CALIFORNIA 
 AGRICULTURAL EXTENSION SERVICE 
 
 CIRCULAR 4 
 
 November, 1926 
 
 IRRIGATION BY 
 OVERHEAD SPRINKLING 
 
 H. A. WADSWORTH 
 
 PUBLISHED BY 
 
 THE COLLEGE OF AGRICULTURE 
 UNIVERSITY OF CALIFORNIA 
 
 Cooperative Extension work in Agriculture and Home Economics, College of Agriculture, 
 University of California, and United States Department of Agriculture cooperating. Dis- 
 tributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. B. H. Crocheron, 
 Director, California Agricultural Extension Service. 
 
 UNIVERSITY OF CALIFORNIA PRINTING OFFICE 
 
 BERKELEY, CALIFORNIA 
 
 1926 
 
Digitized by the Internet Archive 
 
 in 2011 with funding from 
 
 University of California, Davis Libraries 
 
 http://www.archive.org/details/irrigationbyover04wads 
 
IRRIGATION BY OVERHEAD SPRINKLING 
 
 H. A. WADSWOETHi 
 
 INTRODUCTION 
 
 Although the irrigation of truck crops by overhead sprinkling has 
 long been a common practice in some parts of the United States, with 
 some citrus fruits irrigated this way in Florida, the application of 
 water by overhead sprinkling has but recently become a factor in 
 California orchard irrigation practice. Though scattered installations 
 which have been in operation for some years are to be found in various 
 parts of the State, the majority now in operation have been established 
 since 1924. 
 
 Irrigation by sprinkling is an attempt to imitate rainfall. "Water 
 is carried in pipes under such pressure that when released from 
 sprinkler heads or from perforated pipes, the surface to be irrigated 
 is sprinkled with the coarse drops of a heavy shower. In details, 
 individual installations may differ widely, but in general, the prin- 
 ciple is the same. Certain manufacturers of sprinkling equipment 
 recommend distribution from horizontal pipes supported above the 
 surface of the ground and equipped with non-corrosive nozzles or jets 
 at fixed intervals along them. Such an installation can serve a zone 
 of a length equal to that of the pipes and of a width determined by 
 the available pressure and by the number of lines. Other manufac- 
 turers recommend rotary sprinklers. When these are used, sprinkler 
 heads somewhat similar in design to revolving lawn sprinklers are so 
 located in the area to be irrigated that the overlapping circles of 
 application completely cover the area. 
 
 Sprinkler equipment is relatively costly regardless of the type of 
 distributing system selected. Many installations which are designed 
 to eliminate all labor of irrigation except the opening of a valve or 
 the starting of a pump represent an investment up to $300 an acre. 
 Under favorable conditions, when the operator is willing to handle 
 some portable sprinkling equipment, the initial cost may be reduced 
 to one-half of this amount or less. When natural pressure is not 
 available for the operation of a sprinkler installation, pumps must be 
 included in the plan. In such cases the first cost of the system will 
 be increased by the cost of the pump with its fittings, and the annual 
 
 1 Assistant Professor of Irrigation Investigations and Practice and Assistant 
 Irrigation Engineer in the Experiment Station. 
 
4 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [CiRC. 4 
 
 cost will be increased by the carrying charges on this additional 
 investment and by the cost of the power consumed. 
 
 Because of the large investment represented by sprinkler equip- 
 ment, the practice of overhead irrigation has been mainly limited to 
 the irrigation of high-value crops on high-priced land. In California, 
 numerous plantings of oranges, lemons, avocados, and nursery stock 
 are being irrigated by this method. Sprinkling is often practiced in 
 truck-growing areas where soil, market facilities, and climatic con- 
 ditions warrant the expense involved. Because of the flexibility of 
 the system and the possibility of irrigating small tracts efficiently 
 with a minimum of labor, overhead irrigation is rapidly finding favor 
 with poultrymen as a means of watering chicken runs and of irrigat- 
 ing small areas for green feed. The method is also sometimes used for 
 the irrigation of lawns and ornamental shrubs. 
 
 OVERHEAD SPRINKLER LINES 
 
 Sprinkler installations for the irrigation of orchards, nurseries, 
 and truck gardens fall into two general classes: perforated overhead 
 pipes, sometimes called overhead nozzle lines, and revolving sprinkler 
 systems which water circular areas. 
 
 The distribution of irrigation water in the form of small jets 
 forced through openings in the shell of the pipe was the first method 
 used. In these early installations a few lengths of pipe were per- 
 forated and the water forced through them by a simple hand force 
 pump. Since these perforations were not reinforced with non-cor- 
 rosive metal, the holes gradually became irregular in sliape or entirely 
 clogged. 
 
 Modern sprinkler lines carry patented nozzles of non-corrosive 
 material. These are screwed into tapped holes drilled through the 
 shell of the pipe. The holes through these nozzles are intended to be 
 so shaped that particles of rust, which may be carried through the 
 pipe, cannot clog them. It is extremely important that the nozzles in 
 a pipe line be set in a straight row. Special drilling machines have 
 been designed to facilitate this. 
 
 LOCATION AND DESIGN OF NOZZLE LINES 
 
 A strip of land 50 feet wide can be irrigated from a single over- 
 head line if that line be so arranged that it can be rotated through 
 a turning union and the angle of the jets changed. When the angle 
 of the jet is 45 degrees above horizontal, greatest distance is secured. 
 Hence, the total angle available in the turning union should be 90 
 
1926] 
 
 IRRIGATION BY OVERHEAD SPRINKLING 
 
 degrees. Considerable attendance is required with installations of this 
 sort if changes in angle of jet and consequently in the area served 
 are made by hand. Turning machines consisting of small turbines, 
 driven by the flow of water in the vertical supply type, have been 
 devised. These attachments slowly turn the pipe line through the 
 required angle. Need for personal attendance is practically obviated 
 by the use of this device. 
 
 The details of the installations vary widely with the proposed use. 
 For truck crops and ornamental plantings the pipes may be carried 
 on short posts, or even laid on the ground. When the pipes are carried 
 on posts, these supports are usually about 15 feet apart. When longer 
 spaces are used, it becomes increasingly difficult to turn the line 
 because of its sag. Simple roller bearings can be secured which may 
 be placed on the posts as an aid to easy turning. For short lines the 
 bearings may be eliminated and the lines held in place by metal straps 
 over the tops of the posts. Even in good installations with abundant 
 pressure, lines longer than 700 feet are not to be recommended. 
 
 Many growers object to the obstruction to cultivation which results 
 from placing sprinkler lines on short posts. Posts carrying the pipe 
 lines about six and one-half feet above the ground permit the passage 
 of men and horses under the lines and eliminate most of this trouble. 
 Four by four inch redwood posts make suitable supports for sprinkler 
 lines. They should be long enough to be set in the ground 21/2 or 3 
 feet and should still give a 6I/2 foot clearance. When greater per- 
 manence is required, sections of IVi-inch or li/2-inch iron pipe set in 
 concrete footings may be used. 
 
