74- CORN 



ticeable. The dependence of yield upon climate is seen when the av- 

 erage production per acre for the state of Iowa for a term of years is 

 considered. Under similar conditions, aside from climate, the yield 

 for Iowa has varied from 14.8 bushels to 45.8 bushels per acre. During 

 two successive seasons, yields of 14.8 bushels and 38 bushels per acre, 

 respectively, were produced. That all the differences mentioned are 

 due largely to climate is indicated by the fact that they occur over a 

 wide range of soil and correspond closely to difference in climate. 



That other factors, such as crossing, natural selection or "survival 

 of the fittest," and conscious and unconscious selection by man, are 

 also partly responsible, is very probable. 



CLIMATE AND VARIETIES.** Whatever caused the original 

 form of varieties, it is evident that a slight change in climate will 

 affect corn seriously; but after a few years it adjusts itself to the new 

 conditions and becomes fully acclimated. It was by su-^h a process 

 that the cultivation of corn has been gradually extended northward 

 in the United States. Today this cereal is grown successtully, where 

 twenty-five years ago its cultivation was impossible. Although the 

 corn plant is so .sensitive to climatic changes, it adjusts itself to them 

 so readily that new varieties can be successfully introduced if they 

 are first grown on a small scale until fully acclimated. The sensitive- 

 ness of the plants, however, suggests that caution should be used 

 abcmt purchasing for field production in a large way, seed from a dis- 

 tant locality, particularly if that locality be in a different latitude. 



EFFECT OF CLIMATE UPON COMPOSITION. Unlike the 

 wheat plant, the chemical composition of which is largely dependent 

 upon climate, corn appears to be but slightly affected by such influ- 

 ences. Richardson *analyzed many samples of corn grown in the va- 

 rious parts of the United States, but from seed obtained from a com- 

 mon source. The variation in the ash content was found to be small; 

 that of oil and crude fiber was proportionately the same as was found 

 in wheat, fairly constant, but the content )f album'niids (protein) 

 did not vary nearly so widely as did those of wheat. These results 

 are supported by analyses of foreign corns by Koenig. "Our conclu- 

 sion must be then, that corn can supply itself with nitrogen, under 

 varied circumstances, but that it rarely is able to assimilate more than 

 a certain amount. The bushels may vary, and the size of the grain, 

 but the quantity of albuminoids is practically unchanged."* From 

 these experiments Wiley concludes that "It is evident that Indian 

 corn, growing as it does over the whole of the United States, is one 



♦Yearbook U. S. Department of Agriculture, 1901. 

 "The relation of climate to variety and type of corn grown is taken up fully in Chapter VI. 



