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Proceedings of Indiana Academy of Science 



The oat soil was highest of all the soils on April 21, but went down 

 in nitrate content during May and June. During July there was an 

 increase, but compared with wheat and corn the nitrate content was 

 low all season. 



The timothy and clover plots showed a low nitrate content through- 

 out the season, being very similar in this respect to the oat plots. The 

 highest point of 8 parts per million was reached on August 12. 



The curves on the graph of the clover and timothy and oat plots 

 only represent the averages of two plots, while the ones for wheat and 

 corn represent the average of six and five, respectively; hence the two 

 former curves are probably not as reliable for those particular crops as 

 are the ones of wheat and corn. 



The following general conclusions can be drawn: 



(1) Corn soil shows higher nitrifying power than do wheat, oat 

 or clover and timothy soils. 



(2) Wheat soil shows a higher nitrifying power than oat or clover 

 and timothy soils. 



(3) Clover and timothy and oats seem to have a depressing effect 

 on nitrification processes in the soil. 



TABLE VII.^AVERAGE NITRATE CONTENT 



