THE TILLAGE OF THE SOIL 67 



Clover and rye are also apt to become too hard 

 and dry if allowed to grow to maturity. Herb- 

 age which does not decay quickly when plowed 

 down may seriously injure the crop, for that 

 season (74a). For the covering of herbage, the 

 furrow should be broad and deep ; and if the 

 land is to be surf ace -tilled shortly after the 

 plowing, care should be taken that the furrow- 

 slice turns down rather flat, so as to completely 

 cover the plants. 



93. (d) The deeper the plowing, the greater 

 the water- storage reservoir will be, other things 

 being equal; but the plowing may be so very 

 deep as to bring the unproductive subsoil to the 

 surface, in which case the increase of storage 

 capacity may be overbalanced by the loss of 

 available fertility. On most soils and for most 

 crops, eight or nine inches is a sufficient depth 

 for the plow. Shallow soils are both too dry and 

 too wet. They are too dry, because much of the 

 rainfall is lost in surface drainage or by very 

 rapid evaporation. They are too wet after every 

 hard rain, because the water is held near the 

 surface (79a). 



94. (e) If a hard-pan is near the surface, 

 deep plowing will break it up, although the 

 most permanent remedy may be under-drainage. 

 In very porous soils, however, it may be neces- 

 sary to form a hard-pan in order to prevent 



