CORN IN THE GREAT PLAINS AREA. 
arc water supply, physical condition of the seed bed, and a certain 
recognized, although not fully understood, effect of the crop immedi- 
a t ely preceding. Uniformity in these factors is largely restored by the 
cultivation or crop- 
ping of a single season. 
After a careful study of 
the data, it seemed ad- 
visable to present in 
this bulletin the yields 
of corn as determined 
by the cropping and 
treatment of the land 
in only the one year 
immediately preced- 
ing the growth of the 
crop. 
In the study that 
is here made only the 
more important and 
obvious results will be 
discussed. The tables 
themselves when crit- 
ically studied show 
much more than is 
here mentioned. No 
attempt is made to 
study rotations as a 
whole. There are 
cumulative effects of 
rotations and farm- 
ing systems that are 
not negligible, but 
which are not dis- 
cussed here. Other 
studies have shown 
that these effects are 
of far less immediate importance than the effect of the preceding 
crop, the preparation of the seed bed, and the seasonal conditions. 
AREA COVERED BY THESE STUDIES. 
The area (fig. 1) included in these investigations covers a part of 
ten States: Montana, North Dakota, South Dakota, Wyoming, 
Nebraska, Colorado, Kansas, Oklahoma, Texas, and New Mexico* 
It extends from the ninety-eighth meridian of longitude to the foot- 
hills of the Rocky Mountains and from the Canadian border to the 
thirty-second parallel of latitude. 
Fig. 1.— Sketch map of the Great Plains area, which includes parts of 
ten States and consists of about 400,000 square miles of territory. 
Its western boundary is indicated by the 5,000-foot contour. The 
location of each field station within the area is shown by a dot within 
a circle (0). 
