Publication of The College of 
 
 UNIVERSITY OF CALIFORNIA 
 
 James C. Marr TllC BORDER 
 
 METHOD OF 
 IRRIGATION 
 
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 •'-. 
 
 CALIFORNIA AGRICULTURAL 
 Experiment Station 
 Extension Service 
 
 CIRCULAR 408 
 
The BORDER METHOD 
 
 Ditch or pipeline for water supply 
 
 Direction 
 
 of slope or fall 
 
 of strip check 
 
 Levees 
 
:f IRRIGATION 
 
 its Design, Construction, and Use in California 
 
 Border irrigation is the most popular method of applying water 
 to close-growing crops, and sometimes to orchards, in the state 
 of California. 
 
 The American Society of Agricultural Engineers describes 
 border irrigation as "... a method applying water to land be- 
 tween parallel ridges or borders. The strips of land between 
 adjacent borders have no cross slopes, but may have a grade in 
 the direction of the irrigation." 
 
 The parallel ridges are usually called levees. The strips of land 
 between the levees are usually called strip checks. 
 
 This circular tells how to design, construct, and use a border 
 irrigation system efficiently, either for temporary or permanent 
 facilities. It discusses and tells how to shape levees to allow for 
 different uses to which they may be put. It discusses and recom- 
 mends types of machinery that are best adapted to the various 
 operations performed in constructing border systems. It gives 
 some recommendations for the operation of a border system that 
 will enable farmers to make the best use of their facilities. 
 
 The drawing on the left is probably oversimplified, but shows 
 the main features of a typical border irrigation system — features 
 that are discussed more thoroughly in this circular. 
 
 The Author: James C. Marr is Lecturer in Irrigation and Associate Special- 
 ist in the Experiment Station, Davis. 
 
I 
 
 N border irrigation, water is turned into the upper, or higher end of each strip 
 check and allowed to move down the slope. While it may seem a simple matter to 
 design such a system, the principles of design must first be mastered. But before 
 anything else, you should decide whether you need a temporary or a permanent 
 system. 
 
 TO DESIGN A GOOD SYSTEM 
 you need knowledge and skill 
 
 A temporary system 
 warrants minimum outlay 
 of time and money 
 
 Temporary border-irrigating systems 
 are used in cultivated orchards, for pre- 
 irrigating land which is to be planted 
 in row crops, and for watering early- 
 maturing annual crops. 
 
 After grading and cultivating the land, 
 you can construct a satisfactory system 
 for temporary use by making a single 
 trip with a ridger or a border disk. 
 
 Levees formed by this method are nar- 
 row and sharp crested. They would not re- 
 main serviceable if they were repeatedly 
 run over by farm machinery, as is often 
 necessary in an alfalfa field. Furthermore, 
 the ridger or border disk leaves a furrow 
 or trough on either side of the levees, 
 which should be dammed at regular inter- 
 vals, in order to keep the water spread 
 over the strip check. These conditions 
 
 make it difficult to control the flow of 
 water, and also require much extra labor 
 during irrigation. 
 
 Nevertheless, the inconvenience and 
 extra work involved are more than offset 
 by the saving in time and expense that 
 would be required for building up, and 
 later flattening out, the more permanent 
 type of levee. 
 
 A permanent system 
 is needed for alfalfa 
 
 When perennial crops, such as alfalfa, 
 clover, or pasture, are irrigated, the strip 
 checks must last for years. Therefore, 
 they should be built to insure the best 
 possible use of water, with minimum 
 labor necessary for operation and main- 
 tenance. To this end, the strip checks are 
 prepared so that the irrigation water will 
 spread evenly across them without the aid 
 of cross dikes or furrows. 
 
 CROSS SECTION SHOWING A TEMPORARY BORDER SYSTEM 
 
 Water collects in troughs 
 
 instead of spreading evenly 
 
 over surface of checks 
 
 [4] 
 
Levees should be substantial enough to 
 stand the impact of harvesting equipment, 
 or the trampling of livestock, and of a 
 shape that will allow the water to wet all 
 the way through them. Levees are ar- 
 ranged on the field to suit the require- 
 ments of the crop being handled. 
 
 Finally, the length of the strip checks 
 should be so planned that when water is 
 let into them, the soil will be wetted at all 
 points to within at least 80 per cent of the 
 same depth. 
 
 Type of soil is important in irri- 
 gating pasture. Because of the wide range 
 in soil and topographic conditions that 
 can be used for growing pasture, the 
 border method is carried on under con- 
 ditions peculiar to the demands of irri- 
 gated pasture. 
 
 Soil used for growing pasture usually 
 consists of deep clay, or a shallow topsoil 
 over hardpan. It absorbs water slowly. 
 The grasses and legumes ordinarily 
 planted for pasture will, therefore, de- 
 velop shallow root systems. In order to 
 keep the crop supplied with sufficient 
 moisture, irrigation must be light and 
 frequent. 
 
 Pasture land may be rougher and 
 steeper than land suitable for most other 
 border-irrigated crops. Here, then, the 
 irrigation layout for pasture land usually 
 serves only one purpose — to furnish 
 water for the pasture — and other farm 
 operations need not be considered. 
 
 Alfalfa has special needs. Alfalfa 
 and other deep-rooted, close-growing 
 perennial crops raised for hay or seed, 
 require an irrigation layout designed to 
 water deeply and to facilitate the harvest 
 and removal of the crop. 
 
 Cross slopes and irrigation slopes are 
 generally small. Strip checks should be as 
 wide as possible to make them convenient 
 for operating farm implements. Wide, 
 low levees are usually desirable. 
 
 By way of identification— top photo shows a 
 ridger; the center photo, a border disk; lower 
 photo shows a temporary ievee system with 
 dams. 
 
 ^ , 
 
 [5] 
 
Ideal strip checks 
 should have no 
 cross slope 
 
 The surface crosswise of a strip must 
 be such that as the irrigation stream 
 enters the strip check and flows down the 
 slope, it will completely cover the ground 
 surface between the levees. Strip checks 
 should be constructed flat in both direc- 
 tions, for approximately the first 30 feet 
 next to the irrigation supply ditch, or 
 pipe line. 
 
 A small cross slope is allowable. 
 Since the depth of water in a strip check 
 during an irrigation is at least 2 inches 
 and may be as much as 5 inches, some 
 departure from the 0.00 slope may occur. 
 It is considered acceptable practice, for 
 example, to disregard a cross slope of 0.2 
 foot per 100 feet, when border spacings 
 range from 30 to 40 feet. This is an 
 allowance per strip check of 0.06 to 0.08 
 foot, or, roughly, one inch. 
 
