THE PRINCIPLES OF SOIL IMPROVEMENT 95 



tion. The man who buys a "worn out" farm will endeavor first 

 to bring the soil to the condition which will make it as good as, 

 or better than, it was before it was first used for farming. 



The principles of soil improvement are numerous, but they 

 may be chiefly grouped under the following headings: better 

 tillage; the frequent use of green crops as manure; more frequent 

 use of barnyard manure, and more attention to its proper manage- 

 ment; drainage of heavy soils, even where the land is not too wet; 

 irrigation not only in arid regions but in humid climates; intelli- 

 gent use of commercial fertilizers. All of these are considered in 

 this chapter with the exception of drainage and irrigation. For the 

 latter see the next chapter. 



BETTER TILLAGE 



Plowing of the land is the most expensive operation of farming. 

 The actual cost in labor, time and equipment for plowing the 

 fields of a given farm is so great that the operation is readily 

 neglected. Many fields which would be improved by plowing 

 once or perhaps twice a year are often put under a system of crop 

 rotation whereby the plowing may not be necessary more than 

 once in three or four years. A farm manager who is endeavoring 

 to improve his soils should study the benefits of plowing and other 

 forms of tillage. If he finds that more frequent plowing would 

 greatly benefit the soil he should if possible adopt a system of 

 cropping which will give a return in money, as well as in improved 

 condition of the field, for the extra labor expended. If the soil be light 

 the cost of an extra plowing in a year is not so great as for heavy 

 soils. The owners of light soils often find it profitable to plow 

 twice a year once for the turning under of the stubble or other 

 remains of the main crop, and once for turning under the green 

 manure crops between the seasons of the main crops. In such 

 cases the increased money returns come from the increased yields 

 of the main crop because of the presence of the green manure. 

 The cost of deep plowing is sometimes reduced by the use of a 

 tractor (Fig. 70). 



Reference has already been made to the importance of plowing 

 soils very deep. Deep tillage has its limits. The importance of 

 emphasizing deep tillage arises from the fact that many of the 

 "run down" farms of America are plowed entirely too shallow. 

 In determining the depth for plowing a field this is a good rule to 

 follow: Turn up very little of the subsoil each time the surface 



