478 THE PRINCIPLES OF SOIL MANAGEMENT 



plow. The purpose of this implement is to break up 

 and loosen the subsoil without mixing the material 

 with the soil. It consists essentially of a small mole- 

 like point on a long shin. This implement is drawn 

 throng! i the bottom of the furrow, and fractures and 

 loosens the subsoil to a depth of eighteen inches or two 

 feet. It is often useful on soils having a dense, hard 

 subsoil, but its use requires the exercise of judgment, 

 as the process may prove very injurious if done out of 

 season. As a general rule, it is best to use the subsoiler 

 in the fall when the subsoil is fairly dry, and in order that 

 the subsoil may in a measure be recompacted by the 

 winter rain. Spring subsoiling is seldom advisable in 

 humid regions, owing to the danger of puddling the sub- 

 soil or the possibility of its remaining too loose for best 

 root development, if performed when the subsoil is too 

 dry to puddle. 



339. Cultivators. There are more types of cultiva- 

 tors than of any other form of soil-working implements. 

 These may be grouped into: (1) Cultivators proper. 

 (2) Leveler and harrow type of cultivators. (3) Seeder 

 cultivators. These implements agree in their mode 

 of action on the soil, in that they lift up and move it 

 sidewise with a stirring action which loosens the struc- 

 ture and cuts off weeds, and to a slight degree covers 

 rubbish. However, the action is primarily a stirring 

 one, and, in general, it is much more shallow than that 

 of the plow. One important fact should be kept in mind 

 in cultural operations, especially just following the plow. 

 That is, to do the work when the soil is in the right 

 moisture condition. Particularly is this true in the 



