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Soil and Water InteractionSoil and Water Interaction

and Its Importance In Aquacultureand Its Importance In Aquaculture

Dr. Dr. SubhenduSubhendu DattaDatta

Sr. ScientistSr. Scientist

CIFE, Kolkata CentreCIFE, Kolkata CentreSALT LAKE CITY, KOLKATA, INDIASALT LAKE CITY, KOLKATA, INDIA

IntroductionIntroduction

�� Soil is a key factor in aquaculture. Most of the pond is built fSoil is a key factor in aquaculture. Most of the pond is built from rom and in soil. and in soil.

�� Many dissolved and suspended substances are derived from Many dissolved and suspended substances are derived from contact with soil. contact with soil.

�� Pond soil are store house for many substance that accumulate in Pond soil are store house for many substance that accumulate in the pond ecosystem and chemical and biological process the pond ecosystem and chemical and biological process occurring in the surface layer of pond soil influences water occurring in the surface layer of pond soil influences water quality and aquaculture. quality and aquaculture.

�� Hence an understanding of soil properties and the reaction and Hence an understanding of soil properties and the reaction and process in soil can be useful in pond aquaculture.process in soil can be useful in pond aquaculture.

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POND SOILPOND SOIL

�� Material composing the bottom of streams, lake and ponds are Material composing the bottom of streams, lake and ponds are known as sediment, mud or soil. known as sediment, mud or soil.

�� The pond bottom is originally made of terrestrialThe pond bottom is originally made of terrestrial’’s soil and when s soil and when the pond is filled with water the bottom becomes wet. the pond is filled with water the bottom becomes wet.

�� Mixture of solid materials and with water is called Mixture of solid materials and with water is called ‘‘mudmud’’. .

�� Solids settle from the pond water and cover the pond bottom is Solids settle from the pond water and cover the pond bottom is ‘‘sedimentsediment’’..

�� Basic function of pond soil is an embankment that impound water Basic function of pond soil is an embankment that impound water and and forms barrier to seepage so that pond will hold the water. forms barrier to seepage so that pond will hold the water.

�� Substances continually settle from pond water into the pond bottSubstances continually settle from pond water into the pond bottom om

�� For example For example -- suspended solid, particles of soil and organic matter that suspended solid, particles of soil and organic matter that eroded from pond bottom and insides of levees by water current aeroded from pond bottom and insides of levees by water current and nd wave action, manure and uneaten feed from management inputs and wave action, manure and uneaten feed from management inputs and remains of plants and animals produced with in the pond. remains of plants and animals produced with in the pond.

�� Substances also enter from solid phase of soil from the aqueous Substances also enter from solid phase of soil from the aqueous phase phase through ion exchange, adsorption and precipitation. through ion exchange, adsorption and precipitation.

�� For example For example -- potassium can be exchanged for other potassium can be exchanged for other cationcation on the soil, on the soil, phosphorus can be adsorbed by soil and CaCOphosphorus can be adsorbed by soil and CaCO33 may precipitate from may precipitate from solution and become a part of the bottom soil matrix.solution and become a part of the bottom soil matrix.

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�� Substances that enter the soil may be stored permanently, or theSubstances that enter the soil may be stored permanently, or they may y may be transformed to other substance by physical, chemical or biolobe transformed to other substance by physical, chemical or biological gical means and lost from the pond ecosystem. means and lost from the pond ecosystem.

�� For example For example -- phosphorus adsorbed by pond soil can become buried phosphorus adsorbed by pond soil can become buried in the sediment and lost from circulation with the pool of availin the sediment and lost from circulation with the pool of available able phosphorus. phosphorus.

�� Organic matter deposited on the pond bottom is decomposed to Organic matter deposited on the pond bottom is decomposed to inorganic carbon and released to the water as carbon dioxide. inorganic carbon and released to the water as carbon dioxide.

�� Nitrogen compound may be denitrified by pond soil microorganism Nitrogen compound may be denitrified by pond soil microorganism and lost to the atmosphere as nitrogen gas.and lost to the atmosphere as nitrogen gas.

�� Bacteria, fungi, algae, higher aquatic plants, small invertebratBacteria, fungi, algae, higher aquatic plants, small invertebrates es and other organism know as benthos live in and on the bottom and other organism know as benthos live in and on the bottom of the soil.of the soil.

�� Crustaceans and some species of fishes spend much time on the Crustaceans and some species of fishes spend much time on the bottom soil and many fish lay eggs in the nest built in the bottom soil and many fish lay eggs in the nest built in the bottom. bottom.

�� Benthos serves as food for some aquaculture species. Benthos serves as food for some aquaculture species.

�� It also involved in gas exchange, primary and secondary It also involved in gas exchange, primary and secondary productivity, decomposition and nutrient cycling.productivity, decomposition and nutrient cycling.

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�� Substances stored in the pond soil can be released to the water Substances stored in the pond soil can be released to the water through ion exchange, dissolution until equilibrium attained through ion exchange, dissolution until equilibrium attained between solid phase and liquid phase. between solid phase and liquid phase.

�� The equilibrium concentration may be too low for optimal The equilibrium concentration may be too low for optimal phytoplankton growth or the equilibrium concentration of a phytoplankton growth or the equilibrium concentration of a heavy metal may be too high enough to cause toxicity to aquatic heavy metal may be too high enough to cause toxicity to aquatic animal. animal.

�� Microbial decomposition is extremely important because organic Microbial decomposition is extremely important because organic matter is oxidized to COmatter is oxidized to CO2 2 and ammonia and other nutrient and ammonia and other nutrient element is released. element is released.

�� Carbon dioxide and ammonia are highly soluble and quickly Carbon dioxide and ammonia are highly soluble and quickly enter the water. enter the water.

