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Salinization: Causes, Classification, and Control Measures

This research article discusses the causes, classification, and control measures of salt-affected soils (SAS). It provides an overview of salt-affected soils, including saline, alkaline, sodic, maritime, and continental salt-affected soils. The article also examines the preconditions of salt accumulation and the practical classification of salt-affected soils. Furthermore, it explores the effects of salts on crop yields and presents the salt balance and secondary salinization. Finally, it discusses the possibilities of salinity control, including leaching and drainage, reversible processes, prevention, and saline seep-control.

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Salinization: Causes, Classification, and Control Measures

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  1. SALINIZATION VÁRALLYAY György Research Institute for Soil Science and Agricultural Chemistry Hungarian Academy of Sciences, Hungary

  2. IntroductionSalt-affected soils (SAS) are widespread all over the world. In addition to the constraints of scarcity or too much water in these soils, the basic fertility and land use capability of these soils is directly related to a few chemical properties, such as salinity and sodicity (Szabolcs, 1991).

  3. Definitions • Salt affected soils: formed under the influence of soluble salts • Saline soils: soils with high amount of water soluble salts • Alkaline soils: all soils having alkaline reaction • Alkali soils: soils having strongly alkaline reaction and high amount of Na+ (Na- salts, exch. Na) • Sodic soils: Having high amount of Na2CO3 (Na2CO3) • Maritime salt affected soils: Soils formed under the direct/indirect influence of the presence of the sea. • Continental salt affected soils: Soils formed without the direct/indirect influence of the presence of the sea.

  4. The preconditions of salt accumulation 1. • Salt resources • Local weathering • Surface water • Subsurface waters • Human activities • Transporting agents • Wind, water Horizontal transportation: large watershed with small accumulation area Vertical transportation: geological strata to accumulation horizon

  5. The preconditions of salt accumulation 2. • Driving force for solution movement • Relief • Hydraulic gradient • Negative water balance • Limited drainage conditions • Poor vertical drainage of soil profile • Poor horizontal drainage of the area

  6. Classification of Treitz, 1924 of the saline and alkali soils of Hungary 1. Saline soils yielding nitrates 2. Soils yielding soda (temporary salt efflorescences) 3. Alkali soils (there are no salt efflorescences) A. Alkali soils on sand B. Alkali soils on clayey substances -alkali soil of plateaus -alkali soil without CaCO3 -alkali soil with CaCO3 -alkali soil in depressions

  7. Practical classification of Hayward and Wadleigh, 1949 Soil ECe ESP pH Non saline <4mS/cm <15 <8.5 Alkali(=sodic) <4mS/cm >15 >8.5 Alkali(=sodic) saline >4mS/cm >15 <8.5 Saline >4mS/cm <15 <8.5

  8. ECe (electrical conductivity of soil saturation extract) and the effects of salts on the yield of field crops according to the general scheme of Richards (1954). ECe (mS/cm) class Effect on plants ------------------------------------------------------------------------------------------------ 0-2 Salinity effects mostly negligible 2-4 Yields of very sensitive crops may be restricted 4-8 Yields of many crops restricted 8-16 Only tolerant crops yield satisfactorily > 16 Only a few very tolerant crops yield satisfactorily -----------------------------------------------------------------------------------------------------

  9. Salt balances Total: Qt (ECSP, ECSE, SP) Profile: Qt / fd (for layers or horizons) Ions: Qi t: day/week/month/year…. Season vegetation period..etc Reason(s) factorial salt balances

  10. Solonchaks

  11. Solonetz soils

  12. Salt-affected soils in Europe

  13. Secondary salinization 1.

  14. Secondary salinization 2.

  15. Possibilities of salinity control • Leaching and drainage • Preconditions • Reversible processes (Low Na+ saturation, moderate physical deterioration) • Adequate amount of good-quality water • Good vertical drainage of the soil profile (Light texture, good hydraulic conductivity, Cl-SO4 type salinization, low alkalinity, low ESP) • Good horizontal drainage of the area • frost-free period after the vegetation season • Drain water reservior • Prevention • Quality control of irrigation water • Stabilization of ground water table • Prevention of rise • Lowering • Saline seep-control

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