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Text № 2: Soils characteristics

The soil of a place owes its characteristics to such things as the parent rock material, climate, topography, and decaying plants and animals. Hundreds of different types of soil result from the interaction of these elements. Any particular soil is unique because of its mix of properties (such as color and texture) and composition (including organic content and the action of soil colloids).

Colloids are small soil particles. Their properties and influences on soil are complex and often important. Soil acidity (or alkalinity), for example, is a result of the alteration and integration of soil colloids. Acid soils are characteristic of cold, moist climates; alkaline soils typically are found in dry areas.

Color is perhaps the most obvious soil property. A dark color usually indicates an abundance of organic materials, and red, the presence of iron compounds. Generally, however, color is a result of the soil-forming processes.

Soil texture, which determines a soil’s ability to retain and transmit water, refers to the proportion of particles of different size in the soil. Sand is the coarsest measure of soil texture, silt is intermediate, and clay is the finest. The U.S. Department of Agriculture has developed a soil classification system that indicates the most important soil types for an area of the country.

Aridisols, found mostly in the Southwest are low in organic content and have little agriculture value. Spodosols generally develop in cool, moist climates, found in northern Florida. Tundra soils, which also have little agricultural valua, are associated with a cold, moist climate such as Alaska. Highland soils, found in West Virginia, Utah, and Alaska, are little developed and agriculturally worthless. Mollisols are grassland soils of the semiarid and subhumid climates of the Central, North Central and Pacific Northwest sections of the country. Alfisols are second only to molisols in agricultural value. They are soils of the mid-latitude forest and the forest-grassland boundaries. Ultisols represent the ultimate stage of weathering and soil formation in the United States

Complete the following sentences

…………………is unique because of its mix of properties and composition.

Colloids are ……………………………………………….

…………………… is a result of the alteration and integration of soil colloids.

Acid soils are ………………………………………………………….

A dark color usually indicates ………………………………………………

Soil texture, which determines ………………………………………………

The U.S. Department of Agriculture has developed……………………….. ………………………………………………

…………………...are low in organic content and have little agriculture value.

Highland soils…………………..are little developed and agriculturally worthless.

Ultisols represent the ultimate stage of………….. and soil formation ……………………….

3. Match the first column with the second.