THE MAIN TYPES OF SOIL 5? 



effected when clay is dried in the sun and 

 piled in heaps mixed with combustible 

 material, which is subsequently fired and 

 the whole mass roasted. This is an agri- 

 cultural process, called clay burning, which 

 at one time was commonly practised upon 

 the strong lands of England. During the 

 process of roasting, a certain amount of 

 mineral plant food was liberated, and when 

 the burned material was scattered upon the 

 fields this plant food became available for 

 the use of crops. But the main object of 

 burning clay and spreading it on land at the 

 rate of 50 to 100 tons per acre was to provide 

 material which would modify the plastic 

 character of the clay, and, by imparting 

 greater friability, facilitate tillage operations. 



For most agricultural purposes the soil that 

 gives the best return is a loam, which consists 

 of an intimate admixture of clay and sand 

 in varying proportions. According as one or 

 other of these substances predominates we 

 have a clay loam or a sandy loam. In its 

 physical properties a loam stands more or 

 less intermediate between a sand and a clay. 

 While manurial substances are more liable to 

 loss on a loam than on a clay, their action is 

 more rapid ; and, on the whole, loams admit of 



anures of all kinds being very fully utilized. 



