CORN IN THE GREAT PLAINS AREA. 7 
and summer tilled so that each year a crop is grown after summer 
tillage and a plat is summer tilled for cropping the next year. The 
remainder of the field is in rotations in which each plat is known by 
a rotation number and letter. On the field diagram the separation 
of rotations is indicated by heavy lines. The movement of the crops 
in the rotation is from Z to A, and from A back to the letter that 
marks the other end of the rotation. 
In figure 3 the diagram is filled out to show the cropping in 1914. 
The letters following the crop indicate the treatment given the 
ground in preparation for the crop: SP. stands for spring plowed, 
FP. for fall plowed, Fal. for summer tilled, GM. for green manured, 
D. for disked, etc. 
As an illustration, rotation 14 may be used: In 1914, plat A of this 
4-year rotation was planted to corn on spring-plowed ground, B was 
in wheat on disked corn ground, and C was in winter rye after fall 
plowing. Plat D was in oats where winter rye had been turned under 
the preceding year. In 1915, A will be in wheat, B in winter rye, C 
in oats, and D in corn. 
VARIETIES. 
In these investigations no attempt was made to grow the same 
variety at different stations. The aim was to select a variety well 
adapted to the conditions of the station where it was grown. The 
same variety has not been grown at any station during the entire 
period of the investigations. When a variety was obtained that was 
thought to be better adapted to local conditions than the one pre- 
viously grown, a change was made. 
At most of the stations, early-maturing varieties have been used. 
In the northern part of the area the growing season is so short that 
only very early varieties are at all safe. Increasing altitude with its 
correspondingly cooler nights, or decreasing water supply, has much 
the same effect as increasing latitude. At Hays, North Platte, and 
Amarillo varieties are grown that are somewhat larger and later 
maturing than those grown at the other stations. 
DETERMINATION OF YIELDS. 
The corn is harvested either when mature or when growth is 
stopped by frost. It is cut with a binder and shocked in the field. 
The shocks stand until cured, usually about a month. They are then 
weighed and the sound corn, if any, is husked and weighed. Where 
sound corn is produced, the yield as tabulated is given in bushels in 
the column headed " Grain." The column headed " Stover" * shows 
the total weight when no grain is produced and the difference be- 
1 In the tables of this bulletin only the term "stover" is used, because the corn was husked whenever 
marketable or whenever it was produced in sufficient quantity to warrant husking. In cases where the 
yield of grain was not sufficient to warrant husking the term "fodder" would be more exact. 