 When the cross slope exceeds this aver- 
 age amount it is advisable to level the 
 strip checks individually by one of the 
 methods described on page 14. Under 
 these circumstances, the slope will be 
 taken up by a difference in elevation on 
 either side of each levee. 
 
 Difference in elevation has limits. 
 Terraces in border-irrigated fields are 
 a nuisance, and should be minimized as 
 much as possible. The trouble they cause 
 increases with their height. They become 
 difficult to cross with farm machinery. 
 Confining the water to individual strip 
 checks, especially in rodent-infested 
 fields, may become impossible. Finally, 
 when the terraces are so high and so steep 
 that they cannot be watered and cropped, 
 they deteriorate into wastelands, and can 
 become a liability of no small conse- 
 quence. 
 
 A 0.2 to 0.3 foot drop between succes- 
 sive strip checks does not cause too much 
 trouble. If that amount is exceeded, the 
 land should first be benched or widely 
 terraced, so that most or all of the cross 
 slope is eliminated. 
 
 The same objections may be made to 
 an occasional major terrace. Sometimes 
 these may be avoided by grading out the 
 excess cross slope over an entire field; or, 
 when it is practical to do so, by locating 
 the borders at right angles to the con- 
 tours. 
 
 Sometimes it is possible to make widely 
 spaced terraces less objectionable by lo- 
 cating them along drainage lines, access 
 roads, or similar breaks in the cultivated 
 area. 
 
 What is an 
 irrigation slope? 
 
 An irrigation slope is commonly under- 
 stood to be the amount of fall per unit 
 length of strip check, expressed in feet 
 fall per 100 feet of length, such as 0.5 
 foot per 100 feet; or in per cent, such as 
 
 5' 
 
 Y^, x 100 = 0.5 per cent. 
 
 Land is usually leveled for irrigation 
 as economically as possible; and, if con- 
 ditions permit, the border system must 
 be made to conform to the resulting irri- 
 gation and cross slopes. 
 
 Therefore, though irrigation slope is a 
 very important factor in design, it can- 
 not always be ideal. Adjustments to im- 
 prove irrigation performance can be 
 made, however, within slope limitations, 
 by changing the size of the irrigation 
 stream or the length or width of the strip 
 check. 
 
 Slope limitations for alfalfa. The 
 slope limitations for border-irrigated 
 alfalfa are 0.15 per cent minimum and 
 approximately 1.5 per cent maximum. A 
 uniform slope ranging from 0.2 to 0.3 
 per cent is usually ideal. 
 
 The maximum slope that can be used 
 depends on the erodability of the soil, the 
 manner in which the crop can be started, 
 and the spacing of the levees. Clay with- 
 stands erosion better than silt. A protec- 
 tive cover of young alfalfa started either 
 by winter precipitation, sprinkling (see 
 Sprinkling for Irrigation, Circular 388 of 
 the California Agr. Exp. Sta.) or by 
 
 [6] 
 
corrugation irrigation (see The Corru- 
 gation Method of Irrigation, U.S.D.A. 
 Farmers' Bui. 1348), will prevent the 
 serious erosion that would otherwise 
 occur. 
 
 Narrow strip checks cut down 
 erosion. Because the irrigation streams 
 required to fill narrow strip checks are 
 small, the water is less likely to channelize. 
 
 Thus, to irrigate a clay soil on a 1.5 
 per cent slope without serious erosion, a 
 plant-covered surface and narrow strip 
 checks of 20 feet would be required. 
 
 Slope limitations for pasture range 
 from 0.15 to 0.5 per cent minimum, to 
 about 4 per cent maximum. The mini- 
 mum slope that can be safely used de- 
 pends on the permeability of the soil 
 profile. Irrigated pastures are usually 
 planted on soils that either limit the 
 amount or prevent the deep percolation 
 of water. 
 
 If percolation is merely retarded and 
 not completely stopped, the minimum 
 slope may be 0.15 per cent. If percolation 
 is virtually stopped by an impervious soil 
 layer, the slope should be 0.5 per cent or 
 more. 
 
 Slope aids drainage. A slowly per- 
 meable soil will drain internally and may, 
 therefore, be irrigated on flat slopes. But 
 a soil underlaid by impervious material 
 at depths of a foot or less is easily water- 
 logged during irrigation, unless surface 
 drainage is provided for by the use of 
 somewhat steeper slopes. Poor drainage 
 frequently results in the dying out of the 
 crop, which is gradually replaced by 
 watergrass and sedges. 
 
 Since permissible irrigation slopes are 
 greater for pasture than for alfalfa, this 
 problem of erosion may be a very real 
 one. It can be met by the use of extra- 
 narrow strip checks and smaller unit irri- 
 gation streams. 
 
 Uniform slopes used only when 
 necessary. A uniform irrigation slope 
 is usually the most desirable and it is best 
 to conform to it as much as possible. But 
 in some types of soils and topography — 
 
 such as rolling, upland areas with soils 
 not deep enough to permit much level- 
 ing — it is necessary to irrigate with non- 
 uniform slopes. 
 
 Nonuniform slopes cause the water to 
 flow unevenly down the strip checks. 
 Where the grade flattens out, the water 
 will be deepest and will remain longest. 
 To the degree that this occurs, the levees 
 must be reinforced to confine the water 
 to the individual strip checks. 
 
 Nonuniform slopes also result in un- 
 equal depth of water penetration, a con- 
 dition which varies with the porosity of 
 the soil. If the soil is porous, the loss of 
 water by deep percolation in the stretches 
 with little slope will be high. If the soil is 
 clay, the steep stretches may not receive 
 sufficient water. 
 
 Length of strip 
 
 check depends on slope 
 
 and size of stream 
 
 It is essential that a strip check be of 
 the proper length in relation to the irri- 
 gation slope and the size of the irrigation 
 stream. This will make possible (within 
 practical limits) uniform depth of water 
 penetration from the upper to the lower 
 end of the strip check. 
 
 If the strip checks are long, the irri- 
 gation slope and irrigation stream small, 
 and the permeability or water intake rate 
 of the soil high, the upper end of the field 
 will receive more water than the lower. 
 
 Faster irrigation aids water dis- 
 tribution. Faster irrigation, accom- 
 plished by increasing the irrigation slope, 
 using a larger irrigation stream, and 
 shortening the length of the strip check, 
 will tend to correct such faulty water 
 application. 
 