Soil PropertiesSoil Properties

�� Soil consists of weathered mineral organic matter. They are a Soil consists of weathered mineral organic matter. They are a product of interaction among parent material, climate and product of interaction among parent material, climate and biological activity. biological activity.

�� It is well known that soil differ from place to place on the earIt is well known that soil differ from place to place on the earth th surface and beneath a given site the soil profile consists of surface and beneath a given site the soil profile consists of horizontal layers that change in characteristics with depth givehorizontal layers that change in characteristics with depth given n below the land surface.below the land surface.

�� The most active fraction of soil is clay particles, because of The most active fraction of soil is clay particles, because of electric charge and large surface area and the organic matter, oelectric charge and large surface area and the organic matter, of f its biological activity and high chemical reactivity. its biological activity and high chemical reactivity.

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�� The pore spaces among the mineral fragments and organic matter The pore spaces among the mineral fragments and organic matter are filled with air and water. are filled with air and water.

�� In flooded water air is completely displaced by water. In flooded water air is completely displaced by water.

�� This greatly impedes the movement of oxygen into append soil, This greatly impedes the movement of oxygen into append soil, because the oxygen must move over by diffusion or be carried because the oxygen must move over by diffusion or be carried along with water that seeps through the soil. along with water that seeps through the soil.

�� Coarse texture soil is better oxygenated than fine. Coarse texture soil is better oxygenated than fine.

�� Pond soil often are fine textured because they usually have at lPond soil often are fine textured because they usually have at least east 2222--30% clay content will limits seepage and they have higher 30% clay content will limits seepage and they have higher percentage of organic matter than terrestrial soil. percentage of organic matter than terrestrial soil.

�� Pond soil is highly reactive, have oxygen demand and tend to Pond soil is highly reactive, have oxygen demand and tend to become anaerobic.become anaerobic.

�� In addition to this specific chemical compounds in soil have In addition to this specific chemical compounds in soil have a pronounced affect on aquaculture. a pronounced affect on aquaculture.

�� Soil that have been highly weathered and contain appreciable Soil that have been highly weathered and contain appreciable quantities of aluminum oxides and hydroxides or acidic and quantities of aluminum oxides and hydroxides or acidic and water in contact with acidic soils have low total alkalinity andwater in contact with acidic soils have low total alkalinity andpoorly buffered against pH change. poorly buffered against pH change.

�� The presence of iron pyrite in pond soils can results in The presence of iron pyrite in pond soils can results in extreme acidity because sulphuric acid is formed from pyrite extreme acidity because sulphuric acid is formed from pyrite oxidation. oxidation.

�� Free calcium carbonate in soils leads to high concentration Free calcium carbonate in soils leads to high concentration of total alkalinity and total hardness of overlie water.of total alkalinity and total hardness of overlie water.

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The four most important soil features for The four most important soil features for

aquaculturalaquacultural production are production are

�� TextureTexture

�� Organic matter Organic matter

�� pHpH

�� Presence or absence of particular soluble Presence or absence of particular soluble

compound that may have beneficial effect or compound that may have beneficial effect or

harmful to water quality.harmful to water quality.

Some important reaction and processes controlling Some important reaction and processes controlling

pondpond--soilsoil--water interaction arewater interaction are

ReactionsReactions�� Dissociation:Dissociation: CaCOCaCO33 + CO+ CO22 + H+ H22O = CaO = Ca2+2+ + 2HCO+ 2HCO33

--

�� Precipitation:Precipitation: AlAl3+3+ + H+ H22POPO44 + 2H+ 2H22O = Al(OH)O = Al(OH)22HH22POPO44 +2H+2H++

�� Hydrolysis:Hydrolysis: AlAl3+3+ + 3H+ 3H22O = Al(OH)O = Al(OH)33 + 3H+ 3H++

�� Neutralization:Neutralization: HCOHCO33-- + H+ H++ = H= H22O +COO +CO22

�� Oxidation:Oxidation: NHNH44++ 2O2O22 = NO= NO33

-- +2H+2H++ + H+ H22OO

�� Reduction:Reduction: SOSO442+2+ + 4H+ 4H22 = S= S22-- +4H+4H22OO

�� Complex Formation:Complex Formation: CuCu2+2+ + CO+ CO3322-- =CuCO=CuCO33

�� Adsorption:Adsorption: adsorption of phosphorus on soil colloidsadsorption of phosphorus on soil colloids

�� CationCation Exchange:Exchange: K (Soil) = K+ (Water)K (Soil) = K+ (Water)

�� Hydration:Hydration: AlAl22OO33 + 3H+ 3H22O = AlO = Al22OO33.3H.3H22OO

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ProcessesProcesses

�� SedimentationSedimentation:: Soil particles in runoff settle to pond bottomSoil particles in runoff settle to pond bottom

�� DecompositionDecomposition:: Microorganisms break down soil organic matter.Microorganisms break down soil organic matter.

CHCH22O + OO + O22 →→ COCO22 +H+H22OO

�� PhotosynthesisPhotosynthesis:: Benthic algae produce organic matter and Benthic algae produce organic matter and releaserelease oxygen.oxygen.

6CO6CO22 + 6H+ 6H22O = CO = C66HH66OO66 + 6O+ 6O22

�� DiffusionDiffusion: Oxygen diffuses into bottom soil from water above : Oxygen diffuses into bottom soil from water above

�� Seepage:Seepage: Water carrying dissolved substance seeps downward Water carrying dissolved substance seeps downward into the pond soilinto the pond soil

�� Erosion:Erosion: Water current in pond erode the bottom soilWater current in pond erode the bottom soil

�� Suspension:Suspension: Particulate matter eroded from the bottom is Particulate matter eroded from the bottom is suspended in pond water.suspended in pond water.

