152 



AGRONOMY 



the puddling which it lias undergone is often apparent for 

 years in the inferior plants along its course. A heavy rain in 

 summer often puddles the surface layer of soil so completely 

 as to form a crust thick enough to prevent small seedlings 

 from forcing their way up to the surface. 



Mulches. Quite as much water evaporates from a saturated 

 soil as from a free water surface. As fast as it is removed 

 from the surface, more rises by capillarity to take its place. 



Photograph by S. L. Allen & Co., Philadelphia 



FIG. 109. Cultivating corn with the horse cultivator 



The underside of a board or other object lying on the ground 

 is constantly kept wet by the rise of water in this way. A 

 windy day dries up the soil by removing the water as fast as 

 it rises. This steady loss of moisture from the soil can be 

 checked by any sort of loose cover. The mulch of stable 

 manure or other litter often spread on the ground about 

 newly planted trees and shrubs is placed there for this pur- 

 pose, though such mulches are not desirable for growing 



