Báo cáo khoa học nông nghiệp " REPORT ON BASELINE SURVEYS IN CANTHO AND AN GIANG PROVINCES " pdf

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Ministry of Agriculture & Rural Development

Project Progress Report
CARD Project 023/06/VIE


MS3: REPORT ON BASELINE SURVEYS IN CANTHO
AND AN GIANG PROVINCES





24
th
April , 2009

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Baseline study had been carried out during October-November 2007 at Cantho city and
during January-February 2008 at An Giang province to assess environment pollution
from disposal of waste of catfish aquaculture ponds and implications for sustainable
agriculture production. Two districts of Cantho city (O’Mon and Thot Not) and two
districts of An Giang (Chau Phu and Phu Tan) were selected based on high numbers of
fishpond present in these districts. Primary information relating to techniques, socio-
economics and environment were recorded by interviews with farmer individually, and
was supplemented by observations to evaluate or confirm data. This was followed by

contact with local officers to collect secondary data as needed. Two groups of farmers
were chosen (rice growing and fish raising groups) in equal numbers at each site. A total
of 240 questionnaires were collected for data analysis.

I. Socio-economics aspects
Farmers practicing fishpond culture in Cantho are a little younger than those who
carried out rice cultivation (43 compared to 49 yrs.); however, there were no difference in
ages between these two groups in An Giang province (Table 1). In An Giang province,
fish raising farmers were also rice growing farmers, who turned to the fish farming
system in order to increase their income. By contrast, fish raising farmers in Can Tho are
mainly migrants, who hired or bought land from local farmers which explains why the
fish raising farmers are younger and with higher formal education level than rice growing
farmers.
Rice culture has long been practiced in the Cuu Long delta. Most of rice growing
farmers have more than 20 years experience in rice farming. Meanwhile the freshwater
fish industry has recently expanded. The data on number of years’ experience in fish
culture clearly showed that this industry was developed during less than 10 years.
The family size was not very much varied between two types of farming system. It is
about 5 persons/family including a labour force of 3-4. Land tenure areas for rice farming
in both Can Tho and An Giang are much higher than areas used for fish culture. The
reason might be due to total cost for raising fish is much higher than rice farming (Table
1).
Most of farmers in Cantho and An Giang had concrete or brick houses (80-90%).
Thatch house cover less than 10% of rice farming but it is about 15-20% in the case of
fish culture. Some fish raising farmers are migrants who stay on site temporarily to look
after their fish. They also have permanent houses at other places.
The Cuu Long delta has abundant of water that is why rice or fish culture mainly
rely on canals or rivers as their water source. Survey data revealed that water pollution is
a concern for 15-25% farmers. The evaluation of water quality between upper stream and
down stream has also been clearly shown by fish raising farmer in An Giang and Cantho.

The grade of good and medium was in reverse order between An Giang and Cantho. The
reason might be water of upper stream from Cambodia is still clean because fish culture
is mainly practiced in Cuu Long delta. Waste water was discharge directly to water
source by about 70% in An Giang and 80% in Cantho. Fish raising farmers having
settling ponds are quite few (5-8%) and about 15-25% used waste water for rice
cultivation.



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Table 1. General socio-economics aspects of rice and fish farming households
Cantho An Giang
Items
Fish culture Rice culture Fish culture Rice culture
Age of household head 43 49 47 47
Level of education 7/12 5.5/12 5.7/12 5.8/12
Years of experience 3.6 20 9.4 20
No. persons/family 5.3 5.5 5.2 4.8
No. labourers/family 3.4 3.6 3.7 3.0
Land tenure area (ha) 0.6 1.2 0.58 1.50
House types (%)
- Concrete
- Brick
- Thatch

43
42
15

23

73
4

42
39
19

48
44
8
Irrigation water source Canal
and/or river
Canal
and/or river
Canal
and/or river
Canal
and/or river
Water quality (%)
- Good
- Medium
- Bad