CHEMISTRY OF POND MUDCHEMISTRY OF POND MUD�� When pond is flooded with water, the first effect of flooding isWhen pond is flooded with water, the first effect of flooding is to drive out the air from to drive out the air from

the soil.the soil.

�� Then the aquatic bacteria in the soil become active, decomposingThen the aquatic bacteria in the soil become active, decomposing the organic matter in the the organic matter in the newly water logged soil and using up the oxygen. newly water logged soil and using up the oxygen.

�� This lead to anaerobic conditions and the pond mud is in a reducThis lead to anaerobic conditions and the pond mud is in a reduced state and the flooded ed state and the flooded soil comes to contain carbon dioxide (COsoil comes to contain carbon dioxide (CO22) but no oxygen (O) but no oxygen (O22). ).

�� Under such conditions, sulphates are reduced to Under such conditions, sulphates are reduced to sulphidessulphides (SO(SO44 to S) nitrogenous to S) nitrogenous substances to ammonia (NHsubstances to ammonia (NH33), Iron occurs in the reduced form (Fe), Iron occurs in the reduced form (Fe2+2+) and some of the ) and some of the organic matter to methane (CHorganic matter to methane (CH44). ).

�� Because of ammonia, the soil becomes alkaline and because of preBecause of ammonia, the soil becomes alkaline and because of presence of ferrous ion sence of ferrous ion complex, the colour of the soil becomes a more or less intense bcomplex, the colour of the soil becomes a more or less intense bluelue--black. black.

�� The water overlaying the mud becomes oxygenated partly because tThe water overlaying the mud becomes oxygenated partly because the water dissolve he water dissolve oxygen from the air and partly due to the oxygen (Ooxygen from the air and partly due to the oxygen (O22) release during the ) release during the photosynthesisbyphotosynthesisbythe aquatic plants presents in the pond phytoplankton, which soothe aquatic plants presents in the pond phytoplankton, which soon develops there.n develops there.

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CHEMISTRY OF POND MUDCHEMISTRY OF POND MUD (continued(continued……))

�� This oxygen will oxidize the surface skin of the pond mud (1 to This oxygen will oxidize the surface skin of the pond mud (1 to few mm thick few mm thick only) and develop on oxidized only) and develop on oxidized microzonemicrozone. .

�� Where ferrous iron (FeWhere ferrous iron (Fe2+2+) becomes ferric (Fe) becomes ferric (Fe3+3+), ), sulphidessulphides (S) becomes sulphates (S) becomes sulphates (SO(SO

44) and ammonia (NH) and ammonia (NH33) becomes nitrate and nitrite. ) becomes nitrate and nitrite.

�� Because of disappearance of ammonia (NHBecause of disappearance of ammonia (NH33) and the appearance of acid, this ) and the appearance of acid, this

layer becomes acidic and the surface of the pond mud turned fromlayer becomes acidic and the surface of the pond mud turned from blue blue –– black black to yellow to brown in colour due to the presence of ferric compoto yellow to brown in colour due to the presence of ferric compounds (Fe).unds (Fe).

�� This phenomenon can almost always be seen when the mud of a ponThis phenomenon can almost always be seen when the mud of a pond is d is exposed, for example when it is drained to take the crop of fishexposed, for example when it is drained to take the crop of fish, the foot prints of , the foot prints of men working in the mud are deep blue or black, the undisturbed mmen working in the mud are deep blue or black, the undisturbed mud is yellow. ud is yellow.

�� But almost as one looks, the exposed black reduced soil takes upBut almost as one looks, the exposed black reduced soil takes up oxygen from the oxygen from the air and turns yellow.air and turns yellow.

Mechanism of Release of Nutrients from SoilMechanism of Release of Nutrients from Soil

�� The yellow ferric iron compound chiefly the hydroxide at the oxiThe yellow ferric iron compound chiefly the hydroxide at the oxidized surface layer dized surface layer are usually in a very finely divided or colloidal state and thisare usually in a very finely divided or colloidal state and this colloidal ferric colloidal ferric hydroxide together with colloidal hydroxide together with colloidal humichumic substances make a mud which has highly substances make a mud which has highly absorptive properties for both acid and basic radicals. absorptive properties for both acid and basic radicals.

�� As long as the iron compound on the surface layer of the mud werAs long as the iron compound on the surface layer of the mud were in ferric state, e in ferric state, the surface was strongly adsorptive of positive ions, such as amthe surface was strongly adsorptive of positive ions, such as ammonia, calcium, monia, calcium, manganese and of negative ions such as phosphates and silicates.manganese and of negative ions such as phosphates and silicates. But nitrate and But nitrate and nitrite were not adsorbed.nitrite were not adsorbed.

�� During temporary cutting of oxygen from the surface layer of theDuring temporary cutting of oxygen from the surface layer of the mud (which may mud (which may be caused by excessive respiration at night, or by lack of circube caused by excessive respiration at night, or by lack of circulation of water or it lation of water or it may be, in deep ponds, a longer term phenomenon due to layering may be, in deep ponds, a longer term phenomenon due to layering of water), the of water), the adsorbed ions are released into the water often in considerable adsorbed ions are released into the water often in considerable quantities. quantities.

�� The reduced iron has no power to hold, then diffuse up into the The reduced iron has no power to hold, then diffuse up into the pond water and pond water and are taken up by plants and then by fish.are taken up by plants and then by fish.

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REDOX POTENTIALREDOX POTENTIAL ((RhRh))

�� When the oxidation taking place in surface of the mud and When the oxidation taking place in surface of the mud and reduction at lower levels, the electrical charges on the moleculreduction at lower levels, the electrical charges on the molecule of e of electrolytes and ions in these two soil layers are responsible felectrolytes and ions in these two soil layers are responsible for or differences in potential i.e. differences in potential i.e. RedoxRedox potential.potential.

