92 MANUAL OF GARDENING 
often; and the depth of the pulverization is often extended 
by means of the subsoil plow. This subsoil plow does not turn 
a furrow, but a second team draws the implement behind the 
ordinary plow, and the bottom of the furrow is loosened and 
83. Forms of subsoil plows. 
broken. Figure 82 shows a home-made subsoil plow, and Fig. 
83 two types of commercial tools. It must be remembered that 
it is the hardest lands that need subsoiling and that, therefore, 
the subsoil plow should be exceedingly strong. 
Preparation of the surface. 
Every pains should be taken to prevent the surface of the 
land from becoming crusty or baked, for the hard surface estab- 
lishes a capillary connection with the moist soil beneath, and is 
a means of passing off the water into the atmosphere. Loose 
and mellow soil also has more free plant-food, and provides 
the most congenial conditions for the growth of plants. The 
tools that one may use in preparing the surface soil are now 
so many and so well adapted to the work that the gardener 
should find special satisfaction in handling them. 
If the soil is a stiff clay, it is often advisable to plow it or dig 
it in the fall, allowing it to lie rough and loose all winter, so that 
the weathering may pulverize and slake it. If the clay is very 
