SPRING WHEAT IN THE GREAT PLAINS AREA. 7 
the calculation is from the left. For a rough comparison of seasons, 
the hottom line of the first half of the table gives an average of all 
plats for each year, the average of the yearly average yields appear- 
ing in the last column to the right. > 
Throughout the tables, where wheat is shown as following corn 
on either fall or spring plowing, it is in a 3-year rotation in which 
the other crop is oats. Where wheat is shown as following oats 
on fall or spring plowing, it is in a 3-year rotation where in the third 
year the land is either cropped to corn or is summer tilled. Where 
wheat follows wheat under any treatment it is in a system of con- 
tinuous cropping to wheat by the method indicated. 
The methods of operation have been similar at all stations. Fall 
plowing is done early, except after crops like corn that are not 
removed from the ground early. It is done to a good depth, the 
standard being set at 8 inches. Ground may be either worked down 
or left rough over winter. Spring-plowed land may be disked in the 
fall or may be undisturbed until spring, when plowing is done just 
before seeding. Plowing is done to a good depth, usually at about 
8 inches. This applies to all wheat plats except one plat at each 
station on which wheat follows wheat. The stubble of this plat is 
undisturbed until spring, when it is plowed shallow (at about 4 
inches) and is then given a minimum of cultivation, which usually 
consists of one or two harrowings. In those cases where an addi- 
tional plat appears under spring plowing after wheat, it is plowed 
deep instead of shallow. 
Under the subhead " Listed" there is shown at some stations the 
yield from one plat continuously cropped to wheat. Instead of 
plowing this plat, it is furrowed out with a lister at the time of fall 
plowing. It is cultivated down level by seeding time. 
Under the subhead "Subsoiled" there is shown at the stations 
where it has been tried the results from a plat continuously cropped 
to wheat. At the time of plowing, a subsoil plow is run in the bot- 
tom of the furrow, usually loosening the soil to a total depth of about 
14 inches. The variation from this depth is hardly more than 2 
inches either way. In general, subsoiling has been done two years 
in succession and then omitted for two years. 
. Under the subhead " Disked" is given the average of a consider- 
able number of plats of wheat following corn. These occur in alter- 
nate cropping to wheat and corn, in 3-year rotations in which the 
other crop is oats, and in 4-year rotations in which the other crops 
are summer tillage and oats or barley. In sod rotations, wheat on 
disked corn ground is the third crop after breaking the sod. At 
some stations are shown additional plats on disked ground following 
potatoes and following sorghum. These are in 4-year rotations. 
85751°— Brill. 214—15 2 
