Land Draixage axd Soil Efficiency 183 i 



entrance of roots into tile 



The tile is sometimes clogged b}' the development of roots that gain 

 entrance through the joints of the tile. The depth at which the tile are laid 

 has very little to do with this difficulty. It is determined by the presence of 

 a perpetual flow of water in the tile from some spring. In dry periods 

 this water seeps from the joints and moistens the soil, which condition 

 attracts the roots. Protection of the upper half of the joint against the 

 admission of silt is some aid in preventing the entrance of roots into the 

 tile. 



CONSTRUCTION OF OUTLETS 



The construction of a drainage system should begin at the outlet and 

 end at the same place. There must be a sufficient grade to dispose of the 

 water at the outlet. After the remainder of the system is constructed, the 

 outlet should be carefully protected, especially if the grade is sHght. This 

 part of the system is especially in danger of being closed by tramping, 

 caving of banks, freezing, gro^i;h of roots, and other obstructive processes. 

 If possible the water should have a free drop from the end of the tile. It 

 is usually ad\nsable to build up an abutment of concrete or stone, with an 

 apron on which the water may fall without cutting out the bottom of 

 the ditch. 



In laying out the ditch as few outlets should be provided as practicable. 

 Where several laterals might empty into an open ditch, it is often better 

 to drop back a couple of rods from the open ditch and put in a submain 

 to receive all these laterals. This arrangement gives one outlet, 

 instead of several, to be finished and cared for from year to year. 



COST OF DRAINAGE 



The cost of drainage varies greatly, depending on the nature of the soil, 

 the presence of stones and roots, the depth, the size of tile, the season when 

 the work is done, the method of construction, and the local labor conditions. 

 For 3- or 4-inch tile the cost of the finished ditch per rod in soil not par- 

 ticularly foul with stone and roots is 60 to 90 cents per rod. On a system 

 of 2560 rods constructed by hand where the size of tile ranged from 

 3 to 10 inches, the average cost per rod including all charges was 68 cents. 

 Systems aggregating 8398 rods were constructed under the same manage- 

 ment and on the same farm by using a traction ditching machine. The 

 size of tile ranged from 3 to 13 inches, and the average cost was 63 cents 

 per rod. Some of the work done with the machine was more difficult 

 than any done by hand. The range in the cost of tile per rod was 17.5 

 cents to 94.5 cents. The average cost of trenching with the machine 

 was 17 cents per rod. The cost of drainage on this farm was $29.74 to 



