Crop Rotation 293: 
TABLE 8. 
Nitrifying Power—Difference between Fresh and Incubated Samples. 
Average of Nitrates—Parts Per Million 
Crop — 
Mar. Apr. May June July |} Aug. | Sept. | Oct. |Ave. Mo. 
| 
(CORN oe eee 18.95 19.53 26.12 | 42.61 13.03 37.78 12.37 7.04 22.18 
(ORGY 3 sangeet ee 23.06 30.35 17.30 15.45 13.37 4.94 13.35 a2e 15.63 
Wh) ise OS eee 21.00 26.89 17.26 17.42 12.87 4.43 7.56 7.82 14.65 
ESR 4 ee |) 26.61 25.26 32.92 22.36 7.55 3.94 13.81 39.77 21.48 
PAN CTAR EG! fe ras At fuha' 22.40 25.51 23.40 24.46 11.70 12.77 lea 157460 |Aatecie 
The highest average difference between the fresh and incubated 
samples was found in June for the corn plots, in April for the oats and 
wheat plots, and in May for the soybean plots. The amount of nitrates 
used by the crops and leached from the soil would affect this curve 
directly. 
SUMMARY. 
1. The rate of nitrate formation is very greatly increased by cul- 
tivation of the soil. 
2. The corn and soybean plots, which were cultivated, showed a high 
nitrifying power as compared to the wheat and oat plots, which were 
not cultivated during the growing season. 
3. The effect of the previous crop and treatment of the soil on 
nitrate production is not nearly as important as that of the growing 
crop and the soil treatment. 
4. Corn and soybeans are heavy feeders while wheat and oats 
are less vigorous nitrate feeders. 
5. The highest nitrifying power as determined by the methods em- 
ployed in this work was in July for the corn plot, and in June for the 
wheat, oat and soybean plots. 
6. The addition of lime to acid soils makes conditions for the devel- 
opment of nitrifying bacteria much more favorable. 
7. The rate of nitrate production in the plots in the Purdue Ex- 
periment Station Field No. 6 is not a limiting factor to plant growth. 
Purdue University. 
BIBLIOGRAPHY. 
1. Brown;. 2: E:; 
Iowa Research Bulletin No. 6. 
22 Deherain; eb seks, 
Compt. Rend. 125, 1897. 
8. King, F. H., and Whitson, A. R., 
Wisconsin Bulletin No. 93, Report Wisconsin Experiment Station, 1900. 
4, Laws, C. B., Gilbert, J. H., and Warrington, R., 
Journal Royal Agricultural Society 19, 1893. 
5. Noyes, H. A., 
Journal of Industrial Chemistry 11, 213, 1919. 
6. Voorhees, E. B., Lipman, J. C., and Brown, P. E., 
New Jersey Bulletin No. 210. 
