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Claude E. Boyd

School of Fisheries, Aquaculture and Aquatic Sciences

Auburn University, Alabama 36849 USA

The Theory and Practice of Shrimp PondBottom Soil Management

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Basic Soil Science Concepts for

Aquaculture

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Holds pond water (not water quality issue)

Accumulates sediment

Exchanges cations with water

Removes phosphorus from water

Source of combined nitrogen to water

Removes oxygen from water column

Source of potentially toxic microbial metabolites

Soil acidity neutralizes alkalinity in water

Source of nutrients in water via dissolution ofminerals

Habitat for benthic food organisms

Harbors pathogens

Role of Pond Soil

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Soil triangle. To use, mark percentage clay and percentage sand on the

appropriate axes. From these points, project a line inward from the

clay axis and parallel to the sand axis and another line from the sand

axis parallel to the silt axis. The interaction of the two projected lines

will denote soil texture.

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Pond on Sandy Soil

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Turbid Water Supply

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Pond Filled with Sediment

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Average rate of sediment accumulation isroughly 1.0 cm/yr, but is much faster during the

first 2 or 3 years that a pond is used.

Sediment accumulates forming a unique profile

with distinct horizonsupper 4 or 5 cm effects

water quality.

Heavy mechanical aeration may greatly

accelerate erosion.

Comments on Sedimentation

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HORIZONS IN SEDIMENT PROFILE

FLOCCULENT LAYER

MIXED

SEDIMENT

LAYER

Oxidized (aerobic)

Reduced

(anaerobic)

MATURE STABLE

SEDIMENT

TRANSITIONAL

LAYER

ORIGINAL, UNDISTURBED

POND BOTTOM

PO

ND

SOILPROFILE

WATER HORIZON CHARACTERISTICS

F

S

M

T

P

Water with high concentration of mineral

and organic solids, aerobic

Sediment with high water content and

low dry bulk density, abundant organic

matter, well stirred by physical and

biological agents, thin aerobic surface

but anaerobic below

Sediment with medium water content

and intermediate dry bulk density,

abundant organic matter, not stirred,

anaerobic

Transition between M and P horizonswith characteristics intermediate

between M and P horizons, not stirred,

anaerobic

Low water content and high bulk

density, usually compacted, low organic

matter, not stirred, anaerobic

}So

Sr

}MT

PT

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Brown Oxidized soil

Black Reduced soil underneath

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Aerobic Saprophytic

MicroorganismsThese organisms use oxygen in

respiration to decompose organic

matter to carbon dioxide, mineralnutrients, and water. The typical

equation for aerobic decomposition is:

Organic Matter + O2 CO2+ H2O + Mineral

Nutrients

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Fermentation

When anaerobic conditions exist, some

organisms can use intermediate organic

metabolites as electron acceptors. An

example of a fermentation reaction is:

C6H12O6 2CH3CH2OH + 2CO2

Also, can have end products such as

formate, propionate, lactate, etc.

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Denitrification

Some bacteria can use oxygen from

nitrate when no dissolved oxygen is

available as illustrated by the followingreaction:

6NO3-

+ 5CH3OH 5CO2+ 3N2+ 7H2O +6OH-

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Reduction of Ferric Hydroxide and

Manganese Oxide

Some bacteria can derive oxygen from

iron and manganese compounds.

CH3COOH + 2H2O 2CO2+ 8H+

Fe(OH)3+ 3H+ = Fe2++ 3H

2O

MnO2+ 4H+= Mn2++ 2H2O

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Sulfate Reduction

Sulfate-reducing bacteria use

sulfate as an oxygen source asshown below:

SO42-+ 4H+ S2-+ 4H2O

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Methane Bacteria

Methane-producing bacteria use

oxygen from carbon dioxide asillustrated in the following

equation:

8H++ CO2 CH4+ 2H2O

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Date

7/05 9/05 11/05 1/06 3/06 5/06

P

otassium

(mg/L)

0

10

20

30

40

50

60

70First treatment

Second treatment

Third treatment

Changes in potassium concentration following three potassium

additions of 50 mg/L each in laboratory soil-water systems.

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Potassium loss from water and adsorption by soil

over 8 months in laboratory soil-water systems with

56 L of water and 9.6 kg soil.

Variable Average

Potassium loss from water

(mg/L) 89

(mg/tank) 4,982

Exchangeable potassium adsorption by soil

(mg/kg) 136

(mg/tank) 1,284Potassium fixed by nonexchange process

(mg/kg) 390

(mg/tank) 3,568

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Number of Consecutive Exposures

0 2 4 6 8 10 12 14

Potass

ium

adsorbedbyso

il(mg/kg)

0

100

200

300

400

500

Potassium adsorption by samples of original pondsoil from an inland shrimp farm in Alabama.

Samples were exposed twelve consecutive times to

50 mg/L potassium (potassium chloride in distilled

water) in a shaker trial.

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Soil is source of substances to water viadissolution of minerals. Possibly, most

important are carbonate and silicate minerals

that dissolve to give alkalinity as illustrated with

calcium carbonate and silicate:

CaCO3+ CO2+ H2O Ca2++ 2HCO3

CaSiO3+ 2CO2+ 3H2O Ca2++ 2HCO3-+ H4SiO4.

Dissolution of Minerals

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Neutralization of Exchangeable Acidity in Soils

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Mangroves

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Mangrove Soil

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Pyrite Formation

2CH2O + SO42- H2S + 2HCO3

Fe(OH)2+ H2S FeS + 2H2O

FeS + S FeS2

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Pyrite Oxidation

FeS2+ 3.75O2+ 3.5H2O Fe(OH)3+ 2SO42-

+ 4H+