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Understanding Solonetz Soils: Definition, Characteristics, and Importance

Solonetz soils, also known as alkali or sodic soils, feature a dense, clay illuviation horizon with high sodium or magnesium ions. Revealing their natric horizon within 100 cm, these soils exhibit specific texture, clay content, and structural criteria. The diagnostic features of Solonetz soils hold significance for soil diagnostics, correlation, and preservation.

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Understanding Solonetz Soils: Definition, Characteristics, and Importance

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  1. Solonetz (SN)(from R. sol, salt, and etz, strongly expressed) Soils with a dense, strongly structured, clay illuviation horizon that has a highproportion of adsorbed sodium and/or magnesium ions. Internationally used terms: `alkali soils' and `sodic soils'

  2. Solonetz soils

  3. Definition of Solonetz Soils having a natric horizon within 100 cm from the soil surface.

  4. Natric horizon • A natric horizon must: • 1. have sandy loam or finer texture and at least 8 percent clay in the fine earth fraction; and • 2. have more total clay than an overlying coarser textured horizon (exclusive of differences which result from a litholo­gical discontinuity only) such that: • - if the overlying horizon has less than 15 percent total clay in the fine earth fraction, the natric horizon must contain at least 3 percent more clay; or • - if the overlying horizon has 15 percent or more and less than 40 percent total clay in the fine earth fraction, the ratio of clay in the natric horizon to that of the overly­ing horizon must be 1.2 or greater; or • - if the overlying horizon has 40 percent or more total clay in the fine earth fraction, the natric horizon must contain at least 8 percent more clay; and • 3. have a distinct increase in clay content within a vertical distance of 30 cm if the natric horizon is formed by clay illuviation. Else, the increase in clay content between the overlying and the natric horizon must be reached within a vertical distance of 15 cm; and • 4. have no rock structure in at least half the volume of the horizon; and • 5. have columnar or prismatic structure in some part of the horizon, or a blocky structure with tongues of an eluvial horizon in which there are uncoated silt or sand grains, extending more than 2.5 cm into the horizon; and • 6. have an exchangeable sodium percentage (ESP[1]) greater than 15 within the upper 40 cm of the horizon, or more exchangeable magnesium plus sodium than calcium plus exchange acidity (at pH 8.2) within the same depth if the ESP exceeds 15 percent in some sub-horizon within 200 cm from the surface of the soil; and • 7. have a thickness of at least one tenth of the sum of the thickness of all overlying horizons, with a minimum value of 7.5 cm. • [1] ESP = exchangeable Na x 100 / CEC.

  5. Natric horizon 1. have sandy loam or finer textureand 2. have more total clay than an overlying coarser textured horizon and 3. have a distinct increase in clay content within a vertical distance … and 4. have no rock structure in at least half the volume of the horizon; and 5. have columnar or prismatic….. and 6. have an exchangeable sodium percentage (ESP) greater than 15 within the upper 40 cm of the horizon, or more exchangeable magnesium plus sodium than calcium plus exchange acidity (at pH 8.2) within the same depth if the ESP exceeds 15 percent in some sub-horizon within 200 cm from the surface of the soil; and 7. have a thickness of at least one tenth of the sum of the thickness of all overlying horizons, with a minimum value of 7.5 cm. ESP = exchangeable Na x 100 / CEC

  6. Natric horizon 1. have sandy loam or finer textureand 2. have more total clay than an overlying and 3. have a distinct increase in clay … and 4. have no rock structure; and 5. have columnar or prismatic….. and 6. have an exchangeable sodium percentage (ESP) greater than 15 within the upper 40 cm of the horizon, or…and 7. have a thickness with a minimum value of 7.5 cm.

  7. Most common units: Vertic*, Salic*, Gleyic*, Mollic*, Alcalic*, Gypsic*, Duric*, Calcic*, Stagnic*, Humic*, Albic*, Takyric*, Yermic*, Aridic*, Magnesic*, Haplic*. Association with other soils: Natric and sodic soils of other great groups

  8. Solonetz Ochric Natric Stagnic Calcic Vertic Salic Gleyic Mollic Gypsic Duric Calcic Stagnic Humic Albic Takyric Yermic Aridic Magnesic Haplic gleyic

  9. Solonetz Vertic Salic Gleyic Mollic Gypsic Duric Calcic Stagnic Humic Albic Takyric Yermic Aridic Magnesic Haplic Calci-Gleyic Solonetz (Stagnic)

  10. Importance of diagnostics in correlation Natraqualf GleyicSolonetz ochric ochric natric natric loess loess National priorities can be preserved

  11. 1 1 1 1 3 3 2 2 3 3 4 4 4 4

  12. End of Solonetz

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