CLASSIFICATION OF SOILS. 33 



Soils may also be classified according to the rapidity with 

 which the humus is decomposed, as : — 



Very active soils : Such as dry porous sand and calcareous 

 soils, in which the decomposition of humus is excessively 

 quick. 



Active soils : Such as moderately moist loamy sand, sandy 

 loam and loamy marl, in which the decomposition of 

 humus proceeds at a rate favourable for growth, without 

 actually exhausting the supply of organic matter. 



Moderately active soils : Such as stiff clay, wet soil, heather 

 soil, where the decomposition is too slow for a healthy 

 development of most plants. 



Inactive soils : Such as peat soil, shifting sand, etc., in 

 which, either from excess of moisture or absence of 

 humus and rest, little or no decomposition takes place. 



b. Classificafion accordinij to Physiral Properties. 



Of the various physical properties the degrees of consistency 

 and of moisture are of special importance in sylviculture. 

 According to consistency, soils may be classified in the following 

 manner : — 



Light soils : All soils which contain much coarse grained 



sand or much humus. 

 Loose soils : Such as peat and moor soils, which are elastic 

 and swell during rainy weather ; they are also much 

 lifted by frost. 

 Binding soils : Soils of moderate cohesion, such as fine 

 grained loamy sands, coarser grained sandy loams, 

 calcareous soils, especially marl. 

 Heavy soils : Such as fine grained loam, clay with coarse 



sand. 

 Stif soils : Such as clay with a limited quantity of fine 



grained sand. 

 In classifying soils according to the degree of moisture, a 

 distinction must be made between the average degree of 

 s. D 