 Obstruction to cultivation can be still further reduced by the use 
 of high poles which may be from 100 to 200 feet apart. The nozzle 
 line is then suspended from a wire cable which joins the tops of these 
 poles and hangs in the form of a catenary between them, the wires 
 supporting the nozzle lines carrying specially designed galvanized 
 iron hooks equipped with simple roller bearings at their lower ends. 
 The nozzle lines fit into these hooks and can be brought to the proper 
 height by adjustment of the wires leading from the supporting cable. 
 
 Because of unavoidable sag in the cable, the height of the poles 
 supporting it should be considerably greater than the height required 
 for the nozzle line. Suitable poles can be made from standard tele- 
 phone poles having a diameter of 8 to 10 inches at the base and 6 to 8 
 inches at the top. These poles should be set in holes at least 6 feet 
 deep and should be tamped firmly in place. For greater permanence, 
 footings of concrete may be used. Since any deflection of the high 
 posts from their original position would result in a further sagging 
 
6 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [CiRC. 4 
 
 of the cable and a consequent distortion of the nozzle line, it is well 
 to anchor the end posts with guy wires fastened to ' ^ deadmen. ' ' These 
 "deadmen'' may be any massive concrete or wooden members buried 
 3 or 4 feet below the surface and attached to an anchor rod which 
 terminates in an eyebolt above the surface. The "deadmen" should 
 not be closer to the base of the pole than a distance equal to one-third 
 its height. Guy wires attached to these anchor rods by means of 
 turnbuckles give rigid support for the poles. Future sag in the line 
 can be corrected by the turnbuckles. 
 
 The weight of the cable to be used depends upon the spacing of 
 the poles, the length of the pipe line to be supported, and the pipe 
 sizes which make up that length. Most manufacturers who produce 
 sprinkling equipment of this sort maintain an engineering office where 
 information as to the suitable spacing of poles and the required cable 
 sizes can be secured. When such advice is not available, an engineer 
 familiar with sprinkling systems should be consulted and his advice 
 followed. No detailed design of sprinkler lines can be given which 
 would be suitable for common use, since each installation must be 
 considered individually before an intelligent design can be offered. 
 In general, the nozzle lines should be at right angles to the supply 
 lines and should run the long way of the area to be irrigated, in order 
 that obstruction to cultivation may be minimized. If the pipe sizes 
 making up the nozzle lines are wisely chosen, and if sufficient pressure 
 is available, the lines may be as far apart as 50 feet, if necessary to 
 secure a better location in the field. 
 
 The pipe sizes to be used for overhead sprinkling lines depend 
 upon the type of nozzle used, the pressure available at the intake of 
 the line, and the distance between nozzles. 
 
 As has been stated above, the overhead sprinkling line finds its 
 greatest popularity in nursery work, truck growing, and ornamental 
 planting. The oldest installations in California were of this type and 
 were the first ones used for the irrigation of citrus trees. The practice 
 of overhead sprinkling did not spread among citrus growers, however, 
 because of the obstruction offered to cultural practices by the sup- 
 porting posts. Horizontal lines have also proved a great inconvenience 
 in the handling of fumigation tents. Furthermore, it is probable that 
 the fine stream issuing from a nozzle of the type used on such lines 
 increases evaporation loss. Figure 1 shows a typical overhead sprinkler 
 line in operation. 
 
^^^^] IRRIGATION BY OVERHEAD SPRINKLING 
 
 FITTINGS FOR NOZZLE LINES 
 
 In addition to the special brass nozzles which are essential to satis- 
 factory operation of a sprinkler installation of this sort, there are 
 other fittings which reduce difilculties of installation and make for 
 greater convenience in operation. Automatic turning equipment has 
 already been mentioned, as has also the simple roller-bearing saddle, 
 in which a long length of pipe may rest and still turn easily. The 
 saddle is supplied with several base fittings for use with various 
 methods of support for the sprinkler line. Turning unions completely 
 
 Fig. 1. — General view of overhead sprinkler line. Sprinkling from a perforated 
 horizontal pipe, which may be rotated through a turning union, is a popular means 
 of applying water to ornamental plants, vegetables, and poultry runs. 
 
 assembled are sold by manufacturers of sprinkler equipment. Ordi- 
 narily a perforated conical strainer is built into the union so that 
 water entering the nozzle line may be kept free from dirt, which might 
 clog the fine nozzle openings. For extensive installations where several 
 parallel lines are to be turned in unison, the power supplied by the 
 turbine of the automatic turning equipment is inadequate and 
 hydraulic oscillators may be obtained in that case. The reciprocating 
 action of the central oscillator is carried to the turning unions which 
 are operated by carefully balanced cables. 
 
8 
 
 CALIFORNIA AGRICULTURAL EXTENSION SERVICE 
 
 [CiRC. 4 
 
 Flushing valves are usually installed at the end of each nozzle line 
 to permit the removal of dirt and scale from the line without the 
 necessity of dismantling. 
 
 Difficulty is often experienced in assembling sections of drilled 
 pipe since the couplings must be tight and the nozzles in the several 
 sections in perfect line. The use of quick-acting couplings with 
 squared sockets makes it impossible to assemble the pipe unless the 
 nozzles in the several sections are in perfect alignment. 
 
 COS 
 
 fe 
 
 
 % 
 
 \\v 
 
 i 
 
 't 
 
 ^Po//er 
 tiear/ng 
 
 M > Jurnina 
 
 > Turning 
 union 
 
 S<H 
 
 'T'^sf^jrT^^^r^-j^, 
 
 
 n 
 
 Oofe 
 vo/ve 
 
 K-"'i. 
 
 Vi 
 
 "P^imwn^^Tims^T 
 
 77^^^//^/// 
 
 ^ 
 
 Fig. 2. — Detail of typical sprinkler line assembly. The special fittings required 
 for the installation of overhead sprinkler lines can be secured only from manu- 
 facturers of sprinkling equipment. 
 
 Other equipment such as gate valves, couplings, tees, and unions, 
 which may be necessary for assembly, is common to all pipe work and 
 need not be considered. Figure 2 shows the detail of a sprinkler line 
 assembly. 
 
 WATER REQUIRED FOR OPERATION 
 
 For outdoor irrigation, with nozzles spaced on 3-foot or 4-foot 
 centers, a supply of one gallon per minute for every 15 feet of line 
 should be provided. AVith uniform application over a strip 50 feel 
 wide, such a flow would provide an irrigation of one inch in about 
 eight hours. 
 
