INTRODUCTION XV 



million bushels of corn in a single year, or twice the 

 maximum grown up to this time. Such a doubling of 

 the crop is by no means impossible, since yields of from 

 fifty to one hundred bushels per acre, and even more, 

 are becoming increasingly common. Moreover, corn 

 readily adapts itself in various varieties to the soil and 

 climate of all sections, it is easy of cultivation, and its 

 value, both as a human food and a feed or forage for 

 animals, encourages a wide growth. The superiority of 

 the corn plant over other crops in these respects invites 

 carelessness in its cultivation, and this accounts for the 

 apparently low average yield per acre, which, however, 

 is generous in comparison with the small grains. 



Special emphasis should also be placed upon the 

 corn plant as a renovating crop, whereas wheat and 

 other small grains have relatively an exhaustive effect 

 upon the soil. Unlike wheat, the production of which 

 depends upon an ample supply of available nitrogen in 

 or to the soil, maize possesses wonderful ability to 

 gather in and assimilate nitrogen in many forms, as 

 well as other elements of nutrition. To what degree 

 the corn plant actually takes nitrogen from the air, 

 either of the atmosphere or of the soil,* experience 

 shows that, if the land contains an abundance of phos- 

 phoric acid and potash, the more expensive nitrogen 

 need not be largely applied in order to produce large 

 and profitable crops of corn. Herein lies the explana- 

 tion of the great yields produced under years of suc- 

 cessive cropping in the American corn belt. This fact 

 also demonstrates the fundamental value of corn in 

 crop rotation, and its restorative effect upon the soil's 

 fertility. 



The various chapters which follow tell their own 

 story, but a wealth of valuable data is also given in 

 the Appendix— notably, the results in the now historic 



