SORGHUM EXPERIMENTS ON THE GREAT PLAINS. 
from year to year, but if properly distributed it is nearly always 
sufficient to produce a fair sorghum crop. (See Table 1.) Uncer- 
tainty as to when a dry period is coming, however, makes it impos- 
sible to adjust the date of seeding so as to avoid the drought or vary 
the cultural methods to minimize its effect to the degree that would 
be possible if the wet and dry periods were uniform from year to 
year. 
Fig. 2.— Map of the Great Plains area, which includes parts of 10 States and consists of about 400,000 square 
miles of territory. Its western boundary is indicated by a 5,000-foot contour. The location of each 
field station within the area is shown by a dot within a circle (©). 
Associated with the low and unevenly distributed rainfall are 
relatively high summer temperatures, generally low atmospheric 
humidity, high wind velocity, and a large proportion of clear days, 
all of which result in a high rate of evaporation and a decrease in 
the effectiveness of the rainfall. The monthly, seasonal, and annual 
precipitation and the seasonal evaporation for each of the eight field 
stations in the sorghum belt are given in Table 1, for the period of 
years during which the experiments have been in progress at the 
