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Bottom soil quality in Tilapia ponds of different

age in Thailand

Taworn Thunjai1

. Claude E Boyd2 & Mali Boonyaratpalin3

LThailand Department of Fisheries, Kasetsart University Campus. Bangkok. Thailand

2Department of Flsheries and Allied Aquacultures. Auburn University. Auburn. AL USA

3Thailand Department of Fisheries. Kasetsart University Campus.. Bangkok.. Thailand

Correspondence: Dr C E Boyd. Department of Fisheries and Allied Aquacultures. Auburn University. Auburn. AL 36849. USA. E.mail:

[email protected]

Abstract

Bottom soil samples were collected from 35 ponds in

the vicinity of Samutprakarn. Thailand. Ponds ran.

ged in age from 3 to 39 years and had been used con-

tinuously for production of tilapia. Liming materials

had been applied in large amounts. and bottom soils

of all ponds had pH above 7. low exchange acidity.

and free carbonate. Pond soils orten contained be-

tween 1% and 2% total sulphur. suggesting that they

were potential acid-sulphate soils. However. acidity

from sulphide oxidation was not expressed because

carbonate in the soil neutralized it. Concentrations

of total carbon seldom exceeded 4% and the averagefor organic carbon was 1.90%. The correlations be-

tween pond age and both total carbon and organic

carbon concentration were weak (r = 034 and 036respectively). Concentrations of nitrogen in bottom

soils did not differ with pond age and ranged from

0.1% to 0.3% with an average of 0.19%. The average

ratio of concentrations of carbon and nitrogen was

11. Acid-extractable phosphorus concentrations

averaged 217 mg kg -1. but the phosphorus adsorp-

tion capacity averaged 768 mg kg -1 suggesting that

soils still have considerable reserve capacity to ad-

sorb phosphorus. Ponds can be used annually for

semi-intensive production of tilapia. and presumably

other species. for many years witl10ut serious deteri-

oration of bottom soil quality.

Keywords: Tilapia. bottom soils. soil carbon.

liming

Introduction

Water quality in aquaculrure ponds is influenced by

the exchange of substances between soil and water.

but only a few studies have clearly demonstrated re-lationships between bottom'soil quality and fish pro-

duction in ponds (Boyd 1995), Nevertheless. many

aquaculturists believe that soil quality deteriorates

rapidly in semi-intensive and intensive aquaculture

ponds and that older ponds tend to have low pH and

high concentrations of organic matter in bottom

soils. There have been a few studies of the relation-

ship between pond age and bottom soil quality (Tuck-

er 1985: Munsiri. Boyd & Hajek 1995: Munsiri. Boyd.

Teichert-Coddington & Hajek 1996: Ritvo. Dixon.

Lawrence. Samocha. NeilL & Speed 1998:Tepe &Boyd

2002). and the results of these studies do not support

the opinion that pH declines markedly and organicmatter accumulates to high concentrations in older

ponds.

The most common practices used in pond soil

management are liming. drying of pond bottoms

between crops, and sediment removal (Wurtz 1960:

Chien 1989: Boyd 1995). Liming causes bottom soil

pH and concentrations of total alkalinity and total

hardness in pond water to increase. However. the

necessity for annual or more frequent liming. as

often done. is not supported by research findings.

Drying pond bottoms between crops can accelerate

the decomposition of organic matter and oxidizereduced substances in soil (Wurtz 1960: Boyd &

Pipoppinyo 1994). The benefit of sediment removal

on sediment quality is not well established and likely

is unnecessary unless sediment is so deep that

it causes a loss of pond volume or interferes with

pond management (steeby, Kingsbury. Tucker &

Hargreaves 2001:Tepe &Boyd 20(2).. Concentrations

of nitrogen and phosphorus increase in pond soils

over time (Masuda & Boyd 1994: Munsiri et al. 1995:

Ritvo et al. 1998). It is not known if the ratio of

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Materials and methods

Ponds and management

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Samples

Analyses

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Results and discussion

Total alkalinity and total hardness

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Sediment depth

Thickness of S horizon and bulk density

Soil pH and exchange acidity

Total sulphur

Soil carbon

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Nitrogen and phosphorus

Conclusions

Acknowledgments

References

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