SOIL FERTILITY AND 

 PERMANENT AGRICULTURE 



PART I 

 SCIENCE AND SOIL 



CHAPTER I 



FOUNDATION FACTS AND PRINCIPLES 



Science. Science means knowledge, nothing more and nothing 

 less. It does not mean theory unsupported by fact. To plow 

 the land and plant the seed and cultivate the crop is art, or prac- 

 tice. To know what the soil and air contain and what the crop 

 requires is science. If 10 cents are taken from 70 cents, only 60 

 cents remain. This is science, knowledge, fact, and not mere 

 opinion. In the study of soil fertility we must make large use of 

 two well-established exact sciences, mathematics and chemistry. 

 Several other sciences furnish much exact data, but in some 

 branches the data thus far secured are not sufficient to fully reveal 

 the controlling facts and principles. 



Chemistry. Chemistry is the science which deals with the com- 

 position of matter. All material things are composed of about 

 eighty primary substances, called elements, which may exist sepa- 

 rately or in various combinations, called compounds. About forty 

 of the elements are more or less common, the others being rare 

 elements. Air and soil and plants and animals contain less than 

 twenty elements that are of interest to agriculture; while only 

 ten different elements are known to be essential for the making of 

 agricultural plants. (One other element, chlorin, may be essen- 

 tial, but, if so, only in minute quantity.) 