30
52
18

55
22
23

51
25
24

46
39
15
Wastewater discharge
- River or canal
- Paddy
- Settling pond

80
15
5

100

68
24
8

100

Variation on water quality was a concern for farmers (Table 2). Water quality is
good during flooding time (Aug. to Dec) mainly because of large flows of water which
dilute and wash away pollutants. Waste from fishpond was the major source causing
pollution of rural areas both at An Giang and Can Tho. More than 50 % of people in An
Giang used river water for living purposes but more or less this proportion of people in

Cantho utilized tubewell water. This figure also represented the severity of water
pollution in river and forcing people to use tubewell water. Threats for fish culture might
also come from pesticides discharge from paddy. The severity was more in down stream
where pesticides were accumulated.
Rainy season and just after flooding time also had good water for irrigation but it
was only accepted by 30 % of total farmers being interviewed.

II. Economic efficiencies in rice and fish culture
Survey data demonstrated that fish farming generated much higher benefit than
rice about 410 millions dong/ha for fish in comparison with 9 millions/ha for rice.
However; total cost for raising 1 hectare of fish was 1,894.6 million dong compared to
only 12.1 millions dong for rice (Table 3).
There was not much difference between Cantho and An Giang province regarding
economic efficiency in agriculture production for rice and fish farming. Most of farmers
raising fish had to get loans either from banks or neighbours but percentages of rice
farmers borrowing money were below 50% because total investment for rice production
is much less than for fish culture (Table 4).

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Table 2: Quality of water for irrigation and for living & drinking in rural areas
Items An Giang (%) Can Tho (%)
Water source for living & drinking
River 57 17
Tube well 13 57
Public water supply 30 26
Water quality for living purpose
Good 46 80
Medium 18 13
Bad 36 7

Reason for bad quality of water
Waste from fishpond 91 37
Pesticides from paddy 9 15
Others 0 48
Time having good water quality for
irrigation

Flooding 62 58
Winter-Spring 7 13
All year round 7 5
Rainy season 28 17


Table 3: Comparison of economic efficiencies in rice and fish farming in Cantho
Items Fish farming (X
Mil. dong)
Rice farming
(X Mil. dong)
T value
Total cost/ha 1894.6 12.1 6.2**
Yield/ha 170 6.9 6.2**
Total income/ha 2305 21.2 6.4**
Profit/ha 410.2 9.1 4.9**
Income/family/year 178 24.8 5.4**


Table 4: Credit sources for agricultural production.
Items Cantho An Giang
Rice farmers borrowing money (%) 35 44
Farmer raising fish borrowing money (%) 89 95

Sources of credit
Bank 32 63
Private 3 4
Company (non-currency) 65 33
Interest rate/year (%)
Bank 14 14.6
Private 43 48
Company 26 27.6

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Percentages of farmers in An Giang province accessing credit from banks were
higher than that in Cantho (Table 4). This might be because infrastructure of An Giang
was better than in Cantho or roads networks in An Giang favoured transportation.
However, late payment agreement between farmers and companies or traders were more
common in Cantho than in An Giang. The reason might be due to trading and factories in
Cantho had long been developed in Cantho. Generally, interest rate/month was about 1%
for bank, approximately 2% for agreement of late payment and up to 4% for individual or
private sources.

III. Farmer practices in rice and fish farming
III.1 Rice production
Use of agricultural chemicals is unavoidable in rice production to control insects
and pests but misuse of these will contaminate soil, water and the food chain. Survey data
in Table 5 showed that brown plant hopper and blast were the most common threat to rice
production in the Cuu Long Delta. 84% of farmers in Cantho and 77% in An Giang used
insecticides to control brown plant hopper. Chemicals for protecting rice against other
insects (leaf folder, stemborer, thrips, bugs, etc.) were second in importance and they had
been applied only by 16% of farmers in Cantho and 23% of farmers in An Giang
province. More than 50% of farmers in Cantho and An Giang bought fungicides to

