DRY-FARMING 



face from the sun and to break the 

 connection between the water-bearing 

 sub-soil and the exposed evaporating 

 surface, is termed a mulch. In garden- 

 ing operations leaves, manure, coarse 

 hay, straw, grass clippings, etc., are com- 

 monly used. Such mulches of loose or- 

 ganic material are very effective — even 

 more so than a mulch of fine earth — but 

 they hinder the continual stirring of the 

 land, which promotes aeration and nitri- 

 fication.^ Stones serve practically the 

 same purpose as a mulch, if they happen 

 to be spread thickly upon the surface of 

 the ground, as they shield the land from 

 evaporation and so tend to keep the soil 

 cool and moist. In the bleak, wind- 

 swept county of Caithness, in the far 

 north of Scotland, the writer has known 

 of cases in which the removal of the nu- 



^ Process of changing nitrogen into nitric acid and 

 nitrates. 



82 



