PRECIPITATION 



75 



of those crops which tends more than any other to maintain a uni- 

 form composition and to vary less under environment. It is this char- 

 acteristic of Indian corn which enahles it tn be srrown with success 

 under such widely varying conditions."* This,** of course is not tak- 

 ing selection into consideration. 



RELATION OF CORN GROWING TO PRECIPITATION. In 

 the production of a corn crop water is of the utmost importance. The 

 yield obtained is more often decided or limited by this factor than 

 by any other. Corn does not require so much water for each pound 

 of dry matter produced as do many other crops, but the large total 

 weight of this crop more than overbalances such a consideration. 

 Whereas, the average amount of water transpired by plants is usually 

 given as, 500 pounds for each pound of dry matter, the amount for corn 

 is 300 pounds. 



The following table is inserted here as a basis for the di'-cussions 

 which are taken up. It shows the figures from which charts Nos. 8, 9, 

 10, 11 and 12 were made. 



TABLE NO. 16 



Showing Average Yield of Corn, Mean Annual Temperature and Rainfall of 



Iowa for 25 Years, 1890-1914 inclusive. 



CORN YIELD— AVERAGE IN IOWA FOR 25 YEARS ' , 



Yea^ 



1890 

 1891 

 1892 

 1893 

 1894 

 1895 

 1896 

 1897 

 1898 

 1899 

 1900 

 1901 

 1902 



Average 



bu. 



Year 



Average 



.28 

 .38 



29 

 .35.7 



14.8 



38 



39 



29 



34.5 

 . 3G.3 



43.3 



20.2 

 . 34.0 bu 



1903 

 1904 

 1905 

 190G 

 1907 



1908 

 1909 

 1910 

 1911 

 1912 

 1913 

 1914 



, 31 

 36 

 37.2 

 41 

 29 5 



.35.9 

 34.6 

 39.8 

 32.9 

 45.8 

 34.9 

 38.0 



Average 34.5 bu. 



MEAN ANNUAL TEMPERATURE AND RAINFALL OF IOWA FOR 25 YEARS 



Year 



Temp. 



1890 

 1891 

 1892 

 1893 

 1894 

 1895 

 1896 

 1897 

 1898 

 1899 

 1900 

 1901 

 1902 



48.0 

 47.3 

 46.6 

 45.7 

 49.7 

 47.2 

 48.6 

 47.8 

 47.7 

 47.3 

 49.3 

 49.0 

 47.7 



Rainfall 



31.30 

 32.90 

 36.58 

 27.59 

 21.94 

 26.77 

 37.23 

 26.98 

 31.34 

 28.68 

 34.05 

 24.41 

 43.82 



Year 



1903 

 1904 

 1905 

 1906 

 1907 

 1908 

 1909 

 1910 

 1911 

 1912 

 1913 

 1914 



Temp. 



47.2 

 46.3 

 47.2 

 48.4 

 48.0 

 49.5 

 47.4 

 48.6 

 49.5 

 46.4 

 49.7 

 49.1 



J{a nfall_ 



35.39 

 28.51 

 36.56 

 31.60 

 31.61 

 35.26 

 40.01 

 19.87 

 31.37 

 28.89 

 29.95 

 31.93 



I 



*Yearbook Dept. Agriculture, 1901. 

 **See Page 130, Result,s at Wisconsin Experiment Station wliere fertilizer was used. 



