Báo cáo khoa học nông nghiệp " Cuu Long Rice Research Institute " pdf

Ministry of Agriculture & Rural Development

Project Progress Report

SECOND SIX-MONTHLY REPORT
4th July, 2008

1


Table of Contents
1.

Institute Information ___________________________________________________ 3

2.

Project Abstract _______________________________________________________ 4

3.

Executive Summary ____________________________________________________ 4

4.

Introduction & Background _____________________________________________ 6

5.

Progress to Date _______________________________________________________ 8
5.1

Implementation Highlights ________________________________________________ 8

5.2

Smallholder Benefits_____________________________________________________ 19

5.3

Capacity Building _______________________________________________________ 20

5.4

Publicity _______________________________________________________________ 20

5.5

Project Management ____________________________________________________ 20

6.

Report on Cross-Cutting Issues__________________________________________ 20
6.1

Environment ___________________________________________________________ 20

6.2

Gender and Social Issues _________________________________________________ 21

7.

Implementation & Sustainability Issues ___________________________________ 21
7.1

Issues and Constraints ___________________________________________________ 21

7.2

Options________________________________________________________________ 21

7.3

Sustainability___________________________________________________________ 21

8.

Next Critical Steps ____________________________________________________ 22

9.

Conclusion __________________________________________________________ 22

10.

Statuatory Declaration__________________________Error! Bookmark not defined.

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1. Institute Information
Project Name

023/06VIE

Vietnamese Institution

Cuu Long Rice Research Institute

Vietnamese Project Team Leader

Dr. Cao van Phung

Australian Organisation

Murdoch University

Australian Personnel

Dr. Richard Bell

Date commenced

April 2007

Completion date (original)

February 2010

Completion date (revised)

March 2010

Reporting period

October 2007 – March 2008

Contact Officer(s)
In Australia: Team Leader
Richard Bell
Name:
Professor
Position:
Organisation Murdoch University

Telephone:
Fax:
Email:

+61 8 93602370
+61 8 93104997


In Australia: Administrative contact
Richard McCulloch
Name:
General Manager
Position:
Organisation Murdoch Link

Telephone:
Fax:
Email:

+61 8 93607566


In Vietnam
Name:
Cao Van Phung
Head, Soil Science Dept.
Position:
Organisation Cuu Long Rice Research
Institute

Telephone:
Fax:
Email:

+84 71 861452
+84 71 861457



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2. Project Abstract
In total, 240 questionnaires of rice and fish farmers were collected (2 districts).
Stakeholders were concerned about surface water pollution because of its effects on their

business sustainability and livelihood. There were about 15-24 % of the farmers
(including both fish and rice farmers) stating that water quality is bad. There are only 3-8
% of fishpond holders having settling ponds, 15-24 % of them practice waste recycling on
paddies and the rest discharge fishpond waste directly to the waterways.
A field study on the use of solid fishpond waste for rice cultivation was established
during the wet season 2007 at Cuu Long Rice Research Institute. There were no
significant differences in rice yields over all treatments. The experiment was repeated in
the dry season 2008, and produced similar results. That is, 1/3rd to 2/3rd of the inorganic
fertiliser recommended for rice can be omitted when applying solid waste at 1-3 t/ha.
Results from 4 trials indicated that that irrigation of rice by wastewater from fishponds
can save 33 % of recommended N, and 50 % of the recommended P and K. rice yields.
Further decrease in N and P fertiliser resulted in reduced yield.

3. Executive Summary
Questionnaires for the baseline study were formulated in consultation with researchers of
Can Tho University, and with extension officers in Can Tho city and An Giang provinces. In
total 240 questionnaires of stakeholders (rice farmers and fish farmers) were collected (2
districts/site). The results showed that all stakeholders were concerned about surface water
pollution because of its effects on their business sustainability and livelihood. There were
about 15-24 % of the farmers (including both fish and rice farmers) stating that water quality
is bad. There are only 3-8 % of fishpond holders having settling ponds, 15-24 % of them
practice waste recycling on paddies and the rest discharge directly to the waterway. In
Cantho, farmers practicing fish culture are richer, have more formal education and are
younger than those carrying out rice cultivation. However, about 15 % of fishpond holders
are recent migrants who have bought or rented lands from local farmers. In An Giang, fish
farmers had similar age and education profiles to rice farmers suggesting that here fish
farming was carried out as a diversification of farm activities. Impacts reported on water
quality include greenish-black colour, bad smell, high turbidity, causing itching on contact.
Moreover, farmers raising fish recognised that percentages of disease-infected fish were
much higher (about 15%) than before (< 5 %). The demand for effective and economical

solutions for control of water pollution is the first priority of stakeholders. Only 10 % of fish
farmers surveyed in An Giang and 25 % of those in Cantho expressed the intention to
increase production in the future. Notwithstanding their concern about water quality, few
expressed an intention to construct settling ponds (3-7%) in the future.
The survey of farmers’ practices on fishpond waste treatment was completed during the dry
season 2007 at 2 sites (An Giang province and Can Tho city). Most (68-80 %) of the wastes
(liquid and solid) are pumped directly into waterways (rivers or canals). In the case of
fishponds located nearby big rivers (Tien and Hau), waste is apparently diluted by the large
volume of water flow and it is not reported to cause much problem in comparison with

4


discharge situated at the far end of small rivers or canals. A concern requiring management
of waste discharge into paddy fields arises from the content of nitrogen in waste causing
yield loss by lodging. However, judicious use of waste in balance with inorganic fertiliser
application may increase rice yield in some cases as reported below.
During the dry season 2007, we conducted a study on 32 paddies comprising 16 fields that
received waste through discharge from fishponds while the others did not. Results showed
that rice yields in fields receiving waste were 0.8-1.0 tonnes/ha higher than those that did not
receive waste. This is attributed to higher available nitrogen, phosphorus, potassium as well
as secondary and micronutrients.
A field study on the beneficial use of solid fishpond waste for rice cultivation was established
during the wet season 2007 at the experimental farm of Cuu Long Rice Research Institute.
Three dosages of waste at the rate of 1, 2 and 3 tonnes/ha were applied in combination with
1/3 and 2/3 dosages of inorganic fertilisers. The 100 % rate of inorganic fertilisers (60N40P2O5-30K2O) served as the control. There were no significant differences in rice yields
over all treatments. This indicated that uses of solid waste from fishpond can save money for
farmers by reducing fertiliser inputs. The experiment was repeated in the dry season 2008,
and produced similar results. That is, 1/3rd to 2/3rd of the inorganic fertiliser recommended
for rice can be omitted when applying fishpond solid waste at 1-3 t/ha.