�� Reducing conditions prevails when potential is below +350 Reducing conditions prevails when potential is below +350 millivoltsmillivolts and above it, and above it, oxidisingoxidising conditions occur. conditions occur.

�� Therefore, the values of Therefore, the values of redoxredox potential in the pond mud will potential in the pond mud will give an idea about binding or releasing the ions of nutrient give an idea about binding or releasing the ions of nutrient materials from pond mud.materials from pond mud.

FATE OF ADDED FERTILIZERSFATE OF ADDED FERTILIZERS

�� The binding and releasing by adsorption on the pond mud applies The binding and releasing by adsorption on the pond mud applies not not only to the nutrients naturally only to the nutrients naturally occuringoccuring in the soil, but also to fertilizer in the soil, but also to fertilizer added to the pond. added to the pond.

�� The phosphate in the fish pond remained in the soil, adsorbed onThe phosphate in the fish pond remained in the soil, adsorbed on the the oxidisingoxidising layer of the mud on colloidal ferric hydroxide and in layer of the mud on colloidal ferric hydroxide and in absence of the oxygen (Oabsence of the oxygen (O

22). ).

�� Ferric ion is reduced to ferrous ion and phosphorus is released Ferric ion is reduced to ferrous ion and phosphorus is released in in soluble form in the water. soluble form in the water.

�� Phosphate is also incorporated in the bodies of microPhosphate is also incorporated in the bodies of micro––organisms. organisms. These two factors account for the residual effect of These two factors account for the residual effect of phosphaticphosphaticfertilizers and subsequent release under suitable condition evenfertilizers and subsequent release under suitable condition even after 4 after 4 years of application.years of application.

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HH22S TOXICITYS TOXICITY

�� The hydrogen The hydrogen sulphidesulphide gas which is frequently detected in the gas which is frequently detected in the mud during the construction of the ponds could poison the fish. mud during the construction of the ponds could poison the fish.

�� But so long, as the surface layer of the mud is oxidizing, this But so long, as the surface layer of the mud is oxidizing, this very poisonous gas, deadly to fish, could not possibly diffuse very poisonous gas, deadly to fish, could not possibly diffuse into the water, for the into the water, for the sulphidesulphide could soon be oxidized to could soon be oxidized to harmless harmless sulphatesulphate. .

�� If a free circulation of the pond water is impeded, as for If a free circulation of the pond water is impeded, as for example by dense vegetation, then the smell of the gas appears.example by dense vegetation, then the smell of the gas appears.Clearance of vegetation will minimize the chance of HClearance of vegetation will minimize the chance of H22S toxicity S toxicity in this case.in this case.

�� Due to all these fact described above the pond mud has been Due to all these fact described above the pond mud has been described as the described as the ““Chemical laboratoryChemical laboratory’’ of pondof pond””..

�� Relationship between pond soil and aquatic animal production is Relationship between pond soil and aquatic animal production is mostly indirect. mostly indirect.

�� Soil affects nutrient concentration in the water, which in turn Soil affects nutrient concentration in the water, which in turn influence plant productivity. influence plant productivity.

�� In pond where aquaculture species depends on natural food for In pond where aquaculture species depends on natural food for their growth & development, fertility of soil is key factor their growth & development, fertility of soil is key factor regulating the fish production. regulating the fish production.

�� In pond where feeding of fish comes from the feed; fertility of In pond where feeding of fish comes from the feed; fertility of soil is not as important, but in that condition also soil conditsoil is not as important, but in that condition also soil condition ion is extremely important in determining the water quality and the is extremely important in determining the water quality and the survival and growth of fishsurvival and growth of fish

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Importance of pond bottom soil in fertilized pondImportance of pond bottom soil in fertilized pond

�� The mineral composition of pond water is to a large degree is reThe mineral composition of pond water is to a large degree is reflection of mineral flection of mineral compositions of the soil.compositions of the soil.

�� the colloidal fraction of soil consisting of the colloidal fraction of soil consisting of humichumic substance, hydroxide gel and clay is a substance, hydroxide gel and clay is a powerful absorbent of soluble mineral nutrient and governs theirpowerful absorbent of soluble mineral nutrient and governs their availability availability

�� The pond soil is the medium is which live microorganism responsiThe pond soil is the medium is which live microorganism responsible for decomposition of ble for decomposition of organic matter and transformation of chemical elements.organic matter and transformation of chemical elements.

�� The pond soil is the source of food organism for fish.The pond soil is the source of food organism for fish.

�� At the same time pond soil can indirectly effect the aquacultureAt the same time pond soil can indirectly effect the aquaculture production throughproduction through

�� Pond soil can be source of toxic metabolites that can enter watePond soil can be source of toxic metabolites that can enter water and harm aquatic animal r and harm aquatic animal healthhealth

�� Sedimentation can smother aquatic organism and can destroy fish Sedimentation can smother aquatic organism and can destroy fish nesting sitesnesting sites

�� Sub optimal soil texture and ph may limit production of benthos,Sub optimal soil texture and ph may limit production of benthos, which is the food of many which is the food of many aquatic animals.aquatic animals.

Effect of aquatic animal on the pond soilEffect of aquatic animal on the pond soil

�� Fish stir the bottom by producing the water current when they swFish stir the bottom by producing the water current when they swim, im, and many species make shallow depression for nesting and some and many species make shallow depression for nesting and some species stir bottom when capturing the prey. species stir bottom when capturing the prey.

�� Stirring pond bottom can reused sediment. Pond stocked with goldStirring pond bottom can reused sediment. Pond stocked with goldfish, common carp or other bottom feeding fish often are turbid fish, common carp or other bottom feeding fish often are turbid with soil particles suspend. with soil particles suspend.

