THE DRAINAGE OF FARM SOILS 201 



of water a year, in the Eastern States, and much 

 more than that in the arid regions. 



These objections are sufficiently forceful to 

 make dramage_byLjnpen ditches, entirely impracti- 

 cable when tile_drains ran be used. There are 

 many sections of the country, notably in the South, 

 where it is dangerous to provide any kind of sur- 

 face drainage, because the soil washes so badly. 

 All kinds of surface drains everywhere carry 



V / 



away more fertility than would be lost through 

 under-drains. In most cases it is better that 

 excess water should pass through a soil instead 

 of over it. 



WHEN DITCHES ARE PRACTICABLE 



There are, however, conditions under which 

 surface drainage is not only useful, but is about the 

 only kind of drainage that is at all practicable. In 

 peaty or muck bogs, fresh and salt water marshes, 

 cranberry bogs and the like, the open ditch is the 

 only feasible method of drainage, at least for the 

 larger drains. In these cases the main object is 

 to carry off the flood or surface water; the water- 

 table is not lowered to the depth that is necessary 

 for most farm crops. Whenever it is wished to 

 lower the water-table of such lands to four feet 

 and to plant them with the common farm crops, it 

 is usually necessary to supplement ditching with 

 tile drainage. 



Tile drains cannot be laid in marshes in which 

 the peat is not well rotted until they have been 

 partially drained by open ditches. When a peat 

 soil is drained it shrinks; if tile drains had Been 

 laid the tile would soon be found too near the sur- 

 face. In such cases it is preferable to first put in 