Fifteen isolates of Pseudomonas stutzeri were selected from liquid and solid waste of catfish
ponds located along the Tien river, in the Mekong Delta, Vietnam using SW-LB medium
(artificial seawater Luria-Britani medium) supplemented with 10 mM NH4 and NO3. Eleven
isolates were identified as Pseudomonas stutzeri based on similarity of PCR-16S rRNA using
universal primers and specific primers. Four isolates were effective in lowering soluble N
(NH4, NO2 and NO3) levels in fishpond water from 10 mg/L to negligible amounts after four
days. Further experiments are underway to determine the fate of N lost from solution and the
relative activity of ammonia oxidation, and nitrite and nitrate reduction by Pseudomonas
stutzeri isolates.
Ozone treatment was evaluated for treatment of wastewater. The levels of ozone produced in
waste water were < 40 % of those produced in shrimp pond water, and effects on water
quality were mixed. No mortality to fish of varying sizes was caused by ozone treatment of
the water. Future laboratory experiments are planned to determine whether ozone can
improve water quality either on its own or in combination with aquatic plants.
Aquatic plants are being evaluated for use in combination with settling ponds to improve
water quality. Results are still being analysed but preliminary examination of them suggests
that N and P levels and total suspended solids are decreased when aquatic plants are grown in
waste water.
AYAD Stephanie Birch will undertake research on vermicomposting in 2008. Experiments
will examine the optimal ratio of rice straw or water hyacinth relative to fishpond sediment.
Two local worms have been recovered in soils at O Mon. In addition the introduced Tiger
worm which is commonly used elsewhere for vermicomposting will be used in experiments.
The relative effectiveness of the three worm species and mixtures of species will be
evaluated.

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The training workshop on Land application of Waste was held at CLRRI on 26-29 December
2007 with 17 participants from the provinces of Cantho, Vinh Long, An Giang and Dong

Thap. Participants were from fisheries, agriculture extension and natural resources
management positions.

4. Introduction & Background
Fishpond aquaculture is as a major industry in the Mekong Delta. However, wastewater and
solid waste discharge from fish ponds is causing pollution of canals and rivers harming the
quality of water used for household purposes and threatening the future of the aquaculture
industry itself. There is a clear and urgent need to develop strategies for reducing waste
discharge from fish ponds so that the fishpond aquaculture industry can continue to support
income diversification in the Mekong Delta, while complying with the water quality
discharge standards outlined in Vietnamese law and regulations (Ministry of Fisheries
2006)1.
Water in fish ponds is replaced frequently generating large quantities for disposal or re-use.
Currently wastewater is mostly discharged into communal rivers and canals, but this has
caused significant downstream water pollution, such that most of the aquaculture is now
located in the headwaters of catchments. In order to reduce pollution, National
Environmental Law introduced in 2005 prohibits direct wastewater discharge into rivers and
canals. Offenders may either be fined or their operation closed until compliance is achieved.
In addition annual emptying and cleaning of solid waste from the base of fish ponds is
essential to control the spread of diseases among fish. This produces an organic-rich slurry
comprising about 35 % solids. Discharging this slurry into communal waterways is also
prohibited under the law. However, there appears to be poor compliance with the law by
operators of fish ponds. Strict compliance with the law without cost-effective treatment and
recycling strategies would have a crippling effect on the fishpond aquaculture industry. It is
critically important to develop effective strategies for fishpond operators so that they can
treat wastewater and solid wastes to meet discharge standards without large costs.
While there is widespread acceptance that water pollution from fishpond discharge is
prevalent, there appears to be little evidence gathered and published on the problem. In
particular there appears to be a lack of baseline water quality data from which to demonstrate
a decline in water quality. Moreover, there is little current monitoring of water quality in the

medium to small sized canals in which the water pollution problem is most obvious. Hence it
remains unclear what water parameters fail to meet the Vietnamese water quality standards,
how frequently breaches occur, where they occur and the key risk factors. From first
principles, it is likely that the water pollution problems are most severe during the dry season
when flushing and mixing of discharge water is least, and in the smaller canals especially
where their flow is blocked by aquatic plants and by barriers.
The Mekong Delta produces 400,000 t of catfish per annum mostly in freshwater ponds.
Most of the fish are exported to the USA, and increasingly to European countries and Japan.
The exported fish must meet sanitary requirements in these markets. A major variable in
producers’ capacity to control the inputs to fish ponds is the water used to fill ponds, which is
drawn from rivers and canals. However, under the cumulative influence of intensive fishpond
aquaculture, a decline in quality of river and canal water from the discharges is limiting
productivity and expansion of fishpond aquaculture by causing the downstream spread of
1

Ministry of Fisheries (2006). Maximum concentration limits allowable for pollutants discharged to
waterways. Regulation No. 02/2006. Issued March 2006.

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bacterial disease and parasites in the water. It may also be impacting adversely on the health
of families that draw significant amounts of their domestic water from these polluted sources.
The challenge of this project is to protect the fishpond aquaculture industry which is a source
of diversified income for farmers in the Mekong delta by treating the waste water and solids
from fish ponds, whilst at the same time protecting the environment and householder users
from water pollution.
The expected outputs are directed to improving competitiveness of fishpond aquaculture
producers in the Mekong Delta. In addition, technologies to be developed will improve
natural resources management by decreasing water pollution from uncontrolled discharge of

