CEREAL EXPERIMENTS AT JUDITH BASIN SUBSTATION. 3 
NATIVE GRASSES. 
In the. original state the bench lands of the Judith Basin are covered 
with grass. The most important native grass is grama grass (Boute- 
loua oligostachya) . Buffalo grass (Bulbulis dactyloides) , western 
wheat-grass (Agropyron smithii, formerly A. occidentals), slender 
wheat-grass (Agropyron tenerum), and needle grass (Stipa comata 
and S. viridula) are also found, but are not as abundant as the grama 
grass. The grasses on the bench land make very good pasture, 
but seldom grow tall enough to be cut for hay. 
CLIMATE. 
Before discussing crop yields or attempting to draw any conclusions 
it is necessary to have in mind the climatic factors affecting crop 
growth. The most important of these factors are (1) seasonal and 
annual rainfall, (2) the seasonal evaporation, and (3) temperature, 
with special reference to the length of the growing season as limited 
by the spring and fall frosts. With the exception of the rainfall 
records from 1898 to 1908, all data on these factors here presented 
have been obtained at the substation at Moccasin. 
PRECIPITATION. 
Table II gives the annual and average precipitation by months in 
the vicinity of Moccasin for the 18 years from 1898 to 1915, inclusive. 
Previous to 1909 the records were taken at Utica, 7 miles southwest 
of the substation. Since that time they have been taken at the 
substation by the Biophysical Laboratory of the Bureau of Plant 
Industry. The average annual precipitation for 18 years (Table II) 
is 16.66 inches. During this time the maximum precipitation in any 
one year was 23.76 inches (1909), and the minimum, 10.42 inches 
(1900). 
The peculiar soil conditions existing at Moccasin and more or less 
throughout the Judith Basin make it nearly impossible to store any 
appreciable amount of moisture in the soil. The seasonal distribution 
of the rainfall, therefore, is of great importance. The growing season 
for spring grains at Moccasin extends from about April 1 to August 10. 
Since the precipitation that falls after the 1st of August has little 
effect on the yields of the crops, the growing season is considered as 
extending from April 1 to July 31. The average precipitation in 
this 4-month period during 18 years is 9.41 inches, or 56 per cent of 
the average annual precipitation. 
