Granulometric soil fraction

DETERMINING THE TYPE OF SOIL. Every soil cousists of mineral particles of varying sizes. The ratio of the particle sizes present in a soil largely determines the properties of the soil. The granulometric composition (texture) of a soil can he precisely determined hy laboratory tests (sieve and sedimentation analysis). Large particles are determined hy sieving and finer ones by sedimentation. The soil type is apparent from the ratio of the individual granulometric fractions. 

Table 2.8. Particle size classes of soil (granulometric fractions of fine soil).

The main soil parameters governing processes of sorption and desorption of trace elements can be presented as follows (i) pH and Eh values (ii) fine granulometric fraction <0.02 mm (iii) organic matter (iv) oxides and hydroxides of Fe, Mn and Al and (v) microorganisms. 

Values vary mainly according to the content of granulometric fraction, from sandy to clay soils. Values vary for pH ranges low for pH 5-6, and high for pH > 7. 

The relative representation of particular fractions in the fine soil is used for classifying soils and earths based on results of their granulometric analyses. Particular species of soils or earths are classified according to the percentage abundance of one or more grain-size categories. 

---