg/L (Bottom layer) with an average
of 153.56 (surface) and 172.64 mg/L (Bottom layer) and a standard deviation of 270.89 and 277.29
mg/L in the surface and bottom layer, respectively (Table 31). Apparently, water collected from the
cassava processing areas has high concentration of TOC, therefore any direct use of water from those
sources for either drinking and/or for cooking purposes should be restricted.
Table 31 Physico-Chemical parameters of water samples collected at/near cassava processing plants
Pailin Kg. Cham
pH TDS
(mg/L)
TOC
(mg/L)
pH TDS
(mg/L)
TOC
(mg/L)
Surface
Min 7.20 50.00 19.50 6.40 132.00 19.50
Max 9.50 1760.00 156.00 8.80 2600.00 819.00
Mean 8.27 343.67 58.50 7.94 596.00 153.56
SD 0.67 438.57 39.00 0.90 843.55 270.89
Bottom layer
Min 7.20 50.00 19.50 5.70 134.00 19.50
Max 9.30 1720.00 156.00 8.50 2450.00 799.00
Mean 8.17 341.20 58.50 7.23 654.14 172.64
SD 0.65 428.94 40.47 1.11 826.05 277.29
Well/ borehole
Min 7.00 463.00 39.00 4.40 140.00 19.50
Max 7.10 680.00 136.00 6.30 372.00 117.00
Mean 7.03 580.67 84.42 5.46 217.00 58.50
SD 0.05 87.80 31.68 0.75 99.36 41.37
Page | 35
Table 32 Physic-Chemical parameters of bottled drinking water, tape water and water samples from
Chaktomouk River
pH TDS (mg/L) TOC (mg/L)
River (Chaktomouk) 7.20 63 49
Tape water 7.2 77 68
Bottled drinking water 6.7-6.9 20-32 19.5
Standard for Protected public water area 6.00 – 9.00 < 1000 Not available
Standard for water area and sewer 5.00 – 9.00 < 2000 Not available
US Drinking water standard Average 3 mg/L
Nevertheless, other than all these negative impacts that the wastewater from cassava processing can
have on the environment and human health, there are also positive impacts of this wastewater. It is
known that wastewater contains both organic material and a rich source of nitrogen, therefore if
appropriately managed; this wastewater can certainly be utilized as liquid fertilizer for rice production.
Reports from farmers who have their rice field adjacent to the cassava processing plants confirm this
efficacy of cassava wastewater in boosting their rice yield. In addition, due to its high contents of
cellulose, hemi-cellulose and starch, cassava processing wastewater can as well be effectively utilized
for the production of ethanol (Vo et al., unpublished).
The other type of waste that produced by cassava processing plants is solid waste. Cassava solid waste
can be unrecoverable starch, the peel and soil/stem debris. This type of waste can also have a significant
hazard to the environment and human health of those communities living nearby the processing plants.
Nevertheless, as compared to wastewater, the solid waste is less hazardous to the farming communities
other than its strong and unpleasant smell. During the process of its breaking down, the solid waste is
reported to produce strong and unpleasant smell that can attract houseflies which causes nuisance and
health threaten to people in the area. In some occasions this unpleasant odour can reach up to 200-300 m
and provide good ground for a complaint and/or attacked by people who live around the processing
areas.
Annually, cassava processing produces big quantity of solid waste and if this is not managed properly, it
can cause a serious pollution to the environment and human life. Results of this study suggested that for
the dried chip processing, one metric ton of fresh cassava root produces about 20 Kg of solid waste
(Table 26). Therefore based on this calculation and the exporting quantity of dried chip of 1,269,653
tons in 2013 (MAFF, 2014) and, with a conversion ratio of fresh root to dried chip is 0.463Kg,
presumably at least 54,844 tons of solid waste was produced by local cassava dried chip processing
plants in that year. This is quite a big amount of solid waste produced by cassava dry chip which
Page | 36
without appropriate management it can be not only a wasteful resource but also a source of
environmental pollution.
Nonetheless, solid waste of cassava processing can be a good feed for animal and aquaculture
production. Cassava peel can be utilized as a medium for mushroom cultivation or is used to produce
compost, and for the production of ethanol and maltose (Henry and Howeler, 1996). Currently, most of
the cassava solid waste is dried in the sun for 3-7 days, and then sold to the manufacturing of animal
feed at a low price.
3.3 Awareness of cassava processors on waste management and their constraints in adopting new
waste management
Based on results of individual survey with cassava processing managers in both provinces, we could see
that only 56 per cent of all the interviewed personnel are aware of the impacts that cassava processing
wastes can have on the environment and human health (Table 33). Among all processing plants,
awareness of dried chip processing managers is still limited (18 out of 31), while dried starch and wet
starch processors are fully aware of the problems.
