THE SOIL AND ITS MANAGEMENT 



53 



A granite rock, which consists of quartz, feldspar, and usually 

 mica, is broken down by the action of the weather. Through the 

 decomposition of feldspar and mica, clay is formed. This clay, 

 with the quartz grains of the granite, forms soil. Other rocks 

 are similarly weathered 

 to form coarse-grained, 

 medium-grained, or fine- 

 grained soils, according 

 to the conditions under 

 which the rock is broken 

 down. 



The largest areas of 

 residual soils are found 

 in the Southern states, 

 the Appalachian Moun- 

 tain region, and the 

 Rocky Mountain states. 

 Many of these soils are 

 very productive. 



54. Cumulose soils. 

 Soils formed largely by 

 the accumulation of or- 

 ganic matter in shallow 

 lakes or in channels or 

 arms of rivers are called 

 cumulose soils. The re- 

 mains of water plants, 

 such as reeds, rushes, 



FIG. 29. Sir John Bennet Lawes (1814-1900) 



A celebrated agricultural scientist. The founder of 

 the Rothamsted (England) Experiment Station, 

 where a number of noteworthy discoveries in soil 

 and mOSS, gradually ac- management, crop rotation, and animal nutrition 

 T . . have been made 



cumulate in such places 



and become mixed with more or less mineral matter, and are 

 known as muck, or peat, soils. In the Northern states many 

 old lake beds have been filled with these soils and are now used 

 for growing truck crops, such as celery, onions, and cabbage, 

 while in some cases they are used for growing general crops. 

 When drained, such soils are very valuable, but some require 