1926] IRRIGATION BY OVERHEAD SPRINKLING 
 
 PEESSURE EEQUIREMENTS 
 
 A pressure of from 25 to 35 pounds per square inch is required at 
 the head of a nozzle line for satisfactory distribution. In cases where 
 this pressure is not available or where it cannot be created without 
 prohibitive cost, special nozzles should be used which are designed for 
 low pressure operation. Planning such a low pressure system is a 
 special problem which should be undertaken only under advice from 
 a reliable manufacturer of sprinkling equipment of this sort. 
 
 When the sprinkler lines are remote from the source of pressure, 
 much more pressure is required at the source than can be used at the 
 intake end of the nozzle line. Pressure is always consumed when 
 water is forced through a pipe line. This loss results in the necessity 
 of overcoming the resistance to flow, which is offered by the relatively 
 rough interior and small diameter of the supply pipe. The amount 
 of pressure necessary to overcome this friction varies with the amount 
 of water carried, the length of the line, the size of the pipe, the 
 material of the pipe, and its age. Methods of determining the pres- 
 sure consumed under given conditions will be discussed under a con- 
 sideration of the design of supply pipes. 
 
 REVOLVING SPRINKLER SYSTEMS 
 
 As has already been indicated, sprinkling heads cannot distribute 
 water over a given rectangular area as uniformly as a well operated 
 sprinkler line because of the overlap of the circles of application 
 which are necessary to insure complete coverage. With field crops, 
 nursery plantings, and truck crops, where the location of sprinklers 
 is not rather rigidly fixed by planting arrangement, part of this 
 objection can be obviated. When sprinkler heads can be located on 
 a hexagonal pattern and every head placed at an equal distance from 
 every other head adjacent to it, only about 15 per cent of the area 
 served will be within the zones of overlap, provided the spacing is 
 properly determined according to the spread which may be expected 
 from a single head. In cases where the location of the heads cannot 
 conform to a true hexagonal spacing because of the planting scheme — 
 or for some other reason — the amount of overlap must be increased 
 if complete coverage is provided. No real objection is offered by this 
 necessary overlap, since all sprinkler heads throw less water to the 
 extreme circumferance of the circle of coverage than is applied to the 
 
10 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [ClRC 4 
 
 central area. The overlap tends to equalize any lack of uniformity 
 of application which may result from a single head. 
 
 Many commercial sprinkler heads now on the market throw water 
 with fair uniformity over a circle with a 60-foot diameter when a 
 pressure of from 15 to 18 pounds per square inch is available at the 
 head. With an expected diameter of coverage of 60 feet, sprinkler 
 heads should be located so that each head is 52 feet from its neighbors 
 in every direction. Such a spacing can be effected by staggering the 
 sprinkler heads on feed lines which are parallel and which are 45 feet 
 apart. This plan of installation is evidently impossible in orchards 
 that are planted on the rectangular system. Several plans of layout 
 are shown in figure 3. In this figure, plan A is a hexagonal instal- 
 lation for truck gardens, nurseries, or for orchards planted on the 
 hexagonal plan. Plans B, C, and D are superimposed upon rect- 
 angular orchard plantings. 
 
 LOCATION AND COST OF SPEINKLEES IN PEEMANENT PLANTINGS 
 
 In orchards set on the rectangular plan, with 24-foot spacings, a 
 close approximation to the ideal installation suggested above can be 
 reached by establishing sprinkler heads in alternate trees in alternate 
 rows. When such a scheme is adopted, the diameter of a single circle 
 of coverage must be two and one-half times the distance between 
 trees, if complete coverage is to be obtained with a minimum of over- 
 lap. Under the condition given the diameter of coverage required for 
 most efficient distribution is 60 feet. 
 
 Some growers object to locating heads directly over a tree. The 
 accumulation of excess water at the trunk of the tree, because of 
 unavoidable leaks in the sprinkler heads and the difficulty of handling 
 fumigation tents over trees equipped with sprinkling stands, are given 
 as criticisms of this method. Growers who disapprove of such an 
 arrangement sometimes install sprinklers in the centers of the tree 
 squares. The diameter of coverage required is the same in either case. 
 Some obstruction to cultivation must be caused by an installation in 
 which the sprinkler pipes rise from the centers of the tree squares. 
 
 Some types of sprinkler heads are designed for greater coverage 
 than the 60-foot diameter usually served by the more common heads. 
 It is difficult to use these special heads advantageously in orchards 
 on common spacings, because of the unavoidable overlap which must 
 be allowed to obtain complete coverage. If sprinkler heads are placed 
 in every third tree in every second row, the circle of application from 
 a single head must have a diameter equal to about three and one-third 
 
1926] 
 
 IRRIGATION BY OVERHEAD SPRTNKIJNG 
 
 11 
 
 Fig. 3. — Typical layouts of permanent sprinkler installations, 
 
 A. A hexagonal installation reduces the overlap of circles of coverage to a 
 minimum. Each head is the same distance from its neighbors in every direction. 
 Such a method of installation is not adapted to orchards on a rectangular plant- 
 ing plan. 
 
 B. A common metliod of installation in rectangular plantings is to establish a 
 sprinkler head in every second tree in every second row. The sprinkler heads are 
 not equally spaced. 
 
 C. Economy in underground piping results when individual sprinklers can be 
 located in every second tree in every third row. The distribution is lacking in 
 uniformity. 
 
 D. When sprinklers of large diameters of coverage are used auxiliary sprinklers 
 are sometimes installed to insure complete coverage without excessive overlap. 
 
12 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [CiRC. 4 
 
 times the distance between the trees. With trees planted on 24-foot 
 distances, for example, the diameter of application required would be 
 about 80 feet, and undesirable inequalities in application would 
 necessarily result. 
 
 Some manufacturers, particularly those who specialize in sprink- 
 ling devices for golf greens, offer sprinklers wdth great diameters of 
 coverage for orchard use. The advantage in using such heads lies 
 in economy in underground piping. The great disadvantage is that 
 undesirable inequalities of distribution must exist if the sprinkling 
 heads be located with respect to existing tree rows. In some instal- 
 lations with large-diameter heads, a dry area is allowed to remain 
 between the circles covered by four large sprinklers. This dry area 
 is covered by a small sprinkler fed from a lateral leading from the 
 nearest main. 
 
 TYPES OF SPRINKLEE HEADS 
 
 Sprinkler heads designed for orchard work fall into four main 
 classes, as follows : 
 
 (1) Solid heads carrying no moving parts. With these, water is 
 broken into drops by impact against a baffle plate in the top of the 
 head. The drops are forced through ports in the top or side of the 
 head by the pressure in the line. Such heads usually serve areas of 
 small diameter, their advantage being that they have no moving parts, 
 which eventually necessitate replacements, and that there is freedom 
 from leakage when in operation. 
 
