IRRIGATION 
8l 
a gentle shower the foliage is cleansed and the effect is 
to encourage the most healthful and vigorous growth ; 
(6) insecticides, fungicides, and liquid fertilizers may be 
applied through the water lines though this practice is 
not common ; (7) the cost of installation is low, consider- 
ing the merits of the system. It varies from $175 to 
$300 an acre. 
Water may be pumped directly into the system, or 
reservoirs may be constructed to hold it. When water 
FIG. 17. ONE TYPE OF UNION FOR OVER-HEAD 
IRRIGATION SYSTEM 
from a city reservoir can be secured at a reasonable price 
the problem is very simply solved. A great many grow- 
ers, however, pump directly into the system. The water 
mains or feeders should be of ample capacity to supply 
the nozzle lines, which should be of galvanized pipe and 
of the size indicated in the accompanying table. The lines 
are generally 50 feet apart in outdoor irrigation, and 
should be supported on posts 15 to 25 feet apart. One 
and one-fourth inch pipe is generally used for posts, 
although sometimes cedar or locust posts are used. 
