242 CROP PRODUCTION 



been gradually worn away from the solid mass that 

 originally formed the surface of the earth, together with 

 the remains of plant and animal life that have been 

 accumulating for millions of years. 



It seems hard to beheve that soils have thus come from 

 rocks and ledges, especially if one lives in a prairie region 

 where rocks are few and far between, and where the soil 

 is deep, mellow, and rich. But if one lives near or can 

 visit a rocky, mountainous region, it is comparatively 

 easy to see many stages in the process of soil formation. 

 What at first sight seems to be a bare cliff shows upon 

 closer examination various greenish patches on the 

 surface. These are low forms of plant life that get their 

 materials for growth chiefly from the air and the water. 

 At the bottom of the cliff one is likely to find a mass of 

 rock fragments of many sizes that have dropped from 

 the face of the cliff; these pieces of rock are often more 

 or less mixed with Httle fragments of plant growth that 

 have fallen from above. We thus have the beginning 

 of soil formation through the mixture of rock particles 

 and fragments of plant life. In this material higher 

 plants soon grow, and when they die their remains are 

 added to enrich and enlarge the mass of soil. 



In a general way this is the process of soil formation 

 which is taking place throughout the world. The soil 

 originally formed in one place may have been carried 

 by streams of water, by constant winds, or by the action 

 of the great ice glaciers of a previous age from one 

 locahty to another. So even the deep soil of a rich prairie 

 region may have come from far away during the long 

 ages in which the world was getting ready for man to 

 occupy it. 