 (2) Rotary sprinklers carrying small and simple moving parts. 
 These throw water over a greater distance than could be served by a 
 solid head. This wider distribution may be due either to the impact 
 of a revolving member against the jet, or to the centrifugal action 
 imparted by short arms. The pressure of the water in the riser 
 revolves the moving parts. Such heads usually have a greater capacity 
 than solid heads and usually cover a larger area. Some heads in this 
 class carry a thrust bearing, which is subject to wear. When this 
 wear becomes appreciable, the head leaks and the leakage runs down 
 the stand pipe, causing an undesirable accumulation at the base. One 
 manufacturer of a popular head in this class provides a simple ball- 
 bearing to accommodate this thrust with a minimum of wear. 
 
 (3) Long arm sprinklers depending on centrifugal force for the 
 distribution of water. Arms of brass or galvanized iron pipe are 
 screwed into specially designed heads, which screw on the riser pipes. 
 These heads contain thrust bearings, usually of babbit or monel metal 
 against brass. The arms are bent near their outer ends so that they 
 
1926] 
 
 IRRIGATION BY OVERHEAD SPRINKLING 
 
 13 
 
 form a slight angle with the diameters of the heads, as indicated by 
 the longer sections of the arms. When water is forced through these 
 arms, the reaction to the issuing stream causes the heads to revolve. 
 Caps of special design are screwed to the ends of the arms to promote 
 uniform distribution. In many cases the cap of one arm carries a 
 round hole which throws a solid jet to the extreme circumference of 
 
 Fig. 4. — Types of sprinkler heads. Sprinkler heads should be selected after 
 consideration of the required diameter of coverage, the capacity of each head 
 under the available pressure, and the water supply. 
 
 the wetted circle. The other end sometimes carries an aperture of 
 such design that a fan-shaped jet is provided, which serves the inner 
 zones of the area. When the arms of such sprinklers are of galvanized 
 iron pipe, the bending to form off-set ends may result in scales of 
 rust w^iich may lodge in the discharge orifices and stop the head. 
 
 (4) Geared sprinklers, designed to secure greater coverage than 
 can be obtained by the common long arm type. This end is achieved 
 
14 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [CiRC. 4 
 
 by having part of the water escape through a central jet of such 
 design that a large throw can be obtained. The remaining water is 
 sent through a rotary sprinkler head which supplies the inner zones 
 of the area. The rapid revolution of this rotor moves the large central 
 jet by means of a more or less elaborate gear train so that the whole 
 circumference can be served. Many sprinklers in this group are 
 adjustable so that varying quantities of water can be sent through the 
 central jet. Increasing the quantity discharged through the central 
 jet makes for increased application on the circumference of the circle 
 of coverage and a lighter application near the center. Several 
 sprinkler heads in common use are shown in figure 4. 
 
 UNIFOEMITY OF COVEEAGE FEOM EEVOLVING SPEINKLEES 
 
 An ideal sprinkler head should apply water uniformly over the 
 diameter of coverage. While this ideal cannot be reached, it has been 
 approximated closely by several modern sprinklers. When many 
 sprinklers are to be used for the irrigation of a large rectangular 
 area, a slight ''feathering out" in the uniformity of application near 
 the circumference is not a great disadvantage, since the overlap of 
 these circles of coverage occurs on the zones of lighter application and 
 tends to equalize them. 
 
 Many observations have been made in an effort to determine the 
 uniformity of application resulting from standard sprinkler heads of 
 modern design. Except for solid heads, which are not widely used in 
 orchard practice, all sprinkler heads are, to some extent, adjustable. 
 Any adjustment tends to influence the uniformity of distribution. 
 Light rotary heads can be adjusted by a slight constriction in one or 
 all of the small tubes through which water is discharged. A slight 
 bend in the soft metal of these tubes also affects the uniformity of 
 distribution. 
 
 Long arm sprinklers can be adjusted in two ways. One method 
 is to change the terminal orifices. Most manufacturers send long arm 
 sprinklers into the field with an assortment of brass outlet fittings to 
 be used on the ends of the arms. Changing a large holed fitting for 
 a small one results in increasing the application on the circumference. 
 Equipping both ends of the arms with such orifices in place of fitting 
 one end with a notched or diamond-shaped orifice results in excessive 
 application on the circumference and almost no application near the 
 center. Long arm sprinklers can also be adjusted by backing the 
 arms out of the head so that the angle formed by the offset in the arm 
 
1^20] IRRIGATION BY OVERHEAD SPRINKLING 15 
 
 with the horizontal may be changed. If, however, the arms are backed 
 out so far that the plane described by the main part of the arm and 
 the offset is vertical, there can be no revolution and consequently no 
 distribution. 
 
 As has been mdicated, geared sprinklers can be adjusted by chang- 
 ing the proportion of the whole flow which passes through the central 
 jet. This can be done by the manipulation of a needle valve behind 
 the central jet, if one is provided, or by changing the brass orifice cap 
 which covers the jet. 
 
 Changes in the pressure under which a head is operating may 
 affect the uniformity of distribution resulting from that head. 
 
 For these reasons it seems unnecessary to give results obtained 
 from distribution tests. In most cases heads must be adjusted after 
 installation to accommodate minor and perhaps unintentional changes 
 in the head itself and to adapt the head to the pressure available at 
 the particular location. Tests for uniformity can be easily made in 
 the field. In making such a test cans of uniform cross-section are 
 placed at equal distances along one radius of the circle to be covered. 
 At the end of a given period, absolute equality of distribution is 
 reflected by equal depths in the several cans. Such a test should be 
 run for several hours before reliable conclusions can be reached. A 
 refinement of this method lies in catching the water in funnels estab- 
 lished at equal distances along a radius and collecting the drainage 
 water from such funnels in glass test tubes of equal diameters. Minor 
 inequalities of distribution are more quickly and accurately detected 
 by this method. A day with little or no wind should be chosen for 
 such tests, since a very slight breeze will result in a great distortion 
 from the normal coverage. 
 
 PEESSURE EEQUIREMENTS FOE EEVOLVING SPEINKLEES 
 
 Since the pressure under which a sprinkler head operates affects 
 its uniformity of distribution, recommendations as to suitable pres- 
 sures should be closely adhered to. Most solid and rotary sprinklers 
 operate eff'ectively under a pressure of 15 pounds per square inch at 
 the head. Long arm sprinklers require more pressure for successful 
 operation than solid heads. Geared sprinklers ordinarily require more 
 pressure for operation than sprinklers of any other type because of 
 the mechanical losses in the gear train. Large geared sprinklers, such 
 as are used for the irrigation of parks or golf greens, are sometimes 
 designed for operation under pressures as great as 100 pounds per 
 
16 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [CiRC. 4 
 
 square inch. Manufacturers claim a diameter of 175 feet for the 
 circle of coverage of geared sprinklers under such pressures. The 
 pressures recommended by manufacturers are usually those required 
 at the heads. Gages should be installed at the top of the standpipe 
 and immediately beneath the thrust bearing, if the actual pressure 
 under which a head is operating is to be measured. If such a location 
 is impracticable, a gage may be installed nearer the ground. If this 
 is done, the reading on the gage should be reduced by as many pounds 
 as is represented by the height of the sprinkler above the gage, divided 
 by 2.31. This reduced pressure will closely approximate the pressure 
 at the head. 
 