 But shortening the strip check is 
 usually better. The best remedy for 
 unequal water penetration often lies in 
 reducing the length of the strip check — a 
 simple matter if the topography and type 
 of soil permit the use of unlined ditches. 
 Strip checks can be shortened by opening 
 up another field ditch across the checks, 
 
 [V] 
 
and watering the lower end of the field 
 from the second ditch. The extra ditch 
 can be quickly and inexpensively built 
 with an implement similar to the one 
 shown below. Since it can be easily filled 
 in with a 3- or 4-bottom plow or other 
 suitable implement, the ditch need not be 
 an obstruction during harvest. 
 
 But if the water must be conveyed to 
 the strip checks by a lined ditch or pipe 
 line, the cost of the new ditch might be 
 prohibitive. In such cases, necessary ad- 
 justments can be made by changing the 
 size of the irrigation stream, or, if pos- 
 sible, altering the irrigation slope. 
 
 Field conditions affect length. No 
 single figure for the length of the strip 
 check can be cited as ideal under all field 
 conditions. Tables 1 and 2 will help to 
 determine the appropriate length to which 
 the strip checks may be extended when 
 land is first prepared for irrigation. 
 
 Irrigation trial runs should next be 
 made, in the manner described on page 
 22. Then, if the depth of water penetra- 
 tion is found to be excessive, inadequate, 
 
 or nonuniform with the upper and lower 
 ends of the field, the length of the strip 
 checks can be changed accordingly. 
 
 Strip checks may vary from 200 
 to 2,000 feet in length. Deep, sandy 
 soils should usually be irrigated in strips 
 from 200 to 300 feet long. Clay soils, with 
 a water intake rate of around 0.2 foot per 
 hour, should be irrigated very slowly, 
 and in relatively long strips. With slowly 
 permeable soils, upwards of 2,000-foot 
 runs will result in uniform distribution 
 of the water. 
 
 Under ordinary conditions, however, it 
 is advisable to adopt about half that dis- 
 tance, or about 1,000 feet, as the ideal 
 maximum length. 
 
 Pay close attention to the water. 
 In border-irrigating, it is necessary to 
 know when the water reaches the lower 
 ends of the strip checks, so that the water 
 may be cut off, or cut back, at the proper 
 time. It is also part of the irrigator's job 
 to kill gophers, to strengthen levees where 
 necessary, and to see that the water en- 
 tirely covers the strip checks at all points. 
 
 A custom made ditcher such as this may be used for shortening strip checks. 
 
 [8] 
 

 
 
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 The entire length of the strip check 
 must, therefore, be inspected several 
 times during an irrigation, and the dis- 
 tance should be such that the strip check 
 will be covered by a man walking as often 
 as is necessary. 
 
 Width of strip check 
 depends on 4 factors 
 
 Width of strip check, another way of 
 saying "the spacing of levees," depends 
 on four controlling factors: the amount 
 of cross slope, the steepness of the irri- 
 gation slope, the size of the irrigation 
 stream available, and crop to be grown. 
 
 Amount of cross slope. The effect 
 of this has already been touched upon; it 
 has been implied that the strip checks 
 should be of a width which, at successive 
 border lines, would make unnecessary a 
 difference in elevation of more than 0.2 
 to 0.3 foot. Thus, a cross slope of 1 per 
 cent, or one foot for each 100 feet width 
 of field, would allow a maximum width 
 of strip checks of from 20 to 30 feet. 
 
 Steepness of the irrigation slope. 
 Steep irrigation slopes call for narrow 
 strip checks, because the large streams of 
 water required for wide strip checks tend 
 to channelize and cause serious erosion. 
 Thus, for the flattest irrigation slopes — 
 which range from 0.15 per cent to 0.3 
 per cent — any convenient strip width up 
 to 100 feet or more may be used. 
 
 For slopes that range from 0.4 to 0.5 
 per cent, it is recommended that strips 
 from 20 to 30 feet wide be used. For 
 greater slopes, the maximum width 
 should be from 15 to 20 feet. 
 
 Size of the irrigation stream. The 
 amount of water available may limit the 
 width of the strip checks. E.g. if 225 
 g.p.m. are available for irrigating a soil 
 which requires a unit flow of water of 9 
 g.p.m. for each foot-width of strip check, 
 the maximum width of the strip check that 
 can be irrigated would be 25 feet. 
 
 Kind of crop to be grown. When a 
 crop such as alfalfa or clover is mowed, 
 raked and baled, or threshed, most farm 
 
 [10 1 
 
operators make the width of the strip 
 check correspond to the width of their 
 harvesting equipment. In this way they 
 avoid unnecessary crossing of the levees. 
 
 Widths usually start at 40 feet and may 
 be increased by 20-foot increments; or 
 they may be 40, 60, 80, and 100 feet wide. 
 A 40-foot strip check is sufficient for six 
 sweeps of a 7-foot mower, with some 
 allowance for overlap. The increment of 
 20 feet provides room for three additional 
 sweeps of the mower. 
 
 These distances are also practical for 
 other farm equipment. 
 
 In order to allow machinery to pass 
 from one strip check to another without 
 crossing levees, it is sometimes necessary 
 to discontinue the levees 15 or 20 feet 
 from the lower end of the field. It will still 
 be necessary to cross the levees at the 
 upper end of the field — an operation 
 usually entailing the lifting of the cutting 
 bar. 
 
 In some cases this spacing of levees 
 
 may not be necessary. When the wide, 
 low levee described on page 12 can be 
 used, it will prove less of a hindrance 
 during harvest. 
 
 The width of strip checks in irrigated 
 pastures harvested entirely by grazing 
 need not be gauged to accommodate har- 
 vesting machinery. Such strip checks may 
 range in width from the generally recog- 
 nized minimum of 15 feet to the maxi- 
 mum of 100 feet or more. However, if the 
 crop is to be cut for seed occasionally, a 
 minimum of 20 feet is recommended. 
 
 Shape of levees 
 depends on 3 factors 
 
 Levees should be designed and con- 
 structed to meet three requirements : They 
 should confine the irrigation water to the 
 individual strip checks; they should wet 
 through sufficiently to support the crop 
 on the borders; and they should be easy 
 to cross with farm implements in fields 
 harvested with machinery. 
 
