Chestnut Soils

a soil type occurring in arid steppes. The soils cover large areas of Turkey, Mongolia, northern China, the United States, and Argentina. In the USSR chestnut soils are widely found in the Kazakh SSR, in the southern part of the Ukrainian and Moldavian SSR’s, in the Northern Caucasus, in the southern part of Western Siberia (Kulunda), and the arid parts of the Volga Region. Isolated pockets of chestnut soils are encountered in central Siberia (the Minusinsk Depression and the Tuva Basin) and in Transbaikalia. In all, chestnut soils cover about 107 million hectares in the USSR.

The climate in the chestnut soil zone is continental and arid. The genetic and zonal properties of chestnut soils include deficient drainage, a shortage of productive moisture, alkalinity, and soil heterogeneity. The parent material consists chiefly of calcareous deposits with a predominance of loess like loams, calcareous sandy loams, loesses, calcareous sands, sandy loams, and alluvium. Chestnut soils contain carbonates and, in most cases, gypsum in the lower part of the profile. The presence of readily soluble salts causes the alkalinity of chestnut soils. The upper (humus) horizon has a chestnut color to a depth of 13– cm, and its structure is cloddy-granular or cloddy-silty. The absorbing complex is largely saturated with calcium (as much as 70– percent) and magnesium (15– percent). Nonsolonetzic chestnut soils contain up to 0.2–.3 percent water-soluble salts, and solonetzic soils contain 0.2–.3 percent in the upper portion and 0.5– percent at a depth of 120– cm.

Chestnut soils are divided into three subtypes: dark chestnut, chestnut, and light chestnut, based on differences in the salt profile, humus content and composition, and depth of occurrence of calcareous deposits, gypsum, and readily soluble salts. The humus content depends on mechanical composition. The dark chestnut clayey and loamy soils contain 3.5–.5 percent humus and the light loamy and sandy loamy soils 2.5– percent; in the chestnut soils, the humus content is 2.5–.5 and 2.0–.5 percent, respectively; and in the light chestnut soils it is 1.5–.5 and 1.2–.8 percent, respectively.

In their mechanical composition, chestnut soils are subdivided into clayey, heavy loamy, medium loamy, light loamy, sandy loamy, and sandy soils. The solonetzic chestnut soils are distinguished by poor physical properties, such as a rapidly decomposing structure and low porosity and permeability. The reaction of chestnut soils is usually neutral or slightly base (pH 7.0–.5). Such crops as wheat, barley, oats, millet, corn, and sunflowers are grown on dark chestnut and chestnut soils. On light chestnut soils, used chiefly for pastures and hayfields, farming is possible with irrigation.