Soil Texture

A soil is generally characterised by the size of its particles. A clayey soil may thus be described as fine, sandy as coarse, while silt is an intermediate (Fig. 6.1). The standard unit for the measurement of soil particles is the millimetre, but a smaller unit is the micron (1 micron = 0.001 mm), which is applicable, for instance, to the measurement of soil colloids. In sandy soil, the size of individual grains varies between 0.05 and 0.2 mm which are visible to the naked eye. The individual grains of clayey soil are 0.002 mm in diameter. Silty soil is finer than sand but coarser than clay. Its particles are found to have a diameter between

0.02 and 0.002 mm.