FORTY-SECOND ANNUAL, CONVENTION 39 



RESTORING AND RETAINING SOIL FERTILITY. 



By Cyril G. Hopkins, University of Illinois. 



I think that you wih agree with me that we have no more 

 important subject than the productive power of the soil. There 

 are important uses to be made of the crops produced, and one 

 of them is for dairy purposes, but if we do not produce the 

 crops from the soil, then we will not succeed in any kind of 

 farming, whether it be dairy farming, beef production, hog rais- 

 ing, grain farming, or any other kind; so this subject that we are 

 to discuss this afternoon is really the most basic one in all 

 agriculture, and I think you will pardon me, those of you who 

 know parts of what I am going to say, if I first discuss briefly 

 certain fundamental things required for the production of crops. 



We think more about the feeding of animals than of plants, 

 but food for plants is just as important as for animals; and in 

 a way plants are more dependent upon being properly fed than 

 animals, because at least a part of the year animals have some 

 sort of privilege to wander about and gather their own food, 

 while plants have not such opportunity — they ''must stand and 

 take it." 



There are ten different things required to produce a corn 

 plant. I think everyone who has anything to do with the grow- 

 ing of corn should be familiar with the things which corn re- 

 quires. It so happens that two of these essential materials for 

 the iDroduction of crops come from the air, they are carbon and 

 oxygen in form of carbon dioxide. So long as the wind blows 

 over the field the supply of carbon dioxide will be provided 

 by nature. A third, hydrogen, is supplied by water absorbed 

 by the roots, while the carbon and oxygen are taken in through 

 the pores in the leaves. Those three produce sugar and starch 

 and most of the materials that are contained in butter, but there 

 are seven other elements also essential, one of which is nitrogen, 

 without which you cannot make casein, cannot make any muscle 



