CHAPTER III 

 WHAT WE FIND IN SOILS 



Having come now to the point where soils are made, 

 we may with all propriety consider their physical nature, 

 and then the treasures they hold fast secured in their 

 earthy storehouses. Not that soil making has ended, for 

 this process goes on forever. Only this : a time has been 

 reached in their development when, with the aid of tillage 

 tools, the most productive and useful of plants might now 

 be grown for the highest profit of man. 



Let us go out into the field itself. Of what is this soil 

 made? was at one time the first inquiry. Naturally, it 

 was said that soils were derived from the original rock 

 formations. We have discussed already the agencies that 

 have made our soils. No single one is responsible for 

 yours or mine. That we possess these soils, there 

 is no doubt. What brought them to us, what 

 placed particular soils within the limits of our possessions, 

 what influence or agency made them rough or 

 level, good producing or poor producing, is not 

 the problem now. 



Four kinds of soil materials. Our present inquiry is 

 in reference to their physical conformation, to their com- 

 ponent parts, to the minerals composing them. These ma- 

 terials are : sand, silt, clay, and humus or organic matter. 

 All productive soils contain these materials, but not in 

 the same proportions. There is a wide difference in the 

 quantities of each in our many varieties of soil. A pre- 

 ponderance of one of these materials over the normal 