�� organism which borrow in the bottom loosen the soil and make it organism which borrow in the bottom loosen the soil and make it more susceptible to erosion by water current, and burrowing actimore susceptible to erosion by water current, and burrowing activity vity mixes the sediment and also enhances the aeration of the upper smixes the sediment and also enhances the aeration of the upper soil oil by facilitating the exchange of pore water with pond water. by facilitating the exchange of pore water with pond water.

�� Benthic organism dies and contributes organic matter to the soilBenthic organism dies and contributes organic matter to the soilhence aquatic animal are contributing to the development of soilhence aquatic animal are contributing to the development of soils. s.

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Soil properties and pond aquacultureSoil properties and pond aquaculture

�� BanerjeaBanerjea studied the relationship between soil studied the relationship between soil

properties and fish production. According to properties and fish production. According to

him fish production is classified as:him fish production is classified as:--

�� -- LowLow <200 kg<200 kg

�� -- AverageAverage 200200--500 kg500 kg

�� -- HighHigh >500 kg>500 kg

200200--300 300 ppmppm100100--200 200 ppmppm<100 <100 ppmppmExchangeable Exchangeable

calcium ioncalcium ion

1010--151555--1010<5 & >15<5 & >15Carbon nitrogen Carbon nitrogen

ratioratio

1.51.5--2.5 %2.5 %0.50.5--1.5 %1.5 %%0.5%0.5Organic carbonOrganic carbon

>500 >500 ppmppm250250--500 500 ppmppm<250 <250 ppmppmAvailable Available

nitrogennitrogen

>60 >60 ppmppm3030--60 60 ppmppm<30 <30 ppmppmAvailable Available

phosphorusphosphorus

6.56.5--7.57.55.55.5--6.5& 7.56.5& 7.5--8.58.5<5.5&>7.5<5.5&>7.5pHpH

HighHighAverageAverageLowLowParameterParameter\\Fish Fish

productionproduction

And also ideal clay content in pond soil is ranging from 25 % to 50 %

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Classification of soilClassification of soil

<0.002mm<0.002mm<0.002mm<0.002mmClayClay

0.0020.002--0.02mm0.02mm0.0020.002--0.05mm0.05mmSiltSilt

0.050.05--0.1mm0.1mmVery fine sandVery fine sand

0.20.2--2mm2mm0.10.1--0.25mm0.25mmFine sandFine sand

0.250.25--0.5mm0.5mmMedium sandMedium sand

0.20.2--2mm2mmo.5o.5--1mm1mmCoarse sandCoarse sand

11--2mm2mmVery coarse sandVery coarse sand

>2mm>2mm>2mm>2mmGravelGravel

ISSSISSSUSDAUSDAParticle fraction nameParticle fraction name

Pond bottom managementPond bottom management

�� Soil properties and relationship among pond soil, water Soil properties and relationship among pond soil, water quality and aquaculture production has been discussed. quality and aquaculture production has been discussed.

�� It has been shown that initial soil condition in new It has been shown that initial soil condition in new pond sometimes unsatisfactory and of soil may pond sometimes unsatisfactory and of soil may deteriorate over time in response to demand imposed deteriorate over time in response to demand imposed on them by aquaculture practices, so little treatment is on them by aquaculture practices, so little treatment is needed for improvement of soil condition. needed for improvement of soil condition.

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LimingLiming

�� Soil acidity is management concern because both total alkalinitySoil acidity is management concern because both total alkalinityand total hardness of pond water is closely associated with and total hardness of pond water is closely associated with bottom soil acidity. bottom soil acidity.

�� The total alkalinity and total hardness should be > 20 mg/L to The total alkalinity and total hardness should be > 20 mg/L to maintain enough buffering action, pH 6maintain enough buffering action, pH 6--9.5 and sufficient 9.5 and sufficient dissolve inorganic carbon to support good phytoplankton dissolve inorganic carbon to support good phytoplankton growth. growth.

�� For crustacean pond it should be >50 mg/L because of For crustacean pond it should be >50 mg/L because of importance of carbonate and bicarbonate in importance of carbonate and bicarbonate in moultingmoulting..

Pond with acid Pond with acid sulphatesulphate soilsoil

�� Potential acid Potential acid sulphatesulphate soil is identified by a high total soil is identified by a high total sulphursulphur concentration concentration (>0.75 % or low pH (2(>0.75 % or low pH (2--3) upon drying for several days. 3) upon drying for several days.

�� Effects of this acid Effects of this acid sulphatesulphate soil are low pH, low alkalinity of water and low soil are low pH, low alkalinity of water and low aquaculturalaquacultural production.production.

Ways to deal with acid Ways to deal with acid sulphatesulphate soil aresoil are--

�� Drain the soil and wait until natural oxidation and leaching remDrain the soil and wait until natural oxidation and leaching remove the acidity.ove the acidity.

�� Dry the bottom soil periodically and then flush it with water toDry the bottom soil periodically and then flush it with water to remove acidityremove acidity

�� Lime to neutralize the acidity Lime to neutralize the acidity

�� Prevent the oxidation of iron pyrite so that acidity is not exprPrevent the oxidation of iron pyrite so that acidity is not expressed.essed.

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Bottom soil sterilizationBottom soil sterilization

�� To prevent pathogen from surviving between To prevent pathogen from surviving between

aquaculture crops and infecting the fish and crustacean aquaculture crops and infecting the fish and crustacean

stocked. stocked.

�� The most The most sterilantssterilants used are burnt lime, hydrated lime, used are burnt lime, hydrated lime,

and chorine compounds. and chorine compounds.

�� The first two can raise the pH and kill the pathogen, The first two can raise the pH and kill the pathogen,

while chlorine is directly toxic to kill the pathogen.while chlorine is directly toxic to kill the pathogen.

ProbioticsProbiotics

�� A number of products are promoted to enhance beneficial chemicalA number of products are promoted to enhance beneficial chemicaland biological processes and to improve soil quality. and biological processes and to improve soil quality.

