Se ee ee ee OEE ee 
SSS 
‘ 
; 
il 
; 
i 

18 BULLETIN 495, U. S. DEPARTMENT OF AGRICULTURE. 
At 25 pounds pressure the capacity was 0.46 cubic foot (3.5 gallons) 
per minute with a fair lateral spread of 35 feet. The zone receiving 
the greatest amount of water was found to be a circular area 4 feet in 
diameter immediately about the nozzle. The amount received per 
square foot of area decreased uniformly with the distance from the 
nozzle. 
The most striking results obtained from these tests and from similar 
tests with 7 other nozzles were the great ranges in capacities and 
the uneven distribution beneath individual nozzles. Every nozzle 
tested placed a large percentage of the total discharge on a small 
portion of the area it was supposed to irrigate. Solid and adjustable 
types placed the maximum amount in an annular ring having a radius 
about three-fourths that of the sprayed area. ‘The rotary nozzles 
placed the maximum quantity of water close to the center and the 
quantity diminished rapidly with the distance from the nozzle. 
The results of these tests, when considered in connection with the 
impossibility of fitting a set of circular areas together to cover a 
field without overlapping (fig. 9), bring out the difficulties in obtain- - 
ing an even distribution of water with a stationary nozzle spray sys- 
tem. The cost of the system exceeds that of the hose and portable 
nozzle and in many cases that of the overhead equipment. The cost 
of operation is about the same as that of the overhead, but the effi- 
ciency and adaptability to the irrigation of delicate farm corps are 
generally less unless a larger amount of water is needed in a shorter 
time than the overhead system will supply. However, the stationary 
nozzles do not clog readily from rust or other particles. present n_ 
many waters and operate on low pressures, which are advantages 
greatly in their favor, often sufficient for their adoption. This type 
cf spray system often is considered more sightly than overhead types. 
while the operation is quite simple and automatic. Where it is de- 
sired to keep the cost low, block pipe can be used largely in the 
distribution system. The distribution is assisted greatly by a hght 
breeze, but the field for this type of spray irrigation at present. is 
largely confined to light soils that take water rapidly for the growing 
of crops and lawns that will stand a coarse spray. 
STATIONARY OVERHEAD SPRAY SYSTEMS. 
The development of a stationary overhead spray system marked 
the beginning of rapid progress in spray irrigation for commercial © 
crops. The original overhead system consisted of a few lengths of © 
steel pipe set on parallel rows of posts and connected to a hand force 
pump. A series of small holes was drilled in the shell of the pipe, 
through which water could be forced in the form of a spray. The 
holes gradually became clogged or irregular in shape, due to the 
















