Reclaiming Slick-Spots and Salty Soil

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Soils, which do not respond to normal management practices, are called “problem soils.” Acid soils are often considered problem soils for this reason. Correction of acid soils by liming is discussed in OCES Facts 2229. Two other kinds of problem soils are salty (saline) soils and slick-spot (alkali or sodic) soils. A third kind of problem soil often develops from slick-spots when they are poorly managed. This is the saline-alkali soil, which results when slick-spots become salty. Although all problem soils may be identified with poor crop production, these soils have other similarities and differences, which are important to know before attempting to improve or reclaim them. Saline soils are soils, which contain at least 2,600 ppm soluable salts in the solution from a soil saturated with water. The salt content is estimated by laboratory measurement of how well the soil water conducts electricity, and saline soils are those with an electrical conductivity of 4,000 micromohs/ cm (equivalent to 2,600 ppm soluble salts). This level of salts is great enough to reduce production of salt-sensitive crops. Alkali soils are soils, which contain enough sodium (Na) to cause 15 percent of the cation exchange sites to be occupied by sodium. Sodium in the soil prevents clay particles (and other very small, collodial sized particles such as humus) from coming together and forming large soil aggregates. When soil contains 15 percent or more exchangeable sodium most of the clay and humus particles arc unattached or dispersed. These soils commonly have a pH of 8.5 or above (alkali). Some Oklahoma soils become dispersed when the exchangeable sodium is as low as 7 percent. Productive agricultural soils often have less than 1 percent exchangeable sodium. …. The excess sodium in alkali soils does not allow soil particles to easily attach to one another. As a result alkali soil is dispersed, and not friable and mellow like saline soil. Instead, alkali soil is greasy when wet (“slick-spot”), especially if it is fine textured, and often very hard when dry. This poor physical condition makes these soils difficult to manage. They are often either too wet or too dry for tillage…. Gypsum is the most effective soil amendment for removing sodium from the soil particles. Gypsum is a slightly soluble salt of calcium and sulfate. This means that gypsum will react in the soil slowly, but for a long time….

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