SET #7...SET #7 • Soils in arid and semi-arid regions. Redistribution of calcium carbonate and...
Transcript of SET #7...SET #7 • Soils in arid and semi-arid regions. Redistribution of calcium carbonate and...
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SET #7• Soils in arid and semi-arid regions. Redistribution of
calcium carbonate and gypsum is an important mechanism of horizon differentiation in soils in the dry zone.
• Soluble salts may accumulate at some depth or, in areas with shallow ground-water, near the soil surface. – SOLONCHAKS with a high content of soluble salts,– SOLONETZ with a high percentage of adsorbed sodium
ions,– GYPSISOLS with a horizon of secondary gypsum
enrichment,– DURISOLS with a layer or nodules of soil material that is
cemented by silica, and– CALCISOLS with secondary carbonate enrichment.
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SolonchaksSolonchaks (SC)(SC)
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Solonchaks (SC)from R. sol, salt, and R. chak, salty area
Soils that have a high concentration of `solublesalts‘ at some time in the year. Solonchaks occur mainly in arid and semi-arid climatic zones and to coastal regions in all climates.
Often in seasonally or permanently waterloggedareas with grasses and/or halophytic herbs, and in poorly managed irrigation areas.
Common international names:`saline soils' and `salt-affected soils'.
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Solonchaks
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16° 17° 18° 19° 20° 21° 22° 23°
22° 23°21°20°19°18°17°16°
48°48°
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BUDAPEST
B a l a t
o n
SALT AFFECTED SOILS IN HUNGARY
Chloride and/or sulpha te solonchakSodic solonchakCalcareous meadow s olone tzCalcareous meadow s olone tz turning into steppe formationCalcareous solone tzic meadow soilMeadow solonetzMeadow solonetz turning into s teppe formationSolone tzic meadow soilChernozem and meadow chernozem s alty in deeper layersPotentia l s a lt affected soils
Compiled in RISSAC GIS Labin 1996 based on Szabolcs, Várallyay and Mélyvölgyi (1974) Hungarian Unified Map Projection System
0 50 100 150 Kilometers
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Definition of Solonchaks
Soils1. having a salic horizon starting within 50 cm from the soil surface; and
2. lacking diagnostic horizons other than a histic, mollic, ochric, takyric, yermic,calcic, cambic, duric, gypsic or vertic horizon.
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Salic horizonmust, throughout its depth:• Have an Electrical Conductivity (ECe) of the
saturation extract of more than 15 dS m-1 at 25oC at some time of the year; or an ECe of more than 8 dS m-1 at 25oC if the pH(H2O) of the saturation extract exceeds 8.5
• have a product of thickness (in cm) times salt percentage of 60 or more; and
• have a thickness of 15 cm or more.
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Genesis of SolonchaksThe most extensive occurrences of Solonchaks are in inland areas where evapotranspiration isconsiderably greater than precipitation, at least during a greater part of the year.
Salts dissolved in the soil moisture remain behind after evaporation / transpiration of the water and accumulate- at the surface of the soil (`external Solonchaks'), or
- at some depth (`internal Solonchaks').
P
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Composition of accumulated salts
Having in a 1:1 aqueous solution:
a soil-pH > 8.5 and HCO3 > SO4 > Cl : Carbonatic
SO4 > HCO3 > Cl : Sulphatic
Cl > SO4 > HCO3 : Chloridic
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HisticGelicVerticGleyicMollicGypsicDuricCalcicPetrosalicHypersalicStagnicTakyricYermicAridicHyperochricAcericChloridicSulphaticCarbonaticSodicHaplic
SOLONCHAKS
Salic horizon
ESP > 15
pH > 9HCO3 > SO4 > Cl
gleyic
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HisticGelicVerticGleyicMollicGypsicDuricCalcicPetrosalicHypersalicStagnicTakyricYermicAridicHyperochricAcericChloridicSulphaticCarbonaticSodicHaplic
SOLONCHAKS
Carbonati-gleyic Solonchak (Sodic)
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`Puffed SolonchakSolonchak with fluctuations in the morphology of salts
High concentration of Sodium sulphate
At night: temperature at the soil surface is lowair humidity is highneedle-shaped mirabilite crystals(Na2SO4).10H2O) The push fine soil aggregates apart
↓↑At day time: dry, hot
mirabilite convert to water-free thenardite(Na2SO4)Soft and fluffy surface
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End of Solonchaks