68 THE PRINCIPLES OF AGRICULTURE 



leaching. This is done by plowing at the same 

 depth each year, so that the land becomes com- 

 pacted under the furrow. Loose and sandy lands 

 may need shallow plowing rather than deep 

 plowing. 



95. (/') Land which is turned up loose soon 

 dries out, because so much surface is exposed to 

 the air. In spring, it is often necessary to make 

 lands warm and dry, especially if such, crops as 

 corn and potatoes and cotton are to be planted; 

 and this is done by very early plowing. The 

 slices should not be turned down flat, but 

 allowed to lie up loose and broken, and the 

 harrow should not be used until the soil begins 

 to be dry and crumbly. Care should be taken 

 not to plow clay lands when wet, however, else 

 they become lumpy and unmanageable. 



96. {g) Freezing and thawing often pulverize 

 and improve heavy lands, particularly clays. 

 Fall plowing, therefore, may be advisable on 

 lands which tend to remain lumpy. The results 

 are best when the furrow-slices are left in a per- 

 pendicular position (as in Fig. 21), and when 

 the harrow is not used until the following spring. 

 Heavy clays tend to puddle (81) or to cement 

 together if fall plowed, but the danger is least 

 when there is herbage (as heavy sod or stubble) 

 or manure on the land before it is plowed. 



97. Subsoiling. When it is desired to loosen 



