Crop Rotation 283 
Crop ROTATION AS AFFECTING NITRATE PRODUCTION. 
I. L. BALDWIN, U. L. CoBLE AND J. W. CHAMBERLAIN. 
One of the great outstanding problems of the modern scientific 
farmer is that of maintaining and improving the soil fertility. It is 
in connection with this great problem that the science of Soil Bacteri- 
ology, the study of the habits and activities of the microbic flora of the 
soil and their relation to soil fertility and plant growth, has recently 
developed. Although investigations in this field have just begun, enough 
has been done to prove that such scientific studies are highly valuable 
in solving some of the problems relative to the question of soil fertility 
and plant growth. 
As yet few scientific investigations have been reported on the 
effect of various crops and crop rotations on the nitrate content of the 
soil. As a result the following studies relative to the nitrate content 
and nitrifying power of the Rotation Plots of the Purdue Experiment 
Station Field No. 6 were undertaken. 
A brief description of the plots and the experiment being con- 
ducted by the Purdue Station will be of value in interpreting the re- 
sults of these studies. 
The soil is a Sioux silt loam, containing some gravel and is under- 
laid by a gravel subsoil. The top soil is shallow, and just below at 
varying depths there is a hard layer somewhat similar to a hardpan. 
This soil dries quickly and packs easily. The organic matter content is 
fairly high. 
The plots were laid out in 1889, as test plots one-tenth acre in size 
in strips fourteen feet wide separated by strips seven feet wide. In 
each’Series there are seven test plots, four treated with manure or fer- 
tilizer, and three checks. The purpose of the experiment was to test 
the relative value of manure and commercial fertilizers applied to differ- 
ent rotations. 
At first only one crop of the rotation was grown each year, but 
in 1911 the plots were divided sc that each crop of the rotation is grown 
every year. As a result some plots are smaller than others. 
The accompanying map will give some idea of the relative size and 
position of the plots. 
HISTORY OF LITERATURE. 
Until within a generation ago it was not known that nitrification 
was a bacterial process. The transformation of organic nitrogen was 
regarded as a purely chemical reaction and was extensively studied 
from that standpoint. 
The work of Kuhlman, Bossingault, Schlosing and Muntz, War- 
rington and Winogradski and other investigators showed the true na- 
ture of nitrification and the organisms responsible were isolated and 
studied. 