�� These products include cultures of living bacteria, enzyme. These products include cultures of living bacteria, enzyme. Preparations composted or fermented residues, plant extracts, anPreparations composted or fermented residues, plant extracts, and d other concoctions. other concoctions.

�� There is no evidence from research that any of these products wiThere is no evidence from research that any of these products will ll improve soil quality. improve soil quality.

�� Nevertheless, they are not harmful to the culture species, surroNevertheless, they are not harmful to the culture species, surrounding unding environment, workers, or quality of aquaculture products.environment, workers, or quality of aquaculture products.

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Oxidation of pond bottomOxidation of pond bottom

�� Techniques that enhances dissolved oxygen Techniques that enhances dissolved oxygen

concentration at the pond bottom, increases the concentration at the pond bottom, increases the

redoxredox potential in the surface layer of soils. potential in the surface layer of soils.

�� This lessens the possibility of migration of toxic This lessens the possibility of migration of toxic

metabolite from deeper, anaerobic soil into the metabolite from deeper, anaerobic soil into the

pond water.pond water.

During growth periodDuring growth period

�� Low pH can retard decomposition of organic matter Low pH can retard decomposition of organic matter and permits its accumulation and cause a high oxygen and permits its accumulation and cause a high oxygen demand in the surface layer of soil. Low concentration demand in the surface layer of soil. Low concentration of nitrogen retards the decomposition of organic matter of nitrogen retards the decomposition of organic matter because soil micro organism can use oxygen from because soil micro organism can use oxygen from nitrate when molecular oxygen depleted. nitrate when molecular oxygen depleted.

�� Nitrogen fertilizer should be applied to static pond at Nitrogen fertilizer should be applied to static pond at 10 kg N/ha every 2 or 4 weeks. 10 kg N/ha every 2 or 4 weeks.

�� Liming and nitrogen fertilizer can be more effective in Liming and nitrogen fertilizer can be more effective in enhancing the aerobic microbial activity when aeration enhancing the aerobic microbial activity when aeration is used to supplement the oxygen supply. is used to supplement the oxygen supply.

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Bacterial amendmentsBacterial amendments

�� Bacteria capable of nitrogen fixing, prevention off flavor, reduBacteria capable of nitrogen fixing, prevention off flavor, reduction in the ction in the properties of blue green algae, less nitrite, nitrate, ammonia aproperties of blue green algae, less nitrite, nitrate, ammonia and phosphate ; nd phosphate ; more dissolve oxygen and more rapid organic matter degradation cmore dissolve oxygen and more rapid organic matter degradation can an achieved.achieved.

AeratorsAerators

�� Different type of aerators is mainly paddle type of aerator, verDifferent type of aerators is mainly paddle type of aerator, vertical pump tical pump aerators, propeller aspirator and diffused air aerators. aerators, propeller aspirator and diffused air aerators.

�� The main advantages of adopting aerators are:The main advantages of adopting aerators are:

�� Prevent thermal stratificationPrevent thermal stratification

�� mixing of pond water and provide better oxygenationmixing of pond water and provide better oxygenation

�� Enhance the decomposition of organic matter and thus Enhance the decomposition of organic matter and thus preventingpreventing anaerobic condition.anaerobic condition.

�� In most case aeration should be applied at 2In most case aeration should be applied at 2--3 kilo watt/ha to 3 kilo watt/ha to improve the condition at the soil water interface. improve the condition at the soil water interface.

�� Bottom animal disturb bottom soil and improve aeration by Bottom animal disturb bottom soil and improve aeration by encourage movement of oxygenated water with in the soil mass. encourage movement of oxygenated water with in the soil mass. The process is called as The process is called as ““BioturbationBioturbation””..

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Chemical oxidantChemical oxidant

�� Application of sodium nitrate to Application of sodium nitrate to eutrophiceutrophic lake prevents highly lake prevents highly reduced condition in sediment since here nitrate is function as reduced condition in sediment since here nitrate is function as an an oxidant and poises the oxidation reduction potential.oxidant and poises the oxidation reduction potential.

NONO33 +2H+2H++ +2e+2e-- =NO=NO22 +H+H22OO

�� Similarly calcium peroxide releases oxygen as followsSimilarly calcium peroxide releases oxygen as follows

2CaCO2CaCO22 + 2H+ 2H22O = 2Ca(OH)O = 2Ca(OH)22 + O+ O22

�� And also hydrogen peroxide releases oxygen as followsAnd also hydrogen peroxide releases oxygen as follows

2H2H22OO22 →→2H2H22O +OO +O22

�� Among them sodium nitrate is cheaper than peroxide and less Among them sodium nitrate is cheaper than peroxide and less hazardous to handle.hazardous to handle.

�� Hydrogen Hydrogen sulphidesulphide released from anaerobic pond soils can be released from anaerobic pond soils can be harmful to shrimp and fish. This can be controlled through harmful to shrimp and fish. This can be controlled through application of potassium permanganate to oxidize Happlication of potassium permanganate to oxidize H22SS

4KMnO4KMnO44 +3H+3H22S S →→ 2K2K22SOSO44+ 3MnO+ 3MnO22 +3H+3H22OO

�� But treatment cannot be highly successful because KMnOBut treatment cannot be highly successful because KMnO44 is is highly soluble.highly soluble.

�� A possible method for preventing HA possible method for preventing H22S in pond is through Iron S in pond is through Iron application. Where iron reacts with Happlication. Where iron reacts with H22S and precipitates it as S and precipitates it as highly insoluble Ferrous highly insoluble Ferrous SulphateSulphate

Fe +HFe +H22S S →→FeSOFeSO4 4

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DRY PERIODDRY PERIOD

�� During the water During the water –– logged period where the pond mud is under anaerobic logged period where the pond mud is under anaerobic conditions and alkaline in reaction, oxidation processes of orgaconditions and alkaline in reaction, oxidation processes of organic matter cannot nic matter cannot be completed and oxygen (Obe completed and oxygen (O

22) debt is built up of these partially oxidized ) debt is built up of these partially oxidized products of fermentation. products of fermentation.