 Ui4.4"J+ t4.V+| 
 
 ^.^-^''/^.^'O /, . vV^s!'//^ 
 
 S'-o" 
 
 ^■V"^ V-tf S/^SA- <W^ x/^AS »>S 
 
 Wide type levee separating strip checks of equal elevation. 
 i4.4^|« — 28.2" 
 
 -5' 
 
 */ 
 
 3>2 
 
 s^yT//^ //-^ '/*> y^ <y? y^ '/* /'"•*■ ,f 
 
 S'-o" 
 
 Wide type levee separating strip checks of different elevation. 
 
 //^S/o '/* '/*"*"*■ '/* //-■* 'S~*yfr 
 
 //->// </o //^S/^//* /A> /A- /A /A /A\ "/^ 
 
 2-o 
 
 Narrow type levee dividing strip checks of equal elevation. 
 
 U — 9"t -JL- io"± — » 
 
 //* '/* '/* "*'''* **"* "* >/> ^yT f 
 
 -£ 
 
 3h" 
 
 '/O Y\ * //•*■ "^ ''<*• ' r <> 
 
 2-o 
 
 Narrow type levee separating strip checks of different elevation. 
 
 [ii] 
 
The wide, low levee shown in the 
 accompanying drawing illustrates all 
 three. The levee, suitable for use on fields 
 with little cross slope, has sufficient 
 strength and body to prevent its being 
 undermined by the irrigation water. The 
 long, flat side slopes allow the irrigation 
 water in adjacent strip checks to cover 
 the maximum amount of levee surface. If 
 the levees are not too high, they will wet 
 through sufficiently to permit the growing 
 of crops on their surfaces. The gradual, 
 sloping sides and low crest provide an 
 easy crossing for farm implements. 
 
 This type of levee is usually about 8 
 feet wide; 4 to 6 inches in settled height. 
 
 If the wide type of levee were used with 
 the maximum cross slope, the water sur- 
 faces in adjacent strip checks might be 
 too far apart during irrigation to wet 
 through at the border lines. 
 
 Correct use of a narrow levee. 
 Narrow levees are advisable when the 
 cross slope approaches the maximum. On 
 fields requiring little use of machinery, 
 they are adequate. 
 
 As the drawing shows, water has a 
 much better chance of wetting through 
 when the narrow levee is used. If water 
 fails to wet completely through the 
 narrow-type levee, only a very narrow 
 strip of dry soil will be left — at best. Such 
 a strip produces no return, and it pro- 
 vides a place for the growth of fox-tail 
 and other undesirable plants. You should 
 note here that borders, to sustain a good 
 crop stand, must be compact and firm. 
 
 For close-growing perennial crops, the 
 narrow type of levee has its drawbacks. It 
 offers greater obstruction to the move- 
 ment of farm machinery across the strip 
 checks than the broad levee, and it does 
 not hold up well under vehicular traffic. 
 
 The narrow levee is usually about 2 
 feet wide; 4 to 6 inches in settled height. 
 
 What is the ideal 
 shape for the field? 
 
 A rectangularly shaped field with a 
 natural slope, or a graded surface which 
 
 permits the use of strip checks of equal 
 length, is best. 
 
 An extreme case of a badly shaped field 
 would be a triangular one which requires 
 that all strip checks be of different 
 lengths. It is almost impossible to irri- 
 gate such a field without waste-water run- 
 off. When the strip checks are of different 
 lengths, constant attention is required 
 during irrigation to wet all of them with 
 the same amount of water, without waste 
 or runoff. 
 
 It is possible, though not always prac- 
 tical, for the irrigator to equalize the time 
 that water remains on each strip, and, in 
 the same operation, prevent excessive 
 waste-water runoff from the short strips. 
 
 Sometimes the irrigator will cut back 
 the irrigating stream. In this operation, 
 when the water has reached the lower end 
 of the short strips, the stream is reduced 
 to the amount of water being absorbed. 
 The irrigator then allows this stream to 
 run until the longest strip has been irri- 
 gated. 
 
 This procedure is sometimes followed. 
 Too often, however, because of the irri- 
 gator's tendency to save on labor and 
 waste the water, cutting back the stream 
 does not work out. 
 
 Occasionally a better solution to the 
 problem will be found in land leveling, 
 perhaps with the relocation of a natural 
 drainage channel. Many ill-shaped fields 
 can be squared up in this manner — 
 although it sometimes proves too expen- 
 sive to be feasible. 
 
 At any rate, the farmer should consider 
 this question when planning land-leveling 
 operations. 
 
 Consider the direction 
 of irrigation 
 
 In localities having strong prevailing 
 winds, strip checks should be laid out 
 lengthwise with the wind. In order to 
 prevent wind interference during harvest, 
 this point must also be remembered when 
 planning to level the land. 
 
 To cut down on unnecessary crossing 
 
 [12] 
 
of the borders with the harvesting ma- 
 chinery, border-irrigated alfalfa and 
 clover fields are usually mowed, wind- 
 rowed and baled, or threshed, lengthwise 
 of the strip checks. 
 
 If the strip checks lie perpendicular to 
 the wind the windrows will be exposed 
 broadside to the wind action, the crop 
 will roll before a strong wind, and there 
 will be leaf or seed loss. This is a poor 
 arrangement for harvesting seed. 
 
 Provide surface 
 drainage 
 
 Pasture, especially, should be provided 
 with a means of quick surface drainage. 
 According to Irrigated Pastures in Cali- 
 fornia, Circular 125 of the California 
 Agr. Ext. Ser., ground surface should be 
 dry enough for grazing without damage 
 to soil or crop as soon as the plant growth 
 reaches the proper maturity for feeding. 
 Most soils used for pasture are slowly 
 permeable and, unless provision is made 
 for surface drainage, remain wet for long 
 periods between irrigation operations. 
 
 Relatively steep slopes of 0.5 per cent 
 or more, with adequate wasteway facili- 
 ties, are desirable. If the irrigation slope 
 is relatively flat (0.15 to 0.2 per cent) 
 and the soil is of the slowly permeable 
 type, adequate surface drainage can usu- 
 ally be obtained by the use of short strip 
 checks, together with an adequate waste- 
 way across the lower end of the field. 
 
 For extremely flat slopes, it is best 
 to construct the borders with a ridger, 
 or a border disk, shown on page 5, leav- 
 ing the furrow or trough on either side 
 open, to serve as a drain towards the 
 waste ditch. 
 