Table 33 Awareness of cassava processors on the impacts of cassava wastes
Cassava processing
Total % Dried Chip Dried Starch Wet Starch Sagu Saray
Aware 18 3 1 1 23 56
Do not aware 13 0 0 5 18 44
Total 31 3 1 6 41 100
Apparently, managers of dried and wet starch processors know well about the impacts of their
processing wastes can have on the environment and human health (Table 3. 10), however due to some
reasons, their waste management is still not appropriately developed as it should be. Two main
constraints that they have indicated are the lack of adequate funding for setting appropriate waste
management plant and the lack of information on new developed technologies on waste management.
When asked many processors responded with enthusiasm in building their own processing plant toward
nationally and internationally recognized standard. However, the uncertainty of local cassava market
and the lack of capital investment restrain them from realizing their dream into the reality. It is true as
many of these local cassava processing plants, especially dried chip processing, are of limited capital
investment and less competitive as compared to their counterparts in the neighboring countries. Some
cassava processors mentioned of their suspicion on new technology despite it is workable in the other
Page | 37
countries. For instance, at least in one occasion, using cassava processing waste for biogas was
interested by the processor, but he is still suspicious about the efficacy of the technology in his local
condition and due to this reason, he is therefore reluctant to invest in establishing the system at his
processing plant.
In practice, all the processing plants have already set up their own waste management system which
contains several waste ponds for the collection of wastewater discharged from the factory. It is likely
that this collected wastewater is left for natural disinfection without using any chemical treatment.
Number of ponds, shape and size are so variable depending on the management decision and the
available capital investment of each concern processing plant. It is obvious that most of the cassava
processing plants have tried their best to establish waste management system. However, it appears that
the system does not follow technical specification, therefore it produces strong unpleasant smell for the
nearby villages and, it is prone to be flooded during the rainy season. In such circumstance, wastewater
that is contained in each pond can then be discharged freely into rice fields or other open water sources
in the area. Vigorous crop growth in the nearby rice fields, in such circumstance, is believed to be
affected by the discharged cassava processing wastewater into the field.
It is well accepted that technology to establish waste management system is available in the country, but
unfortunately those developed technologies are more suitable for larger scale rather than for small and
medium cassava processing plants (Picture plate 4). Furthermore to the gap of this technology
availability, there are other barriers exist that hinder the adoption of the newly developed waste
management system in cassava processing. Those include information gap, limited capital investment
and the degree of confidence of the cassava processing managers on new technologies.
Among the largest dried cassava starch processing plants in the country, TTY has put an investment
plan to build wastewater treatment system and biogas recovery system under the carbon-offset
mechanism but their project is likely on hold due to financial constraints.
Picture plate 4. Waste water treatment tank at TTY factory
Page | 38
CONCLUSION
Cassava production in Cambodia has expanded exponentially for the last ten years to become the second
largest crop production in the country after rice. Majority of cassava farmers have less than 10 hectares
of cultivated land and the production can be found in two ecosystems, on flat and sloppy land. About
half of the cassava growing is found on sloppy land at the north west region of the country including
Pailin. Despite soil erosion is still not a major concern but with change in climate, it can have a strong
impact to sustainable cassava production in the country.
We found no differences in soil nutrients as well as the level of pH, soil humidity and organic matter in
the areas under cultivation of cassava and those areas under the cultivation of other crops and wild
habitats. Despite it is contradicted to the general belief that cassava plantation can uptake excessive
amount of nutrients from the soil and for that reason can lead to soil nutrient depletion and soil erosion,
this finding suggests that cassava has a similar nutrient withdrawal from the soil as compared to the
other crops. The result of this finding is strongly supported by many authors who concluded that cassava
extracts even less nutrients from the soil than most other food crops.
The expansion of cassava production is probably resulted from changing cropping system which is
prioritized by farmers based on market demand and crop productivity output rather than by claiming
new forest land as previously believed. It is suspected that forest had been earlier cleared for
commercial purpose and/or for the production of other crops such as maize before it has been
transferred to cassava. Nevertheless, as forest data is not available or very difficult to be obtained a
conclusive remark about the effect of cassava production on deforestation cannot be drawn. It is
suggested that this subject should be further analysed in order to provide clear picture on the
relationship between cassava expansion and deforestation.
There are three types of cassava processing plant in Cambodia. Those are dried chip, dried starch and
wet starch processing. Cassava processing produces big quantity of solid and liquid wastes that can have
negative impact to the environment and human health. Through their strong and unpleasant smell
wastewater and solid wastes, cause a hostile environment for farming communities living nearby. In
addition, the aesthetic and beauty of the environment is also substantially affected by cassava processing
if they are not properly managed. Unless these wastes are treated properly and well protected from
leaking to the water stream in the areas, the use of water originated from those areas for drinking and/or
cooking should be avoided.
More than 50 per cent of cassava processing managers recognize the problems arising from their
processing wastes and for that reason most of the processing plants have already set up their own waste
management structure. However, it appears that most of the structures do not follow technical
Page | 39
specification, therefore it produces strong unpleasant smell for the nearby villages and, it is prone to be
flooded during the rainy season. In such circumstance, wastewater that is contained in each pond can
then be discharged freely into rice fields or other open water sources in the area.
