86 



SOILS AND FERTILIZERS 



leaves the field in an uneven condition. It is a common 

 practice in disking to lap over one half the distance 

 each time so that the ground may be left practically 

 level. 



The disk harrow is a good weed exterminator and is 

 often used instead of the plow when shallow tillage is 

 desired, as when oats follow corn in rotation. 



Other forms of disk harrows having special uses are 



the cutaway har- 

 row and the spad- 

 ing harrow. 



DRAINAGE 



Land is never in 

 perfect condition 

 unless well drained ; 

 that is to say, un- 

 less all the water 

 that falls on it or 

 flows over it can 

 soak down to the 

 minimum depth 

 needed for the de- 

 velopment of grow- 

 ing crops and then 

 find vent, either 

 through a naturally 

 porous soil or by 

 artificial channels. 

 The housewife makes a practical application of this 

 principle when she puts her house plants in a flower 

 pot which has a hole in the bottom. Without this 



FIG. 30. Opening a Ditch with a Plow. 