control rice blast; other fungal diseases had also been controlled but in less than 50% of
cases. Survey data showed that 90% of farmers in Cantho applied correct dosages of
agricultural chemicals but this figure in An Giang was lower than in Cantho (only 77%).
Timing for chemical applications was varied depending on occurrences or observations
on outbreak of pests. Farmers in An Giang province had a tendency to spray chemicals
based on observation (80%) but farmers in Cantho preferred to use chemicals periodically
(52%).
Regarding environmental protection, farmers collected used chemical bottles and
sold plastic wastes for recycling (70% of case in An Giang) or buried them. However,
burning or discarding them were practiced by 60% of cases in Cantho and 16% in An
Giang . These practices should be avoided to reduce air, soil and water pollution (Table
5).
Technology dissemination and transfer to farmers are very necessary to improve
their knowledge for better management of rice and fish farming. This routine work is
done regularly every year. Nearly 70% of farmers in Cantho had been trained in
agricultural production but in An Giang province the proportion was below 50%.
Besides this farmers could also access new technologies through radio or television
(Table 6). Rice varieties is one of the decisive factors to increase yield. All of farmers in
Cantho and An Giang knew ways to get new varieties of rice (through research
institution, centre, state farm and/or exchange with other farmers).
The most severe threat to the environment is burning of rice straw in triple rice
system even though farmers had been taught many alternative methods to mitigate this
effect (straw mushroom cultivation, composting, feeding cattle). Shortage of labour,
time, difficulty in transportation, high cost of petrol, unavailability of space for treating
rice straw are reasons for non-adoption of sustainable straw management (Table 6)


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Table 5. Uses of chemicals in rice production

Items Cantho (%) An Giang (%)
Insecticides
BPH control (Bassa, Applaud, Actara, Apolo) 84 77
Others (Karate, Furadan, Regent, Padan) 16 23
Fungicides
Blast (Beam, Flash, Fuan, Trizole, Kasai,
Repsai)
60 52
Others (Tilt, Anvil) 40 48
Dosage
Recommendation 90 77
Higher than recommendation 8 26
Lower than recommendation 2 7
Timing
Occurrence 48 80
Fixed schedule 52 20
Container treatment
Burning 60 16
Buried 20 5
Throwing 15 9
Recycling (selling) 5 70

Table 6: Accessibility to information on rice production techniques (%).
Items Cantho An Giang
Information
Through radio, TV 90 93
Not watching TV or listening radio 10 7
Attending training course 70 47
Not being trained 30 53
Rice varieties

Self multiplication 33 47
Buying from institution, centre, state farm 32 21
Exchange between farmers 35 32
Use of agricultural by products
Burning 60 92
Selling for mushroom culture 29 5
Feeding cattle 11 3

III.2. Fish production
Catfish has been raised in An Giang province for a long time but culture areas
were limited by numbers of fingerlings that could be harvested naturally (at Chau Doc
district – An Giang province) during flooding time normally at August to October when
they travel down to Cuu Long delta from Tonle Sap catchment of Cambodia. Catfish
industry has been developed very quickly only after the year 2000 when Can Tho

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University developed techniques to produce fingerlings of catfish artificially and
international market for export was established.
Catfish industry is quite new to farmers which is why support by government in
dissemination of technology is really important through broadcasting, printed materials or
even sending technicians to field sites. Data in Table 7 showed that this support to fish
raising farmers was considerable. An Giang province has the largest catfish industry of
the Cuu Long delta both in area and total production. Fish raising farmers in An Giang
paid more attention to information or techniques than those in Can Tho (82% in An
Giang comparison to 75% in Can Tho). They also received support from technicians
more than in Cantho (Table 7). Fish culture requires substantial labour for routine work
such as feeding, pumping water and even guarding at night time as a result numbers hired
labourers in An Giang was much higher than in Can Tho.

Table 7: General information on fish culture

Items Can Tho An Giang
Information accessibility (%) 75 82
Technical support (%) 42 60
Hired labours (%) 38 72
Type of fish culture (%)
Catfish (%) 86 90
Others 14 10
Average time for fish raising (month)
From seed – fingerling 2.1 2.0
From fingerling – selling size 6.2 5.8
Depth of fishpond (m)
Fingerling 1.7 1.5
Selling size 3.3 3.5
Density of fish /m
2
33 35
Conversion factor (feed/meat) 1.5 1.6