fishpond waste water and solids into rivers and canals. The overall Project objective is to
improve the sustainability of fishpond aquaculture production and water quality in the
Mekong Delta. Specific Project objectives are:
•
Develop effective treatment strategies for wastewater and solids from
fishponds before discharge to reduce water pollution;
•
Develop resource recovery and re-use strategies for waste water and solids
from fish ponds including land application and novel end uses;
•
Increase stability of household income from fishpond aquaculture through
encouraging diversification of production and markets in the Mekong Delta.
This project targets fishpond aquaculture, not other types of aquaculture such as cage
aquaculture and shrimp aquaculture. Cage aquaculture is declining in importance due to
rising costs and riskiness of the production system compared to pond culture. Other studies
have examined shrimp aquaculture in brackish water environments (Be, 1997). Shrimp
aquaculture is also under threat due to environmental impacts. Hence, there are lessons to be
learnt from other forms of aquaculture, in particular the need to address environmental issues
that can impact on the sustainability of the industry even when economics for it are
favourable.
Fishpond aquaculture is practiced by three main groups in the Mekong Delta: farmers using
the VAC system to recycle waste water and solid wastes from fish ponds; small farmers who
have both fish ponds and crop land but without integration of these components of the farm;
specialist producers who essentially use all of their land for fish ponds. The VAC system
already practices re-cycling of wastewater and solid waste to recover nutrient resources. In so
doing the level of pollution caused by water discharge is probably decreased. However, there
appears to be little evidence to demonstrate the benefits of the VAC system for downstream
water quality. The present project will assess the impact of the VAC system on water quality
in downstream canals, and as necessary examine modifications to the recycling of
wastewater and solid waste in order to meet water quality standards for discharge. The

second group of producers comprises small farmers who have a few fish ponds within a farm
carrying out crop production for padi and/or fruit trees and vegetables. The present Project is
particularly relevant to these two groups of producers who have sufficient land for
wastewater and solid waste treatment by re-cycling, but are currently discharging wastewater
and solid wastes directly into canals.
Both liquid and solid waste from aquaculture contain carbon and nutrients which can be
recycled on farms to boost production of rice, vegetables and fruit trees, as well as novel
products for small scale agro-industry. Solid wastes can be treated in a number of ways,
including land application, vermi-composting, microbially-activated decomposition and
ozone treatment. However, research is needed to ascertain the potential of each method for

7


treating wastes and improving water quality, and to gather evidence of their effectiveness in
meeting water quality outcomes.
The specialist fishpond producers generally have inadequate land remaining for recycling
wastewater and solid waste. Currently wastes are discharged directly into canals and rivers,
sometimes after treatment with biocides. Further investigation is needed to determine the
impacts of biocides on the downstream environment. In addition, opportunities need to be
explored for cooperative arrangements that allow the disposal of wastewater and solid wastes
from the specialist producers onto neighbouring farmers’ land. However, the best practices
for carrying this out still need to be developed, and once established can be extended to this
group of producers.

5. Progress to Date
Implementation Highlights
Baseline study: Questionnaires for the baseline study were formulated in consultation with
researchers of Can Tho University, and with extension officers in Can Tho city and An Giang
provinces. The survey was conducted in October-November 2007 at Cantho city and

January-February, 2008 at An Giang province. In total 240 questionnaires of stakeholders
(rice and fish farmers were sampled in equal numbers) were collected (2 districts/province)
(Table 1, 2). Results showed that all stakeholders were concerned about surface water
pollution because of its impacts on sustainability of production and livelihoods. There were
about 15-24 % of the farmers (including both fish and rice farmers) stating that water quality
is bad. Only 30-55 % of farmers were fully satisfied with the quality of water available for
fish farming. In Cantho, 80 % of farmers accessed household water from public water
supplies and groundwater and in this province 83 % of farmers were satisfied with water
quality for household use. However, in An Giang, where 57 % of farmers used river water
for household purposes, the level of satisfaction with water quality was only 36 %. Most
farmers (91 %) attributed poor water quality for household use to fishpond farming in An
Giang, but to fishponds (37 %), pesticide use in rice fields (15 %) and other causes (48 %) in
Cantho. Most farmers anticipated that water quality improved during the period of flooding
(September- November).
Farmers practicing fish culture are richer, had more formal education and were younger than
those carrying out rice cultivation, based on numbers of concrete houses, living commodities,
pumping machines and incomes. However, about 15 % of fishpond holders are recent
migrants who have bought or rented land from local farmers. Impacts reported on water
quality include greenish-black colour, bad smell, high turbidity, and skin itching on contact.
Moreover, farmers raising fish recognised that percentages of disease-infected fish is much
higher now (about 15%) than before (< 5 %). The demand for effective and economical
solutions for control of water pollution is the first priority of stakeholders. The investment
cost for raising fish is large and most of farmers lend money from either banks or their
neighbours hence they are concerned about threats to the viability of the operation.
Survey of farmers’ practices on fishpond waste treatment: The survey of farmers’ practices
on fishpond waste treatment was completed during October-November 2007 at Cantho and
January-February, 2008 at An Giang province. Most (68-80 %) of the wastes (liquid and
solid) are pumped directly into waterways (rivers or canals). In the case of fishponds located
nearby large rivers (Tien and Hau), waste is apparently diluted by the large volume of water
flow and it is not reported to cause much problem in comparison with discharge situated at

8


the far end of small rivers or canals. There are only 5-8 % of fishpond holders with settling
ponds, 14-25 % of fishpond farmers who practice waste recycling on paddies and the rest
discharge directly to the waterway. The higher adoption of wastewater recycling was
reported in An Giang (25 %). A concern requiring management when using wastewater
arises from the high content of nitrogen in waste water causing rice yield loss by lodging.
However, as our results below show, judicious use of waste in combination with reduced
inorganic fertiliser application may maintain rice yield and increase it in some cases.
Table 1. General socio-economics aspects of rice and fish farming households from a survey
of 240 farmers practicing rice or fish farming in Can Tho and An Giang provinces.
Can Tho
An Giang
Items
Fish culture Rice culture Fish culture Rice culture
Age of household head
43
49
47
47
(years)
Level of education
7/12
5.5/12
5.7/12
5.8/12
Years of experience
3.6
20

9.4
20
No. labor/family
3.4
3.6
3.7
3.0
Land tenure area (ha)
0.6
1.2
0.58
1.50
House types (%)
48
42
23
43
- Concrete
44
39
73
42
- Brick
8
19
4
15
- Thatch
Water quality (%)
46

