Soil Porosity: Sand, Silt, and Clay
Soil texture is determined by the relative proportion of sand, silt, clay and small rocks (pebbles) found in a given sample. Sand is gritty to the touch and the individual grains or particles can be seen with the naked eye. It is the largest of the three size classes of soil particles. Silt is smooth and slippery to the touch when wet and the individual particles are much smaller than those of sand. These individual particles can only be seen with the aid of a microscope. Clay is sticky and plastic-like to handle when wet. The individual particles are extremely small and can only be seen with the aid of an electron microscope.
Soils are made of particles of different types and sizes. The space between particles is called pore space. Pore space determines the amount of water that a given volume of soil can hold. Porosity refers to how many pores, or holes, a soil has. The porosity of a soil is expressed as a percentage of the total volume of the soil material. Porosity is an important measurement in areas where drinking water is provided by groundwater reserves.
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