RELATION OF SOILS TO ELECTRICITY 43 



acids. Alkaline soils have variable tastes according to 

 the prevailing alkaline compound. The taste of a 

 soil frequently reveals a fault, as acfdity or alkalinity. 



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

 sess, to a variable extent, the power of absorbing 

 gases. When decomposing animal or vegetable matter 

 is mixed with soil, the gaseous products given off are 

 absorbed. Absorption is the result of both chemical 

 and physical action. The chemical changes which 

 occur, as the fixation 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 has the power of absorbing large amounts. 

 This action is similar to that of a charcoal filter in 

 removing noxious gases from water. 



45. Relation of Soils to Electricity. There is al- 

 ways a certain amount of electricity in both the soil 

 and the air. The part which it takes in plant growth 

 is not well understood. The action of a strong cur- 

 rent upon the soil undoubtedly results in a change in 

 chemical composition, but in order to change the 

 composition of the soil so as to render the unavailable 

 plant food available, would require a current destruc- 

 tive to vegetation. When plants are subjected to too 

 strong a current of electricity, they wilt and have all 

 of the after-effects of frost. A feeble current has either 

 an indifferent or a slightly beneficial effect upon crop 

 growth. The slightly beneficial action is not sufficient, 

 however, to warrant its use as yet in general crop pro- 

 duction on account of cost. The action of a weak 