51
55
30
- Good
39
25
22
52
- Medium
15
24
23
18
- Bad
Wastewater discharge method
(%)
100
68
100
80
- River or canal
24
15
- Paddy
8
5
- Settling pond
However, there have been instances reported of farmers applying high levels of salt (NaCl) to
fishponds to control disease. The use of salt-affected wastewater in one case led to failure of
the rice crop. In the long term, the high P in sediment relative to N may cause a build up of

soil P levels, although previous research suggests that the soils of the Mekong delta,
especially the acid sulfate soils, have very high P sorption capacity. We have heard reports
that one farmer constructed a sand bed filter with activated charcoal for the treatment of
waste water from fishponds by using a water recycling system. However, we have not been
able to inspect this system.
Concerning the use of bio-products for water treatment in catfish culture, nearly 50 % of
farmers at both sites used Vikong, BKC, Bioca, Yulai, Aquapure, Prawbac and some others
(Table 3). 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 in water (40% of farmers in Cantho follow this method). According to
farmers, these antibiotics were very effective to control catfish diseases. Fortunately, almost
all of farmer used antibotics at recommended dosage. For sanitary purpose and control of
algae in fishpond, 93% of farmers in Cantho and about 66% in An Giang province applied
9


copper sulphate, BKC, Vikong, chlorine, Juka and even salt or lime (Table 3). Among these,
BKC and chlorine were the most common chemicals which had been used both in An Giang
and Cantho.
Table 2: Quality of water for irrigation and for household use as a % for 240 respondents.
Items
An Giang (%)
Can Tho (%)
Water source for household use (cooking
& drinking)
River/ canal
57
17
Tube well

13
57
Public water supply
30
26
Water quality for household purposes
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 when good water quality is available
for irrigation
Flooding
62
58

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

Table 3: Chemicals used for water treatment in catfish ponds. % of respondents.
Items
Cantho
An Giang
Bio-products (%)
48
43
Antibiotics (%)
72
54
Mixing antibiotics with feed
60
96
Mixing antibiotics with fishpond water
40
4
Water treatment methods
BKC (benzalkonium chloride),
21
28

Vikong
43
5
Copper sulfate
7
8
Chlorine (sodium hypochlorite)
21
10
Others
8
49
Efficacy (2+3)
100
100
Water management is very important in catfish culture. All farmers normally spread
lime or salt along the sides and at the bottom of ponds after constructing new ponds or after
draining out all water during harvesting of fish (Table 4). Dosages of lime and salt varied
from 300-400 kg/ ha/yr. Ponds are kept dried for 3-5 days before refilling with water for the
new crop of fish. 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 that
practiced cleaning of the bottom of the fishpond by pumping out sludge during time of
raising catfish. However, most farmers had to pump sludge out of their pond after harvesting

10


fish (Table 11). The practice of discharge waste directly to water source caused water
pollution. Most of farmers had handheld pH meter to monitor water quality. Other ways to
detect water quality were by observation of water colour or smelling odour of water. If

oxygen is deficient, most fish will come to the surface of water in the early morning; farmers
will then know oxygen in fishpond is sufficient or not.
Table 4: Water management in catfish culture.
Items
Renewed fishpond (%)
Lime (kg/ha)
Salt (kg/ha)
Dried bottom of pond (%)
Days of drying
Added and/or changed water periodically (%)
Percentage of added or changed water
Water quality monitoring
pH
Color or odour
Ammonia and oxygen (from fish behaviour and odour)
Sludge discharged
During raising time (%)
After harvesting

Cantho
100
425
325
100
3.5
98
33

An Giang
100

350
300
100
4
100
33

95
8
62

90
12
65

50
60

50
75

Survey data on diseases of catfish are presented in Table 5. The most severe and
widespread disease to catfish is caused by bacteria (about 90%) besides the others disease
causing death of catfish. The most common symptoms of bacterial disease called
haemorrhage are red colour appearing on the mouth, fins and tail. Other diseases called
swelling head and slimy loss occur but they are of minor importance.
Table 5: Catfish diseases and control measures
Items
Cantho
Symptoms

Haemorrhage
93
Slimy loss
2
Swelling head
5
Occurrence
All year round
26
Rainy season
53
Dry season
8
Flooding time
7
Climate change
6
Control efficacy
High
92
Medium
4
Low
4

An Giang
74
2
24
17

61
6
6
10
82
8
10

Diseases on catfish occurred mainly in the rainy season when catfish are younger
(<1month). Losses due to disease were very high in some cases up to nearly 20% at both

11


sites. In most case, disease can be controlled in Cantho as well as in An Giang at the rate of
92 and 82%, respectively.
During the dry season 2007, we conducted a study on “Effect of waste application on
rice yield in An Giang province”. We selected 32 paddies wherein 16 fields received waste
water through discharge from fishponds while the others did not. Results showed that rice
yields in fields receiving waste water were 0.8-1.0 tonnes/ha higher than those that did not
receive waste (Table 3). This might be due to high nutrient content in waste especially
available nitrogen, phosphorus, potassium as well as secondary and micronutrients (Table 4).
However, organic carbon content in paddies receiving waste was lower suggesting more
rapid decomposition of the organic matter in treated fields.
Table 6. Mean rice yields in paired farmers’ fields at Chau Phu and
supplied with fishpond wastewater for irrigation or river water. Values
fields.
Treatments
Chau Phu
Irrigation with wastewater

7,920 a
Irrigation with riverwater
CV%

Phu Tan districts
are means from 8
Phu Tan
7,436 b

6,898 b

6,613 c

6.1

6.1

Table 7: N, P, K and organic carbon in soils after harvesting rice in fields with and without
application of wastewater to crops.
Chau Phu
Phu Tan
Soil properties
CV%
+ waste
- waste
+ waste
- waste
water
water
water

water
Org C %
1.59b
2.60a
2.24ab
3.05a
37
N%
0.38b
0.16c
0.47a
0.16c
8.9
P%
0.37a
0.22b
0.35a
0.21b
9.2
K%
2.38b
0.95c
2.62a
0.87c
10.3
A survey of the solid waste in fishponds was undertaken in 2007-08 in An Giang Province.
Samples were taken monthly for 5 months from 12 ponds (Table 8). Two ponds in Phu Tan
and in Chau Phu each used pelleted feed, while others used feed prepared on the farm.
Sediment from fishponds contained 4.5-5.5 % C, and 0.2-0.35 % N indicating a favourable
C:N ratio for rapid decomposition. The sediment in the fishponds contained low N relative

to P and K. However, a higher proportion of the total N was in mineral form (NH4- and NO3extractable by KCl). The composition of sediment collected after 4 months was similar to
that collected after 5 months. These results are still being analysed in full and will be
completed in September 2008 as a MSc thesis. Apart from lower N and P concentration in
the solid waste from ponds where fish were fed pelleted feed, there were no obvious
differences in composition of the pond sediment due to the type of feed applied.

