4 INTRODUCTION 



that clothes the earth. "Before literature existed, before 

 governments were known, agriculture was the calling of 

 man. And all the fruits of social progress since then 

 grew from the brown soil." 



The soil changes its clothing. The clothing of the 

 earth is a changing one. It is of as many colors as the 

 coat of Joseph. And this clothing changes not in color 

 only, but in texture, in wearing ability, in usefulness. 

 For are there not many soils that had poverty as their 

 inheritance and still others that had only the fullest 

 riches? Yet both kinds meet at a common point so 

 often the rich have become poor, the poor have become 

 rich. 



All over our land this change is observed. To man's 

 credit, however, we are now at a point in farming where 

 this may be corrected, for we realize that the soil is 

 capable of change and of improvement: it offers a great 

 opportunity for thought and study. Applied here, knowl- 

 edge brings abundant returns. 



The soil and the subsoil. There are two layers of this 

 clothing: the soil and the subsoil, and of course we must 

 give due weight to both with any discussion of crop pro- 

 duction or in any method of land management. In both 

 soil and subsoil are found organic and inorganic mate- 

 rials, although the subsoil contains a greater portion of 

 the latter substances than the soil immediately over it. 



It is in both of these layers that the roots of plants grow, 

 and now that we know more about roots than we did a 

 few years ago, we ought to be able to handle lands with 

 greater certainty and to grow crops with more profit. We 

 know where roots grow; we know the places in which 

 they feed and just how they do their work. Is this not a 

 practical turn ? Roots grow from their tips, and at these 

 points they gather food and drink. With the passing of 



