46 SOILS AND FERTILIZERS 



43. Odor and Taste of Soils. — Soils containing 

 liberal amounts of organic matter have character- 

 istic odors. The odoriferous properties of a soil are 

 due to the presence of aromatic bodies produced by 

 the decomposition of organic matter. In cultivated 

 soils these bodies have a neutral reaction. Poorly 

 drained peaty soils give off volatile acid compounds 

 when dried. The amount of aromatic compounds in 

 soils is very small. 



The taste of soils varies with the chemical compo- 

 sition. Poorly drained peaty soils usually have a 

 slightly sour taste, due to the presence of organic 

 acids. Alkaline soils have variable tastes according 

 to the prevailing alkaline compound. The taste of 

 a soil frequently reveals a fault, as acidity or alka- 

 limetry. 



44. Power of Soils to Absorb Gases. — All soils pos- 

 sess, to a variable extent, the physical power of absorb- 

 ing gases. When decomposing animal or vegetable 

 matter is mixed with the soil the gaseous products 

 given off are absorbed. The absorption is both a 

 chemical and a physical action. The chemical 

 changes which occur, as the absorption of ammonia, 

 are considered in the chapter on fixation. The organic 

 matter of the soil is the principal agent in the physical 

 absorption of gases; peat, for example, has the power 

 of absorbing large amounts. This action is similar 

 to that of a charcoal filter in removing noxious 

 gases from water. 



