Acid Sulfate Soils

1

Presentation
By Narioka, H.
Acid Sulfate Soil in rice production for
Negara Brunei Darussalamin 20112

Acid Sulfate Soil in rice production for
Negara Brunei Darussalam
22 Feb. 2012
Problem Recognition and Problem Soils
Hajime NARIOKA, Professor
Laboratory of Terrestrial Soil and Water,
Division of Environmental Science andTechnology,
Graduate School of Bioresources,
Mie University
1577 Kurimamachiya-cho, Tsu-shi,Mie 514-8507, Japan
Phone/Fax. +81 59 231 9574
e-mail: narioka@bio.mie-u.ac.jp3Study4

A.S.S. team5

A.S.S. field6

A.S.S. field
7

8
Setting of groundwater observation system

9
Setting of groundwater observation system

10
Setting of groundwater observation system

11
Pond which was affected excessively of A.S.S.

12
Jarosite and crack on the surface at rice field

13
Jarosite and crack on the surface of rice field

14

Training items(at field investigation)
1) "Safety First"
2) Existence of ASS by "watch, hear, smell, touch,think"
3) Mechanism of ASS
4) Rice field structure5) Role and importance of irrigation and drainage
6) Field investigation method
7) Experienced soil layer structure of rice field
8) Thought about "improvement of ASS problem“
9) “The Team-work” and each confidence
15

What is the problem (soil)?

16

What is the problem (soil)?
－Poor Soils

Poor soils refer to low potential soil productivity.
Potential soil productivity is the maximum
productivity shown by soil that is optimum in factors
for biological production, including drainage,
inclination conditions, and their combination－Problem Soils

There are a variety of soils; some soils haveserious problems when utilized.
These soils are less productive and unsuitable evenfor the growth of crops because of the presence of
extremely specific chemical, physical and biologicalproperties.
Typical problem soils are peat soil, saline soils
alkaline soils and acid sulfate soils.
Globally, Vertisol, Planosol, heavy clay alluvial soil,
as well as strong weathering soil in the tropical zone
are also considered to be problem soils.
17

Important information forresearch:“Topology and Soil Profiles”

18Topology
Important information－Natural resources－Land use－Topology－Field (in situ)－Environment
19

SoilsImportant items－Poor Soils－Problem Soils
Exercise－Saline Soil
－Acid Sulfate Soil
－Peat Soil
- Vertisols
20

Soil Profiles

Ⅰ
Peat SoilⅡ
Saline Soilin the wood area

ⅢⅣ
Saline Soil
Acid Sulfate Soilin the hazard area
21

Case of Problem Soils- Acid Sulfate Soils- Saline Soils- Vertisols22

Acid Sulfate Soils
Case of Problem Soils
Acid sulfate soils are covered 43.6%of Africa, 38.2% of Southeast Asia and16.6% of South Asia. The area of acidsulfate soils reaches about 12 millionhectares worldwide, most of which islocated in tropical mangroves in Africa
and Southeast Asia. The acid sulfate
soils zone in Southeast Asia isconsidered to be potential farmland,but is not farmed because of its strong
acidity.
Acid sulfate soils oxidizes whensulfate oxides in the soil are supplied
oxygen due to land draining, leading tothe formation of sulfuric acid andsubsequent strong acidification of the23soil to pH 3 or lower.

Saline Soils
Case of Problem Soils

Saline soils are distributed in the semi-arid, arid,
coastal and poor-draining zones in the world.
Definition by the U.S. Department of Agriculture (USDA)：－Electric Conductivity (ECsat; saturated extract) ≧ 4 mS/cm－Exchangeable Sodium Percentage (ESP) ＜ 15%－pH ＜ 8.524

Vertisols
Case of Problem Soils
Black Cotton Soil (Africa andIndia), Regur (India), Gray andBrown Soils of Heavy Texture(Australia) etc.
This requires material with ahigh shrink-swell potential plus
alternate wetting and drying.
Vertisols are very slowly
permeable, once the cracks swell
shut, and slow infiltration is aproblem in irrigation.
They have a low plant-available
water-holding capacity, but arelatively high total water-holding
capacity. Because of their low
permeability, once they have
wet-up, Vertisols are good forpaddy (wet) rice culture, because
entrapped (diked) water does not25
leak away.

Strategies

26

Strategy (1)(Important information and items
are understood and developed intothe strategy)－Investigation/Research－Administration(government policy)－Civilian Activity(civilian productivity)－Living Persons(human life)27

Strategy (2)1．Time scale and spatialscale
2．Topological information(landform, coastline andwater boundary)
3．Policy in the country(viewpoint to theproblem)
4．Meaning of"Development, Protection
and Conservation"
28

Strategy (3)(The necessary information)－Map (soil, soil profiles, landuse, vegetation, topological,etc.)－Remote sensing, GIS etc.
－Soil researcher－Professional of the Soil
Investigation－Soil Science－Soil Conservation－Consideration of"Development, Protection
and Conservation"
29

Plan Formulation for
Improvement/Conservation30

Procedure forapproaching
1．Policy (viewpoint tothe problem)
2．Time scale andspatial scale
3．Land resources(landform, coastlineand water boundary)Necessary
information (1)－Map (soil, soilprofiles, land use,vegetation,topological, etc.)－Remote sensing,
GIS etc.
32

Necessary
information (2)－Soil researcher－Soil investigater－Soil scientist－Engineer－Designer
33

Research forland use
1. Check point(1)Soil properties(2) Water condition(3) Land classification inconsideration oftopography and social

Research forland use
2. Strategiesa) Drainage and dry field farmingby control of groundwaterb) Rice field production byirrigation and flood controlc) Mixed cultivation by control ofgroundwater leveld) Land condition which pyrite isoxidized or note) Local community in regional
participationf) others

