256 AGRICULTURE 



saved by keeping the surface covered with a fine soil mulch, 

 and what moisture is drawn up toward the surface from the 

 ground water by capillary attraction is also conserved for 

 the crop that is to follow. 



4. Soil Drainage 



Necessary as water is to plants, however, much of our 

 soil needs drainage to rid it of an oversupply of free or 

 gravitational water. There are some eighty million acres of 

 marsh lands in the United States. The greater part of this 

 waste territory would make excellent farm land if properly 

 drained. 



But perhaps fully as important is the occasional small 

 piece of wet ground on farms now under tillage. In cer- 

 tain regions there is hardly a farm that does not have its 

 low marshy places where crops drown out in wet times, or 

 which are allowed to lie without cultivation. In nearly all 

 cases this land could be made the equal of the remainder 

 of the farm by drainage and a little care. 



Surface drainage. Surface drainage is never so 

 thorough and satisfactory as underdrainage, yet it will often 

 improve conditions enough to pay. By surface drainage 

 is meant the opening of runs or ditches to allow the escape 

 of surface water that otherwise would stand on the soil, 

 flood over lower ground, or percolate down to add to the 

 gravitational water already in the subsoil. 



Low ground is sometimes plowed in narrow strips, the 

 frequent dead furrows allowing surface drainage. If there 

 is a slight slope and the furrows can open freely at the end, 

 this will prove of great benefit. Where such simple drain- 

 age will not serve, it is sometimes necessary to construct 

 open ditches, though these should give way to underdrain- 

 age when this is possible. For underdrainage is under most 



