9 66 



Journal of Agricultural Research 



Vol. VI, No. 24 



and wheat. The effect of manure, however, was not very marked on 

 either, being somewhat more pronounced in the case of timothy. When 

 calcium carbonate was added to the test samples the only noticeable effect 

 of the crop is the low position held by corn and wheat in absence of ma- 

 nure. 



The fact that the addition of calcium carbonate to samples eliminates 

 to a large extent the very large and unmistakable differences, otherwise 

 detectable, raises the question as to which method probably more accu- 

 rately represents field conditions. We shall only call attention to the 

 fact that Lohnis and Green (11) vigorously maintain that the addition of 

 calcium carbonate is essential, while Temple (21) has shown that with 

 organic sources of nitrogen vigorous nitrification is possible even in acid 

 soils. Table VI gives the results of an experiment to determine the effect 

 of varying the quantity of nitrogen and calcium carbonate added. This 

 test was run in order to determine the specific quantity of calcium carbo- 

 nate necessary to insure maximum nitrification and also the correct 

 amount of nitrogen to be added. 



Table VI. — Effect on nitrate formation of varying the quantity of calcium carbonate and 



nitrogen added to soil 



° Nitrogen constan t, calcium carbonate varying. 

 b Calcium carbonate constant, nitrogen varying. 



c Nitrate originally in soil. 



The amount of nitrate formed in seven days is so insignificant that 

 we have left the 7-day data out of consideration. It is interesting, 

 however, to note that those plots which rank high for 28 days also rank 

 high for 7 days. 



A study of the relative position of the different plots at the various 

 analyses shows clearly that the method used is reliable for detecting 