It is recognized that newly developed waste management technologies are available in the country, but
they are more suitable for larger scale rather than for small and medium cassava processing plants
which are still struggling to keep their business going. Limited access to those new technologies and the
lack of confident on them are considered the main barrier for developing eco-friendly cassava
processing industry in the country.
Page | 40
RECOMMENDATIONS
Mitigation measures to sustain the country cassava production
It is clear from this study that there is a tendency of yield decline in cassava production in both
provinces. Most influential reasons for yield drop include the decline in soil fertility, invasion of pests
and diseases, and the use of poor planting materials. Despite it is still not a major issue in the country
cassava production, the reported incidence of soil erosion is of concern and along with climate change it
can have a great impact to the future production of cassava unless some mitigation measures have been
taken.
Therefore in order to make cassava production in Cambodia sustainable, some adaptation practices can
be considered, those are:
1. Contour Intercropping
Sloping cassava production can be found in most parts of the cassava production in Pailin and in
some part of Kampong Cham. Soil erosion has though been reported in both provinces. If the
upland areas of Kampong Cham and Pailin will get more rains as it is projected, with the effect
of climate change, soil erosion can be a significant threat to the future cassava production in the
country. Unfortunately, despite damage caused by soil nutrient depletion and erosion are noted,
research support on this subject is still at low profile and it is hard to present the evidence of the
damage by any quantitative figures.
To prevent this climate related risk, a contour intercropping practice is recommended. Cassava is
to be planted on established vegetative/cropping contours. Following a row of lemon grass, a
scrub leguminous plant Leucaena is planted in one high density hedge row. These
complementary two plants hedgerows are to provide as a supporting ground to minimize soil
erosion and keep nutrient leaching especially in heavy rains. In addition to protect the soil from
erosion, Leucaena plant which is known as nitrogen fixation plant can enrich
monocropping/unfertilized cassava production soils a free additional source of nitrogen.
Furthermore Leucaena leaves are rich in protein that can be used for animal production, while
lemon grass which is known of its insect propelling effect can also be good for culinary. The
size of the contours varies depending of the sloping pattern, the steeper is the slope the closer is
the contour. To keep the area of cassava plantation from direct contact with rain drop, a fast
growing crop such as pumpkin is to be planted at the same time of cassava planting. Research
however is needed to identify appropriateness of this practice on different degrees of slopes.
This proposed intercropping is a model that can be modified based on sloping and socio-
economic conditions and, market demand for any specific location.
Page | 41
2. Adequate integrated nutrient balance
As earlier reported, concern about yield decline due to soil fertility depletion is relatively strong
and therefore mitigation measure (s) to convert cassava production back to a more sustainable
system is needed. Application of balanced nutrients, type and quantity, required by the crop can
definitely enhance the growth of cassava especially at the early stage. It is well known that due
to its slowness in growth at the early stage, the areas cultivated to cassava remain open for a
certain period after planting. It is a very critical situation that can lead to large scale soil erosion,
therefore enhancing growth at the early stage is quite important for cassava production. Healthy
plant as a result of proper fertilization can also enhance protective reaction of the crop to the
attacks of pests and diseases. Integrated nutrient management by using combination of fertilizers
including chemical fertilizers, organic manure or compost is also advisable for a sustainable
cassava production in Cambodia.
Even though it is seen as an important measure to alleviate the problem, no fertilizer rate for
cassava has been recommended by any research institution in Cambodia including CARDI. Yet,
result from one experiment in Kampong Cham conducted by CARDI in 2011/2012 has indicated
that the use of compound fertilizer of 15:15:15 (N:P:K) in the rate of 200 Kg/ha plus 50 kg/ha of
a single potassium fertilizer (KCl) produced the highest yield (23 tons per hectare), while a
combination use of 200 kg/ha of 15:15:15 with 10 tons of cow manure yielded 20 tons per
hectare that was comparable to the previous rate but have the highest starch content (27%)
(CARDI, 2012).
It is recognized that for its early growth cassava requires equal amount of nitrogen (N),
phosphorous (P) and potassium (K), but that changes as the plant ages. Depending on which soil
type cassava is grown, demand for N, P and K vary accordingly. Nevertheless, results of long
term experiments in many cassava growing countries have indicated that the most limiting
nutrient to cassava production is potassium (Howeler, 2014) and the rate of 2:1:2 or 2:1:3 for N,
P and K, respectively, are recommended (FAO, 2013).
The lack of fertilizer recommendation rate for cassava production in the country is clearly
demonstrated the need of technical supports that the national research institutions in Cambodia
such as CARDI to come up with their future research strategies in order to develop all essential
technologies to help sustaining cassava production in the country.
