IV.] 



MULCHES 



117 



season through, preserved more soil moisture than the 

 shallower cultivation, but by keeping the soil immedi- 

 ately below the mulch more moist and therefore with a 

 better developed water film, it also enabled this layer to 

 lift more moisture from the 3 or 4 foot depth into the 

 top or second foot, a position more available for the 

 crop. Thus the average of three determinations of 

 tvater content on 16th July gave the following results : 



On this occasion it is seen that the upper 2 feet of 

 soil are being kept moister by their greater power of 

 ifting water from the lower layers, which actually con- 

 tain more water under the i|-inch mulch than under 

 the 3-inch mulch. 



Although the gardener uses the hoe freely to estab- 

 ish soil mulches, he also employs dung, grass-clippings, 

 ind even straw to the same end, anything to break the 

 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 

 7 orm any continuity of water film between subsoil and 

 milch ; moreover, the evaporation of the water they 

 :hemselves contain helps to keep the temperature down, 

 rhe great drawback to their employment is that they 

 prevent the continual stirring of the ground which 

 Dromotes 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 

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