There was not much difference in time of raising fish or depth of fishpond as well
as density of fish per square metre between the two locations. However, density was quite
varied among farmers from the lowest of 12 fish to the highest of 60 fish/m
2
. There was a
high positive correlation between fishpond size or area and total fish harvesting (r =
+0.842) but negative correlation between area and depth of fishpond (r = -0.365).
Farmers having larger areas can raise high numbers of fish so they can harvest more than
those who have smaller area. On the other hand, farmers holding small areas wanted to
increase their production by increasing fish density/m
2
. This had been proved by negative

correlation between area and fish density (r = -0.520).
Farmers in Cantho preferred to use pellets for raising catfish while those in An
Giang mainly prepared feed by themselves due to availability of discard sea fish from the
adjacent coastal Kien Giang province. As a result, conversion factor from feed to meat in
An Giang was higher than in Cantho and this figure was more or less the same in Dong
Thap province which had a conversion of 1.47 (Pham quoc Nguyen 2008). Cantho and
Dong Thap had many feed companies which were close to fishpond sites. In preparation
of ball feed, most farmers had to add additives either in the form of concentrated premix

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comprising vitamins, enzymes and minerals besides using some traditional inputs like
rice bran, soybean and broken rice. Most farmers gave feed two times per day (Table 8)
normally at early morning and before sunset. Others fed catfish once or four times per
day but these practices were not common in the Cuu Long delta. Regarding the quantity
of feed given per time, all of farmers at two sites said they supplied just sufficient food
for fish about 1/10 of fish weight because surplus feed can ruin water quality. The most
common practice by farmer to detect any change in water quality was done by
observation of water colour.

Table 8: Feed quality and feeding times/day
Items Can Tho An Giang
Type of feed (%)
Pellet (from industry) 55 27
Ball (self produce) 37 58
Mixed (pellet+ ball) 8 15
Use of additive 88 66
Types of additive
Vitamin 64 69
Enzyme 57 74
Minerals 23 36

Times of feeding/day
Once 23 12
Twice 43 78
Three time 27 10
Four time 7 0
Observation
Detection of surplus feed 33 40
Changing feed 32 10

Catfish raising ponds experience high fish mortality. Survey data indicated that
losses for raising seed was about 50% and that of commercial fish was a little more than
20% (Table 9). Diseases spreading by polluted water and fish sources were among causes
for high mortality. Different diseases on catfish were reported (Table 10) mainly caused
by parasites and virus. Farmers blamed fish sources for fish death but the main reason for
this was caused by carrying high numbers of fingerlings in close bag or container. During
transportation they were hurt by scratching because catfishes have very sharp spines on
their heads. Another reason is caused by changing environment when fishes were put in
to new ponds for raising. Those two causes collectively cause high mortality when re-
stocking ponds. According to farmers, environment also affected fish heath but this was
not so important in comparison to the other two cases cited above.
Interviewed on planning for catfish production in the near future, most farmers in
An Giang province (85%) and Cantho (68%) said they do not have any intention to invest
more on catfish production. This revealed that farmers were not so happy with catfish
production because there are a lot of uncertainties in price of selling fish, inputs (feeding,
chemicals for water treatment and diseases controls). Under market oriented economics
system, low level educated farmers should be assisted in production in order to increase

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their profits. Only 25% of farmers in Cantho and 11% of those in An Giang planned to
increase their production. Again this data confirms that catfish production could not

attract more farmers to invest on this job. Planning for set up settling ponds was also not
being considered by most of the farmers interviewed. Quite a few farmers were reluctant
to answer during interview but really they have never think about it.

