8 BULLETIN 9Y6, U. S. DEPARTMENT OE AGRICULTURE. 



seasonal rainfall, the varying quantities deposited by different showers 

 and the manner in which it falls are not shown. These will be better 

 understood by a careful study of the data in Table II, which contains 

 a record of the daily rainfall, with monthly totals, throughout the 

 6-year period from 1914 to 1919, inclusive. 



The annual and seasonal rainfall was sufficient to produce fair to 

 good yields of the grain-sorghum crops in all the years during which 

 these experiments were conducted; but in several seasons the low 

 yields obtained were due largely to the unfavorable distribution of 

 the moisture. This may occur in several ways: (1) Much of the 



fiPf?/L MAY JUNE JULY Y?UG. SEPT. 



Fig. 4.— Average monthly precipitation and. evaporation, in 

 inches, at the Amarillo Cereal Field Station during the 

 growing season (April to September) in the 7-year period 

 from 1913 to 1919, inclusive. 



annual rainfall may come within a short period, either near the 

 beginning, in the middle, or at the end of the year; (2) the seasonal 

 rainfall may be sufficient in quantity but poorly distributed; or (3) 

 the rainfall may be fairly evenly distributed and about sufficient in 

 quantity and yet be unsuitable for crop production, as when it occurs 

 in light showers which do not penetrate the soil and are soon evapo- 

 rated. The seasons of 1916 and 1918 are good examples of the last- 

 mentioned condition. Showers amounting to less than half an inch 

 may add little or no moisture if followed by high winds and bright 

 sunshine, which cause rapid evaporation. 



