Irrigation By Means oe Underground Porous Pipe 15 
3. With deep-rooted crops, such as alfalfa, or with orchards, 
this form of irrigation may be practiced with success as far as lateral 
percolation is concerned, but the 'cost of installation is so great that it 
cannot be recommended. 
4. There has been no clogging of the lines due to the entrance of 
roots for the four years that the system has been in service. 
5. The water used for this system was drain water which con¬ 
tained some alkali, but it was evidently not sufficient to cause disin¬ 
tegration of the tile lines as no trouble on this score was encountered. 
6. A very small stream of water can be sucessfully used with 
a subirrigation system of this kind. A stream that would not answer 
at all for surface irrigation might be more than ample to supply a pipe 
system for subirrigation on a much larger area. 