Table 9: Percentage of mortality and causes
Items Cantho An Giang
Mortality rate
Fingerling 47 52
Commercial fish 22 24
Causes of loss
Diseases 50 32
Fish source 37 57
Environment 13 11
Current fish status
Having disease 68 72
Stable 27 24
Not know 5 5
Planning for future production
No plan 68 85
Increase production 25 11
Make settling pond 7 4

Concerning on the use of bio-products and chemicals for water treatment in
catfish culture, nearly 50% of farmers at both sites had used Vikong, BKC, Bioca, Yulai,
Aquapure, Prawbac and some other products (Table 10). They also used antibiotics to
control mainly bacterial diseases in the digestive tract of catfish. Some common
antibiotics like Amoxycilline, Cotrim, Penicilline, Kanamycine, Oxamet and Tetracylline
had been used mainly by mixing into feeds in An Giang (96%) or putting directly into
water (40% of farmers in Cantho following this method). According to farmers, these
antibiotics were very effective to control catfish diseases. Fortunately, almost all of

farmer used antibiotics at recommended dosage otherwise these chemicals will cause
problems to the environment and possibly in international markets also. For sanitary
purposes and control of algae in fishpond, 93% of farmers in Cantho and about 66% in
An Giang province applied copper sulphate, BKC, Vikong, Chlorine, juka and even salt
or lime (Table 10). Among these BKC and chlorine were the most common chemicals
which had been used both in An Giang and Cantho.
Water management is very important in catfish culture for new and current used
ponds. All farmers normally spreaded lime or salt along the sides and bottom of pond
after making a new one or after draining out all water after harvesting fish from ponds.
Dosages of lime and salt varied from 300-400 kg/ ha. Pond will then be kept dried from
3-5 days before pumping water in for a new crop. More than 95% of farmers changed
and/or added water to fish ponds regularly (about 1/3 volume of pond) and there was
about 50% farmers at both sites who practiced bottom of fishpond cleaning by pumping
out sludge while raising catfish to secure good water quality. However, all of farmers had

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to pump sludge out of their pond after harvesting fish (Table 11). The practice of
discharging waste directly to water source could caused water pollution. Most of farmers
had handheld a pH meter to monitor water quality. Other ways to detect water quality
were by observation of water colour or smelling the odour of water. If oxygen is deficient
most of fishes will come to surface of water early morning; farmers will then know
oxygen in fishpond is sufficient or not.

Table 10: Chemicals used for water treatment.
Items Cantho An Giang
Bio-products (%) 48 43
Antibiotics (%) 72 54
Mixing to feed 60 96
Mixing with fishpond water 40 4
Water treatment 97 100

BKC 21 28
Vikong 43 5
Copper sulfate 7 8
Chlorine 21 10
Others 8 49
Efficacy (2+3) 100 100


Table 11: Water management in catfish culture.
Items Cantho An Giang
Renewed fishpond (%) 100 100
Lime (kg/ha) 425 350
Salt (kg/ha) 325 300
Dried bottom of pond (%) 100 100
Days of drying 3.5 4
Filled up and/or changed water periodically (%) 98 100
Volume of added or changed water 1/3 1/3
Water quality monitoring
pH 95 90
Colour or odour 8 12
NH
3
and Oxygen 62 65
Sludge discharged
During raising time (%) 50 50
After harvesting (%) 60 75

Survey data on diseases of catfish are presented in Table 12. The most severe and
widespread disease to catfish is caused by bacteria (about 90%) causing death of catfish.
The most common symptoms of bacterial disease called haemorrhage producing red

appearance on mouth, fins and tail. Other diseases are called swelling head and slimy loss
but they are of minor importance.


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IV. VAC survey in Cantho City:
A broad survey of VAC practices was carried out in the suburb of Cantho city at 2
districts, namely Binh Thuy and Phong Dien. Orchards or fruit tree plantations were
mainly kept on elevated soil adjacent to ditches or ponds. Longan, milky fruit, durian,
rambutan or oranges/lime are the most common fruit trees in these areas. Duck has been
raised in the largest numbers among others like chicken or pigs. Fishes like tilapia, silver
carp and Osphonerrus gouramy are mainly raised in ditches in between raised beds of
orchards. These species are raised in low density (<30 fishes/m
2
) and they did not cause
water pollution. Catfish other than Pangasianodon hypophthalmus namely Clarias
botrachus, Clarias gariepinus, Clarias macrocephalus or hybrid of these two first species
have been raised in ponds for selling in local markets only. Cultivation of Clarias sp. (or
walking fish) caused higher surface water pollution than Pangasianodon sp. because
waste waters were mainly discharge to small rivers or canals. The typical characteristics
of waste water from Clarias sp. ponds are black in colour, very high in turbidity, BOD
and COD and stale smelling (Table 14). The most striking effect of liquid waste from
Clarias pond is causing death to all other natural fishes. Sludge in Clarias fishpond is not
significant because most of solid wastes are always stirred up by large numbers of fish
present in ponds (about 120-150 fishes per m
2
of pond surface) and then it is mixed up
with liquid and then discharged to environment. However, suspended particles will then
be settled along water ways and filling up the canals which obstructs navigation.
There was not much variation in size and depth of fish ponds between two