12


Table 8. Pond sediment composition from a survey of 12 catfish farms in An Giang province, 2007-08. Values are from samples at 4 and 5
months and represent an overall average of 62 samples, or an average of 15 samples from ponds that use pelleted feed with standard errors (SE).

%P

%K

NH4+
NO3 -N Olsen P Exch K
(mg/kg) (mg/kg) (mg/kg) % Fe

% Mg

Cu
Zn
Ca
Cd
% Mn (mg/kg) (mg/kg) (mg/kg) (mg/kg)

%C
5 months

Pellet feed
SE
Overall
mean
SE
4 months
Pellet feed
SE
Overall
mean
SE

%N

4.64
0.47

0.23
0.02

1.13
0.05

266
37.6

49.2
5.24

194

9.6

3.61
0.41

0.06
0.00

0.05
0.01

35.7
1.37

107
6.5

162
67.3

3.2
0.26

4.98
0.31

0.32
0.03

1.13

0.03

276
25.1

48.1
3.05

216
11.6

3.90
0.30

0.06
0.00

0.05
0.00

34.6
0.75

111
3.8

134
31.5

3.1

0.21

5.22
0.58

0.30
0.03

0.28
0.08

1.13
0.03

406
24.1

37.3
3.37

145
19.4

4.84
0.55

0.06
0.00

0.04

0.00

28.3
1.63

100
5.1

128
64.0

4.8
0.43

5.73
0.57

0.34
0.02

0.39
0.05

1.13
0.02

410
15.5

46.8

3.47

152
12.0

5.35
0.36

0.07
0.00

0.04
0.00

28.2
0.77

100
3.1

126
31.8

5.5
0.39

13


Water quality sampling: Three study areas have been selected: Chau Phu and Phu Tan

in An Giang Province; Thot Not in Cantho district. In addition, water sampling is
proposed for Binh Thuy and Phong Dien districts near Cantho city, in areas practising
VAC. So far water sampling has only taken place in Chau Phu district in Dec 2007April 2008.
District
Chau
Phu

Phu Tan

Thot Not

Binh
Thuy

Phong
Dien

Aquaculture
system
Large fishponds,
recent
development

Closest drainage

Small drain
discharging
through gates to
large canal
Large fishponds, Discharging

recent
through gates to
development
small canal
Large fishponds, Mainly to
operating
8 canals, some
years
was discharged
on padi
Small fishponds Small canal

Small fishponds

Small canal

Feeding
Own feed
mixing plus
pellets
Own feed
mixing plus
pellets
Pellets and
own feed
mixing
Pellets feeding
at fingerling
about 1 month
then own feed

mixing
Pellets feeding
at fingerling
about 1 month
then own feed
mixing

Waste recycling
practiced
Some farmers use
liquid waste from
fish ponds for rice
cultures
Controversies on
liquid
waste
application on rice
Settling pond, tree
lot irrigation, rice
padi application
Landfill
on
orchard, watering
vegetable and rice

Landfill
on
orchard, watering
vegetable and rice

The sampling occurred in 5 ponds in Chau Phu and 7 ponds in Phu Tan ponds:
Pond water (surface),
Pond water (2 m depth),
Drain water at gate
Downstream 100, 200, 300, 400, 500 m
A confluence of canal with nearest river
Cross section of points across the canal
In addition depths across the canal and flow rate of water in the canal were measured.
Sampling occurred once per month for 5 months. Water samples were collected from
all points before discharge began and then starting 1 hour after discharge commenced.
Water quality measurements:
Chemical properties: pH, EC, BOD, COD, NO3, P, S,
Biological properties: E coli, Total coliform, Staphyllococcus, Salmonella.
However, a number of factors will be considered in sampling:
1. Control sites- Most catchments will have background inputs of pollutants to canal
water from rice farming, and human settlements. The background impact of these on

14


water quality needs to be determined by water sampling at control sites beyond the
influence of fishponds. The location of the control sites will vary from site to site.
2. Low tide sampling- During low tide water drains out of the catchment and at this
time discharge of wastewater is most likely. Sampling should coincide with such
periods of discharge to capture the peak in pollution events.
3. High tide sampling- During high tide back flow of water from rivers and main
canals to small canals occurs. Refilling of fish ponds is likely during these times.
Sampling should also be planned to coincide with such periods of discharge to capture
the base load in pollution events.
4. Sampling protocols- Protocols should describe sampling locations (depth, distance

from bank), cleaning of sampling bottles, storage conditions for samples after
collection.
5. GPS positioning of sampling sites- To ensure sampling is repeated at the same
positions GPS coordinates should be taken for sites.
6. Water quality- after the MSc student finishes sampling in April, further sampling is
needed for July (before main rainy season) and October (end of main rainy season) to
provide a complete view of the annual cycle of pollution from fishpond waste water.
7. The variables expected to contribute to pollution levels from fishpond waste water
are:
size of the canal into which discharge occurs; tide level;
time of the year;
distance from discharge;
frequency of wastewater changes in pond;
density of fishponds discharging from drain;
whether solid waste or only waste water is discharged;
the extent of wastewater treatment in settling ponds or padi fields.
It was agreed in principle that the focus of the project was not on dispersion of waste
water in canals, which could be complex and require extensive sampling points,
repeated frequently over time, but rather the water quality in drains discharging into
the main canals.
Field experiment on the use of solid fishpond waste for rice: A field study on the
beneficial use of solid fishpond waste for rice cultivation was commenced during the
wet season 2007 at the experimental farm of Cuu Long Rice Research Institute. Three
dosages of waste at the rate of 1, 2 and 3 tonnes/ha were applied in combination with
1/3 and 2/3 dosages of inorganic fertilisers. The 100 % rate of inorganic fertilisers
(60N-40P2O5-30K2O) served as the control. There were no significant differences in
rice yields over all treatments. This indicated that uses of solid waste from fishpond
can save money for farmers by reducing fertiliser inputs. This experiment was
repeated during the dry season 2007-2008 at the same site. Results in the dry season
verified that yields of rice can be maintained with 1/3rd or 2/3rd of the recommended

inorganic fertiliser dose, when combined with 1 to 3 t of aquaculture solid waste/ha. A
third crop of rice has been planted on the plots with additional solids from the
fishponds.
Recycling of waste water for rice irrigation:
Results of field experiments at Chau Phu indicated that rice yields of all treatments in
the wet season 2007 were not statistically different (Table 9). However, in the dry
season 2008 rice yields of T1 and T2 were highest and were statistically higher than