 CAPACITIES OF SPRINKLER HEADS 
 
 Sprinkler heads vary widely in capacities. This is due partly to 
 differences in design and partly to the pressures for wdiich various 
 heads may be recommended to insure greatest uniformity of distri- 
 bution. 
 
 For heads commonly used for orchard irrigation, such as rotary 
 sprinklers and certain types of long arm sprinklers, a discharge 
 sufficient to cover the circle of coverage to a depth of one inch in four 
 or five hours may be considered as typical. Geared sprinklers may, 
 and usually do, discharge more than that indicated above. Solid 
 heads of various makes differ widely in discharge under operating 
 pressures. 
 
 Since knowledge of the amount of water discharged by a single 
 head is of great importance in the design of a sprinkler installation, 
 tests have been run on a few modern heads under varying pressures. 
 
 A solid head popular in the citrus areas of the southern states 
 was found to discharge 7.6 gallons per minute under a pressure of 
 35 pounds per square inch. Under a pressure of 20 pounds per square 
 inch, the discharge dropped to 5.9 gallons per minute, and 10 pounds 
 gave only 3.8 gallons. 
 
 Two makes of long arm sprinklers in common use in California 
 showed almost identical capacities for similar pressures. These heads 
 discharged 6.9, 5.3, and 3.8 gallons per minute when operated under 
 pressures of 35, 20, and 10 pounds per square inch, respectively. 
 
 As has been stated, geared sprinklers have greater capacities than 
 either solid heads or long arm sprinklers. One geared sprinkler used 
 in parks and on golf greens discharged 17.3 gallons per minute under 
 a pressure of 35 pounds per square inch. Under pressures of 20 
 pounds per square inch and 10 pounds per square inch, the discharge 
 was 13.4 and 9.4 gallons per minute, respectively. 
 
1926] 
 
 IRRIGATION BY OVERHEAD SPRINKLING 
 
 17 
 
 When the discharge of a certain head nnder the recemmended 
 pressure is known, the time required for an application of one inch 
 of water can be readily computed by the following simple formula : 
 
 II D = diameter of the wetted area in feet, and 
 
 G.P.M. = capacity of the head in gallons per minute, then 
 
 r P M N/ 199 ^^ hours run required for an application of one 
 (x.r.M. X 1-- i^^]^ Qj^ ^j^g wetted zone. 
 
 This equation is based upon the assumption that evaporation losses 
 are negligible. 
 
 Fig. 5. — Botary sprinklers in operation. Permanent installations represent 
 a high first cost and are most popular in high producing areas. 
 
 TYPES OF INSTALLATIONS FOR USE WITH REVOLVING HEADS 
 
 Permanent Sprinkler Installations. — Installations which are pro- 
 vided with fixed riser pipes connected to underground laterals, are 
 sometimes called permanent sprinkler installations. Such an instal- 
 lation is shown in operation in figure 5. AVith this type it is possible 
 to irrigate an entire field or any part of it by an adjustment of the 
 valves which are at the intake ends of the laterals and in the indi- 
 vidual riser pipes. The number of sprinklers that can be carried by 
 a single lateral, the capacity of each head under the available pres- 
 sure, the topography of the area to be served, and, in some cases, the 
 head of water available are factors which affect the design. Since 
 these considerations vary widely in different areas, it is inadvisable 
 to copy an existing successful installation unless it is definitely known 
 
18 
 
 CATJFORNIA AGRICULTURAL EXTENSION SERVICE 
 
 [CiRC. 4 
 
 that conditions are similar. Every problem of permanent sprinkler 
 design is a special problem which must be undertaken only after the 
 governing factors are known. A typical plan for a permanent instal- 
 lation is shown in fiefure 6. 
 
 . SuppfL/ pipe —. — : ., J 00 6.PM. at 60 /hj. pressure ^3" 
 
 + t f <- » — ^-^ » f — » / + f + — t 
 t -t ■*- -f + +-'+--1-1/+- +- ■♦-,' + 
 
 + / + 
 / 
 
 t » — r 
 + t 1- 
 
 
 ^^ 
 
 -f — +y -T 4 
 
 / 
 -h Y 1- t 
 
 t? 
 
 * f 4-V » 
 
 f + /» 
 
 4.A- 
 
 + '^. 
 
 + + 
 
 f-— T f \ 4- T- F ? T ^^ =F r i-\ + 
 
 + + +\4--f-+t + + + + +§^ 
 
 
 ■I 
 
 ^ TTT T— TT T T T ¥ =T T + ^ + 
 
 4 4 '^+ + \+ -*- 4- 4 ^ 4- + -u + 
 
 / ^ 
 
 rt •-t — ^ • JL » * ■ — _L m. — 
 
 ^-f- 
 
 4^'. 4 Y 
 
 ■^/'. 
 
 /<«7 
 
 Fig. 6. — Typical plan for permanent installation. The pipe sizes indicated 
 above are suitable only for the conditions indicated and for installations in which 
 both main and laterals are level. The dotted lines indicate the point at whicli 
 1-incli pipe must change to 1^4 -inch pipe. Every installation is a special problem 
 and must be so considered. The circles represent coverage and indicate the 
 extent of overlap. 
 
 It is evident from the consideration of the location of sprinkler 
 heads, that laterals in the case of permanent plantings must be 
 installed adjacent to alternate rows in the grove, if heads giving 
 
1^26] IRRIGATION BY OVERHEAD SPRINKLING 19 
 
 common diameters of coverage are to be used. Risers, capped by 
 sprinkler heads, start from tees located on the laterals below alternate 
 trees. A fair approximation to ideal distribution can be obtained in 
 this way. 
 
 Six sprinkling heads on a single lateral are commonly used with 
 sprinklers of ordinary capacities. A 10-acre area of usual shape 
 (Vs niile square) can be satisfactorily irrigated, if a main pipe line 
 runs through the center of the tract and if laterals branch to each side 
 from crosses installed on the main opposite the selected tree rows. 
 Each lateral on a 10-acre tract must carry six risers to insure com- 
 plete coverage. It is customary to consider larger areas as multiples 
 of such units. In such a case, the main mentioned above would become 
 a lateral of the larger installation, while the laterals would become 
 branches from laterals of the larger installation. Since available 
 water and available pressure can rarely be developed for the simul- 
 taneous operation of more than 10 acres, the multiple installations 
 suggested above are very rare. 
 
