2 BULLETIN 495, U. S. DEPARTMENT OF AGRICULTURE. 
The introduction of gas, oil, and electric power for operating 
_pumps on the farm has provided means of elevating water to the 
higher lands and generating sufficient pressure to produce the desired 
spray. Engineers have devised systems of piping and special spray 
equipment for irrigating all areas by spray methods and have intro- 
duced automatic devices which reduce labor. 
The object of this bulletin is to familiarize the farmer with con- 
ditions under which spray irrigation may be undertaken profitably, 
suggest possible water supplies, and illustrate typical pumping ma- 
chinery and distribution systems, so as to aid the prospective irri- 
gator in determining whether spray irrigation should have a place 
in his farm operations. It is also intended to present information 
necessary in working out an intelligent design and installation of 
a spray system. 
ECONOMIC CONDITIONS JUSTIFYING SPRAY IRRIGATION. 
The cost of spray-irrigation systems depends upon the type in- 
stalled as well as upon conditions peculiar to each farm. A portable 
outfit may cost as little as $50 per acre for the field equipment, while 
a stationary distribution system may cost as much as $150 per acre.* 
To these figures must be added the cost of a main pipe line leading 
from the water supply to the fields and usually the cost of de- 
veloping a water supply and installing a pumping plant. These 
additional items may bring the total outlay per acre up to two or 
three times the cost of the distribution system, especially on small 
acreage. Assuming a cost of $250 per acre on a stationary plant for 
a small acreage, the farmer should be able to increase his annual 
returns from each acre to cover approximately the following charges: 

SIXSHEr Cent LMtERESE OM S2DO a la Te Ts ae ee $15. 00 
Hive percent, depreciation on equipment]. =) sts e eee eee 12. 50 
Two per cent, maintenance and repairs_222 2 = as 1A Sh ea) SLES Sage eee 5. 00 
Cost of fuel and oil at 4 cents per 1,000 gallons of water pumped for 
G)ACHORUI CH OS 2.00. |G eg sg eek Sd ee ns * 6. 50 
Daborain irricatine, mam 6G daystat po es oe ee eee ee 12. 00 
Total overhead and operating expenses”. =i) see ee ees eee 51. 00 
It will be noted that $51 per acre per year is necessary in returns 
to cover overhead and operating expense incidental to the spray 
system. To realize a fair profit from the irrigation plant, the crops 
must increase in value something more than $51 per acre. In the 
case of berry, tobacco, and orchard crops the increase must be derived _ 



1The subjects of lawn and greenhouse irrigation are not included in this bulletin. 
2Cost of pumping estimated for a plant operating at 50 per cent efficiency against a | 
total head of 150 feet, using gasoline as fuel. The amount of water pumped annually is 
assumed at 6 acre-inches as a typical duty of water in the Atlantic Coast States where 
spray irrigation is most extensively used. More arid sections require larger amounts. 
=p 