15


the other treatments (T3, T4 and T5) (Table 9). The higher yields in T1 and T2 are
attributed to the acidity of soils in which phosphorus is a key factor for crop growth
(Cong et al. 1995). This explains why yields in T3 were low. Besides that, nitrogen in
T3, T4 and T5 was low and not sufficient to achieve potential yields for the dry
season. Rice yield in the wet season is usually lower than in dry season in the Cuu
Long Delta due to lower solar radiation (Hung et al., 1995). Analysis of soil, straw
and grain samples at harvesting time showed no significant difference among
treatments in concentrations of N, P and K (data not shown).
Results in Table 10 indicated that rice yields in T1 and T2 were the highest yield and
they were significantly greater than others. This suggests that irrigation by wastewater
from fishponds can save 1/3 of recommended N, and 1/2 of the recommended P and
K. By comparison, treatment T2 and T4 showed that further decrease in nitrogen
fertiliser resulted in reducing yield. T3 had the lowest yield because this treatment did
not use P which on these soils also limits growth and N use efficiency (Cong et al.,
1995). Macro and secondary nutrient uptake of Phu Thanh sites showed that plots
with high yield were also high in nutrient uptake (kg/ha) in straw and grain except P
in straw of Phu Thanh 1 (data not shown). In the experiment at Phu Thanh 2, nutrient
uptake in grain followed the same trend as in the experiment Phu Thanh 1 but K and
Ca uptake in straw was not statistically different among treatments (data not shown).

Table 9: Rice yields (t/ha) in Chau Phu district for the wet season (WS) 2007 and dry
season (DS) 2008. Values are means of three replicates. All plots were watered with
fishpond waste water 5 times in the wet season and 10 times in the dry season
Treatments (N-P-K kg/ha)
WS2007
DS2008
T1 (90-26.2-49.8)
3.99
5.59
T2 (60-13.1-24.9)
4.38
5.58
T3 (30-00-24.9)
3.91
4.21
T4 (30-26.2-24.9)
3.96
4.32
T5 (00-13.1-60)
3.91
4.62
LSD5%
NS
0.885
CV%
14.0
11.8
Table 10: Rice yields (t/ha) of Phu Tan at two sites in the dry season 2008. Values are
means of three replicates. All plots were watered with fishpond waste water 10 times
Treatments (N-P-K kg/ha)

Phu Thanh (1)
Phu Thanh (2)
T1(90-26.2-49.8)
6.89
5.74
T2(60-13.1-24.9)
7.34
5.47
T3(30-00-24.9)
5.05
4.08
T4(30-26.2-24.9)
6.19
5.02
T5(30-13.1-24.9)
4.91
5.06
T6(00-13.1-49.8)
4.52
4.39
LSD5%
0.162
0.683
CV%
15.3
7.6
Water quality in fish ponds: Water was collected from 12 fish ponds in Chau Phu and
Phu Tan districts. Results are still being analysed and will be fully reported in the
MSc thesis of Ms Wang in September 2008.

16


Microbial treatment of wastewater: Excess soluble NH4+- nitrogen (N) may
accumulate in fish-pond water used to produce catfish in the Mekong Delta and have
harmful effects on fish health as well as water quality after discharge. The aim of this
study was to explore the potential for reducing soluble N load in fishpond wastewater
using naturally occurring denitrifying bacteria. Fifteen isolates were selected from
liquid and solid waste of catfish ponds located along the Tien river, in the Mekong
Delta, Vietnam using SW-LB medium (artificial seawater Luria-Britani medium)
supplemented with 10 mM NH4 and NO3. Eleven isolates were identified as
Pseudomonas stutzeri based on similarity of PCR-16S rRNA using universal primers
and specific primers. Four isolates were effective in lowering soluble N (NH4, NO2
and NO3) levels in fishpond water from 10 mg/L to negligible amounts after four
days. Further experiments are underway to determine the fate of N lost from solution
and the relative activity of ammonia oxidation, and nitrite and nitrate reduction by
Pseudomonas stutzeri isolates. Dr Cao Ngoc Diep will spend 3 months at Murdoch
(July-September) to undertake detailed experiments on the fate of N lost from solution
inoculated with Pseudomonas stutzeri isolates. Molecular biology tools will be used
in the laboratory of Professor Ho to indicate which N transformation pathways are
being activated by P. stutzeri to decrease wastewater N levels
Vermi-composting: Solid waste from fishpond was collected for composting and
vermi-culture testing in the green house of the CLRRI. AYAD Stephanie Birch will
undertake research on vermicomposting in 2008. Experiments will examine the
optimal ratio of bulking agents, rice straw or water hyacinth, relative to fishpond
sediment. Two local worms have been recovered in soils at O Mon. In addition the
introduced Tiger worm which is commonly used elsewhere for vermicomposting will
be used in experiments. The relative effectiveness of the three worm species and
mixtures of species will be evaluated. Subsequent experiments will determine the
fertiliser value of the vermicompost compared to inorganic fertiliser.

