124 SOILS 



eight or nine inches deep. If the soil is damp and 

 it is desired to dry and warm it for an early plant- 

 ing, say of corn, it should be plowed more shallow 

 than ordinarily. This is not advocating shal- 

 low ^plowing for heavy lands in general, but stat- 

 ing what may be done in certain cold, wet and late 

 seasons. 



Eight inches may be considered deep plowing 

 for many soils ; rarely is it practicable to plow more 

 than eleven inches deep. Most field crops feed 

 much more deeply than is commonly realised. 

 Corn, parsnips and sweet potato roots occupy 

 the ground to a depth of four or five feet and may 

 go several feet deeper, depending upon the nature 

 of the subsoil. It is safe to say that, on an aver- 

 age, the roots of field crops forage five to six feet 

 deep. But most of the feeding roots are in the 

 plowed ground, because this is the richest, warmest 

 and the oest ventilated part of the soil. Therefore, 

 the deeper the soil is plowed, within certain limits, 

 the greater will be the productivity, because more 

 of this congenial pasturage is provided for the roots. 



Subsoiling. The subsoil sets a limit to the depth 

 at which certain soils can be plowed. It may be 

 yellow or of a different nature than the surface 

 mould, and contain a large amount of raw plant 

 food. If much of this raw soil is mixed with the 

 surface soil the productivity of the land is apt to be 

 seriously reduced for a number of years, or until 

 weathering has acted upon the subsoil brought to 

 the surface. About 1850 there was a widespread 

 discussion in this country on the advantage of 

 deep plowing. It led to the introduction of an 

 implement with two plows upon one beam; a 

 small one which turned a furrow three or four 

 inches deep followed by a larger one which ran six 



