METHODS OF PLOWING 125 



or eight inches deeper, turning its furrow-slice upon 

 that of the smaller plow. These plows proved 

 impracticable, chiefly because they left the raw 

 subsoil on top of the ground and buried the rich 

 surface soil at the bottom of the furrow. 



The introduction of the subsoil plow, a little 

 later, remedied this fault. This follows the plow 

 and stirs the soil in the bottom of the furrow to a 

 depth of five to ten inches, but does not bring it to 

 the surface. There are two types of subsoil plows. 

 One is shaped something like a harrow tootn ; the 

 other consists of a wedge-like shoe on the lower 

 end of the bar. There is much difference of 

 opinion concerning the value of the subsoil plow 

 in general farming. It is not used nearly as much 

 as it was fifteen years ago. The general conclusion 

 seems to be that it is 01 service only on the heavier 

 soils, which need better aeration and need to be 

 deepened. But the soil that is loosened by the 

 subsoil plow quickly falls back and becomes 

 compact again, so subsoiling affords only tem- 

 porary relief. Moreover, subsoiling may be a 

 positive injury to some soils by destroying the 

 earthworm burrows that effectively aerate and 

 drain the subsoil. 



The lessened appreciation of the subsoil plow 

 in recent years is due largely to the more general 

 practice of under-drainage. Under-drainage loosens, 

 deepens and aerates the soil permanently and to a 

 much greater depth than subsoiling. Subsoiling 

 should follow, not precede, under-drainage. It 

 augments every good effect of drainage. At present 

 the use of the subsoil plow is confined mostly to 

 fairly well-drained lands which have a hard and 

 dry subsoil; and for breaking up a hard-pan that 

 is close to the surface. Subsoiling is usually in- 