 One of the advantages of overhead sprinkling as a means of apply- 
 ing irrigation water is the flexibility of the method. Localized areas 
 of light soil can be irrigated frequently and lightly, while the heavier 
 soils can be watered heavily and more infrequently. Valves located 
 at the heads of laterals supplying water to heavy soils make it possible 
 to cut out these areas when water is required by lighter soils under 
 the same unit. Globe valves may be used for this purpose, although 
 simple cut-off valves are suitable, since the valve will usually be 
 entirely open or entirely closed. The valve in either case will be 
 below the surface of the ground, since it must be installed on the 
 underground lateral. It should be protected by a short length of 
 casing which ends at the surface of the ground or slightly above it. 
 
 It is practically impossible to select pipe sizes for a lateral with 
 such exactness that each riser on that lateral will be supplied with the 
 pressure required for best distribution. A small valve is usually 
 installed on each riser so that pressures may be equalized and each 
 sprinkler head supplied with the specified pressure. In some cases 
 a special fitting, carrying a valve and a strainer, is incorporated in 
 each riser at a convenient height. This fitting is so designed that the 
 strainer can be cleaned of scale accumulation and other debris in the 
 water without dismantling the riser assembly. Such fittings also 
 provide a convenient point at which the riser may be temporarily 
 removed if it interferes with fumigation. Figure 7 shows a riser pipe 
 equipped with a strainer and valve fitting. 
 
20 
 
 CALIFORNIA AGRICULTURAL EXTENSION SERVICE 
 
 rClRC. 4 
 
 In other installations, a strainer is built into the head. Such a 
 design may entail the use of a ladder when the strainer is to be 
 cleaned. 
 
 Fig. 7. — Detail of permanent riser a8seml)ly. The offset fitting carries a 
 strainer and a valve by which inequalities of pressure can be accommodated. The 
 riser can be dismantled at this fitting for cleaning or replacement. 
 
 Some means of draining the pipe system should be provided. 
 Repairs and replacements can best be made on empty lines. In areas 
 where freezing weather is to be expected, lines should be drained. 
 
1926] IRRIGATION BY OVERHEAD SPRINKLING 21 
 
 Drain plugs should be installed at the end of each lateral and at the 
 end of the main, if local conditions would cause an accumulation of 
 water at that point. Common plugs screwed into terminal couplings 
 provide a cheap and satisfactory means of drainage. In cases where 
 "the laterals run up hill from the main, the drain plug should be 
 installed in a tee connected by a short nipple to the discharge end of 
 the cut-off valve on that lateral. 
 
 The design of a satisfactory sprinkler installation is complex and 
 requires considerable familiarity with the principles involved in the 
 flow of water in pipes. Some discussion of the design of sprinkler 
 layouts and a friction head table for iron pipe of small diameters is 
 furnished in this circular as an aid to those who are removed from 
 the service furnished by manufacturers of sprinkling equipment. 
 
 As may be suggested from the list of materials required for a 
 permanent sprinkler installation, the cost of such a system is high. 
 Under average conditions, when tree rows are from 20 to 24 feet apart 
 and when sprinkler heads are located in alternate trees along these 
 lines, a cost of $300 an acre is not unusual. This cost is based upon 
 pipe prices obtained in the spring of 1925. When truck crops or 
 nurseries are to be irrigated and a more efficient location of sprinkler 
 heads is effected, this cost may be slightly reduced. Iron pipe has 
 the unfortunate property of an ever decreasing diameter due to the 
 formation of scale within the pipe. This property is apparent even 
 when pipes carry only the purest water. If an installation is planned 
 for a 20-year life, pipe sizes which will have ample capacity during 
 the whole period should be chosen. A layout based upon the capacities 
 of new pipe might be considerably cheaper than the estimate given 
 above. The estimate of .$300 an acre is based upon a design in which 
 the capacities of pipes ten years old are considered. 
 
 Portahle Sprinklers Operated from Underground Laterals. — Many 
 growers are prohibited from using a permanent installation because of 
 the high first cost or because of unwillingness to accept the high annual 
 overhead charge which such an installation would entail. The use of 
 portable stands attached by '^^-inch garden hose to outlets carefully 
 located on an underground distributing system provides for the con- 
 venience and benefits of overhead sprinkling without the high first 
 cost of a permanent installation. 
 
 There is no standard design for portable sprinklers. In most cases 
 growers build sprinkler stands from materials at hand and cap them 
 with purchased sprinkler heads. In some cases the riser pipe is 
 mounted on a light wooden platform by means of a bend elbow. Guy 
 wires run from the corners of the stand to the top of the riser. A tee 
 
22 
 
 CALIFORNIA AGRICULTURAL EXTENSION SERVICE 
 
 [ClRC. 4 
 
 or elbow fitted with a hose-tliread adapter, allows for the connection 
 of a supply hose. Another common type is made entirely of pipe 
 sections and fittings. A %-inch pipe cross, fitted with 3-foot lengths 
 of %-inch pipe, furnishes the base. The riser pipe starts from a tee 
 connected to one arm of the cross by a short nipple. Three of the arms 
 from the cross are sealed by caps, while the fourth is fitted with a 
 hose thread-adapter which allows the entrance of water. Guy wires 
 
 4'x4' P/ofform 
 
 Fig. 8. — Detail of portable sprinkler stand. Such stands are usually home- 
 made except for the sprinkler head. The use of a drop elbow at the base of the 
 riser pipe simplifies the connection with the supply line. 
 
 are essential for all types of portable stands. Figure 8 shows a satis- 
 factory design for a portable sprinkler stand. Figure 9 shows such 
 stands in operation. 
 
 Hose lengths used to connect portable stands to underground out- 
 lets should be less than 50 feet long because of the great pressure losses 
 in such material. When the hose is in use short bends should be 
 avoided. Hose is at best short lived and should be carefully drained, 
 coiled, and stored in the shade between irrigations. 
 
 It is evident that economy in underground piping can be effected 
 by the use of portable sprinklers operated by hose lengths of 50 feet. 
 
1926 
 
 IRRIGATION BY OVERHEAD SPRINKLING 
 
 23 
 
 Such underground laterals are ordinarily placed under every fifth 
 or sixth tree in the grove. The outlets are usually short risers, con- 
 nected to the underground lateral by means of tees, and capped by 
 
 Fig. 9. — General view of portable sprinklers in operation. The use of such 
 portable sprinklers reduces the first cost. Flexibility in operation can be gained 
 by the use of such an installation. 
 
24 
 
 CALIFORNIA AGRICULTURAL EXTENSION SERVICE 
 
 [CiRC. 4 
 
 common garden faucets equipped for hose couplings. Trees shelter- 
 ing such outlets are often flagged in some way, to insure prompt 
 identification during irrigation. 
 
