8 SOILS AND FERTILIZERS 



prove that nitrification was the result of the workings 

 of living organisms. These have since been isolated 

 and studied by Warington and Winogradsky. 



During recent years the agricultural experiment 

 stations of this and other countries have made soils a 

 prominent feature of their work ; some of the results 

 obtained are noted in the following chapters. Our 

 knowledge regarding the chemistry, physics, geology 

 and bacteriology of soils is still far from complete, 

 bat many facts have been discovered which are of the 

 greatest value to the practical farmer. The literature 

 relating to soils and fertilizers has become very exten- 

 sive, and in the classification of agricultural subjects 

 for study, soil forms one of the main divisions of 

 agronomy. 



In soil investigations it has frequently happened, 

 owing to imperfect interpretation of results and to 

 the presence of many modifying influences, that the 

 conclusions of one investigator appear to be directly 

 contradictory to those of another. This is well 

 illustrated in the investigations relating to the 

 assimilation of free atmospheric nitrogen, where 

 seemingly opposite conclusions now form a complete 

 theory. 



A scientific study of soils is valuable from an edu- 

 cational point of view, as well as because the practical 

 knowledge obtained can be utilized in the production 

 of crops. In the cultivation of the soil it should be the 

 aim to conserve the fertility and to produce as large 

 yields as possible of the most valuable crops. This 

 can be accomplished only as the result of a thorough 

 knowledge of soils and fertilizers. 



