310 DRY-FARMING 
Making and maintaining a soil-mulch 
After the land has been so well plowed that the 
rains can enter easily, the next operation of impor- 
tance in dry-farming is the making and maintaining of 
a soil-mulch over the ground to prevent the evapora- 
tion of water from the soil. Jor this purpose some 
Fie. 79. Spike tooth harrow. 
form of harrow is most commonly used. The oldest 
and best-known harrow is the ordinary smoothing har- 
row, which is composed of iron or steel teeth of various 
shapes set in a suitable frame. (See Fig. 79.) For 
dry-farm purposes the implement must be so made as 
to enable the farmer to set the harrow teeth to slant 
backward or forward. It frequently happens that in 
the spring the grain is too thick for the moisture in the 
soil, and it then becomes necessary to tear out some of 
the young plants. For this purpose the harrow teeth 
are set straight or forward and the crop can then be 
