102 TILLAGE— MOVEMENTS OF SOIL WATER [chap. 



A similar trial made on a light loam at Wye during 

 a dry period in the spring of 1902, gave the following 

 percentages of water in the wet soil. 



There can be little doubt that the earlier land 

 which is intended for spring corn, or particularly for 

 roots, can be moved in the spring, the more water 

 will be saved for the use of the subsequent crop, and 

 the easier will a good tilth be established. The chief 

 danger lies on the very fine sandy soils which, when 

 in a loose condition, are apt to run together under 

 heavy rains and afterwards cake on drying. 



Hoeing and Mulches. 



The principles which have already been developed 

 to explain the effect of an early spring ploughing in 

 saving subsoil water, apply even more markedly to 

 all the later spring and summer cultivations, hoeing 

 and the like, which have for their object the mainten- 

 ance of a loose tilth upon the surface. The loose soil 

 becomes itself dry, but by reason of its discontinuity 

 and coarse-grained condition, does not conduct the 

 moisture from the firm subsoil to the surface exposed 

 to sun and wind. Under these conditions the only 

 loss will be of that water which evaporates from the 

 moist soil into the air spaces of the loose upper layer 

 and then diffuses into the atmosphere ; the deeper the 

 loose layer thus formed, the more effective will it be, 

 and if it is destroyed by a fall of rain, which consolidates 



V 



