1914] Lipman-Burgess: Amtyionification and Nitrification in Soils 131 



fact, however, the toxicity of no one of them is very marked. 

 AA^hile this latter observation is in accord with the findings of 

 J. G. Lipman above referred to, the former result is entirely at 

 variance with them. It is significant to remark in this connec- 

 tion, however, that the agreement between duplicate determina- 

 tions was on the whole much better in our experiments than in 

 those carried out at the New Jersey Experiment Station and 

 should therefore render our results more trustworthy. Indeed, 

 as the authors of the New Jersey bulletin state, for their work 

 "there is not sufficient evidence upon which to base conclusions." 

 Comparing the relative toxicities of the salts tested by us it 

 would appear that copper is the most toxic, zinc the next, lead 

 the next, and iron the least toxic of the four sulfates. This 

 assertion is based on the fact that at the highest concentrations 

 at which it was used, copper depresses ammonification by about 