Chemical treatment of wastewater: Researchers at Cantho University are examining
ozone treatment of wastewater to determine effectiveness in disease control and in the
mineralisation of organic compounds in fishponds. Previous research indicates that
bubbling ozone through wastewater can be an effective treatment in brackish water
shrimp ponds.
The initial experiment involved ± ozone treatment of 500 L tanks with fish stocked in
the tanks. Ozone treatment did not raise levels in wastewater above 0.14 mg/L, by
contrast with the higher levels of enrichment achieved in brackish water (0.36 mg/L).
Effects on water quality were mixed. No evidence of mortality of catfish was
observed in the ozone treated water regardless of fish size. Several laboratory-scale
experiments are planned to determine the effectiveness of ozone treatment in
oxidation of organic matter and disinfection of bacteria in wastewater.
Use of aquatic plants to improve water quality: Aquatic plants in combination with
settling ponds may be an effective means of improving water quality before discharge
to canals. Two experiments were conducted by a BSc student from An Giang
University. In the first experiment, 5 types of aquatic plant (including water hyacinth)
were evaluated in still solutions, while in a second experiment a flow-through system
was used to determine effectiveness of species in improving water quality. Analysis

17


of results is still under way but there does appear to be a decrease in soluble N and P
and a decline in total suspended solids in wastewater with aquatic plants growing in it.
Workshop on Land application of Waste 26-29 December 2007
17 participants attended the Workshop at CLRRI from 26-29 December. They were
from the provinces of Cantho, Vinh Long, An Giang and Dong Thap. Participants
were from fisheries, agriculture extension and natural resources management
positions.
The following hand out materials were provided to the participants:

Application of Wastes to Land. A Literature Review. 81 pages.
An
abbreviated version of the following report- McGowan, J., Pullumannapallil, P
and Bell, R.W. (2002). Application of Wastes to Land. A Literature Review.
Report for the Department of Environment and Conservation (NSW). Centre
for Organic Waste Management, Murdoch University, Perth WA.
Environmental Science Report Series No 07/1. pp. 147.
Overview of the opportunities and principles for land application of waste to
land (Powerpoint slides)
Soil properties relevant to waste application (Powerpoint slides)
Principles and methods of waste application (Powerpoint slides)
Environmental Impacts of land application of waste (Powerpoint slides)
The following 7 papers were distributed to participants. They were chosen to illustrate
different aspects of the land application of wastes to land.
MacLeod, J.A and Kuo, S., Gallant, T.L. and Grimmet, M. 2006. Seafood
processing wastes as nutrient sources for crop production. Can. J. Soil
Science 86, 631-640.
Hati, K.M., Biswas, A.K., Bandyopadhyay, K.K., Misra, A.K. (2007). Soil
properties and crop yields on a Vertisol in India with application of distillery
effluent. Soil Tillage Research 92, 60-68.
Duffera, M., Robarge, W.P. and Mikkelson, R.L. (1999). Estimating the
availability of nutrients from processed swine lagoon solids through
incubation studies. BioResource Technol. 70, 261-268
Yadav, R.K., Goyal, B., Sharma, R.K., Dubey, S.K. and Minhas, P.S. (2002).
Post-irrigation impact of domestic sewage effluent on composition of soils,
crops and groundwater- A case study. Environment International 28, 481486.
Alvarenga, P., Palma, P., Goncalves, A.P., Fernandes, R.M., Cunha-Queda, A.C.,
Duarte, E. and Vallini, G. (2007). Evaluation of chemical and
ecotoxicological characteristics of biodegradable organic residues for
application to agricultural land. Environment International 33, 505-513.

Haynes, R.J. and Naidu, R. (1998). Influence of lime, fertilizer and manure
applications on soil organic matter content and soil physical conditions: a
review. Nutr. Cycl. Agro-ecosystems 51, 123-137.
The workshop was run in Vietnamese, or with translation of English talks into
Vietnamese. In retrospect, it would have been more effective if more of the written
materials had been translated beforehand into Vietnamese. Some activities planned
had to be modified because the level of English reading was not adequate for the task.

18


The critical review of journal paper was not feasible as the participants found the
technical English level too difficult to understand. Similarly the exercise on nutrient
budgets would have been improved if the spreadsheet had been in Vietnamese. We
have agreed to revise the spreadsheet to make it more easily understood to a nonspecialist, and translate it into Vietnamese for distribution to the participants.
Feedback from participants
The following comments were made about the workshop.
1. The VAC system seems ideal for treating the fishpond waste. (This was noted, but
it was pointed out that the CARD programme directed us to work mostly on larger
fishponds).
2. The workshop increased awareness of the environmental impact of fishpond waste.
3. Participants learnt a lot about soils and their relevance to land application.
4. The Excel nutrient budget calculator was considered a very useful tool for
providing advice to fishpond operators and farmers on how to manage nutrients when
applying wastewater to padi fields.
During the workshop, participants reported on farmer innovations in waste treatment.
Some farmers use the compounds: AS3 and ADL. Further investigation will
be carried out to determine the nature and effectiveness of these compounds.
One farmer has implemented a sand bed and activated carbon filtration
system. The fishpond is used to raise fingerlings so the organic pollutant load

is not as high as fishponds. However, the pond is located a long distance from
a water source making it impractical to pump water daily. The filtration beds
are 1.5 m deep, with layers of sand (0.5 m), overlying gravel (0.5 m) and
activated carbon (0.5 m). Water from fish pond is circulated through the beds
to maintain water quality. This system will be located and investigated further.
It was suggested that native grasses may be used as a substitute for activated
C. The source of activated C was not known, although char from rice husks is
commonly available.
Waste treatment November 2008
The observations made above from the first workshop are relevant to planning the
second. The workshop should be run in Vietnamese, or with translation of English
talks into Vietnamese. To make it more effective the main written materials are being
translated beforehand into Vietnamese.
There are many relevant waste treatment problems that could be effective case studies
for the workshop:
Seafood processing liquid and slid waste
Municipal waste treatment
Food processing waste
Wetland treatment systems
Smallholder Benefits
Water discharge from fishponds can be used for rice cultivation to recover the soluble
nutrient content in the waste water. Present indications are that smallholders
cultivating rice can save at least 1/3 of the inorganic fertilisers currently applied, and
possibly 50 % in the case of P and K. However, omitting N and P fertiliser completely
caused depressed yield, indicating that the wastewater did not supply sufficient N and

