Impacts of soil acidity in wet zone Sri Lanka

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Possible Impacts of Soil Acidity in Wet Zone, Sri Lanka.

R.M.T.D. Madusanka.AS2012135

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Content.What is a acidic soil?What makes soil acidic?Wet zone soil types.Possible impacts of soil

acidification.1. Nutrient shortage for plants.2. Toxicity of elements for plants.3. Difficulties in weed Control.4. Impact on Aquatic biota.5. Impact on soil fauna (invertebrates).6. Impact on Aquatic biota. 7. Impact on Human health.8. Impact on infrastructure.9. Impact on soil structure.

Some incidents in wet zone.1. Use of NH4(SO4)2 fertilizers in tea

plantations.2. ‘Nilwala Flood Protection Scheme

(NFPS)

3. Rathupaswala water crisis.4. Fluoride and acidity.5. Accumulation of Cadmium in vegetables.6. Adsorption of carbofuran.

Conclusion.References.

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What is an acidic soil?Acid soils have been defined by the soils having pH less than 5.5 in 1:1 soil-water

suspension (USDA)

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Wet zone soil types

Red- yellow podzolic soils.

Immature brown loams.Reddish brown latosolic

soilsBog soils & Acid swamp

soilsAlluvial soils.Regosols.

Source: NRMC, Department of Agriculture

Comprehensive soil map of Sri Lanka

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What makes soil acidic?

Inherent CharacteristicsParent Material.Soil forming environment.

Other FactorsExcessive rainfall.Organic matter decay.Acid rains.Uptake of alkaline

nutrients by plants.Addition of acidic

fertilizers.

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Soil acidity and wet zone.Land use patterns are developed according to the

natural acidic soil.Lowland tropical rain forests.Commercial crop plantations.

(Tea, Rubber, coconut, pineapple)Forest plantations. (Pine, Eucalyptus)

Due to above other factors soil become more acidic. It will cause adverse impacts on human and

environment.

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Possible impacts of soil acidification.

1. Nutrient shortage for plants.2. Toxicity of elements for plants.3. Difficulties in weed Control.4. Impact on Aquatic biota.5. Impact on soil fauna (invertebrates).6. Impact on Aquatic biota. 7. Impact on Human health.8. Impact on infrastructure.9. Impact on soil structure.

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1. Nutrient shortage for plants.

The amount of available Ca , Mg, Mb is lower in acid soils.

Leguminous plants are seriously affected.

N,P, S, Cu & Zn can be unavailable in extream acidic conditions.

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2. Toxicity of elements for plants. Al ToxicityInhibits the root growth of the plants.Inhibit the various physiological process of

processes.Restricts the uptake of Ca+2, P and H2O

Mn–toxicity Necrosis. Fe-toxicity Browning of the leaves.

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3. Difficulties in weed Control.Optimum soil pH for plant growth between pH5.0

and 6.5 pH values below this range causing a significant

reduction in plant viability.Weed invasion in low pH soils is common.

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4. Impact on Soil microbes.

Reduce the microbial populations in the soil.

Decreases the activity of nitrifying bacteria.

Reduce the nodule formation in Leguminous roots.

Slight acidity of soil increases the mycorrhizal occurrence and establishment.

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5. Impact on soil fauna (invertebrates).Reduce the populations of soil fauna(worms ,Termites) in

large changes in pH.Decline the structural quality of the topsoil for plant growth.

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6. Impact on Aquatic biota. Acidic soils cause acidity in waterways.Affect adversely on aquatic flora and fauna.Reduce aquatic biodiversity.

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7. Impact on Human health. Availability and mobility of heavy

metals are increased.

Crop plants can take up those metals readily.

Diseases in humans.Bio accumulate in food chains.

Biological degradation of soil pollutants will decrease in acidic soils-May cause health problems.

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8. Impact on infrastructure.

Negative effect on the stability of concrete.

concrete will deteriorate with the corrosion of the steel,carbonates in the concrete

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9. Impact on soil structure. Organic matter degrades into small fractions &

provide the glue that holds the soil particles together.

Because of soil acidification organic matter degradation is reduced.

Bonding of the soil particles get weaken. Vegetation reduced on the soil. More susceptible to be degraded. Thus the potential for soil losses due to water and

wind erosion are also increased.

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Some Incidents

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Soil acidity impacts in Wet Zone.

1. Reduced yield in tea plantations by NH4(SO4)2 fertilizers.

Continuous use of NH4(SO4)2 resulted in decline in soil pH significantly.