 Another saving resulting from the use of portable sprinklers as 
 compared with permanent installations is in the initial investment 
 in the risers and sprinkling heads. Long arm sprinklers which throw 
 relatively large quantities of water are ordinarily used on portable 
 
 60 O.PM. 
 ^"A y^^ Pressure 
 
 -H'i 
 
 U" 
 
 /r 
 
 -£" 
 
 d" 
 
 ^" 
 
 1^ 
 
 d 
 
 /i 
 
 /r 
 
 vi 
 
 Fig. 10. — Suggested design for underground pipe system under assumed con- 
 ditions of available supply and pressure. Each sprinkler is operated from a 
 separate lateral. Note the economy of smaller pipe necessary in this scheme of 
 installation as compared with that shown in figure 11. 
 
 sprinklers. Six portable sprinklers are usually operated at once, and 
 only that number need to be provided for the usual 10-acre instal- 
 lation. Economy can be gained by designing the underground pipes 
 so that each lateral carries but one sprinkler, rather than by locating 
 all the sprinklers along one lateral and finishing the zone within 
 reach of that lateral before the next is begun. With the latter plan 
 of distribution, the first section of the lateral line must be of sufficient 
 
1926] 
 
 IRRIGATION BY OVERHEAD SPRINKLING 
 
 25 
 
 size to accommodate the water supply necessary for the five sprinl^lers 
 below it in addition to that used by the first. A further saving results 
 in possible reduction in the diameter of the main supplying these 
 laterals, since the required capacity of the main is reduced at each 
 turnout. Figures 10 and 11 illustrate the saving which may be 
 effected by this design. 
 
 60 aPM. 
 
 
 \^// SO"^ Pressure 
 
 • 
 
 
 
 ^5" 
 
 
 
 a"pipe^ 
 
 e"p/pe^ 
 
 jE^aoh spnnk/er ^/Ves 
 
 ^\ 
 
 Fig. 11. — Suggested design for underground pipe system for use with portable 
 sprinklers when eaeli lateral must have sufficient capacity for the simultaneous 
 operation of six sprinklers. 
 
 Except for the drain plug required at the end of each lateral, few 
 fittings are needed for a sprinkler installation of this type. Valves 
 regulating the flow into the laterals may be eliminated; pressure 
 adjustment into individual sprinklers may be effected by manipulation 
 of the garden faucet serving the stand. 
 
 Portable installations of this type represent an investment of about 
 $100 an acre, including the cost of the portable sprinkling stands. 
 Isolated installations in which secondhand pipe has been used are 
 estimated by the owners to have cost even less. 
 
26 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [CiRC. 4 
 
 Portable Sprinklers Operated from Portable Surface Laterals. — 
 A further decrease in cost can be effected by the use of portable 
 laterals in place of the underground laterals used in permanent instal- 
 lations. Such installations are neither popular nor common, since the 
 saving in cost by using them is, to a great extent, offset by the 
 increased labor cost of operation. 
 
 A main underground line of sufficient size to carry the quantity 
 of water required for the operation of the portable stands is laid on 
 the long axis of the area to be served. This line is equipped at 
 intervals of about 100 feet with risers capped by 2-inch hydrants fitted 
 for connection to 2-inch rubber hose. A short length of^ such hose 
 furnishes a flexible connection between the hydrant and a portable 
 lateral of li/2-iiich pipe, which is assembled on the surface of the 
 ground and which extends down the center of the zone to be served. 
 The sections of pipe which make up the surface lateral are fitted at 
 intervals of about sixty feet with 3/4-inch garden faucets. Portable 
 stands are connected by means of hose to these outlets in the surface 
 lateral, and a zone as long as the lateral and as wide as can be reached 
 by the length of hose used, is irrigated before the lateral is moved. 
 When one zone is completed, the surface lateral is taken apart, carried 
 to a position opposite the next riser on the main, and reassembled. 
 
 It is evident that the economy of pipe design which is possible if 
 each lateral carries but one sprinkler cannot be effected with instal- 
 lations of this type. The main must be large enough to carry the 
 entire flow to its end; since there is but one lateral, it must be large 
 enough to carry all the sprinklers. 
 
 DESIGN OF SUPPLY PIPE SYSTEMS FOR SPRINKLER 
 INSTALLATIONS 
 
 Because of its closely limited cross-section and the roughness of 
 its bore, iron pipe offers appreciable resistance to the flow of water. 
 The smaller the pipe the greater is the resistance ; and if the pipe size 
 remains the same, a greater resistance is offered to a large flow than 
 to a small one. The resistance to flow offered by a pipe can best be 
 measured by the loss in pressure which results when water is forced 
 through the pipe. If 100 feet of 2-inch pipe be fitted with a pressure 
 gage at each end, and a stream of water be forced through that pipe, 
 the gage at the outlet end will record less pressure than the gage at 
 the inlet end. This loss of pressure measures the resistance offered 
 by the 100 feet of 2-inch pipe to the flow of the quantity of water 
 which was forced through. If the pipe were 200 feet long, the differ- 
 
1926] 
 
 IRRIGATION BY OVERHEAD SPRINKLING 
 
 27 
 
 ence between the gage readings would be twice as great. No simple 
 proportion exists between the loss in pressure and the quantity of 
 water. 
 
 TABLE 1 
 
 Pressure LO'SSes in Pounds peu Square Inch for 100 Feet of Common Iron 
 Pipe of Varying Diameters and for Varying Flows 
 
 Gallons 
 
 Pipe sizes in inches 
 
 per 
 minute 
 
 Va, 
 
 1 
 
 134 
 
 W2 
 
 2 
 
 2H 
 
 3 
 
 3M 
 
 4 
 
 5 
 
 6 
 
 7 
 
 5 
 
 4 55 
 6 35 
 10.82 
 16 45 
 
 1.40 
 1.97 
 3.38 
 5.06 
 7.10 
 9.52 
 12 10 
 
 0.36 
 0.52 
 0.69 
 0.89 
 1.86 
 2.47 
 3.16 
 3.94 
 4.80 
 7.18 
 10 16 
 
 
 
 
 
 
 
 
 
 
 6 
 
 
 
 
 
 
 
 
 
 
 8 
 
 0.41 
 0.62 
 0.87 
 1.16 
 1.47 
 1.83 
 2.25 
 3.38 
 4.75 
 6.36 
 8.13 
 10 00 
 
 
 
 
 
 
 
 
 
 10 
 
 0.22 
 0.31 
 0.41 
 0.52 
 0.64 
 0.78 
 1 18 
 1.66 
 2.21 
 2.85 
 3.55 
 4.29 
 6 02 
 7.96 
 10 25 
 
 
 
 
 
 
 
 
 12 
 
 
 
 
 
 
 
 
 14 
 
 
 0.14 
 0.18 
 0.22 
 0.26 
 
 40 
 0.56 
 0.74 
 0.95 
 1.19 
 
 1 43 
 2.01 
 2.68 
 3.42 
 
 4 25 
 
 5 51 
 7.28 
 9.68 
 
 
 
 
 
 
 
 16 
 
 
 
 
 
 
 
 
 18 . . 
 