3. Minimum and contour tillage
This practice is particularly recommended for cassava production at sloping areas where are very
likely prone to soil erosion. Instead of plowing in a normal way or along the slop, it is
Page | 42
recommended that plowing should be reduced to none or minimum depending on soil
conditions. Similarly tillage should be conducted as much as possible on contour.
4. Production of clean planting materials
Results from this study have strongly suggested that a rapid boom of cassava production in
Cambodia has brought new threats from pests and diseases that originated in other countries.
The free exchange of planting materials across the border is very likely to bring in the country
infected cassava planting materials. Due to this reason, several important pests and diseases have
emerged and caused severe damage on cassava production in the country. It is evidently shown
earlier where 24 percent of farmers in Kampong Cham have reported of severe damage caused
by pests and diseases on their cassava production (Table 8). It is clear therefore that the use of
healthy planting materials is considered the most effective way in controlling pests and diseases
particularly mealy bug and cassava witches-broom (CWB) in cassava production. Cleaned
planting materials production through different techniques can be employed but it is only
possible if there is a strong collaborative effort between relevant players such as CARDI, GDA,
PDA, RUA, International organizations such as CIAT, and NGOs.
5. Cover crop production system
Cassava has generally a slow initial growth, therefore in the case of heavy rainfall soil erosion
and soil nutrient leaching can be very likely to happen. To prevent this situation, in any
cassava production areas, flat or sloping, the use of cover crop such as pumpkin and/or fast
growing legumes is very effective to mitigate the problem. In addition to preventing soil
erosion, the use of cover crops in cassava production can also be regarded as soil improvement
practice and to help reduce weed infestation.
Page | 43
Sustainable utilization and management of cassava processing wastes
Both cassava processing wastes, solid waste and wastewater, can have strong adverse effect to the
environment and human health, but if properly managed they can be very useful in many ways.
Solid waste
• Solid waste derived from cassava peel can be used as feed in animal and aquaculture production.
This is widely practiced, but does have limitations due to its low digestibility and toxicity of the
peel and, on the availability of supplement protein to the feed. These limitations of solid waste
for animal and aquaculture feed can be overcome through several techniques. One effective way
to increase digestibility and to reduce toxicity of the peel is through fermentation. After the
fermentation cassava peel can be converted into a more digestible substrate and can provide
even to pig and poultry. On the other hand, in order to overcome protein deficiency in animal
feed by using cassava peel, one effective way is to establish fully integrated crop-animal and
aquaculture farming system or Model Farming as it is called by CARDI (2006). Currently, a
common practice applied by many cassava processing plants is to let the produced solid waste be
dried in the sun for 3-7 days before it is sold to animal feed manufactory.
• Other than its use for animal feed, solid waste can also be used as a medium for mushroom
cultivation, to produce compost for other crop production, and also can be used for the
production of ethanol and maltose.
Liquid waste or wastewater
• Ideally waste water should only be used after it has been properly treated. Cassava waste
products can be treated by different ways. One way is to build anaerobic and aerobic lagoons
(ponds) to treat the waste before its disposal. In the condition of anaerobic digestion of cassava
waste, cyanide is released in the form of liquor and then liberated by enzymatic and non-
enzymatic reactions. This system is very effective and environmental sound but requires a large
area of land and large capital investment and therefore is suitable only for the large processing
plant. TTY is likely the only cassava processing plant in the country that has set a challenging
plan to establish this system in their factory, but due to financial constraint the plan is likely to
be on hold at the moment.
In case cassava processing is of small to medium scale, waste water can be treated through
channelling the waste into shallow seepage areas. The areas however should be situated away
from natural water sources.
Page | 44
• Cassava processing wastewater can be effectively utilized as a liquid fertilizer, if it is well
treated. However if the waste is not properly treated and due to its high HCN content that can
have a negative effect on plant growth (Taesopapong and Bhanuprabha, 1987; Bengtsson and
Triet, 1994), the use of waste water for irrigation or as a source of fertilizer should be restricted.
The other problem in using wastewater as a liquid fertilizer is to have an appropriate
concentration of wastewater to be used. There is a need therefore to establish this level through
a research study. Failure to determine this may cause serious damage to the rice plants as high
concentration of dilution can cause a total dead of the crop. Result from a study with duckweed
has indicated that when used as a direct fertilizer for duckweed at a dilution rate greater than
60% (waste in water), all duckweed died, but most of the plant can survive and perform well if
its concentration ranges between 10-20 per cent.
• Other than just using as liquid fertilizer, wastewater can also be used to produce biogas and to
generate electricity. This technology which is well known and has been adopted in many cassava
producing countries is now under construction at TTY and Tay Meng.
Page | 45
REFERENCES
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Agriculture, Forestry and Fisheries, Phnom Penh, Cambodia.
CARDI, 2012. Balanced fertilizer application to maintain or improve soil fertility, Factsheets.
Cambodian Agricultural Research and Development Institute, Phnom Penh, Cambodia.
