284 Proceedings of Indiana Academy of Science 
PEATIONS LEP FILA 
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Later investigations have brought out many of the factors influ- 
encing the process in the soil. 
In 1893 Deherain,’ and later in 1901 King and Whitson,’ compared 
soil stirred and soil not stirred, and found that nitrates were produced 
more rapidly in the stirred soils. This they attributed to better aera- 
tion. 
In experiments conducted in 1907, Voorhees, Lipman and Brown,” 
found decomposition slower under oats and clover than in bare soils. 
In later studies King and Whitson,’ found differences in the nitrates 
produced under the same crop in different plots and under different 
crops. Although the differences in some cases were quite considerable, 
they did not feel justified in drawing any conclusions relative to the 
effect of certain crops. 
Later Deherain,’ claimed that if soil moisture was not lacking, and 
if the loss of nitrate nitrogen in the drainage water and the nitrogen 
in the crop were added, similar nitrification would be found in fallow 
and in cropped lands. This statement, however, has been severely 
criticized and with respect to the question of nitrification under legumes, 
a proposition which has received considerable attention, experiments 
have shown that sometimes more and sometimes less nitrate nitrogen 
may be found than under grain crops.. Among the more recent experi- 
ments are those performed by Brown’ of Iowa which shows the follow- 
ing: 
1. “The rotation of crops brought about a greater nitrifying power 
in soils than continuous cropping either to corn or to clover. 
2. A soil under a three-year rotation of corn, oats and clover pos- 
sessed a greater nitrifying power than one under a two-year rotation 