�� Exposure to air completes this oxidation after resulting in the Exposure to air completes this oxidation after resulting in the release of carbon release of carbon dioxide (COdioxide (CO

22) making the soils slightly acidic.) making the soils slightly acidic.

�� The completion of oxidation releases the contained nutrient mateThe completion of oxidation releases the contained nutrient materials by rials by mineralization and acidic condition cause these materials to remmineralization and acidic condition cause these materials to remain adsorbed in ain adsorbed in the soil, ready for release when the pond is refilled and the oxthe soil, ready for release when the pond is refilled and the oxidation idation –– reduction reduction system sets itself up again.system sets itself up again.

�� The chief advantage of dry period is the restoration of the fertThe chief advantage of dry period is the restoration of the fertility of the pond.ility of the pond.

�� Rack the bottom if dewatering is not possible. Repeated netting Rack the bottom if dewatering is not possible. Repeated netting is useful for this.is useful for this.

During the fallow periodDuring the fallow period……..

�� The rate of soil organic matter decomposition by aerobic processThe rate of soil organic matter decomposition by aerobic process when ponds are when ponds are drained and their bottom are exposed to air is increased by manidrained and their bottom are exposed to air is increased by manifolds. folds.

�� The optimal length of fallow period depends on drying conditionsThe optimal length of fallow period depends on drying conditions and and temperature. temperature.

�� In the dry season pond bottom become so dry after 2 to 4 weeks tIn the dry season pond bottom become so dry after 2 to 4 weeks that microbial hat microbial activity is suppressed by lack of moisture.activity is suppressed by lack of moisture.

�� Unless soil can be irrigated to replenish soil moisture there isUnless soil can be irrigated to replenish soil moisture there is a little value in a little value in extending the fallow period of moisture depleted soil. extending the fallow period of moisture depleted soil.

�� The moisture concentration for processing of organic matter is 1The moisture concentration for processing of organic matter is 10 0 –– 40 % for 40 % for different soil. different soil.

�� Drying of soil rich in iron pyrite can causes extremely low pH. Drying of soil rich in iron pyrite can causes extremely low pH. So acidity must be So acidity must be washed out of soil before ponds are filled and restocked. washed out of soil before ponds are filled and restocked.

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TillingTilling

�� When the soil contain expandable clay dry, cracks forms in the sWhen the soil contain expandable clay dry, cracks forms in the surface and urface and extend to depth of 10 extend to depth of 10 --100 cm into the soil. 100 cm into the soil.

�� Air can penetrate the crack and improve oxygenation but air willAir can penetrate the crack and improve oxygenation but air will not readily not readily penetrate the soil mass comprising of columnar blocks between crpenetrate the soil mass comprising of columnar blocks between cracks.acks.

�� Surface soil dries quickly when compared to deeper soil because Surface soil dries quickly when compared to deeper soil because there is better there is better exchange of water vapour with atmosphere. A surface layer acts aexchange of water vapour with atmosphere. A surface layer acts as a barrier to s a barrier to evaporation.evaporation.

�� Plowing breaks up the surface crusts and columnar blocks that foPlowing breaks up the surface crusts and columnar blocks that form during rm during drying and greatly improves conditions for drying and aeration idrying and greatly improves conditions for drying and aeration in deeper layer of n deeper layer of soil. soil.

�� The most efficient device for plowing soil The most efficient device for plowing soil -- tractor powered tractor powered rototiferrototifer

LimingLiming

�� Objective of fallow period is to aerate soil and encourage oxidaObjective of fallow period is to aerate soil and encourage oxidation of organic matter. The tion of organic matter. The pH range for organic matter decomposition is 7.5 pH range for organic matter decomposition is 7.5 –– 8.5.8.5.

pH pH Agricultural limestoneAgricultural limestone

(Kg /ha)(Kg /ha)

4.54.5--5.0 40005.0 4000

5.05.0--5.5 20005.5 2000

6.06.0--7.0 10007.0 1000

�� Agriculture limestone should be evenly spread over the soil surfAgriculture limestone should be evenly spread over the soil surface, but uniform ace, but uniform application is less critical than when spreading burnt or hydratapplication is less critical than when spreading burnt or hydrated lime for soil sterilization. ed lime for soil sterilization.

�� Agriculture limestone should be incorporated into the upper 5Agriculture limestone should be incorporated into the upper 5--10 cm soil layer by tilling. 10 cm soil layer by tilling. Limestone will not dissolve unless soil contains plenty of moistLimestone will not dissolve unless soil contains plenty of moisture.ure.

�� Burnt or hydrated lime is not recommended as a routine soil treaBurnt or hydrated lime is not recommended as a routine soil treatment between crops. tment between crops.

�� These materials cause an initial high pH that kills microorganisThese materials cause an initial high pH that kills microorganism and retard the m and retard the decomposition rate. Agriculture lime is safer to apply and will decomposition rate. Agriculture lime is safer to apply and will not cause soil pH to rise not cause soil pH to rise above 8.above 8.

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FertilizationFertilization

�� The C: N ratio is between 5&10 in most pond soils and organic The C: N ratio is between 5&10 in most pond soils and organic residues readily decompose if other factor affecting soil residues readily decompose if other factor affecting soil respiration is favorable.respiration is favorable.

�� The C: N is wide in organic soil and fertilization to increase The C: N is wide in organic soil and fertilization to increase nitrogen availability accelerates decomposition. nitrogen availability accelerates decomposition.