19


P for crop requirements without some fertiliser. The technique on irrigating rice with

fishpond wastewater will be disseminated to farmers through the Departments of
Agriculture and Rural Development in Cantho and An Giang provinces.
Fishpond solid waste, when applied at 1-3 t/ha, also contains sufficient nutrients that
fertiliser rates can be decreased by 1/3- 2/3 of present recommendations without loss
of yield.
Capacity Building
Two MSc students from Can Tho University are now completing their theses on
Treating and recycling of solid and liquid waste from fishpond – both are due for
submission in September 2008. Both students are academic staff at An Giang
University and hence are in a position to transfer their knowledge to students of
environmental science at the university.
One BSc student of An Giang University is undertaking a study on the use of aquatic
plants to improve quality of fishpond waste water. Another BSc student of An Giang
University has commenced his thesis entitled “ Effect of waste discharge on water
quality”. A MSc of Canto University will commence shortly on a study designed to
calculate the nutrient budget for fields with fishpond waste application.
The workshop on Land application of Waste, held on 26-29 December 2007, was
attended by 17 participants. They were from the provinces of Cantho, Vinh Long, An
Giang and Dong Thap. Participants were from fisheries, agriculture extension and
natural resources management positions.
Publicity
Papers by Dr Cao Ngoc Diep and Dr Cao Van Phung were submitted to the
International Biosystems conference and will be presented by the lead authors at the
conference in Perth, 6-9 July 2008. Copies of the papers are attached.
During the CLRRI field day in February 2008, about 30-40 farmers and technicians
visited the trial on solid fishpond waste application.
Project Management
Professor Richard Bell visited Cuu Long Rice Research Institute and Cantho
University in December 2007- January 2008 to discuss project progress, discuss plans
for future work, and present the training course on land application of organic waste.

Another visit is planned for June-July 2008.

6. Report on Cross-Cutting Issues
Environment
A primary aim of the present project is to protect the economic benefits of catfish
aquaculture for small farmers in the Mekong Delta, while reducing the impact of
catfish farming on water quality. Initial results indicate that waste water and solid
waste from catfish pods is a valuable source of nutrients for rice. Recycling of the
waste in rice padi fields appears to be an effective means of using significant
quantities which would then not be discharged directly to the canals and streams.

20


Gender and Social Issues
Preliminary results showed that all stakeholders were concerned about surface water
pollution because of its impacts on sustainability of production and livelihoods. About
14-25 % of the farmers (including both fish and rice farmers) reported that water
quality for fishpond farming is bad. Farmers practicing fish culture are richer, better
educated and younger than those carrying out rice cultivation, based on numbers of
concrete houses, living commodities, pumping machines and incomes. However,
about 15 % of fishpond holders are recent migrants who have bought or rented lands
from local farmers. Impacts reported on water quality include greenish-black colour,
bad smell, high turbidity, and skin itching on contact. In Cantho, 80 % of farmers
accessed household water from public water supplies and groundwater and in this
province 83 % of farmers were satisfied with water quality for household use.
However, in An Giang, where 57 % of farmers used river water for household
purposes, the level of satisfaction with water quality was only 36 %. Most farmers
(91 %) attributed poor water quality for household use to fishpond farming in An
Giang, but to fishponds (37 %), pesticide use in rice fields (15 %) and other causes

(48 %) in Cantho. Moreover, farmers raising fish recognised that percentages of
diseases infected fish is much higher (about 15%) than before (< 5 %). The demand
for effective and economical solutions for control of water pollution is the first
priority of stakeholders. The investment cost for raising fish is large and most of
farmers lend money from either banks or their neighbours hence they are concerned
about threats to the viability of the operation.

7. Implementation & Sustainability Issues
Issues and Constraints
None to report.
Options
The next priority of research is to demonstrate that improvements in canal water
quality are achieved when wastewater and solid waste is treated by application to rice
padi fields. This would provide the critical evidence that treatment strategies exist and
provide a basis for encouraging wide scale implementation of this treatment means in
the Mekong Delta. The main economic incentive for farmers to adopt the use of
fishpond waste water or solid waste in padi fields, is the 33-67 % savings in fertilisers
that can be achieved by substituting waste products for a part of the fertilisers
normally applied to rice.
In An Giang, another option to minimise the harmful effects of fishpond pollution of
canal water for household use is to expand the public water supply so that households
have access to treated water. If other means of waste treatment are not effective or
can’t be widely adopted then expansion of the treated public water supply may be
necessary.
Sustainability
None to report.

21

8. Next Critical Steps
Analyse and report on the levels of water pollution by liquid and solid wastes from
fishponds in cases where they are discharged directly to waterways. The report is
expected in September 2008. Follow up sampling of water quality is also planned for
July and October to obtain data from all the key seasons that affect water flow and
quality.
Follow up water quality sampling for paired sites where farmers routinely apply waste
water on padi fields compared to places where farmers discharge wastewater into
canals. The aim is to demonstrate that improvements in canal water quality are
achieved when wastewater and solid waste are treated by application to rice padi
fields. Study sites have been identified in Chau Phu and Thot Nhot to undertake this
study.
Continue experiments on the use of liquid and solid waste for rice cultivation during
wet season 2008. The CLRRI experiment on application of fishpond solid waste will
be continued until crop 6 (it is presently growing crop 3). A new trial will be set up at
CLRRI to quantify the nutrient inputs from fishpond waste water so that a nutrient
budget can be determined for the treatments. Another new trial will be set up in Chau
Phu to more accurately define how much reduction in chemical fertiliser should be
recommended when using wastewater. It is also necessary to define the maximum
rates of solid waste from fishponds that can be safely applied without inducing
excessive vegetative growth and a risk of yield loss from lodging.
Determination of whether ozone treatment of fishpond wastewater can achieve
disinfection and oxidation of organic matter.
Determine the fate of N in wastewater when inoculated with Pseudomonas stutzeri
cultures. This is necessary to establish the mechanism of action of the Pseudomonas
stutzeri isolates.
Identify optimal conditions for vermicomposting of aquaculture solid waste through
Australian Youth Ambassador for Development assignment due for completion late
November 2008.
Conduct a training workshop on waste treatment. CLRRI will host the training course

at CLRRI for 15-20 participants. Professor Ho will visit in November 2008 to jointly
present the course with Dr Phung. Course notes provided by Professor Ho are being
translated into Vietnamese.

9. Conclusion
The investigations support the basis for the project by indicating that water pollution
is perceived to be a widespread problem in the fishpond industry itself. Moreover,
initial field investigations suggest that < 30 % of farmers are using re-cycling or
treatment technologies for waste, yet there appear to be yield benefits or decreases in
fertiliser costs for rice producers from judicious use of fishpond waste.

22