Acid sulfate soils are formed through the bacterial reduction of iron and sulfate in wet, oxygen-limited soils, producing pyrite. Undisturbed acid sulfate soils appear dark and wet with no structure, but when drained or disturbed they turn yellow, brown, and red as pyrite is oxidized, releasing sulfuric acid and lowering the pH. This can cause poor growth of plants and fish, and even fish kills. Proper management of acid sulfate soils is important for agriculture and aquaculture, including drying, tilling, liming, and maintaining water levels.

1. ACID SULPHATE
SOILS
Group number 7
Aquaculture
Livestock Production

2. Formation of Acid sulphate soil…
◦Is mainly in the formation of pyrite.
◦Pyrite formation involves the bacterial reduction.
◦Partial oxidation of the sulphide to elemental sulphur
Figure 1 Southern Cross University Figure 2 pyrite in soil
Microscopic image of pyrite in soil

3. The basic factors of formation of
ASS
◦sufficient supply of
-sulphate,
-iron,
-high organic matter
-Oxygen
◦With the presence of the sulphate
reducing bacteria
Desulfovibric desulfuricans
Desulfomacultom

4. “
How acid sulfate soils formed?
Figure 3 National Guidance for the Management of Acid Sulfate Soils in Inland Aquatic
Ecosystems — Environment Protection and Heritage Council and Natural Resource
Management Ministerial Council (2011)

5. Undisturbed Acid sulphate soil
◦Dark blue-grey (black) & wet
◦No structure
◦Often high in clay
◦But some time can be sand or gravel

6. Disturbed soil
◦Yellow to brown then red
◦Cracks in surface
◦Soil pH 2
◦Naturally
- In swamps
- Specially mangrove
- Salt flats
Figure 4 http://www.gtcc.nsw.gov.au/environment/manning-river-estuary/acid-sulfate-
soils/

7. In fish pond
◦ pH less than 4
◦ Poor growth or absence of algea
Figure 5 Manual on the Production and Use of Live Food for Aquaculture... FAO

8. Indications
◦Association of Rhizophora
Nypo fruticans
◦Fish dies in aqua environment
◦Bitter taste of water
◦Poor & spotty growth of vegetation after
several years of construction
◦Sharp sour-bitter taste of pale yellow
color salts, found near the base of dikes
◦Red lead pole test

9. ◦ Poor response to phosphorus fertilizers
◦ Low fish yield
◦ Slow growth of fish
◦ Slow rate of natural fish food
production
◦ Fish kills due to acidity
◦ Erosion of the pond dike
◦ Soft shell prawns
Problems face in fish farmers
Figure 6
http://www.ozcoasts.gov.au/indicators/marine
_pathogens.jsp

10. Ponds construction and planing
◦ Tratments of pond bottom
1. Dry the pond thoroughly
2. Small drains should be dug to let all remaining
patches of standing water run day
3. Bottom should be tilled after 1 week by tooth
harrow about 10cm depth
4. Pond should fill with brakish water or salt water
5. Measure the pH
6. Continue until constant value
7. Then again totally dry,harrow & refill, measure
pH
8. Broadcast agricultural lime 500kg/ha

11. ◦Figure 7 fishconsult.org

12. Ponds construction and planing
cont…
◦Fish pond dike construction
1
2
3
1. Top cover with top soil
2. Sub soil
3. Bad soil

13. Ponds construction and planing
cont…
◦Treatment for dikes
broadcast 1 kg of agricultural lime per
10 m2 on the slope of the dike along
each pond and 1 kg per 20 m2 on the
top of the dikes between the ponds.

14. Figure 8 fishconsult.org

15. Management
◦Rice hulls
◦Ash of rice hulls
◦Filter press mud from sugar mills
Spread over the ponds bottom
Chicken manure 2t/ha distributed over
the pond bottom
Few days later N fertilizers are
broadcast in the pond water.

16. “
◦Thank you……..