398 



Irrigation and Drainage 



unless the tile are as close as 4 feet apart and very 

 near the surface. 



The second great obstacle in applying sub-irriga- 

 tion is the expense required to purchase and place the 

 necessary lines of tile. In watering strawberries, 



Fig. 123. Difficulty of wetting surface soil by sub-irrigation. 



blackberries, raspberries, and other small fruits, one 

 line of tile would be required under each row. For 

 orchard irrigation, two lines of tile would be needed, 

 one on each side of the row when the trees are small, 

 and the number would have to be increased as the 

 trees reached maturity, until there was at least one 

 every 5 feet. For general field crops, the number of 



