286 Proceedings of Indiana Academy of Science 
possibly the presence of toxic substances. However, the last named fac- 
tor is probably of very little importance. The effect of these differences 
can only be estimated in comparing plots. 
The nitrate content of the fresh samples is taken as an indication 
of the surplus of the amount produced over that used by the crop. 
The difference between the incubated and fresh samples is taken as 
a measure of the additional work done in the laboratory under optimum 
conditions by those groups of bacteria which change the nitrogen of 
complex organic nitrogenous compounds first into ammonia, then into 
nitrites and further to nitrates. 
TABLE I. 
Series I East—Rotation Corn, Wheat 
Plot 1 Wheat Plot 2 Corn 
Nitrates—Parts per million Nitrates—Parts per million 
Month Moisture % - — Moisture °% 
Fresh Incubated Fresh Incubated 
Samples Samples Samples Samples 
March. 21.4 28.45 65.04 20.20 16.42 32.85 
April... 21.1 4.04 26.31 21.70 8.16 36.73 
May... 17.23 3.86 19.30 16.48 3.83 19.12 
June. . * 12558 1.83 21.96 18.49 35.30 82.35 
July . 16.99 11.56 15.41 15.28 79.32 83.01 
Aug... 14.16 7.45 9.07 15.05 132.62 188.30 
Sept... 11298) Pulse eet 3.62 15.10 26.36 56.52 
Oct PPAR eb [orerh na eee 4.14 22.48 12.38 24.76 
Total per period 57.19 164.85 194.39 523.64 
Ave. per month 7.15 20.60 24.29 65.45 
ty 
DISCUSSION OF TABLE 1. 
Series I East—Rotation Corn, Wheat. 
The average nitrate content of the entire period for the fresh sam- 
ples for the corn plot is 24.29 parts per million, as compared to 7.15 
parts for the wheat plot. 
The highest content for fresh samples was reached for corn in Au- 
gust, just after the corn ceased drawing heavily on the nitrates of the 
soil. The highest content for the wheat plot was in March, before the 
crop started good growth, but a second high nitrate content was found in 
July, just after the crop was.,removed. 
The fresh samples for the corn plot showed low from March to 
June, high from June to September, and low again for September and 
October. The wheat plot was high in March, low until July, high for 
July and August, and low again for thé’ remainder of the period. 
For the corn plot, the incubated samples show a much higher aver- 
age for the eight months than do those of the wheat plot,—for corn 
65.45 parts, and for wheat 20.60 parts of nitrates per million parts of 
moisture-free soil. 
It will be noticed that the incubated samples for corn showed highest 
in August, for wheat highest in March. As would be expected, the in- 
cubated samples showed highest during the growing season and lowest 
during the months of less favorable conditions for bacterial action. 
