CEREAL EXPEEIMENTS 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 (Bulhulis dactyloides) , western 

 wheat-grass (Agropyron smithii, formerly A. occidentale), 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, aU 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 Httle 

 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. 



