Basic physical characteristics of the soil

The specific mass, expressed as a ratio of the mass of the solid phase of the soil to the mass of the same volume of water at 4°C. It can also be expressed as a mass of one cm of non-porous soil material in g (g cm ). The soil specific mass depends on specific masses of the main mineral components and on the amount of the humus. The specific mass of a soil poor in humus is thus close to that of silica, feldspar and clay minerals and its value is about 2.6 to 2.7 g cm. Increased humus contents result in a decrease of the soil specific mass to about 2.4 to 2.5 g cm the presence of minerals containing iron can increase the specific mass above 2.7 g cm .  

The bulk density is a mass of a unit volume of soil 1 cm ) in the natural spatial arrangement of the soil, expressed in g cm. It depends on the specific mass and on the porosity, i.e. on the air and water content in the soil. Thus, it is possible to consider the non-reduced bulk density, corresponding to a certain soil volume including its actual moisture and reduced bulk density, which is determined after drying the soil sample at 105°C. 

2 g cm (peats) and 1.8 g cm (solidified earths). Most typically it is, however, between 1.20 and 1.60 g cm. The bulk density usually increases with increasing depth of the profile. 

The porosity is a measure of the total number of pores contained in a certain soil volume and it is expressed as a percentage. It is considered as the most important characteristic among the basic physical quantities. It is calculated from the formula 

The porosity value is also very variable, in medium-heavy structural soils it is between 40 and 50%, in lighter sandy and dense solidified soils it decreases to 25-30% in soils rich in humus and in peat soils it may be as high as 90%. The porosity value depends on the mutual arrangement of soil particles and aggregates affecting the total volume of pores, and their shape, size and situation. 

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