54 THE ESSENTIALS OF AGRICULTURE 



the application of lime and a potash fertilizer to make them 

 satisfactory for crop production. 



55. Transported soils. Transported soils are usually classified 

 as alluvial, glacial, czolian, and colluvial. 



Alluvial soils are those laid down by water along streams or 

 in lakes and ponds. The material from which such soils is 

 formed is washed by rains from the higher land. The muddy 

 water running from hillsides during heavy rains and the muddy 

 water seen in all streams during high water are the result of the 

 washing away of the soil of the higher lands. During high water, 

 as the streams spread over the bordering lowlands, material is 

 deposited, forming the deep soils commonly known as bottom 

 lands. Alluvial soils, when properly drained, are usually very 

 fertile, because of their depth and the fact that they are formed 

 from the rich surface soil of the uplands. There are large areas of 

 such soil along the main rivers of the United States, particularly 

 along the Mississippi, the Ohio, and the Missouri. The large 

 lowland region of Louisiana bordering the Mississippi River, 

 known as the delta region, is made up of material carried by 

 the river. 



56. Glacial soils. Glacial soils are formed by the action of 

 moving ice. A considerable share of the soils of Canada and 

 the northern part of the Mississippi Valley are of glacial origin. 

 The Missouri and Ohio rivers represent approximately the south- 

 ern edge of the area of glacial soils in North America. There 

 are small areas in the Rocky Mountains, but these are not of 

 great agricultural importance. These glacial soils were formed 

 centuries ago when the climate of North America was much 

 colder than it is now and when the northern part of the continent 

 was covered with a layer of ice which moved slowly down from 

 the North, grinding the rocks beneath it, leveling the hills, and 

 filling the valleys. As the ice melted, it left a mass of pulver- 

 ized rock material which now forms these glacial soils. The 

 most important large body of agricultural soil in the United 

 States, that of the North Central states, often known as the 

 corn belt, is of glacial origin. 