CARDI, 2012. Cassava pests and diseases in Cambodia, Factsheets. Cambodian Agricultural Research
and Development Institute, Phnom Penh, Cambodia.
FAO, 2006. World Reference Base for Soil Resources in 2006. Food and Agriculture Organization of
the United Nations, Rome, Italy. 127p.
FAO, 2013. Save and grow cassava: A guide to sustainable production intensification. Food and
Agriculture Organization of the United Nations, Rome, Italy. 130p.
Howeler, R.H, 1991. Long-term effect of cassava cultivation on soil productivity. Field Crops Research
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requireemtn to maintain high yield. The cassava handbook, pp: 411-428.
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MAFF, 2005-2013. Annual Report. Ministry of Agriculture, Forestry and Fisheries, Phnom Penh,
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Oliveira, M.A., Reis, E.M., and Nozaki, J. (2001). Biokenetic parameters investigation for biological
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Putthacharoen, S., R.H. Howeler, S. Jantawat and V. Vichukit. 1998. Nutrient uptake and soil erosion
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APPENDICES
Appendix 1 Time delivery
# Activities Time frame
Jan Feb Mar Apr May
I Contracting
1 Review documents
2 Developing Methodology
3 Contract signed
4 Developing questionnaires
II Field Operation
5 Field survey
6 Soil and water sampling
7
Laboratory testing of collected soil and
water samples
III Data Management
8 Data entry
9 Data cleaning and analysis
10 Report
Appendix 2 locations where study was conducted
Province District Commune Village
Kampong Cham
Dambe
Kok Srok Kok Cha
Kok Srok
Tropeang Pring Tropeang Pring
Prolos Chom Bork
Memot
Treak Bong Kov
Prey
Memot Muk Kras
Tropeang Rieng
Tbaung Khmom
Srolop Tropeang Dom
Angkor Chey
Lgneang Lgneang
Smornh
Pailin
Pailin
Bor Yakha Bor Yakha
O Chra
O Tavao Dey Kraham
Sou Sdei
Sala Krao
Steung Kach Oro El
Bos Om
O Andaung O Andaung
O rusey
Page | 48
Appendix 3 Cassava Production Questionnaires
SURVEY INSTRUMENT ENVIRONMENTAL IMPACT ASSESSMENT FOR CASSAVA
CULTIVATION
We, at the Royal University of Agriculture are conducting this survey to determine the impact
that cassava cultivation can cause on the environment. You have been randomly selected to
participate in this survey. Your responses will be kept anonymous and confidential. Your
participation is voluntary and you may elect at any time to discontinue participation in the
survey. Survey results will be used to improve smallholder cassava growers/processors economy
in a sustainable manner.
Do I have your consent to start the survey? YES (If YES, proceed with the survey) NO
A. Household Identification
A01. Enter the 2-digit code for Province, District, Commune, Village and household number:
A02. Code of enumerator:
A03. Date of visit: dd/mm/yyyy)
B. History
1. Do you grow cassava? � Yes � No, If yes
2. When started to grow cassava? � in 2013 � Before 2013, Year______________
3. What did you plant before cassava? � Forest � Rubber � Corn/maize
� Soy bean � Others _______________________________
4. Why decided to change to cassava? Please describe ........................................................
..............................................................................................................................................
…………………………………………………………………………………………….
5. Have you ever stopped planting cassava, if so why ..........................................................
...........................................................................................................................................
............................................................................................................................................
C. Production practices:
6. Variety name:_________________________
7. Times of planting � Dry season � Wet season
8. What is the size of your cassava plantation _________Ha________m2______________
Province istrict Commune illage use
Page | 49
9. Topography � Flat � Slope,
If slope,
� How slope is the field � Very steep (> 450) � Steep (300-450)
� Medium (150 – 30 0) � gentle slope (< 150)
10. How did you plow for planting � By contour � Up to down
o By contour, times of plowing and harrowing � One �Two �Three
o Up to down, times of plowing and harrowing � One �Two �Three
11. How to prepare for planting � Raised bed � No bed
12. How to plant � vertical (90o ) � 45o � Horizontal (180o)
13. Planting space � 1m x 0.5m �1m x 1m � 1.5m x 1.m
� 1.5m x 1.5m �Other_________________________________
14. Have you noticed of yield declines from year to year � Yes � No
If yes, what is (are) the reason (s). Please list down
15. What did you do if you notice the problem. Please list down
16. How much yield you have received for the last five years
Type of product Yield (Kg/unit area_____________)
2013 2012 2011 2010 Before 2010
Fresh root
17. Have you ever used mulching? � Yes � No
If yes, what type of mulching? ____________________________________________
_____________________________________________________________________
18. Have you irrigated cassava crop? � Yes � No
If yes, what is the source of water
� River �Lake � Pond � Open well � deep well � Other ______
19. How many time did you irrigate � Frequent � 1 time � 2 times � 3 times
20. Have you applied fertilizer? � Yes � No , if No go to Q.20
21. What kind of fertilizer? � Organic � Chemical � Both
Page | 50
22. Provide history of using fertilizer for the past five years
Fertilizer Type Time of application
Rate (Kg/unit area)
2013 2012 2011 2010 Before
2010
1 Organic
2
3
4
5
6
23. Have you applied pesticide? � Yes � No
If yes, why………………………………………………………………….