�� A rate of 100mg N/Kg was necessary to significantly enhance A rate of 100mg N/Kg was necessary to significantly enhance the decomposition of soil organic matter. the decomposition of soil organic matter.

�� Any common nitrogen fertilizer can be used, but sodium nitrates Any common nitrogen fertilizer can be used, but sodium nitrates appear to be most effective.appear to be most effective.

SedimentSediment

�� Pond should be managed to avoid sediment problem. Vegetative covPond should be managed to avoid sediment problem. Vegetative cover on watershed er on watershed will minimize erosion by rainfall and runoff. will minimize erosion by rainfall and runoff.

�� Where wave action causes serious erosion of levees, trees or shrWhere wave action causes serious erosion of levees, trees or shrubs are planted to ubs are planted to make wind breaks and riprap can be placed on vulnerable expense make wind breaks and riprap can be placed on vulnerable expense of levees. of levees.

�� Excessive aeration should not be applied and in aerated ponds, bExcessive aeration should not be applied and in aerated ponds, bottom should be ottom should be hardened in areas with higher water velocities. Tilling pond bothardened in areas with higher water velocities. Tilling pond bottom is aid to drying tom is aid to drying and organic matter decomposition but it encourages erosion in aeand organic matter decomposition but it encourages erosion in aerated pond.rated pond.

�� It is well known in commercial pond aquaculture that maintenanceIt is well known in commercial pond aquaculture that maintenance of water quality of water quality with adequate range for optimal aquatic animal production becomewith adequate range for optimal aquatic animal production becomes more difficult as s more difficult as pond ages. pond ages.

�� The accumulation of sediment enriched with nutrient and organic The accumulation of sediment enriched with nutrient and organic matter is thought to matter is thought to be a major factor causing the intensification of management probbe a major factor causing the intensification of management problems in old ponds. lems in old ponds.

�� So the techniques for removing sediment from old ponds should beSo the techniques for removing sediment from old ponds should be evaluated evaluated Dredges might be a valuable tool for use in aquaculture.Dredges might be a valuable tool for use in aquaculture.

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The following actions should be considered by pond managers who The following actions should be considered by pond managers who wish wish

to maintain good soil condition in the bottoms of aquaculture poto maintain good soil condition in the bottoms of aquaculture ponds:nds:

�� Avoid highly intensive aquaculture operation. High nutrient and Avoid highly intensive aquaculture operation. High nutrient and organic matter organic matter inputs to the ponds lead to soil deterioration.inputs to the ponds lead to soil deterioration.

�� Use conservative fertilization, Use conservative fertilization, manuringmanuring and feeding techniques. Excessive and feeding techniques. Excessive inputs of nutrients and organic matters are wasteful and harmfulinputs of nutrients and organic matters are wasteful and harmful to ecosystem.to ecosystem.

�� Reduce external sediment load by maintaining good vegetative covReduce external sediment load by maintaining good vegetative cover on er on watersheds and using sediment ponds where the water supply is cowatersheds and using sediment ponds where the water supply is contaminated ntaminated with suspended solids.with suspended solids.

�� Moderate mechanical aeration and waters circulation enhance dissModerate mechanical aeration and waters circulation enhance dissolved oxygen olved oxygen concentration in bottom water and in surface layer of soil.concentration in bottom water and in surface layer of soil.

�� Reduce internal sediment load by protecting banks from wave erosReduce internal sediment load by protecting banks from wave erosion and ion and avoiding excessive aeration and water circulation.avoiding excessive aeration and water circulation.

�� Prevent infestation on rooted aquatic Prevent infestation on rooted aquatic macrophytesmacrophytes by maintaining water depts. by maintaining water depts. greater than 0.5mt in all areas of pond. greater than 0.5mt in all areas of pond.

�� encourage plankton growth so that visibility in to the water is encourage plankton growth so that visibility in to the water is not more than 30not more than 30--54 cm. do not allow infestation emergent 54 cm. do not allow infestation emergent macrophytesmacrophytes along levees and in along levees and in shallow water area or mats of floating shallow water area or mats of floating macrophytesmacrophytes..

�� An aggressive liming program in acidic water will maintain Ph toAn aggressive liming program in acidic water will maintain Ph total alkalinity and tal alkalinity and total hardness in desirable ranges.total hardness in desirable ranges.

�� Identify areas with potential acid Identify areas with potential acid sulphatesulphate soils. Use pond construction and soils. Use pond construction and management techniques that minimize exposure of potential acid management techniques that minimize exposure of potential acid sulphatesulphate to the to the air.air.

�� Where possible allow a fallow period to dry soils between aqua cWhere possible allow a fallow period to dry soils between aqua cultural crops. ultural crops.

�� Tilling, liming and fertilization enhance organic matter decompoTilling, liming and fertilization enhance organic matter decomposition between sition between crops in some ponds. Compact tilled soils before refilling pondscrops in some ponds. Compact tilled soils before refilling ponds to reduce to reduce aeration in aerated ponds.aeration in aerated ponds.

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�� Pond soil can be sterilized to destroy fish pathogens. Pond soil can be sterilized to destroy fish pathogens. Application of brunt or hydrated is probably more reliable Application of brunt or hydrated is probably more reliable than chlorination.than chlorination.

�� Future research is needed to determine if chemical Future research is needed to determine if chemical oxidants can be effective in maintaining aerobic condition oxidants can be effective in maintaining aerobic condition in surface layers of bottom soils.in surface layers of bottom soils.

�� Positive benefits of bacterial and enzyme amendments Positive benefits of bacterial and enzyme amendments have to be demonstrated.have to be demonstrated.

�� Pond should be renovated periodically with removal of Pond should be renovated periodically with removal of sediments from deep areas to reshape bottoms and levees.sediments from deep areas to reshape bottoms and levees.