 Avoid runoff, or ponding. It is pos- 
 sible to irrigate alfalfa without runoff or 
 ponding by either cutting back or closing 
 off the irrigation stream, when the water 
 approaches to within about 100 feet of 
 the lower end of the strip check. Allow- 
 ance must be made for the fact that the 
 irrigator may fail to cut off the flow at 
 the proper time. 
 
 Strip checks should, if possible, termi- 
 nate in a wasteway connected with some 
 type of drainage channel. If this is not 
 feasible, ponding may be relieved by let- 
 ting the water spread out widely on the 
 surfaces not yet irrigated, at the lower 
 end of the field. 
 
 The attempt to avoid ponding provides 
 another reason for discontinuing borders 
 15 or 20 feet short of the full length of 
 the field, as mentioned on page 10. Run- 
 off from an irrigated strip check will thus 
 flow into, and up adjacent strips that 
 have not yet been irrigated. When it is 
 time to irrigate the adjacent strips, the 
 irrigation stream is cut off sooner than 
 usual to allow for the already wetted sec- 
 tion at the lower end. It is sometimes 
 desirable to reservoir the waste water and 
 pump it back to the head ditch for reuse. 
 
 Ponding, a result of poor leveling or failure to provide drainage. 
 
 wmm 
 
 warn 
 
 immi^L 
 
 ?0s 
 
 
 .*%,* . ** 
 
THREE WAYS TO CONSTRUCT STRIP CHECKS . . 
 cross checking, ridging, single operation 
 
 Cross checking means scraping the en- 
 tire field at right angles to the proposed 
 strip checks, and dumping sufficient earth 
 along each border line to make the levees. 
 Before this is done, the field should be 
 plowed or disked; after it is done, the 
 strip checks should be smoothed length- 
 wise. 
 
 The cross checking method involves 
 these steps : staking, marking, cross check- 
 ing, plowing, and shaping the borders. 
 
 Staking, Two men should measure off 
 the space between levees on opposite sides 
 of the field. Measurements should be ac- 
 curate, because the strip checks should be 
 of the same width if they are to irrigate 
 evenly. Laths, or long stakes, are driven 
 into the ground to mark the end of each 
 levee. The stakes are flagged so that they 
 may be seen from one end of the field to 
 the other. 
 
 Marking. Using a small, general- 
 purpose tractor, with shovel or chisel 
 attached, the operator makes a shallow 
 furrow or groove between the stakes at 
 the end of each proposed levee. Clearly 
 visible marking greatly facilitates the 
 proper alignment of the levees. 
 
 Cross checking. This means of form- 
 ing the levee dumps is important enough 
 to lend its name to the entire operation. 
 
 It is accomplished by scraping backwards 
 and forwards across the field, perpen- 
 dicular to the proposed strip checks, and 
 dumping the scraper at each border line. 
 
 One operator, running either ahydrau- 
 lically dumped scraper or a turn-over 
 scraper powered by a D-4 tractor or its 
 equivalent, is usually needed. 
 
 The turn over scraper is a home-made 
 device which may be unknown in some 
 communities but is favored by many 
 operators. As the illustration shows, the 
 scraper blade has two cutting edges, re- 
 volves 180° to dump, and then returns 
 to the scraping position. This is con- 
 sidered an easy and accurate method of 
 dumping. Its disadvantage is that it does 
 not remove excessive cross slope, when 
 this condition is met. 
 
 Why remove excessive cross 
 slope? If the cross slope is 0.2 per cent 
 or less, and the border interval is 40 feet 
 or less, there is no need to take the side 
 slope out at the border lines. To make 
 the border dumps, one can scrape the 
 field uniformly with a turn-over scraper. 
 
 But if the cross slope exceeds 0.2 per 
 cent, some cross leveling of the strip 
 checks will be necessary. This can be done 
 during the cross-checking operation, by 
 tapering the depth of scraping from the 
 
 Left, levee dumps made with a scraper; right, a turn-over scraper. 
 
 &■■* *w s 
 
Left, plowing levees with a 5-bottom plow; right, shaper for making borders. 
 
 high to the low side of each strip with 
 the hydraulically dumped scraper. Skill 
 on the part of the operator is essential. 
 
 Plowing. In border construction, 
 plowing means working the levee dumps 
 down into a rough ridge. Two trips (one 
 down and one back) on either side of 
 each row of dumps, with a 5-gang plow 
 set to throw the soil to the center, leave 
 ridges uniform enough to be shaped with 
 other implements. 
 
 Shaping the borders. Any one of a 
 number of border machines can shape, 
 but many farm operators prefer to use 
 the homemade device illustrated. The ma- 
 chine consists of two tools mounted in 
 the same frame, containing an open-end 
 
 V, or ridger, which crowds the soil into 
 a peaked levee. A V, pointing forward, is 
 pivoted at the end of each leg so that the 
 point can be adjusted up or down. 
 
 The machine controls the height of the 
 levee, and makes the straight, flat-sloping 
 sides desirable in a field where harvest- 
 ing machinery will be used. It can be 
 pulled by a D-6 tractor or the equivalent. 
 
 The road grader or a conventional 
 border shaper will be equally effective. 
 
 How long should this operation 
 take? The time consumed by cross- 
 checking depends on the length and spac- 
 ing of the levees. A levee spacing 40 feet 
 wide will require more time than one of 
 80 feet, since twice the length of levee 
 
 Another type of shaper for making borders. This one makes wide, flat-sided levees. 
 
Table 3. 
 
 Detailed requirements* and cost for constructing, by cross check 
 strip checks on a 40-acre square tract of land. 
 
 ■ng, 
 
 Operation 
 
 Number 
 of men 
 
 Hours 
 required 
 
 Man- 
 hours 
 
 Equipment 
 
 Tractor- 
 hours 
 
 Recapitulation 
 
 Cost 
 
 Staking 
 
 2 
 
 2 
 
 4 
 
 
 
 4 man-hours at 
 $1.00 
 
 $ 4.00 
 
 Marking 
 
 1 
 
 4 
 
 4 
 
 Two-plow size 
 tractor with one 
 shovel or chisel 
 
 4 
 
 4 tractor-hours 
 with driver at 
 $4.00 
 
 16.00 
 
 Cross 
 checking 
 
 1 
 
 20 
 
 20 
 
 D-4 or equivalent 
 and turn over 
 scraper 
 
 20 
 
 20 tractor-hours 
 with driver at 
 $5.00 
 
 100.00 
 
 Plowing 
 
 1 
 
 3 
 
 3 
 
 D-4 or equivalent 
 and 5-gang 
 moldboard plow 
 
 3 
 
 3 tractor-hours 
 with driver at 
 $5.00 
 
 15.00 
 
 Shaping 
 
 1 
 
 4 
 
 4 
 
 D-6 or equivalent 
 and shaper 
 
 4 
 
 4 tractor-hours 
 with driver at 
 $6.50 
 
 26.00 
 
 Floating 
 
 1 
 
 12 
 
 12 
 
 D-4 or equivalent 
 and float 
 
 12 
 
 12 tractor-hours 
 with driver at 
 $5.00 
 
 60.00 
 
 
 
 
 
 
 
 Total cost 
 
 $201.00 
 
 
 
 
 
 
 
 Total cost per acre 
 
 5.00 
 
 * Not inclu 
 
 ding precultivation of the f 
 
 teld. 
 
