Soil Salinity

Soil Salinity

Increased amount of soluble salt in soil solution

in soil

Soil Salinity Affects: Soil physico-chemical properties Biological soil properties Soil fertility

Soil Salinity

Source of Salinity Primary minerals From deeper soil layers (soil solution)

evaporation > rainfall Irrigation water Coastal soils High doses of chemical fertilizers

Soil Salinity

Determined Ions

Anions – SO42-, Cl-, CO3

2-,NO3-, PO4

3-

Cations – Ca2+, Mg2+, K+, Na+; Al3+, Fe3+

Methods of DeterminationTotal salinity Measurement of electrical resistance Measurement of electrical conductivity

Determination of single ions by titration by advanced methods

Methodology

Quantitative determination of total salinity by soil ethanol extract conductivity measurement

Weight 10 g of soil into plastic flask Add 50 ml of 50% ethanol Let shake for 45 min Filtration of soil suspension Measurement of soil ethanol extract conductivity

by conductometer

Evaluation – conductivity of ethanol extract

< 30 µS.cm-l : most agricultural soils, with normal (lower) intensity of fertilization and liming, with a minimum load of soil salts

30 - 60 µS.cm-l : mineral-rich soil with moderate to high intensity fertilizing and liming, without the negative effects of salinity

60 - 120 µS.cm-l: soils with a high degree of fertilization and liming in mineral-rich substrates (as well as highly acidic soil) with an increased load of soil salts (in loamy, clay soils without adverse effects)

> 120 µS.cm-l : high load of soil salts with possible negative effects on plant growth and development (especially in drought conditions).

Evaluation – conductivity of water extract

0-2 mS.cm-l :

negligible effect 2-4 mS.cm-l :

highly sensitive plants may be affected (bean, lime) 4-8 mS.cm-l:

most of sensitive plants can give lower yields 8-16 mS.cm-l :

only resistant plants gives satisfactory yields (wheat, olives)

> 16 mS.cm-l :

only highly tolerant plants give satisfactory yields (barley, sugar beet, some palms)

Evaluation – conductivity of water extract

0-4 mS.cm-l :

No salinization 4-8 mS.cm-l :

Slight salinization 8 -15 mS.cm-l:

Moderate salinization > 15 mS.cm-l :

Strong salinization

MethodologyQuantitative determination of selected ions

1. Weight 10 g of soil 2. Add 50 ml of overcooked distilled water3. Let shake for 3 min4. Filtrate the soil suspension into the beaker

CO32- : Move 2-3 ml of filtrate into test tube, add one drop of

phenolphtalein, bring to a boil over burner Pink colour → the carbonates are present

HCO3-: After the pink colour disappearance add one drop of

methyl orange (into the same extract) Yellow colour → hydrogen carbonates are present

MethodologyQuantitative determination of selected ions

Cl-: Move 2-3 ml of filtrate into test tube, add 3-5 drops of HNO3

and 3-5 drops of 5% AgNO3

White precipitate → chlorides are present

SO42-: Move 2-3 ml of filtrate into test tube, add 3 drops of 10%

HCl and 3-5 drops of 10% BaCl2

White precipitate → sulphates are present (insoluble BaSO4 )