CHAPTER VIII. 



Toxicity of Fertilizers, 



A review of the numerous agricultural experiments that 

 have been reported since 1902, indicates that Cyanamid is not 

 equally efficient as a fertilizer in all the conditions in which it 

 has been applied. Cases have been noted where there was ap- 

 parently an unfavorable action on germination of seeds, unless 

 the fertilizer were mixed with the soil several days before the 

 seed was sown. It is also said to be poorly adapted for use on 

 acid moor soils or on very poor sand soils of low activity. 

 Various explanations have been given of the cause of these 

 undesirable effects. In some cases the occasional harmful 

 action on germination has been attributed to the evolution of 

 acetylene from a crude lime-nitrogen containing free calcium 

 carbide; in other cases the causticity of the lime has been 

 blamed, but usually the unfavorable action on acid moor soils 

 or very poor sand soils is charged to the formation of dicyan- 

 diamide by the acids in such soils. 



Meaning of "Poison." — It is well to agree at once upon what 

 is meant by the term "toxin" or "poison." Dr. Paul Wagner^ 

 says "poison, as is known, is a very relative idea, for poisons 

 in great dilution are harmless, and non-poisons in great con- 

 centrations are harmful." It is obvious that the term "poison" 

 could be applied to almost any substance if we do not limit the 

 amount which is understood to be used. Unless, therefore, the 

 amount which is said to be toxic is distinctly specified, it is 

 necessary to assume that the amount used is small and 

 popularly regarded as a safe dose. It is also desirable to agree 

 upon the amount of injury that can be sustained before the 

 effect can be pronounced as harmful. Some substances produce 

 temporary exhilaration, followed by serious depression; other 

 substances produce temporary depression, but leave the subject 

 ^ Arbeit, der Deut. Landw. Ges., No. 129, p. 267, 1907. 



