CROPS AND SOIL IMPROVEMENT 



good bottom, it continues effective. There is no 

 known limit to the durability of a drain made of 

 good tile. 



The Outlet. The value of any drainage system 

 is dependent upon the outlet. Its location is the 

 first thing to be determined. If the land is nearly 

 flat, a telescope level should be used to determine 

 elevations of all low points in the land to be 

 drained. The outlet should permit a proper fall 

 throughout the length of the system, and it should 

 not require attention after the work is completed. 

 If it is in the bank of a stream or ditch, it should 

 be above the normal level of the water in the 

 stream. In times of heavy rainfall water may 

 back up into the main with no injury other than 

 temporary failure to perform its work, but con- 

 tinuous submersion will lead to deposits of silt 

 that may close the tile. 



Locating Main and Branches. There are 

 various systems of drainage. Wherever a branch 

 or lateral joins the main, the means of drainage 

 is duplicated within the area that the main can 

 drain, and the system should call for the least 

 possible waste of this sort. It usually is best 

 that the main take the center line of the low land, 

 laterals being used to bring the water to the main 



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