Due to release of higher levels of hydrogen during hydrolysis of NH4(SO4)2. Nutrient toxicities were there to tea plants.Yield of tea leafs decreased.

Effect of Long-term Application of Urea and Sulphate of Ammonia on Soil Acidity, Soil and Plant Sulphur Status, Yield and Black Tea Quality

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2. ‘Nilwala Flood Protection Scheme (NFPS)To protect the Matara town and other villages from floods.Implementation of the project has led to abandoning of About

1,000ha paddy lands.Rice yield were significantly decreased.Soil acidity which was increased by the project.

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2. ‘Nilwala Flood Protection Scheme (NFPS)How NFPS incease the soil acidity of the area?

– Reduce waterlogged conditions,– Potential acid sulphate soils in the area disturbed and exposed. – Pyrite in those PASS oxidized in to sulphuric acids.– The natural neutralization of acidity by the lime (CaCO3)

contained in the sediment of flood water not taken place.This leads to high amounts acidity in the soil.

(Shamshuddin and Auxtero, 1991)

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Soil acidity impacts in Wet Zone.3. Rathupaswala water crisis.

Ground water alleged by the villagers.Studies show that here is no artificial

impact for the groundwater. Soil being naturally acidic in these areas due to the presence of

laterite minerals.Such soils have high concentrations of iron in the ferric form. hydrolysis of those ferric ions makes acidic water.The average pH not harmful.Groundwater samples in the area do not exceed the SLS

standards for drinking water parameters.Effect of Low pH of Groundwater in Rathupaswala Area, Sri Lanka: A Case Study W.A.V Premalal and D.T Jayewardene

http://3.bp.blogspot.com/-TytVAQPoxjg/UjavsWZDBxI/AAAAAAAAEjs/MaAlPr_JlkE/s1600/Rathupaswala+2.JPG

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4. Fluoride and acidity. Both dry and wet zones of Sri Lanka show higher levels of

fluoride in ground water. Mainly present in the dry zone oxidized water with a slightly

alkaline pH. Acidic soil in the wet zone lowers the Fluoride in the ground

water. Relatively less impact from the high Fluoride in drinking

water in wet zone.

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5. Accumulation of Cadmium in vegetables.Soil pH is one of the major variables that controls Cd uptake by

plants (Jakson and Alloway, 1992; and McLaughlin et al., 1997).Cd uptake in various crops increased by ten-fold when pH

between 5 and 7.2 dropped by one unit. (Del Casthilo and Chardon :1995)

The bio concentration in carrot was the highest while other crops as follows,

Carrot > potato > Knol-khol > leek > cabbage >lettuce.

Accumulation of Cadmium in Intensive Vegetable Growing soils in the Up Country

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6. Adsorption of carbofuran.Carbofuran is a broad spectrum insecticide

commonly used in Sri Lanka.Carbofuran is highly soluble in water and therefore

highly mobile in soil.Under strongly acidic conditions, carbofuran

converts to carbofuran phenol, which is strongly bound to soil by forming a complex with organic matter.

Thus dramatically increase their adsorption (Getzin, 1973)

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6. Adsorption of carbofuran.Prevent the ground water pollution from carbofuran.

Percentage of Ground water contamination

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Acidic soil is a consequence of the soil formation process.Wet zone soils of Sri Lanka are acidic in nature.Land use patterns of wet zone have been established as

compatible for the soil acidity.Other than soil formation there are lot of other factors affect for

the soil acidity.Some are anthropogenic factors.Wet zone soils can be more acidic because of those other factors.Several impacts of this situation can be identified.It will affect more adversely on human & Environment if we not

pay enough attention on this .

Conclusion.

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References.Handbook of soils in Sri Lanka by K.A. De Alwis & C.R. Panabokke.

Soils of Ceylon by F. R. moormann and C R. Panäbokke

Soil acidity,Needs your attention by By Chris Gazey

Accumulation of Cadmium in Intensive Vegetable Growing soils in the Up Country - H.M.P.L. Premarathna, CM. Hettiarachchi and S.P. Indraratne

Adsorption and movement of carbofuran in selected soils of Sri Lanka - D. Kumaragamage, D.A.S. Gamage, M.M.S. Samatha and J.I.L.B. Ratnayaka

Groundwater Quality in Different Climatic Zones of Sri Lanka: Focus on the Occurrence of Fluoride - D. T. Jayawardana, H.M.T.G.A. Pitawalab3 and H. Ishigaa

Development of acid sulphate soils in Nilwala flood protection area, Matara, Sri Lanka - G.W.A.R. fernando and R. K. N. suranganee