IRRIGATION 



73 



and so mounted that it will turn freely upon its 

 bearings. At intervals of every 4 feet along one 

 side of the pipe holes are drilled and small brass 

 nozzles inserted. At one end the pipe is connected 

 to the water main by means of a flexible ground 

 joint which will permit of its being revolved. The 

 nozzles are turned to one side and the water applied, 

 and as the plants become sufficiently watered the 

 pipe is gradually turned until the other side is 



FIG. 28 CROSS-SECTION SHOWING ARRANGEMENT OF TILES FOR 



SUBIRRIGATION 

 (Redrawn from Farmers' Bui. No. 255, U. S. Dept. of.Agr.) 



reached. In this way a strip of ground from 50 to 

 150 feet in width may be watered, but the width of 

 the strip will depend largely upon the direction and 

 velocity of the wind, and the lines of pipe should be 

 placed at intervals of not more than 50 feet. 



Subirrigation as Applied to Celery Growing. By 

 the subirrigation method the water is applied to the 

 roots of the plants through drain tiles or perforated 

 pipes laid on a level a few inches below the surface 

 of the soil. This system is especially adapted to 

 use in back-yard gardens where water under pres* 

 sure is available, and where the area under cultiva- 

 tion is small. Subirrigation will prove most satis- 

 factory where the surface soil is underlaid with clay 



