292 THE FARMER OF TO-MORROW 



ferments of organic matter, or the result of the 

 action of bacteria or fungi, as these agencies 

 are related to plant growth. 



The fact, however, that deleterious sub- 

 stances are to be found in soils that have been 

 cropped set a task for the scientists of the 

 Bureau of Soils. That task was to examine 

 soils, both productive and non-productive, 

 from a wide range of samples and to isolate 

 compounds to be found therein. This is the 

 present task of the Bureau of Soils, and it is 

 a work requiring the best powers of chemists. 

 It is one thing to discover the presence of a 

 complex compound in a given soil or a soil 

 solution; and it is quite another to isolate that 

 compound. Over fifty compounds have been 

 isolated at this writing, and each is being tested 

 separately for its effect on productive soils 

 and its action under different treatments, in- 

 cluding the application of mineral fertilizers. 

 Already there is a wealth of data on the sub- 

 ject, in scientific form, and gradually broad 

 principles of soil fertility are being put for- 

 ward as theories and efforts being made to 

 check these theories by actual practice. 



The most widely found toxin is a compound 

 known technically as dihydroxystearic acid. 



