10 



BULLETIN 076, U. S. DEPARTMENT OF AGRICULTURE. 



Data on wind movement are shown in Table III; also data on 

 temperature. The total wind movement is high for each month 

 during the season in this 6-year period. The lowest total movement 

 recorded in any month was 6,023 miles for July, 1914, and the highest, 

 10,429 miles, or an average of 14.3 miles per hour, for June of the 

 same year. Some days are calm and others are partly so. On other 

 days the wind reaches a very high velocity. A maximum velocity 

 of 35 to 45 miles per hour is not uncommon. Such high winds are 

 often injurious to the grain-sorghum crops. They may cause damage 

 by covering the young plants, by cutting them off with moving 

 particles of soil, by whipping the half-grown plants into shreds, or 

 by blowing down the crop when it is approaching maturity. 



EVAPORATION. 



A great quantity of moisture is lost by evaporation at the Amarillo 

 Cereal Field Station. The prime factors influencing evaporation are 

 precipitation, wind, temperature, and sunshine. The highest evapo- 

 ration naturally occurs in periods of low precipitation, high tempera- 

 tures, strong winds, and bright sunshine. 



Table IV shows the monthly precipitation and evaporation at the 

 station during the six months from April to September in each year 

 of the 7-year period from 1913 to 1919, inclusive. The evaporation 

 measured is from the free water surface of a tank 8 feet in diameter. 

 These data also are shown graphically in figure 4, where the enormous 

 difference between the precipitation and evaporation may be noted 

 at a glance. On the average during this period the evaporation was 

 3.75 times as great as the precipitation. July has a higher rate of 

 evaporation than any other month, averaging 10.8 inches in this 

 6-year period; August has an average of 9.3 inches. 



Table IV. — Monthly, seasonal, and 7-year monthly average precipitation and evaporation 

 at the Amarillo Cereal Field Station during the six vionths from April to September, 

 inclusive, in the 7-year period from 1913 to 1919, inclusive. 



[Data (in inches) obtained at the Amarillo Cereal Field Station in cooperation with the Office of Biophysi- 

 cal Investigations and the Office of Dry-Land Agriculture of the Bureau of Plant Industry, United. 

 States Department of Agriculture.] 



Year. 



April. 



May. 



June. 



July. 



August. 



September. 



Seasonal 

 total. 





Prec. 



Evap. 



Prec. 



Evap. 



Prec. 



Evap. 



Prec. 



Evap. 



Prec. 



Evap. 



Prec. 



Evap. 



Prec. 



Evap. 



1913 



1.7 



1.3 

 4.8 

 1.8 

 .6 

 .5 

 2.5 



7.7 

 6.7 

 4.6 

 6.0 

 7.7 

 7.0 

 6.8 



1.7 

 3.8 

 2.0 

 .9 

 2.8 

 2.4 

 2.0 



9.S 

 6.7 

 6.9 



10.3 

 7.6 



11.0 

 8.7 



2.3 



.7 



1.2 



2.7 



.7 



7.0 

 10.1 



8.8 

 10.7 

 12.5 



1.4 

 1.9 

 3.7 

 1.2 

 2.6 

 2.7 

 2.4 



12.7 

 8.7 

 9.3 

 11.7 

 12.4 

 10.7 

 10.3 



0.5 

 2.5 

 4.6 

 3.4 

 5.5 

 2.2 

 3.4 



10.3 

 8.9 

 7.3 



10.2 

 8.6 



10.3 

 9.2 



5.6 

 1.1 

 4.9 

 2.2 



2.1 



5.9 13.2 53.4 



1914... 



nii 11.3 49 1 



1915... 



6 i' 21.2 42 9 



1916 



7. 7 12.2 56.6 



1917 



6 14 3 , 64 7 



1918 



1.2 10.1 

 3.5 j 9.9 



.7 7. 4 1 9.7 56. 6 



1919 



4.7 7.2 18.4 52.9 







Average... 



1.9 



6.6 



2.2 



8.7 



1.6 9.9 



2.3 



10.8 



3.2 9.3 



3.0 6.9 , 14.3 53.7 

 1 i 



