BROOM-CORN EXPERIMENTS AT WOODWARD, OKLAHOMA, 8 
been eroded more than the soils of the western part. The soil 
types found in this extensive area vary from sand to clay, with the 
loams predominating in the southern and central parts of the area 
and silt loam in the northern. All are friable and easy to cultivate 
as compared with similar types under more humid conditions. They 
are uniformly sweet or nonacid, and under natural conditions contain 
from 3 to 6 per cent of organic matter. In general, low yields are 
due to some climatic factor or factors rather than to a lack of 
soil fertility. 
CLIMATIC CONDITIONS. 
The weather data considered herein were recorded at Wood- 
ward, Okla., during the period from 1908 to 1918, inclusive. 
Woodward is located centrally in the district described. 
The -principal climatic features which influence crop production 
in this section are (1) a limited annual precipitation of irregular 
seasonal distribution and a great loss of water due to run-off during 
torrential summer storms, which are quite common in some locali- 
ties; (2) a relatively low atmospheric humidity; (3) a very high 
rate of evaporation during the summer months; (4) a wide daily 
range of temperature, or hot days followed by cool nights; and 
(5) a high average wind velocity. 
Precipitation. 
Precipitation and its distribution are important factors in crop 
production in the section under discussion. There is usually rain- 
fall enough to grow the crop, but the distribution is not always 
such as to permit the best use by the crop of the moisture which 
falls. In such cases the crop yields are very low, and in extreme 
cases total failure results. 
MONTHLY AND ANNUAL PRECIPITATION, 
Table I shows the monthly, annual, and mean annual precipitation, 
in inches, at Woodward, Okla., during the 11-year period from 1908 
to 1918, inclusive. The mean annual precipitation at Woodward for 
this 11-year period was 24 inches, of which amount 16.5 inches fell 
during the growing season, or from April to September, inclusive. 
Table I shows a wide fluctuation in both the monthly and the 
annual precipitation. In April, 1909, the rainfall was 0.45 inch, and 
for the same month in 1915 it was 7.08 inches, or a difference of 
more than 6 inches between these extremes. May, June, July, 
August, and September each have about the same range of fluctua- 
tion as April. In the annual precipitation the extreme range is from 
14 inches in 1910 to 89 inches in 1915, almost three times as great. 
