554 



THE IRRIGATION" AGE. 



IRRIGATION OF ORCHARDS 



BY SAMUEL FORTIER 

 Chief of Irrigation Investigations, Office of Experiment Stations, U. S. Department of Agriculture. 



THE usual way of irrigating orchards is by means of fur- 

 rows. These vary in depth, length, and distance apart, but 

 this diversity does not tend to create different kinds of fur- 

 row irrigation. The division of this subject is rather due to 

 the means employed of distributing water from the supply ditch 

 to the furrows. In some cases the distribution is effected by 

 making openings in an earthen ditch, in others by inserting 

 wooden or iron spouts in the ditch banks, while in many 

 others flumes having the desired number of openings or pipes 

 with standpipes divide the supply among the requisite number 

 of furrows. These designs and methods will be described un- 

 der their respective headings. 



Earthen Head Ditches. 



Permanent ditches at the head of orchard tracts should 

 be located by a surveyor. The proper grade depends 

 chiefly on the soil. If the soil is loose and easily eroded, 

 a slow velocity is best. On the other hand, the velocity 

 must be sufficiently rapid to prevent the deposition of silt 

 and the growth of water plants. In ordinary soils, a grade 

 of 2 l /2 inches to 100 feet for a ditch carrying 2' cubic feet 

 per second is not far out of the way. The amount of 

 water to be carried varies from l / 2 to 2 or more cubic feet 

 per second. A ditch having a bottom width of 24 inches, 

 a depth of 6 inches, and sloping sides, ought to carry \ l /2 

 cubic feet per second on a grade of half an inch to the rod 

 or 3 inches to 100 feet. Such a ditch may be built, by first 

 plowing four furrows and then removing the loose earth 

 either with shovels or a narrow scraper. The loose earth 

 may likewise be thrown up on the sides and top by means 

 of the homemade implement shown in figure 8. Canvas 

 dams, metal tap- 

 poons, or other 

 similar devices 

 are inserted in 

 the head ditch to 

 raise the surface 

 of water oppo- 

 site that part of 

 orchard where 

 furrows have 

 been made and 

 which is about to 

 be watered. The 

 chief difficulty in 

 this mode of fur- 

 r o w irrigation 

 arises in with- 

 drawing water 

 from the ditch 

 and in distribut- 

 ing it equally 

 among a large 

 number of fur- 

 rows. A skilled 

 irrigator may ad- 

 just the size and 

 depth of the ditch 

 bank openings so 

 as to secure a 



somewhat uniform flow in the furrows, but constant at- 

 tention is required in order to maintain it. If the water is 

 permitted to flow for a short time unattended the dis- 

 tribution is likely to become unequal. Parts of the ditch 

 bank become soft, and. as the water rushes through, the 

 earth is washed away, permitting larger discharges and 

 lowering the general level of the water in the ditch so 

 that other openings may have no discharge. Some of the 

 orchardists of San Diego county, Cal.. insert in niches 

 cut in the bank pieces of old grain sacks or tent cloth. 

 The water flows over these without eroding the earth. 

 Another device is to use a board pointed at the lower end 



From Farmers Bulletin, Xo. 404, Dept. of Agriculture. 



Fig. 8. The Use of the "A" Scraper in Building Head Ditches. 



and containing a narrow opening or slot through which 

 the water passes to the furrow. Shingles are also used 

 to regulate the flow in the furrows. The thin ends of these 

 are stuck into the ground at the heads of the furrows. 



Short Tubes in Head Ditches. 



In recent years short tubes or spouts have been used 

 in many of the head ditches of orchards to divert small 

 quantities of water to furrows. These tubes are usually 

 made of wood, but pipes made of clay, black iron, galv- 

 anized iron, and tin are occasionally used. 



For nurseries and young trees especially, and also for 

 mature trees, a cheap and serviceable tube may be made 

 from pine lath, such as are used for plastering. The 4-foot 

 lengths are cut into two equal parts and four of these 

 pieces are nailed together to form a tube. One of these 

 tubes when placed with its center 2 inches below the sur- 

 face of the water in the head ditch discharges nearly three- 

 quarters of a miner's inch of water, and if placed 4 inches 

 below the surface will discharge more than 1 miners' inch. 

 In southern Idaho the lumber mills manufacture a special 

 lath for this purpose. It is l / 2 inch thick, 2 inches wide, 

 and 36 inches long. If such tubes when thoroughly dry are 

 dipped in hot asphalt they will last a much longer time. 

 In some of the deciduous orchards of California a still 

 larger wooden tube or box is used. Figure 9 represents 

 one of these. It is made of four pieces of J4 by 3^4-inch 

 redwood boards of the desired length. The flow through 

 this tube is regulated by a cheap gate, consisting of a 

 piece of galvanized iron fastened by means of a leather 

 washer and a wire nail. 



The orchard- 

 ist who lives near 

 a manufacturing 

 town or city can 

 often purchase at 

 a low figure 

 pieces of wornqut 

 and discarded pip- 

 ing varying from 

 24 to 2 inches in 

 diameter. Such 

 pipes when cut 

 into suitable 

 lengths make a 

 good substitute 

 for wooden 

 spouts. Tin tubes 

 one-half inch in 

 diameter and of 

 the proper length 

 have been used 

 with good suc- 

 cess. In compact 

 soils, through 

 which water 

 passes very slow- 

 ly, the furrows 

 must be near to- 

 gether, and under 

 such conditions small tin tubes are to be perferred. 



In making use of tubes of various kinds to distribute 

 water to furrows it is necessary to maintain a constant 

 head in the supply ditch. This is done by inserting checks 

 at regular distances. These distances vary with the grade 

 of the ditch, but 150 feet is not far from being an average 

 spacing. In temporary ditches the canvas dam is perhaps 

 the best check, but in permanent ditches it pays to use 

 wood or concrete. An effective wooden check is shown 

 in figure 10. In this the opening is controlled by a flash- 

 board which may be adjusted so as to hold the water at 

 any desired height and at the same time permit the surplus 

 to flow over the top to feed the next lower set of furrows. 



