18 BULLETIN 405, 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 tol>e 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 

 impossibilit}^ 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 in 

 many waters and operate on low pressures, which are advantages 

 greatly in their favor, often sufficient for their adoption. This type 

 of 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 light 

 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 



