THE FOREST NURSERY 



247 



The Skinner system of irrigation, by which a fine spray is uni- 

 formly distributed over the beds is rapidly coming into use in 

 permanent nurseries in the United States. Although costly to in- 

 stall, in the end it usually proves less expensive than any other 

 method of water distribution by sprinkling. In this method of 

 irrigation a series of pipes is supported at a varying distance from 

 the ground, in which small openings are made at from 2- to 4-foot 

 intervals and fitted with special nozzles. 



Both stationary and portable methods of installing the system 

 have been practiced in forest nurseries. When the installation is 



Photograph by E. J. Zavitz 



FIG. 51. The Skinner overhead system of irrigation in operation. 



permanent f-inch pipes with the nozzles at 4-foot intervals are 

 usually used. The pipes are raised on iron or wooden posts from 

 3 to 6 feet above the beds. They are usually arranged parallel 

 to each other and 50 feet apart. Under a water pressure of 30 

 pounds it is possible to irrigate for a distance of 25 feet on each 

 side of ihe pipe when the units are 100 feet long (Fig. 51). The 

 main feed pipe through which the water is brought to the over- 

 head pipes should be at least 1| inches in diameter and the water 

 should have a pressure of at least 25 or 30 pounds. 