• What kind of pesticide?____________________________________________
• How did you know about this pesticide?_______________________________
• Where did you buy it_______________________________________________
Page | 51
• When did you apply it _____________________________________________
24. Mode of harvesting � Machine � Hand pick � Animal plowing
25. Have you cleaned harvested roots with water � No � Yes
If yes, what is the source of water using for cleaning the roots
� River �Lake � Pond � Open well � deep well � Other ______
26. Where do you clean the roots � At the river/lake/pond/well, � Just at the harvested
field � At the house shed/storage
27. What did you do with the harvested roots
Type Amount (Kg)
2012 2013
Home consumption
Feeding animals
Sale Fresh root
Dried Chip
Starch
Sakou
Others
28. What did you do with the cassava stems
� Just keep in the field � Collect and keep as planting materials for next planting
� Burn in the field � Other, please specify_______________________
D. Production share
29. How big is your agricultural production area? ________________Ha__________m2
30. What other crops you have grown for the last five years?
� Corn/maize �Bean � Rice � Others
31. What constraints you are facing with cassava production. Please list down
32. What contribution that cassava has on your household income
Crops/Items Estimated Contribution (%)
Page | 52
2013 2012 2011 2010 Before 2010
Cassava
Rice
Other crops
Animal husbandry
Aquaculture
E. Future Investment
33. What is your future plan
� Stop growing cassava, why____________________________________________
� Grow more cassava, why______________________________________________
� Not sure, why_______________________________________________________
� Any other reasons ___________________________________________________
F. Personal Information
34. What is your educational background: � Never attended � Primary school � High
school � University
35. Household Head: � Male � Female
36. Married status: � Married � Widow (divorced) � Widow (deceased)
37. Number of dependents :___________________________
Thank you for your time!
Page | 53
Appendix 4 Cassava Processing Questionnaires
SURVEY INSTRUMENT ENVIRONMENTAL IMPACT ASSESSMENT FOR CASSAVA
WASTE MANAGEMENT
We, at the Royal University of Agriculture are conducting this survey to determine the impact
that cassava processing can cause on the environment. You have been randomly selected to
participate in this survey. Your responses will be kept anonymous and confidential. Your
participation is voluntary and you may elect at any time to discontinue participation in the
survey. Survey results will be used to improve smallholder cassava growers/processors economy
in a sustainable manner. The survey will take about 20 minutes.
Do I have your consent to start the survey? YES (If YES, proceed with the survey) NO
G. Household Identification
A01. Enter the 2-digit code for Province, District, Commune, Village and household number:
A02. Code of enumerator:
A03. Code of processing plant
A03. Code of interviewee
A04. Date of visit: dd/mm/yyyy)
1. General Information
1.1. What type of business? 1 = sole proprietorship
2= partnership
3= company
1.2. When did you start operating? -----------------------------
1.3. Number of employees/labor Men......................................
Women..................................
1.4. Production/processing area .....................................Sqm
1.5. Locality of the processing
plant
1. Near river/lake
2. Surrounded by cassava/other crop plantation
3. on the middle of the village/city
4. Other (Specify)…………………………….
1.6. What is the capacity of your …………………..…………….tons
Province DistrictD Commune VillageV HouseHo
Page | 54
factory? of…………………………………..per day
1.7. What is the actual operation? …………………..…………….tons
of…………………………………..per day
1.8. How many tons of end-
products do they produce
from 1 ton of fresh roots (or
inputs)?
Product Quantity (ton)/1 ton of fresh roots
Dried chips
Dry starch
Wet starch
1.9. What are the major cassava
products that you process?
Rank them in decreasing
order of quantity produced
(1=the most important).
1= ………………………………………………………………..
2=………………………………………………………………..
3=………………………………………………………………..
4=………………………………………………………………..
5=………………………………………………………………..
1.10. During what month(s) of the
year is the production of these
cassava products highest?
(enter 1 for highest).
1 = Maximum 2 = Moderate
3 = slight
Produ
ct
name
J F M A M J J A S O N D
1.11. What are your main materials
or inputs for your
processing/operation? (Give
example?)
-
-
-
-
1.12. Where do you buy your
material/input from?
-
-
-
-
2. Waste and wastes management
a) Wastes
2.1. What are the wastes/pollutions
from cassava processing?
□ 1= Waste water
□ 2=Solid waste
□ 3=Odor/smell
□ 4=Smoke
□ 5= Noise
Page | 55
□ 6= Air pollution
□ 7= Waste from engine/machine (oil, lubricant,
debris of equipment…)
□ 9=Other
□ 99= Don’t know
2.2. Among those wastes/pollutions,
what is the main
wastes/pollution from your
cassava processing?
