THE IKEIGAT10N AGE. 



303 



The cost of an ordinary head ditch, 

 with four drops or check boxes, would 

 be about $15 for the same tract, or $2.50 

 per acre for both, exclusive of grading, 

 smoothing and leveling. Tin tubes, 0.5 

 inch in diameter, one to each furrow, 

 have sometimes been used instead of 

 the wooden tubes. When set 0.5 inch 

 below the water surface each tube dis- 

 charges about 0.1 miner's inch which is 

 about right for a slope of 3 per cent. 

 The length of the tin tubes is governed 

 by the size of the ditch bank. The 

 tubes are set while the water is in the 

 ditch and are kept at the same level 

 between check boxes. The cost of tin 

 tubes 2 feet long is about $3 per hun- 

 dred. In manv places neither flumes 

 nor tubes are used. Water is taken 

 through cuts in the ditch bank and di- 

 vided among the furrows as evenly as 

 possible by directing it with the shovel. 

 This practice reduces the cost of pre- 

 paring the land for irrigation, but it 

 increases the cost of applying water, 

 and does not secure an even distribu- 

 tion among the furrows. 



Furrows in alfalfa fields are most 

 commonly made by the use of a marker, 

 or furrowing sled. Sleds with more 

 than two runners are sometimes used, 



too A 



Wier Box 

 'xIZ' Flume 



B"x O" Flume 



350' 



N 



LEGEND 



F/ume 



Slope of Land 



Direction of Flow in Flume 



B"x 6" Flume 



330' 



Fig. 18. Manner of placing tubes in ditch bank for furrow irrigation. 



reducing the time required for furrowing, but not pro- 

 ducing quite so satisfactory furrows, since an obstruc- 

 tion under one of the outside runners will lift all but the 

 other outside runner out of the ground and leave obstruc- 

 tions in the furrows, which, if not removed, will cause 

 the flooding of the surface. Sometimes a marker is put 

 on the sled to indicate the place for the next furrow. 



Fig. 17. Showing tract prepared for furrow irrigation. 



inserted in the ditch at the end of each 

 fall of 12 inches. Thus, if the ditch has 

 a fall of 4 inches to 100 feet the checks 

 are placed 300 feet apart. Each check 

 box is provided with a removable flash- 

 board, which, when in place, backs the 

 water to the next check above and at 

 the same time permits the surplus water 

 to flow over its top to supply the 

 checks below (Fig. 20). Lath tubes 16 

 to 24 inches long are inserted in the 

 lower ditch bank about 3 inches below 

 the water level formed by the flash- 

 boards when in place. These tubes are 

 put in while the check is full of water 

 in order that all of each set may be on 

 the same level and that water may be 

 had for puddling. The flow from each 

 tube may be divided among several 

 furrows. Ordinarily a 40-acre farm will 

 require about 30 check boxes and 1,800 

 tubes. Nearly one-half the tubes ought 

 to be 24 inches long to insert near the 

 check boxes where the bank is heaviest, 

 while the remainder may be 16 inches long. The check 

 box shown in the sketch (Fig. 20) calls for 17 b. m. feet 



Fig. 19. Furrower used on experiment farm, Riverton, Wyo. 



For the irrigation of most of the crops grown in the 

 vicinity of Twin Falls, Idaho, the feed ditches are laid 

 out across the field as nearly parallel as possible on a 

 grade of 2 to 6 inches to 100 feet and 300 to 500 feet 

 apart. Furrows are made in the direction of the greatest 

 slope and approximately at right angles to the feed 

 ditches. Starting at the upper end, a wooden check is 



Fig. 20. Check box for furrow irrigation. 



