CEEEAL EXPERIMENTS AT THE AKRON FIELD STATION. 7 



month from April to September, inclusive, in the 8-year period, 1908 

 to 1915, is given in Table IV. The precipitation for the same period 

 is included, and the ratio of precipitation to evaporation each year is 

 also given. The data show that evaporation from the free water 

 surface increases when precipitation decreases, but not in exact ratio. 

 The highest evaporation was recorded in 1911, but the lowest pre- 

 cipitation occurred in 1913. The year of lowest evaporation was 

 1915, which was also the year of highest precipitation. The ratio 

 of precipitation to evaporation over the total period for which records 

 are available is 1 to 2.9. 



Table IV. — Monthly precipitation and evaporation from a free water surface at the Akron 

 Field Station, Akron, Colo., from April to September of each year, 1908 to 1915, 

 inclusive. 



[Data (in inches) from the records of the Biophysical Laboratory of the Bureau of Plant Industry.] 





April. 



May. 



June. 



July. 



August. 



September. 



Total. 





Year. 



& 

 'S 



u 

 Ph 



g 



1 

 > 



1 

 9 



1 



2 



o 

 > 



§ 



.1 

 ft 

 '3 

 £ 



Ph 



i 



r 



§ 



1 

 ft 

 '3 



u 

 Ph 





i 

 ft 



•3 



u 

 P4 



§ 

 •11 



"S 

 > 



1 



1 

 ft 



1 



Ph 



§ 



1 

 > 



g 



1 

 'ft 



1 



o 



M 



o 



ft 



f 



.2 



1908 



1.70 



4.740 



3.. 57 



7.709 



2.35 



8.637 



3.40 



8.474 



1.62 



7.826 



0.22 



8.550 



12.86 



45.936 



1:3.5 



1909 



.40 



4.734 



1.87 



6.825 



3.32 



7.003 



4.61 



9. .396 



3.77 



8.538 



2.16 



5.857 



16.13 



42 353 



1:2.6 



1910 



3.96 



6.387 



2.06 



5.797 



1.38 



8.722 



1.47 



9.763 



3.72 



7.142 



3.81 



5.810 



16.40 



43.621 



1:2.6 



1911 



2.fi3 



5.841 



1.15 



7.323 



1.48 



9.753 



1.34 



9.774 



1.30 



8.944 



2.40 



7. 183 



10.30 



48.818 



1:4.8 



1912 



2.49 



4.576 



2.S6 



7.097 



3. 39 



6.750 



3.58 



7.618 



1.58 



7.048 



1.88 



4.648 



15.78 



37.737 



1:2.3 



1913 



2.19 



4.336 



1.44 



5.8:35 



1.35 



8.178 



1.85 



9.259 



1.14 



9.302 



2. 08 



6.040 



10.05 



42.950 



1:4.2 



1914 



4.01 



4.290 



1.46 



5.608 



3.54 



7.509 



1,66 



8.654 



1. 05 



8.364 



.23 



7.438 



11.95 



41.863 



1:3.5 



1915 



5.19 



4.220 



4.13 



5.033 



3.75 



5.883 



1.10 



6.660 



3.5 



5.820 



1.76 



5.793 



19.44 



33.409 



1:1.7 



Average.. 



2.82 



4.890 



2.32 



6.403 



2.57 



7.804 



2.37 



8.699 



2.21 



7.873 



1.82 



6.415 



14.11 



42.084 



1:2.9 



The precipitation and evaporation in the months of August and 

 September are less important in the production of spring-sown 

 cereals than in the production of those sown in the fall. The ger- 

 mination of winter wheat is often slow and sometimes very poor, 

 due to the scarcity of moisture in the seed bed at the time of sowing. 

 Crop growth and surface evaporation may have exhausted the 

 moisture from the surface below the seeding depth, even though 

 the lower levels contain sufficient moisture to maintain plant 

 growth. 



Very low humidity of the atmosphere, rapid transpiration from 

 growing plants, and high wind velocity are responsible for the rapid 

 and often premature ripening of cereals. For this reason the early- 

 maturing varieties in each gi'oup usually produce a liigluu- quality of 

 grain than the later ones. The growth of all is checked at about the 

 same time. 



