Preface. 



It has long been the custom to regard soil chemistry from one 

 of two diametrically opposed points of view. Either, it has been 

 considered extremely simple, or complex and hopelessly difficult. 

 In either case the impression has generally prevailed that 

 practical work in soil chemistry consists in treating the soil 

 with some solvent or other and analyzing the resulting solution 

 for "available" plant food elements; in other words, that the 

 chemist's role in soil studies is merely that of an analyst. 



Soil chemistry is complex, but not by any means hopelessly so. 

 Unfortunately, the complexity of most of the problems presented 

 has deterred the student of pure chemistry from attacking them, 

 and because they do not offer any material pecuniary rewards, 

 they have not appealed strongly to the investigator in applied 

 chemistry. Investigations in soil chemistry, for their own sake, 

 or for the sole purpose of increasing the sum total of human 

 knowledge concerning the phenomena taking place in the soil, 

 have been comparatively rare. The subject has generally been 

 regarded from the analytical point of view and as incidental to 

 agronomic studies. 



One purpose of this little book is to show the investigator in 

 chemistry who is not limited by the condition that his work must 

 bring some personal financial return, that the soil and its prob- 

 lems offer a field for his efforts quite worthy of ranking along- 

 side the most interesting branches of pure chemistry, as well as 

 being of the very highest importance to the development of the 

 welfare of the human race. Another purpose is to point out 

 the line of attack upon the problems of soil chemistry which at 

 this time offers the largest opportunity for results. In how far 

 the details of the story in the following pages are correct, time 

 with its further investigations will tell. In a sense, the correct- 

 ness of the details is of secondary importance. It is of the first 

 importance, however, that there should be a general recognition 

 that soil phenomena are essentially dynamic in character, and 

 that the investigation of the properties of the soil solution and 

 its relation to crop production is a procedure certain to yield 

 results of positive value. 



