2 BULLETIN 495, U. S. DEPARTMENT OF AGRICULTURE. 



The introduction of pis. 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 ohject 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. 1 

 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: 



Six per cent interest on $250 $15. 00 



Five per cent, depreciation on equipment 12.50 



Two per cent, .maintenance and repairs 5.00 



c.,<t of fuel and oil at 4 cents per 1,000 gallons of water pumped for 



6 acre-inches 2 6. 50 



Labor in Irrigating, 1 man 6 days at $2 12.00 



Total overhead and operating expenses 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 



1 The subjects of lawn and greenhouse irrigation are not included in this bulletin. 



2 Cost 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 al 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. 



