IV.] MULCHES  105 



connection between the water-bearing subsoil and the 

 exposed evaporating surface. Such mulches of loose 

 organic material are even more effective in conserving 

 soil moisture than a fine tilth, there is less tendency to 

 form any continuity of water film between subsoil and 

 mulch; moreover, the evaporation of the water they 

 themselves contain helps to keep the temperature down. 

 The great drawback to their employment is that they 

 prevent the continual stirring of the ground which 

 promotes aeration and nitrification. 



Stones serve almost the same purpose as a mulch, 

 especially when they are impermeable, like flints, and 

 cover the surface at all thickly. They shield the land 

 below from evaporation ; indeed, on picking a flint off an 

 arable field the ground below will generally be found 

 cool and damp. The vineyards of the Rhine, etc., are 

 generally set on steep slopes very thoroughly drained 

 and exposed to the sun; it will be noticed that the 

 utmost care is taken to keep the surface of the soil 

 covered with the broken slaty rock. 



Effect of Rolling. 



Though it has been pointed out that maintaining a 

 loose tilth on the surface is the most effective means 

 possessed by the farmer of saving the soil water and 

 minimising losses by evaporation, yet one of the funda- 

 mental acts of husbandry in the spring consists in roll- 

 ing and otherwise consolidating the land. Particularly 

 is this the case on the chalk and similar light soils ; when- 

 ever a spell of dry weather prevails in the early part of 

 the year the farmer will be observed rolling his seeds, 

 or his spring corn, or his newly sown turnip land, as 

 the case may be ; he will even take a heavy cart 

 wheel down between the drills when the roller will 

 not give him pressure enough. The result of the 