(Use code above)
………………………………………..
2.3. Indicate whether the processing
wastes/pollutions occur in the
processing steps:
(Tick code, check all that apply)
(Note: Figure on row in
processing step are:
1=Peeling
2=Chopping
3=Drying
4=Storage
5= Transportation
9=Other
Wastes/polution Processing Step
1 2 3 4 5 9
□ 1. Waste water
□ 2. Solid waste
□ 3. Odor/smell
□ 4. Smoke
□ 5. Noise
□ 6. Air pollution
□ 7. Waste from
engine/machine (oil,
lubricant, debris of
equipment…)
□ 9. Other: …………
b) Waste Water
2.4. Does your cassava processing
operation produce waste water? □ 1= Yes
□ 2= No [Skip to Q2.5]
2.5. If yes, what processing step that
produce waste water?
1=Peeling
2=Chopping
3=Drying
4=Storage
5= Transportation
9=Other
99= Don’t know
2.6. How much amount of water that
comes from your processing
operation for 1 ton of cassava?
………………………………….Liter/ton
2.7. How dirty/degree of pollution of
the waste water from processing
operation?
(rank from 5 the good quality of
water to 1 the worst of water
quality)
□ 1- Very dirty (Cannot drink by either animal or
human)
□ 2- Dirty (Cannot drink but can use for household
use)
□ 3- Slightly dirty (Can use )
□ 4-Good
□ 5- Very Good quality (Normal
99- Don’t know
Page | 56
2.8. Where the waste water flow
into? □ 1=Water Sources (well, natural pond)
□ 2=Infiltrate into soil (ground water)
□ 3=Run off into growing field
□ 4=Drain into water treatment pond
□ 5= Drain/run off into other
□ 9= Other
□ 99 = Don’t know
2.9. Where and how pollute of the
waste water onto the mentioned
places/area on the right column?
(Tick code, check all that apply)
Polluted Target area Degree of pollution
No Low Modera
te
Hi
gh
□ 1. Water Sources
□ 2. Infiltrate into
soil
□ 3. Run off into
growing field
□ 4. Drain into
water treatment
pond
□ 5. Drain/run off
into other
□ 6. Direct effect on
human
□ 7. Direct effect on
animal
□ 8. Direct effect on
crop
□ 9. Other: …………
2.10. Have you ever treated your
waste water before draining it
outside the processing plant?
□ 1= Yes,
□ 2= No [Skip to Q2.12]
2.11. If yes, how? □ 1= ……………….
□ 2= …………………………
□ 3= …………..
□ 9= Other
□ 99 = Don’t know
c) Solid Waste
2.12.Does your cassava processing
operation produce solid waste? □ 1= Yes
□ 2= No [Skip to Q2.21]
2.13.If yes, what type of solid waste
that produced from processing
operation?
□ 1- Cassava peel
□ 2-Soil debris
□ 3-Cassava flour/flake
□ 4-………
Page | 57
□ 5-…………
□ 9-Other……………
□ 99-Don’t know 2.14.If yes, what processing step that
produce solid waste?
1=Peeling
2=Chopping
3=Drying
4=Storage
5= Transportation
9=Other
99= Don’t know
2.15.How much amount of solid waste
that comes from your processing
operation for 1 ton of cassava?
………………………………….Kg/ton
2.16.How dirty/degree of pollution of
the solid waste from processing
operation?
(rank from 5 the good quality of
water to 1 the worst of water
quality)
□ 1- Very dirty
□ 2- Dirty
□ 3- Slightly dirty
□ 4-Good
□ 5- Very Good quality (Normal)
99- Don’t know 2.17.Where the solid wastes flow
into? □ 1=Water Sources (well, natural pond)
□ 2=Infiltrate into soil (ground water)
□ 3=Run off into growing field
□ 4=Drain into water treatment pond
□ 5= Drain/run off into other
□ 9= Other
□ 99 = Don’t know
2.18.Where and how pollute of the
solid waste onto the mentioned
places/area on the right column?
(Tick code, check all that apply)
Polluted Target area Degree of pollution
No Low Modera
te
Hi
gh
□ 1. Water Sources
□ 2. Infiltrate into
soil
□ 3. Run off into
growing field
□ 4. Drain into
water treatment
pond
□ 5. Drain/run off
into other
□ 6. Direct effect on
human
□ 7. Direct effect on
animal
□ 8. Direct effect on
Page | 58
crop □ 9. Other: …………
2.19. Have you ever treated your solid
waste before throw it out? □ 1= Yes,
□ 2= No [Skip to Q2.21] 2.20. If yes, how? □ 1= ……………….
□ 2= …………………………
□ 3= …………..
