Sub - Irrigation 401 



to the surface along most of the lines of tile, as 

 represented by the dotted area below A. To do this 

 work, 5.8 inches of water on the level were required, 

 but it is quite certain that half this amount applied 

 at the surface in the proper manner would have ren- 

 dered as much service. The time required to apply 

 the water at the surface would have been about the 

 same, but an extra man would have been needed to 

 distribute it, and the furrows would have to be made, 

 so that there is this labor to be offset by the cost 

 of the extra amount of water required for the sub- 

 irrigation. 



But it must be kept in mind that had the field 

 not been underlaid by sand and the ground water 

 surface near the level of the tile, and had the pressure 

 not been held up so as to force the water to rise to 

 the surface, these results could not have been attained 

 with tile placed as far apart as 33 feet. The applica- 

 tion of sub -irrigation to tile -drained areas cannot, 

 therefore, be regarded as the best method of watering 

 in any but special cases. 



It is quite probable that were this system of 

 irrigation to be applied to water-meadows to avoid 

 surface ditches, or even to orchards and small fruits, 

 there might be experienced difficulties arising from 

 the tile becoming clogged, either from sediments 

 moved by the water or by the growth of roots into 

 the lines of tile. 



When the difficulties which have been pointed out 

 as standing in the way of sub -irrigation are con- 

 sidered, and when it is recalled that nitrification in 