locations. Since pond size is not so large, household labour can manage almost all
activities relating to raising fish. Clarias fish reaching weight of 200-250g each
(commercial size) is often sold for meat. Bigger or smaller than commercial size is
difficult to sell unless the price is reduced. Most of Clarias fish raising farmers buy self-
made feed from their neighbours at the price of around 2,500-3,000VND/kg. Clarias fish
could be sold at the price of 12,000-20,000VND depending on demand of local market.

Table 12: Diseases of catfish, occurrence stage and control measure.
Items Cantho An Giang
Symptoms
Haemorhage 54,5 66,7
Swelling head 10,2 6,4
Slimy loss 0,1 4
Occurrence stage
Fingerling up to 1 month 72 88
From 1-3 month old 17 8
More than 3 month old 11 4
Effective Control
Haemorrhage 92 82
Swelling head 77
Slimy loss 100

All of Clarias fish ponds under survey deliver liquid waste directly to waterways
resulting in high pollution in these areas up to the limit that any natural fishes could
survive and navigation is often obstructed due to sludge filling up rivers and/or canals
bases. The conflict between Clarias fish raising farmers and people living in these areas

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are quite common so it is quite difficult to convince them to cooperate. Although local
authorities had issued regulations banning direct discharge waste from fishpond to

waterways but this situation seems out of control. Since most of farmers raising Clarias
fish does not have settling pond or paddy for land application then water pollution in
these areas is very critical.

Table 13: General information on Clarias sp. culture
Items Binh Thuy Phong Dien
Information accessibility (%) 82 75
Technician support (%) 64 50
Hired labours (%) 12 8
Type of fish culture (%)
Clarias sp. (%) 86 92
Others 14 8
Average time for fish raising (month) 3.5-5 3.5-5
From seed – fingerling 1.2 1.3
From fingerling – selling size 7.2 7.5
Size of fishpond (m
2
) 500-3000 1000-3000
Depth of fishpond (m)
Fingerling 1.2 1.1
Selling size 1.8 1.6
Density of fish/m
2
90-120 70-100
Conversion factor (feed/meat) 3,5 3,6


Table 14: Water quality of Clarias fishpond
Items Binh Thuy Phong Dien
BOD

5
(20
0
C) 120 104
TSS (mg/L) 312 258
DO (mg/L) 0.05 0.1
COD (mg/L) 128 117

Although Clarias fish can survive in polluted water, it is also subjected to some
bacterial diseases but percentage of loss is much lower than for Pangasianodon sp. fish.
Chemicals and biochemicals use for cultivation of Clarias fish are more or less similar to
those which are used for catfish culture (Table 15).

Table 15: Chemicals used for water treatment and diseases control of Clarias fish culture.
Items Binh Thuy Phong Dien
Bio-products: biozyme, US-zyme, biomix (%) 56 34
Water treatment (sanitation) 76 82
BKC, 32 24
Vikong 16 22
Copper sulfate, potassium permanganate 39 48
Chlorine, formol 7 110
Soil treatment (zeolite, lime) 62 75



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VAC opportunity and challenge:
VAC systems are located mainly on high elevation areas along rivers. These are
silty soils having high infiltration and percolation capacity which are suitable for growing
vegetables and fruit crops. Chemical fertilisers are mainly used for cultivation that is why

it is hard to find anyone in this system using compost for farming although rice straw,
water hyacinth, pig manure and solid waste from fish ponds are available. Surveys on the
VAC system also revealed that vegetable growers do not like to use vermicompost
produced from cow dungs because they have to pay more labour for controlling weeds.
Although farmers know some benefits of organic manure for cultivation of vegetable and
fruit trees but self-made compost or manure have not commonly used due to the
following reasons:
- Time consuming;
- No visual effect of manure application;
- Shortage of labour in agriculture sector;
- High cost for transportation and application;
- Organic products sold at same price with others;
- Farmers do not know properly how to make organic manures.

