THE TOXIN THEORY OF INFERTILITY 



261 



The Toxin Theory of Infertility.^ — ^A few investigators are 

 supporting the theory that infertility of many soils is due largely 

 to the presence of certain poisons or toxins which probably owe 

 their origin to plant-root excretions and to decomposition of soil 

 organic matter. The supporters of this theory maintain that the 

 beneficial effect of fertilizers on poor soils is due to the power of 

 the fertilizers to neutralize or counteract the effect of these toxins, 

 rather than to the available plant-food elements added. 



Fig. 167. — Diseased wheat on wheat-sick soils. Dead roots and blighted leaves. 



40 years in wheat. (North Dakota Station.) 



Soil 



They have presented data endeavoring to show that increasing 

 the amount of available plant-food elements through the use of 

 fertilizei*s has practically nothing to do with the maintenance of 

 soil fertility. This theory, however, has been accepted by only a 

 few, since other investigators ha^e shown definitely that soils 

 which produce large yields contain more available plant-food 

 material than do soils that produce low jdelds. Furthermore, 

 numerous field tests have demonstrated that crops on poor land 

 are directly benefited by fertilizers and lime. 



Nevertheless, it is conceded that some toxins do form in soils 



3 Conclusions drawn by Whitney and Cameron of the Bureau of Soils, 

 United States Department of Agriculture. 