 
 
 
 is involved. Because less time is lost on 
 turns, less time is required for long strip 
 checks than for short ones. 
 
 On a square, 40-acre tract with levees 
 40 feet apart, the approximate time in 
 man and machine hours needed for each 
 operation is shown in table 3. 
 
 After the levees have been completed, 
 the surface of the strip checks may need 
 to be smoothed lengthwise, in order to 
 remove small irregularities on the soil 
 surface made during the cross checking, 
 plowing, and shaping operations. This is 
 usually done by drawing the strip check 
 drag (shown on page 17) lengthwise of 
 the strip checks, with the sides of the drag 
 parallel to the levees. 
 
 Ridging means forming the levees with 
 a border disk or a ridger (shown on page 
 5) in the same manner as that described 
 for constructing temporary levees. Levees 
 in this instance are usually more substan- 
 tially built. 
 
 The ridging method involves these 
 steps: Staking, marking, building levee 
 foundations, ridging, and leveling strip 
 checks. 
 
 Staking and marking have already 
 been described above in the discussion of 
 cross checking. 
 
 Building levees, A foundation for 
 the levees is usually provided for perma- 
 nent-type strip checks by plowing on 
 either side of each border line, and throw- 
 
 [16 
 
A strip check drag used for individual leveling of strip checks. 
 
 ing the soil to the center. Next, the border 
 disk or the ridger is used to form levees 
 of the narrow, rounded type that are 
 desirable if there is much difference in 
 elevation between adjacent strip checks. 
 At this point, the operator finds that 
 depressions have been left on either side 
 of each levee. Unless these depressions 
 are needed as surface drains for very flat 
 land and heavy soil, they should be re- 
 moved by the crosswise leveling of each 
 strip check. 
 
 Leveling strip checks may be accom- 
 plished in two ways. First, the necessary 
 amount of soil may be graded towards 
 the levees and away from the center line 
 of the strips, using a road-grader operat- 
 ing lengthwise of the strips. 
 
 Or, second, a steel-shod strip check 
 drag of the proper size, weight, and hitch 
 may be used. This implement is drawn 
 lengthwise of the strips, with one corner 
 directed forward, so that the high ground 
 in the middle of the strips is scraped off, 
 
 A machine that is used for making strip checks by the single operation method. 
 
 [17] 
 
Table 4. Requirements and costs for constructing by ridging, strip checks with 
 levees 40 feet apart on a 40-acre square tract. 
 
 Operation 
 
 Number 
 of men 
 
 Hours 
 required 
 
 Man- 
 hours 
 
 Equipment 
 
 Tractor- 
 hours 
 
 Recapitulation 
 
 Cost 
 
 Staking 
 Marking 
 
 Plowing 
 
 levee 
 
 foundations 
 
 Ridging 
 
 Leveling 
 with 12-ft. 
 drag 
 
 2 
 1 
 
 1 
 
 1 
 1 
 
 2 
 
 4 
 
 3 
 
 3 
 
 16 
 
 4 
 4 
 
 3 
 
 3 
 
 16 
 
 Two-plow size 
 tractor with one 
 shovel or chisel 
 
 4-D size tractor 
 and 3-gang 
 moldboard plow 
 
 D-4 size tractor 
 and ridger 
 
 D-4 size tractor 
 and 12-foot 
 drag 
 
 4 
 
 3 
 
 3 
 
 16 
 
 4 man-hours at 
 $1.00 
 
 4 tractor-hours 
 with driver at 
 $4.00 
 
 3 tractor-hours 
 with driver at 
 $5.00 
 
 3 tractor-hours 
 with driver at 
 $5.00 
 
 16 tractor-hours 
 with driver at 
 $5.00 
 
 $ 4.00 
 16.00 
 
 15.00 
 
 15.00 
 
 80.00 
 
 
 
 
 
 
 
 Total cost 
 Cost per acre 
 
 $130.00 
 3.25 
 
 and worked over to the low area next to 
 the levee. First one side of the check is 
 dragged, then the other; thus, the soil is 
 worked away from the middle and to- 
 wards the sides. 
 
 With either method, several trips along 
 each strip may be necessary. 
 
 Is ridging expensive? Except for 
 necessary plowing or disking of the 
 field — which may be charged to expenses 
 involved in seedbed preparation — the re- 
 quirements and costs of the ridging 
 method of constructing permanent strip 
 checks are shown in table 4. 
 Single operation means the simultane- 
 ous forming of levees, and the crosswise 
 leveling of the strip checks. Some prelim- 
 inary plowing or disking of the soil will 
 be necessary before the operation is 
 begun. 
 
 Special implements are needed to 
 do the job. Essentially, these implements 
 
 consist of a V-shaped scraper blade, 
 equipped with an indicator and controls 
 for keeping the blade level. The scraper 
 blade must reach from inside edge to in- 
 side edge of adjacent levees. 
 
 In the implement shown, the blade is 
 12 feet wide. The implement makes a 
 strip check 15 feet wide from the center 
 line of the border on one side, to the 
 center line of the border on the other side. 
 This is the common width of strip check 
 used for irrigating pasture on land having 
 steep irrigation slopes and/or side slopes. 
 
 Sometimes an extension of 3 feet to 
 each end of the 12-foot blade is provided, 
 making possible the construction of strip 
 checks with an over-all width of 21 feet. 
 The blade, which rests on roller bearings, 
 is lifted and kept level by hydraulic con- 
 trols. Its frame is bolted rigidly to the 
 frame of the tractor which pushes it. 
 