Besides the above constraints for production and application of organic manures,
farmers are unaware of the adverse effects of burning rice straw. In triple rice areas,
farmers usually burn rice straw to clear their fields to aid in land preparation after
harvesting the Dong-Xuan crop. The possibility exists for our project to improve farmers’
knowledge in environment protection through training on recycling of agricultural by-
products to make organic manures and to reducing greenhouse gas emissions. Through
training, farmers will understand the role of organic matter in sustainable agriculture
production. This goal is realistic because prices of fertilisers and pesticides are quite high
nowadays. Another opportunity for encouraging farmers to raise earthworm and produce
vermicompost in the VAC system is that earthworms are used for feeding high quality
fishes or prawn. Farmers using VAC can make use of ditches in between ridges for
aquaculture.

V. Surveys on production and consumption of vermi-compost
Vermicompost is directly linked to earthworm raising. Animal manures are very essential
for bedding and feeding earthworms. Hence most worm raising farms are located next to

dairy farms or swine pens. In the Cuu Long delta, earthworm raising farms are
distributed on high elevated land (no flooding) where cattle could be raised easily. There
are quite a few vermicompost farms in Cantho. The situation is different in An Giang
province because of flooding although numbers of cattle in An Giang are among the
highest in this delta. Data on surveys in Cantho (Table 17) showed that number of
farmers used organic manures for rice production were not common mainly because of
low economic efficiency though they were trained on organic farming. However,
numbers of farmers in Binh Thuy and Phong Dien under VAC system used manures were
higher because in these areas they grow fruit trees and vegetables which are higher value
than paddy.



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Table 16: Organic manure production and use for farming at Cantho city
Items VAC system Paddy
Binh Thuy Phong Dien OMon Thot Not
Vermiculture farm 5 1 2 1
Home made manure
- Compost 14 11 5 8
- Org. manure 2 3 1
- Green manure 8 6
Organic manure application 42 38 12 27
Knowledge on organic
farming
65 72 28 16
Training participation (%) 7 4 15 18


VI. Reports on diseases caused by water pollution:

Investigations on diseases attributable to water pollution have also been
completed in OMon and Thot Not districts of Cantho City and in Chau Phu and Phu Tan
districts of An Giang province. According to data collected at the Preventive Medicine
Center in O Mon and Thot Not districts during 2006 and 2007 dengue was increased.
This disease outbreak by the end of 2008 mainly in the south Vietnam; the situation was
most severed in An Giang and Dong Thap provinces (Department of Preventive Medicine
– MOH Vietnam, 2008). Data in Table 16 also indicated that diahorrea in 2007 was
higher than in 2006.
Dengue, diahorrea and dysentery in Phu Tan were much higher than those in
Chau Phu and they had a tendency to increase. These might be related to the closed dike
system at Phu Tan district where water in canals could not be drained. As presented in
Table 2, most of people in An Giang province (57%) are still use river or canal waters as
the main source for living.

Table 17: Epidemic records in 2006 & 2007 at O Mon and Thot Not districts
O Mon Thot Not
Disease
2006 2007 2006 2007
Dengue 179 237 246 546
Typhoid fever 2 0
Diarrhea 159 220 3210 2822
Dysentery 0 1 138 31


Table 18: Epidemic records in 2006 & 2007 at Phu Tan and Chau Phu districts
Phu Tan Chau Phu Disease
2005 2006 2007 2005 2006 2007
Dengue 112 300 495 411 595 438
Typhoid fever 169 153 71
Diarrhea 752 957 1502 189 187 200

Dysentery 202 250 463 21 10


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VII. Impact of water discharged
Effects of discharged liquid waste during the dry and wet season (especially at
flooding time) were observed right at the flush gate, 100 metres upper-stream and 100,
200, 300, 400 and 500 metres of downstream.

pH of water in the canal was measured at 15 day intervals. Data in Figure 1 showed
that pH of waters before opening the flushing gate were a little higher than those
measuring after; however, they were not significance different (P < 0.05) in both dry and
wet season. During flooding time, the difference between these two sets of data were
even smaller than those taken in the dry season because dilution factor during the
flooding time was much greater. Generally pH in the canal after waste water discharge
was still in limits accepted for living use (TCVN-5492-2005).












