SPRING WHEAT ON THE NORTHERN GREAT PLAINS. 11 
VARIETAL EXPERIMENTS. 
This bulletin contains the results of the varietal experiments con- 
ducted on field plats at 11 experiment stations in the northern half 
of the Great Plains area. These investigations were conducted in 
order to determine the variety or varieties best adapted for growing 
in this semiarid section. The available material usually was grown 
in nursery experiments for a preliminary period and only the best 
varieties continued in the plat experiments. These varieties already 
have been discussed. The results obtained are given in Tables III 
to XXI and the principal data, comparing leading commercial 
varieties, in graphic form in figure 1. The experiment stations are 
widely separated and are so located that they represent fairly the 
larger part of the section considered. 
NORTHERN HALF OF THE GREAT PLAINS AREA. 
The section covered by this bulletin includes that portion of the 
Great Plains area extending from the Canadian boundary southward 
to the southern boundary of Nebraska, including portions of six 
States — North Dakota, South Dakota, Montana, Wyoming, Nebraska, 
and Colorado. 
The elevation of this section varies from about 1,500 feet in the 
eastern portion to about 6,000 feet in the western portion, most of 
it lying between altitudes of 2,000 and 4,000 feet. 
The climate is semiarid, the average annual precipitation varying 
from about 14 to 20 inches. In general, the rainfall decreases as the 
elevation increases to the westward across the area. The length of 
the frost-free period also decreases to the westward with the increase 
in altitude and to the northward with the increase of latitude. It 
varies from about 135 days in the southern portion at the lower 
elevations to about 90 days in the northern portion and at the highest 
elevations. Owing to rather high summer temperatures and fairly 
constant wind movement, a considerable loss of soil moisture occurs 
through evaporation. This increases to the southward. 
In general, the soil type of this area varies from clay loam to sandy 
loam, with a gumbo clay soil at Newell, S. Dak. 
The locations of the 11 stations, together with their altitudes above 
sea level, are shown in Table I. The table also gives the normal or 
average annual precipitation at each station and the period of years 
during which records are available. Finally, the prevailing soil type 
at each of the various stations is shown. 
The annual precipitation at any one station varies more from year 
to year than does the average annual precipitation at different sta- 
tions. That portion of the yearly rainfall occurring during the 
growing period for wheat (Apr. 1 to July 31) also varies widely from 
year to year, but, fortunately, it averages from half to two-thirds of 