 From his seat on the tractor (usually 
 
 [18] 
 
of 4-D size) the operator watches a spirit 
 level or a gauge which works on the pen- 
 dulum principle. When the indicator 
 shows that the scraper blade has varied 
 from level, the operator moves the hy- 
 draulic control until the indicator returns 
 to level. Thus, the blade is kept level and, 
 likewise, the strip check. 
 
 When the end of the strip check is 
 reached, the blade is lifted for turning. 
 As soon as the operator is in position to 
 start another strip check, the blade is 
 again let down. As each strip check is 
 
 made, the next one is marked by a small 
 wheel or shovel attached to a rod protrud- 
 ing from the side of the tractor. 
 
 What are the advantages of this 
 method? This equipment is usually 
 made and owned by contractors who han- 
 dle the preparation of land for irrigation. 
 They claim that the equipment is capable 
 of taking out up to 2 per cent side slope, 
 and of completely bordering 5 acres of 
 land per hour. 
 
 A wide-bladed road grader is some- 
 times used in the same manner. 
 
 CONTROL IRRIGATION WATER 
 by pipe line, or by ditch structures 
 
 There are two kinds of structures for 
 controlling irrigation water. When it is 
 necessary to raise the level or water pres- 
 sure in the field head-ditch or pipe line, 
 checks, dams, or gates are used to force 
 the water to flow on the strip checks. To 
 release the water for irrigation, border 
 gates; or siphons through or over the 
 ditch bank; or alfalfa valves set at inter- 
 vals along the pipe line are used. 
 
 What is a 
 pipe line 
 structure? 
 
 When it is necessary to increase the 
 head or water pressure, metal gates which 
 will check or stop the flow of water are 
 installed in standpipes placed in the pipe 
 line at the required intervals. 
 
 Alfalfa valves. These are outlets for 
 turning the water on the field. They are 
 cemented to the tops of riser pipes, which 
 are placed in the pipe line at intervals of 
 every border or every other border, so 
 that each valve may serve one or two 
 strip checks. To avoid erosion, the valves 
 must be set slightly below the ground 
 surface. 
 
 Hydrant distributor head. This is 
 a convenient device for dividing the flow 
 of water between adjacent strip checks. 
 It is portable, and can be quickly installed 
 
 by slipping it over the rim of the valve, 
 which it must fit snugly. 
 
 What is a 
 ditch structure? 
 
 Permanently installed checks, or port- 
 able canvas dams are used to raise the 
 
 A typical standpipe for a concrete pipe line 
 irrigation water supply. 
 
 [19] 
 
An alfalfa valve without distributing head. 
 
 Distributing head for an alfalfa valve. 
 
 water level in head ditches. Water is re- 
 leased for irrigation either through per- 
 manently installed border gates that are 
 set in the ditch bank; portable siphons 
 laid over the ditch banks; or simply by 
 cuts in the ditch bank temporarily left 
 open. 
 
 Check gates and border gates. 
 These are usually installed in permanent 
 ditches which are grazed or sprayed for 
 control of vegetative growth. 
 
 Canvas dams. Since farm imple- 
 ments must sometimes be used for clean- 
 
 ing the ditches of vegetative growth and 
 sediment, it is desirable to keep ditches 
 free of permanent structures. In such 
 cases, the water level in successive ditch 
 sections is raised by means of two canvas 
 dams, set alternately, one below or one 
 above the other. The water is then either 
 siphoned over the ditch bank or taken out 
 through open cuts. 
 
 The design and construction of pipe 
 line structures and ditch structures are 
 fully discussed in Farm Irrigation Struc- 
 tures, Exp. Sta. Cir. 362. 
 
 - av;;.. ; w \ i 
 
 A wooden check gate is permanent. 
 
 Canvas dams are portable with ease. 
 
 [20] 
 
THESE . . . 
 
 are some of the structures 
 needed to help control the 
 flow of irrigation water — to 
 get it where it is needed, in 
 quantities that will be effec- 
 tive. 
 
 Right, a flume type border gate for letting 
 water out of a concrete supply ditch and into 
 the strip check. 
 
 
 Above, mole type of border gate for taking water from supply ditch. Below, portable siphons 
 used to take water over the side of the ditch and into the strip checks. 
 
 H.J». 
 
 ■ 
 
 Ill 
 
 
 [21] 
 
IRRIGATION OPERATIONS . 
 here are some essentials 
 
 Cutting off 
 
 the irrigation stream 
 
 After the stream is cut off at the head 
 ditch, the water continues to move down 
 a check. If water is allowed to reach the 
 lower end at, or before, the time at which 
 it is cut off, and there is no waste ditch 
 to take care of the runoff, it will pond 
 at the lower end. 
 
 Some ponding is bound to occur in 
 border irrigation, but excessive amounts 
 should be avoided. Ordinarily, the irri- 
 gation stream should be cut off or reduced 
 when the water is within 100 feet of the 
 lower end; but in some instances up to 
 300 feet must be allowed. 
 
 Cutting back the 
 irrigation stream 
 
 Because of differences in the length of 
 time the water is in contact with the soil, 
 there is always some unequal penetration 
 of water from the upper to the lower ends 
 of the strip check. If, in one operation, 
 one could apply and maintain a shallow 
 depth of water over the entire strip check 
 for the required time, the depth of water 
 penetration would be uniform and suffi- 
 cient. By cutting back the irrigation 
 stream, a procedure referred to on page 
 12, it is possible to approximate this ideal 
 result. 
 
 By means of a large irrigation stream, 
 water is quickly forced to a point within 
 about 100 feet of the lower end of the 
 strip check before much difference in 
 depth of water penetration at the upper 
 and lower ends can occur. 
 
 If the soil is not wetted deeply enough, 
 the stream is cut back to the size which 
 will maintain a shallow depth of water 
 from one end of the strip check to the 
 other, without causing runoff. 
 
 A rule of thumb. Reduce the flow to 
 from !/2 to s /i of the original amount. 
 Then, continue to irrigate with the smaller 
 
 stream until the soil is wetted to the re- 
 quired depth. 
 
 Trial field runs 
 determine unit flow 
 and length of check 
 
 Field trial runs consist of irrigating 
 several strip checks with different-sized 
 streams of water, and determining the 
 length of time the water remains on each 
 successive 100-foot length of strip. The 
 length of the strip check and the size of 
 the irrigation stream are the two change- 
 able factors which allow the water to re- 
 main an equal, or nearly equal, length of 
 time on each 100-foot length of strip. 
 Properly combined, these factors produce 
 uniform or nearly uniform application of 
 water. 
 
