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T17+notes - Saline and Sodic Soils (Topic 17) Approximately...

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Saline and Sodic Soils (Topic 17) Approximately 1/3 of the irrigated lands in the world are adversely affected by salts! Salts affect 25% of the ten million acres of irrigated cropland in California! I. Saline Soil - a soil that contains sufficient soluble salts to impair its productivity. Soluble salts are those salts that are more soluble than gypsum (CaSO 4 ). Defined as soils having an electrical conductivity value >4 dS/m in a saturated soil paste. Equivalent to 2 grams of NaCl per liter of water. II. Sodic (Alkali) Soil - a soil that contains sufficient exchangeable sodium to impair crop productivity. Have an exchangeable-sodium percentage (ESP) > 15% or sodium adsorption ratio (SAR) > 13. ESP = Na 100 SAR = Na . Ca + Mg + K + Na ([Ca + Mg]/2) ½ Exchangeable Cations Saturated-Paste Extract (soluble cations) The exchangeable cations are in equilibrium with the soil solution; therefore, measuring the exchangeable Na percentage gives a good estimate of the amount of Na in the soil solution, which is measured by the SAR. III. Saline/Sodic Soil - contain high concentrations of both soluble salts and sodium which impair productivity. Have both an exchangeable-Na percentage (ESP) > 15% or sodium absorption ratio (SAR) > 13 and an electrical conductivity value >4 dS/m Saline and sodic soils almost always have a high pH. Sodic soils usually have pH >8.5; may be as high at 11-12.
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This note was uploaded on 01/27/2011 for the course SSO 10 taught by Professor Randydahlgren during the Fall '10 term at UC Davis.

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T17+notes - Saline and Sodic Soils (Topic 17) Approximately...

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