PLOWING, SUBSOILING, AND TRENCHING. 151 



ing itself, that is so beneficial and so lasting in its effect. A well- 

 drained subsoil, that has been once well broken up with a subsoil 

 plow, will never again become so hard and impenetrable to roots 

 as it was before the operation. It opens a way in the lower soil 

 for the deeper entrance of roots, and these are always ready to 

 avail themselves of an opportunity of going down beyond the 

 reach of the drying effect of the sun's rays and of the wind. 

 When the crop is removed, these roots remain and decay in the 

 subsoil, entirely changing its character. The more ready admis- 

 sion that is given to the water of rains and to the circulation of 

 air, hastens the chemical changes in the composition of the sub- 

 soil, and these changes, together with the decay of the roots, 

 will in time bring the soil to the condition of that which has been 

 turned by the surface plow, so that, after a very few years, a 

 subsoil which would have impaired the fertility of the field if at 

 once turned up in large quantities, may be brought to the surface 

 as plentifully as is desired. This, in connection with a gradua 

 deepening of the surface furrow, is the best means of making the 

 soil deeper, — of making more soil to the acre. 



I must repeat, however, that on wet land, the foregoing effects 

 cannot be expected, at least not in a sufficient degree to make the 

 operation advisable. 



The depth of the working of the subsoil plow is regulated by 

 means of a clevis, in the same manner as that of the surface plow, 

 and it may be made to run from six inches to eighteen inches 

 below the bottom of the furrow of the surface plow, according 

 to the character of the subsoil and the strength of the team. As 

 many as eight oxen are sometimes used, and often a single pair 

 will do good work. 



The " trick" of the work is to set the plow as deep as it will 

 work without getting beyond the control of the plowman. It has 

 a wonderful tendency to take too deep a hold, as soon as it passes a 

 point at which the team can exercise a lifting force upon it, and it 

 will sometimes get " set " beyond the power of extrication, except 

 by digging. So far as the plowman has any power to prevent it from 

 going too deep, he must keep it out bv lifting at the stilts. By 