□ 9= Other
□ 99 = Don’t know
a) Odor/smell
2.21.Does your cassava processing
operation produce Odor/smell? □ 1= Yes
□ 2= No [Skip to Q3.1]
2.22.If yes, what processing step that
produce Odor/Smell?
1=Peeling
2=Chopping
3=Drying
4=Storage
5= Transportation
9=Other
99= Don’t know
2.23.How degree/dirty of smell/odor
from processing operation?
(rank from 5 the good quality of
water to 1 the worst of water
quality)
□ 1- Very bad smell
□ 2- Bad smell
□ 3- Slightly bad
□ 4-Not bad
□ 5- Good smell (Normal)
99- Don’t know 2.24.How far of smell/odor from your
processing plant? □ 1=Very far……………………Km
□ 2=Far…………………………….Km
□ 3=Near…………………………...Km
□ 4=Very near…………………….Km
□ 9= Other
□ 99 = Don’t know
2.25. Have you ever treated this
smell/odor? □ 1= Yes,
□ 2= No [Skip to Q3.1] 2.26. If yes, how? □ 1= ……………….
□ 2= …………………………
□ 3= …………..
□ 9= Other
□ 99 = Don’t know
3. Capacity (awareness) and constraint in waste management
3.1. What do you understand by the ……………………………………………………………………………
Page | 59
term of “Waste Management”?
(Read out for him/her if s/he
doesn’t know about)
Definition: Waste Management:
this is the collection, transport,
processing, managing and
monitoring of waste materials
……………………………………………………………………………
……………………………………………………………………………
……………………………………………………………………………
3.2. What is your dream waste
management that you like to
have in your factory
3.3. What constraint (s) that hinder
you of not having that dream
waste management?
…………………………
4. Environmental and social impacts
4.1. Have you noticed any change in
fish population in the area
4.2. Have you noticed any change in
crop production (rice, fruit
trees..) in surrounding area
4.3. Have you noticed any change in
bird population in your area
4.4. How regular your workers get
sick and what are the
predominant sicknesses you
have observed
4.5. How you treat sick worker(s) 1. send to hospital
2. let them rest at home
3. do nothing
4. Other (please specify)………………
4.6. Have you ever received
complaint from residents
and/or local authority in the
area? If yes, what about?
5. Personal Information
5.1. Position of the interviewee
5.2. Qualification
5.3. Years of experience in the
company
Thank you for your time!
Page | 60
Appendix 4
Details address of Food and Chemical Services Laboratory
FCS, # 52, St. New Street, Sangkat Tumnup Teuk, Khan Chamcar Morn, Phnom Penh, Cambodia
Tel. 012 531000/088 5531000
Email: Davinuy@gmail.com
Page | 61
Appendix 5
A brief general description of topography, physical and chemical characteristics of the 3 cassava soil
groups
Labansiek: occurs on the sides of hills or mountains where once ancient volcanoes were. It occupies
1% of the rice growing area. The predominant feature of this soil group is a uniform of red color
throughout profile. The surface soil has a crumb structure with high degree of aggregate stability and
usually friable. The soil surface has clayey texture, very sticky and slippery when wet. The subsoil is
clayey, usually has a deeper red color than the topsoil and is usually friable with crumb structure. The
fertility of this soil is moderate, and soil pH is slightly acid, although it may be slightly alkaline in some
cases. The CEC and organic matter levels are moderate to high, and also has potentially deficient in N,
P, K and S (White et al., 1997).
Kampong Siem: occur in low areas of a varied undulating landscape of small hills and rises, or at the
footslopes of larger hills or mountains. It occupies 2% of the rice growing area. The surface soil is very
dark gray or black; even when dry, it remains very dark. The texture is clayey, and the clay being very
plastic and sticky when wet and hard when dries. There is considerable swelling and shrinking in this
soil with large cracks appearing in the surface soil when it dries. The soil surface is usually has granular
structure. The subsoil also has clayey texture and it is usually gray to light gray than the topsoil. This
soil group develops from two different rock material, basaltic and limestone rocks. They are always
present within the profile or sometimes on the soil surface. This soil pH ranges from slightly acid to
slightly alkaline. The CEC and organic level are high, but level of N, P and K are low (White et al.,
1997).
O'Reang Eu: commonly found in the mid to upper slope of the plateau. It occupies 1% of the rice
growing area. Its position in the landscape is above Kampong Siem soil and below the Labansiek soil.
The gravel is a distinctive characteristic of this soil group. The surface soil has clayey or loamy texture,
vary color from dark gray to very dark brown with variable amount of fine gravel. The surface has
massive structure and is generally hard when dry. The subsoil has clayey to loamy texture and there are
some abundant of medium to coarse size gravels. The color can be varying from dark brown to dark red
or reddish brown. The subsoil has blocky structure. The soil pH is generally moderate acid and level of
organic matter and level of N, P, K range from low to moderate (Seng et al., 2007).
Kampong Siem Group O'Riang Group Laban Siek Group
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