Research forland use
3. OK? or NG?
Development,Conservation,
Protection※Estimation is not easy for"Peat Soil and Acid SulfateSoil“※Mechanism in the field ofAcid Sulfate Soil is
unexplained

Acid Sulfate Soils
Process and Strategy37

Reports
1)Department of Agriculture(2008):
Soils and Land Suitability of theAgricultural Development Areas,
Soil Fertility Evaluation/Advisory
Service in Negara Brunei
Darussalam Volume 1, Contract:
LTN/6/31/2003(10)2)Department of Agriculture(2008):
Soil Management in theAgricultural Development Areas,Soil Fertility Evaluation/Advisory
Service in Negara Brunei
Darussalam Volume 2, Contract:
LTN/6/31/2003(10)38Soil Profiles

Ⅰ
Peat SoilⅡ
Saline Soilin the wood area

ⅢⅣ
Saline Soil
Acid Sulfate Soil39
in the hazard area

What is “ASS”?

40

Acid Sulfate Soil
Characteristics(1) Strong acidity (pH3）(2) Oxidation of deposition below
water surface or mud (locallake or sea)
(3) These are called “Acid SulfateSoil”(ASS) by origin material(4) There is easy to be ASS in theGeologic period
41

Mangrove area
※ ASS in the world isdistributed around12,000,000ha.
※ Most of ASS area is in
Mangrove area.
※ ASS area in Southeast
Asia is “Potentialfarmland”.
42Mechanism of A.S.S.

43

Why is “A.S.S.”
Generation of Acid Soil
has two process.
(1)Accumulation processof sulfide(2) Sulfuric acid processby oxidation.
→Physical, Chemical
and Biologicalprocess44

Accumulation processof sulfide(1)Process:
Marine and Volcanic

Original materials:
Pyrite（FeS2）

45

Sulfuric acid processby oxidation(2)※ Oxidation of Sulfide≦ pH3↓※ Generation ofSulfuric Acid↓※ Pyrite（FeS2）
Chemical and BiologicalOxidation
46化学的酸化FeS2Pyrite
PyriteO2 FeS +7/2O +H →Fe +2SO +2H
222+2+24

FeSO4・7H2O
Melanterite

H+SO42-

風化

蒸発Fe2+

FeSO4・4H2O

Thiobacillus ferrooxidans

Rozenite

微生物的酸化 (T. ferrooxidans)

化学的酸化O2 Fe 1/4O +H →Fe +1/2H O

酸化初期では重要な酸化剤

Fe3+2+2+3+

FeSO4・H2O

2

Szomolnokite

Fe3+

FeS2+2Fe3+→3Fe2++2SO0

パイライト酸化の終了・土壌酸性化の停滞後，土壌の中和過程へ移行
溶解・酸化加水分解

Fe3+3H2O→Fe(OH)3+3H+Fe2+S0

Pyrite（FeS2）

2S0+12Fe3++8H2O→12Fe2++2SO42++16H+溶解

pH4
加水分解・有機配位子の酸化？

3Fe(OH)2++2SO42-→K+KFe(SO4)2(OH)6

H+Fe2+Fe3+4(SO4)6(OH)2・20H2O
Copiapite

Ferrihydrite

酸化初期では重要な酸化剤

Fe3+

酸化Fe(OH)3

化学的酸化

SO42-

脱水

Fe2+KFe3(SO4)2(OH)6
Jarosite
Jarosite

脱水・再配列α-FeOOH
Goethite
pH≧4
加水分解
加水分解？

脱水・再配列α-Fe2O3
Hematite

Thiobacillus thiooxidans & Thiobacillus ferrooxidans
微生物的酸化 (T. thiooxidans and T. ferrooxidans )O2 2S +3O +2H O→2SO +4H0

SO42-2

22+4+

Most suitable temperature “Thiobacteria”: 15-25 ℃

H+Process of Oxidation

図１ パイライトの酸化と関連鉱物の生成過程概要(参考：Nordstrom,1982および日本化学学会,1999)

47

Field of A.S.S.

48

Southeast Asia:
Peat soil and A.S.S.
1. Peat soil, flooding and shallow
groundwater level
2. Natural environments(groundwatert, soil and wildlifeetc.)
3. Local economy and social
4. Farmland development (suitableland use, drainage control,suitable cultivation, suitable
management etc.)49

Problems excavation of A.S.S.
1. Physical and chemical viewpoint of the soil
(1) Affected by the flood with high groundwaterlevel(2) Rapid subsidence of surface soil
(3) Toxic organic matter for crops production(4) Surface soil is acidified when pyrite layer isoxidized(5) Lack of inorganic fertility (artificial manure),and disproportion of effect of fertilizer(6) Groundwater situation and soil environment
is changed(7) others
50Problems excavation of A.S.S.
2. Environmental conservation and management(a) Control of peat soil subsidence andgroundwater flow(b) Water control/management: drainage andirrigation(c) Suitable cultivation system(d) Control of microbe and harmful insect(e) Evaluation of environmental influence, andgeographical investigation(f) Evaluation of social demand(g) Suitable land classification(h) others

51

Soil layer structure (in Japan) of atypical rice field

Ridge/Levee
Irrigate-water
deeperPlow-soil
15～20cm
Hard-pan

10cm

Soil Hardness(Yamanaka)≧24mm
Subsoil52

Seasonal changes of soil surface conditionsin Japana) well-drained in region with low rainfallb) poorly drained in region with high rainfall
53Percolation in saturated and unsaturatedsubsoils in Japan54

Thank you.
ありがとうございました。

55