Figure 1: pH of water in canal before and after opening the flushing gate to discharge
fishpond waste water.

Regarding EC in canal water, data in Figure 2 indicated that EC taken at different
time interval after opening gate were statistically higher than those measured before.

0
50
100
150
200
250
300
350
-100 0 100 200 300 400 500
m
Ec (uS/cm)
Before
After

Figure 2: Electrical conductivity (EC) of water in canal before and after opening the
flushing gate to discharge fishpond waste water.

As with pH, EC values during flooding time were not significantly different
between times of water sampling.

6.9
7
7.1
7.2
7.3
7.4

7.5
-100 0 100 200 300 400 500
m
pH
Before
After

16

Unlike pH and EC, COD values were very significant different before and after
opening the flushing gate even during flooding time. Normally COD of liquid waste
from fish ponds exceeded value allowable for living use ( below 10 mg/L) except
during flooding time (October-January) but they were still in the range accepted for
water discharged from fish ponds (35 mg/L <COD<100 mg/L).

0
20
40
60
80
0 100 200 300 400 500
Distance (m)
COD
After
Before

Figure 3: COD (mg/L ) of water in canals before and after opening the flush gate to
discharge fishpond waste water.

Ammonium levels were high right at the flushing gate and they were decreased with

increasing distance from the gate (Fig. 4). These concentrations generally were higher
than the Vietnamese Standard allowable for living use (less than 0.5mg/L) based on
TCVN5492-2005 but they were still accepted for waste discharge according to
announcement No. 2 of the Ministry of Fisheries. High level of ammonium resulted
in water enrichment in small rivers and canal surrounding fish raising areas which are
generally observed in the Cuu Long delta.

0.0000
0.0200
0.0400
0.0600
0.0800
0 100 200 300 400 500
Distance (m)
Ammonia (mg/L)
After
Before

Figure 4: Ammonium levels of water in canal before and after opening the flushing
gate to discharge fishpond waste water.

In the case of nitrite and nitrate levels taken at different time intervals before and
after opening the flushing gate, they were lower than allowable values for living use

17
even in dry season where nitrite and nitrate levels in canal waters were highly
concentrated.

On average, TSS in canal waters after the opening flushing gate (261± 64 mg/l)
were five times higher than those recording before (54 ± 20 mg/l). Figure 5

demonstrated most of TSS values collected in canals under the effect of waste water
discharge generally were 10-13 times higher than TCVN 5942-1995 (column A- TSS
less than 20 mg/l). Even the allowable value (less than 80 mg/L) for waste from fish
pond discharged to water source under Announcement No 02 of Ministry of Fishery
was generally exceeded.

0
50
100
150
200
250
300
-100 0 100 200 300 400 500
Distance (m)
TSS (mg/L)
After
Before


Figure 5: Total suspended solids levels of water in canal before and after opening the
flushing gate to discharge fishpond waste water.


VIII. Conclusions
Profit from fish production was many times higher than rice cultivation but the
risk and unpredicted factors were also higher. However, there were signs of water
pollution in rural areas mainly due to wastes from fish ponds which were generally
discharged directly to water sources. To mitigate water pollution in order to protect
human health, training on rational use of waste by practical and effective waste

treatments are really needed to increase farmers income and awareness of environment
protection.
Support from government is very necessary in kind of technical assistance and
credit availability to farmers because their educations were low and most of them is still
poor otherwise they are vulnerable to many risks especially present economics crisis.
Organic farming should be encouraged to improve quality of agricultural products while
reducing water pollution by reducing chemicals uses.
Infrastructure of rural areas should be improve as well as sanitation to secure
sustainable production and ensure happy life for farmers