42 BULLETIN 462, U. S. DEPARTMENT OF AGRICULTURE. 
adapted to this purpose. Although the total acreage so irrigated is 
not large the system has attracted considerable attention. The en- 
tire area irrigated by overhead-pipe system does not exceed 10 or 
15 acres. The same method is employed as for the irrigation of 
truck patches, except that it is necessary to keep the pipe lines above 
the foliage of the trees. This is not difficult in the case of small 
trees but trouble is experienced when the trees are large. 
By far the greater area of automatic-sprinkled groves is covered 
by some rotating-nozzle system. This differs from the overhead- 
pipe system only in minor detail. The nozzles should be kept above 
the trees in order that the foliage may not interfere with the dis- 
charge or the distribution of the spray. A large grove irrigated 
by this system is at Lucerne Park, and includes 60 acres. Water is 
taken from a near-by lake and forced through the pipe lines by 
means of a 2-stage centrifugal pump operated by a 35-horsepower 
gasoline engine. The main consists of a 6-inch steel pipe, with 2- 
inch to | -inch laterals running at right angles to the main every sec- 
ond row. The nozzles are set on uprights near a tree, standing 2 
or 3 feet above its top branches. They are spaced 50 feet apart and 
so arranged as to form a diamond-shaped figure. When the plant 
was installed the trees were young, standing above the ground only a 
few feet, but as they attained greater height it was found necessary 
to add a length of pipe to the uprights. The cost of the system has 
been high, that for the first 10 acres totaling over $500 per acre, 
although it was estimated that the entire 60 acres could be put in 
for about $250 per acre. 
When this type of system is in good order it is difficult to find an 
easier way to irrigate a grove. No labor is attached to the process 
other than starting the engine and manipulating a f ew valves. In the 
grove at Lucerne Park the system will water 5 acres at one time, 
applying an inch of water in about 4 hours. Thus, if the plant were 
run continuously for 48 hours, the entire 60 acres could be covered to 
a depth of 1 inch, the water being diverted from one 5-acre unit to 
another once every 4 hours. Other advantages also are claimed, one 
being that it will wash off the red spider, a mite which does con- 
siderable harm to the tree in dry weather. A good washing will 
drive away this pest, but this may be accomplished cheaply by the 
use of any of several insecticides which are applied easily with any 
good spraying machine. Some believe that this system will prove 
a good protector against frost, although this claim is disputed. In 
any event it would be hard to keep a 60-acre grove constantly watered 
with a 5-acre unit. There are certain designs of apparatus which 
will turn water automatically very rapidly from one unit to another, 
but these require a peculiar method of laying out the lines and are not 
in actual practice so far as the writer is informed. 