 A change in soil, or a material depar- 
 ture from a uniform slope, may cause 
 unequal water application — no matter 
 what size of irrigation stream or length 
 of strip check is used. Therefore, before 
 trial field runs are warranted, the land 
 should be examined with these soil char- 
 acteristics in mind. 
 
 How to make a trial field run. 
 Starting at the head ditch, stakes are set 
 at 100-foot intervals along one of the 
 levees within the area selected for the 
 test. Different-sized streams of water are 
 turned into three or more adjacent strip 
 checks. For strip checks 40 feet wide, and 
 clay soil, 600 g.p.m. (15 g.p.m. unit flow, 
 table 1 ) is estimated to be the stream of 
 the proper size. 
 
 Three streams, one 600 g.p.m., one 
 greater, and one smaller, might be used 
 for the test. The advances of the three 
 streams along the strip checks are timed 
 until they reach each stake. As each 
 stream reaches a point within about 100 
 feet of the lower end of the field (or any 
 other distance it might be expected to 
 cover without additional flow from the 
 
 [22] 
 

 
 
 
 
 
 400 
 
 
 
 
 
 
 
 
 300 
 
 
 
 
 
 
 c 
 E 
 
 
 
 
 
 
 Reces^^^ 
 
 
 iv 
 
 
 E200 
 
 .c 
 t> 
 
 E 
 
 
 
 
 
 
 
 -" 
 
 
 
 T. 
 
 
 
 X^ 
 
 
 100 
 
 
 
 
 Jiz- 
 
 2'c 
 
 c 2 
 
 il 
 
 o a 
 5° 
 
 E 
 
 Ml 
 CO 
 
 J - 
 
 ^^^^ 
 
 
 
 
 100 200 300 400 500 600 700 800 900 
 
 Length of strip check in feet 
 
 Graph shows nearly equal water intake opportunity for the whole length of a strip check. 
 
 E200 
 
 
 
 
 
 
 
 
 
 
 
 "®^ J \/ 
 
 
 
 
 Reeession_curve____ 
 
 T 
 
 / 
 
 
 
 T" 
 
 
 1 
 
 
 
 ££■ 
 
 c 
 
 
 •o ^S 
 
 
 
 
 E 
 
 
 
 
 
 n 
 
 
 
 \^^ 
 
 
 
 £ 
 
 J 
 
 Advancec^^^ 
 
 
 
 400 500 600 
 
 Length of strip check in feet 
 
 This shows nearly equal water intake opportunity for first 600 feet of a 1000-foot strip check. 
 
 head ditch) the border gate is closed so 
 that no more water can enter the strip 
 check. 
 
 Now, note the "intake opportunity 
 time." This is the lapse of time from when 
 the water arrives at each stake until it dis- 
 appears, or the length of time that water 
 standing on the ground has an oppor- 
 tunity to enter the soil. As long as the 
 water intake opportunity along the suc- 
 cessive 100-foot sections of strip check 
 remains the same, there is equal penetra- 
 tion and uniform distribution of water. 
 
 Plot the results, as shown on the ac- 
 companying graphs. In the first graph, 
 the recession curve is nearly parallel to 
 the advance curve, indicating that all of 
 
 the stations have about the same intake 
 opportunity. The second graph shows the 
 recession curve as being nearly parallel 
 to the advance curve up to 600 feet, but 
 beyond that point the two curves con- 
 verge. In this case, it is indicated that 
 uniform distribution of water occurs only 
 in the upper 600 feet of strip check. 
 
 Has a sufficient depth of water 
 been applied? The water must wet the 
 soil throughout the plant root zone. The 
 depth of water penetration can be meas- 
 ured by using a metal probe or a soil 
 auger. 
 
 Calculate the depth of water applied 
 according to the method described in the 
 box on page 24. 
 
 [23] 
 
HOW TO CALCULATE WATER APPLICATIONS 
 
 There is a rule of thumb for checking the depth. One inch of rainfall will wet 
 soils which are shown to be dry by the condition of the crop, as follows: 
 Sandy soils ... 12 inches or more in depth 
 Loam soils ... 6 to 10 inches in depth 
 Clay soils ... 4 to 5 inches in depth 
 
 The depth of water that is applied may be calculated for the various units in the 
 
 following ways: 
 
 . .... Cubic feet per second x hours stream is used 
 
 Average depth in inches = r ; ; — 
 
 Area ot strip check in acres 
 
 _ Gallons per minute x hours stream is used 
 
 450 x area of strip check in acres 
 _ Southern California Miner's inches x hours stream is used 
 
 50 x area of strip check in acres 
 _ Statute Miner's inches x hours stream is used 
 40 x area of strip check in acres 
 Example: What is the average depth applied to a Vi-acre strip check in three hours 
 by using a stream of 450 gallons per minute? 
 
 i . 45 x 3 _ . , 
 Average depth = — — — — = 6 inches 
 450 x V2 
 
 If loam soil is being irrigated, a 6 inch depth of water could be expected to wet 
 the soil to a depth of 36 to 60 inches. Following the irrigation, the resulting depth 
 and uniformity of water penetration should be carefully checked with a soil auger 
 or probe. 
 
 The number of hours a stream must run may be obtained from another arrange- 
 ment of the same factors as follows: 
 
 u -ii u j Average depth in inches x area of strip in acres 
 
 Hours stream will be used = - *- - 
 
 Cubic feet per second 
 
 _ Av. depth in inches x 450 x area of strip in acres 
 
 Gallons per minute 
 
 _ Av. depth in inches x 50 x area of strip in acres 
 
 Southern California Miner's inches 
 
 _ Av. depth in inches x 40 x area of strip in acres 
 
 Statute Miner's inches 
 
 Example: How many hours must a stream of 450 gallons per minute be applied to 
 a !/2-acre strip check to wet a clay soil 40 inches deep? 
 
 According to the rule of thumb it requires from 8 to 10 inches of depth of water 
 to wet clay soil to a depth of 40 inches. 
 
 Then ' u ... . . 8 x 450 x V 2 A , 
 
 Hours stream will be used = = 4 hours 
 
 450 
 
 10x450xy 2 CL 
 
 = 5 hours 
 
 450 
 
 Cooperative Extension work in Agriculture and Home Economics, College of Agriculture, University of California, and United States Department of Agriculture co- 
 operating. Distributed in furtherance of the Acts of Congress of May 8, and June 30, 1914. J. Earl Coke, Director, California Agricultural Extension Service. 
 
 16m-3,'52(9181)P.S.