 
 
 
 
 
 
 
 20 
 
 
 
 0.10 
 0.16 
 0.23 
 0.31 
 0.39 
 0.50 
 0.60 
 0.85 
 1 11 
 1.42 
 1.76 
 2.15 
 3.06 
 3.98 
 
 5 10 
 
 6 40 
 7.70 
 9 20 
 
 
 
 
 
 
 25 
 
 
 
 
 
 
 
 
 30 
 
 
 
 
 
 
 
 
 35 
 
 
 
 14 
 17 
 0.22 
 0.26 
 38 
 0.48 
 0.63 
 0.78 
 0.96 
 1.34 
 1.82 
 2 27 
 2.72 
 3.33 
 4 15 
 5.02 
 5.78 
 6 54 
 7.70 
 9.70 
 
 
 
 
 
 40 
 
 
 .. 
 
 
 
 
 
 
 45 
 
 
 
 
 
 
 
 
 50 
 
 
 
 
 0.15 
 0.20 
 27 
 0.35 
 0.43 
 0.53 
 0.74 
 0.99 
 1.26 
 1.56 
 1.91 
 2.25 
 2.68 
 3.12 
 
 3 55 
 
 4 03 
 5.59 
 6 91 
 8.58 
 
 10 40 
 
 
 
 
 60 
 
 
 
 
 
 
 
 
 70 
 
 
 
 
 
 0.09 
 0.12 
 0.15 
 0.18 
 0.25 
 0.33 
 0.42 
 0.53 
 0.64 
 0.76 
 0.90 
 1.04 
 1.20 
 
 1 36 
 1.81 
 2.34 
 
 2 90 
 
 3 51 
 
 
 
 80 
 
 
 
 
 
 
 
 
 90 
 
 
 
 
 
 
 
 100 
 
 
 
 
 
 
 
 
 
 120 
 
 
 
 
 
 
 0.10 
 13 
 0.17 
 20 
 24 
 0.39 
 36 
 41 
 47 
 55 
 73 
 
 91 
 
 1 09 
 1 37 
 
 
 140 
 
 
 
 
 
 
 
 
 
 
 160 
 
 
 
 
 
 
 
 
 180 
 
 
 
 
 
 
 
 
 200 
 
 
 
 
 
 
 
 0.12 
 
 220 
 
 
 
 
 
 
 
 14 
 
 240 
 
 
 . 
 
 
 
 
 
 17 
 
 260 
 
 
 
 
 
 
 
 
 20 
 
 280 
 
 
 
 
 
 
 
 
 0.23 
 
 300 
 
 
 
 
 
 
 
 
 37 
 
 350 
 
 
 
 
 
 
 
 
 0.35 
 
 400 
 
 
 
 
 
 
 
 
 44 
 
 450 
 
 
 
 
 
 
 
 
 
 54 
 
 500 
 
 
 
 
 
 
 
 
 
 65 
 
 
 
 
 
 
 
 
 
 
 
 Table 1 is computed from results of experiments compiled by Williams and Hazen (Williams, 
 Gardner, S., and Allen Hazen. Hydraulic tables. 3rd ed., revised, )/5 p. John Wiley and Sons, Inc., 
 New York). 
 
 A value of 100 has been chosen for the "C" used in the computations indicated in the table above. 
 The use of this value results in an indicated friction loss equivalent to the loss in ordinary iron pipe 
 which has been in service for 10 years. Galvanized iron pipe probably deteriorates less rapidly than 
 common iron pipe. The friction losses, as given in table 1, are probably greater than would be expected 
 in galvanized iron pipe 10 years in service. 
 
 Many engineers have endeavored to determine the pressure losses 
 resulting when certain sizes of pipe are used to convey varying 
 quantities of water. Tables have been prepared from numerous 
 experiments by which it is possible to foretell with some degree of 
 exactness what losses in pressure may be anticipated under given 
 
28 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [CiRC. 4 
 
 conditions of diameter of pipe, length of pipes, and quantity of water. 
 Table 1 shows the pressure consumed by 100 feet of common iron 
 pipe of varying sizes when varying quantities of water, measured in 
 gallons per minute, are discharged. The loss resulting from other 
 lengths can be obtained by multiplying the loss as given for 100 feet 
 by the length of the line in question, divided by 100. 
 
 The use of table 1 makes it possible to compute the pressure 
 required to force any flow of water through a line of any length and 
 diameter. For instance, if a flow of 60 gallons per minute is to be 
 forced through a 2-inch line 300 feet long, a pressure of 18.06 pounds 
 per square inch would be consumed in overcoming the resistance to 
 flow offered by such conditions. If the water is to be delivered at the 
 outlet under a pressure of 20 pounds per square inch, an initial 
 pressure of 38.06 pounds per square inch would be necessary. 
 
 In designing sprinkler layouts, the problem becomes more com- 
 plicated, for in the main pipe line the quantity is being constantly 
 decreased as the laterals are reached. And in the laterals, the flow 
 is being constantly reduced as successive sprinkler heads are supplied. 
 The pipe connecting the last two sprinkler heads on a lateral should 
 be only large enough to carry the quantity required for a single head. 
 The section between the main and the first sprinkler must carry the 
 whole flow necessary for the lateral. 
 
 There is no short cut toward the intelligent design of such instal- 
 lation. Each lateral must be considered in turn, usually starting with 
 the one most distantly removed from the source of water and pressure. 
 Pipe sizes are determined for each section between successive sprinkler 
 heads. If a manufacturer recommends, for the sprinkler head made 
 by him, a working pressure of 15 pounds per square inch then the pres- 
 sure at the foot of the stand must be enough in excess of 15 pounds per 
 square inch to lift the water to the top of the stand and deliver it at 
 the required pressure. One pound per square inch represents the 
 pressure exerted by a column of water 2.31 feet high. If a stand is 
 12 feet high, the pressure at the base of the stand must exceed the 
 required pressure for the operation of the head by 12 divided by 2.31, 
 or 5.2 pounds per square inch. A pressure of 20.2 pounds per square 
 inch, as measured on a gage at the foot of the stand, would be required 
 before satisfactory operation could be secured. 
 
 The pipe joining this last stand in the example given above with 
 the one next to it must be large enough to deliver the quantity of 
 water required by a single head through the length of pipe repre- 
 sented by the distance separating the stands, and must provide a 
 pressure of 20.2 pounds per square inch at the end of the line. The 
 
1926] IRRIGATION BY OVERHEAD SPRINKLING 29 
 
 next section must be similarly determined. In this case, the quantity 
 required for two heads must be considered, since the last head and 
 the next to the last must be supplied. 
 
 The pipe section leading from the main to the first sprinkler on a 
 line must be laro^e enough to deliver the entire flow for the lateral. The 
 pressure requirement at the intake of this lateral must be smaller than 
 that which is available at the source, since there is necessarily some 
 loss of pressure in the main connecting the source of water with the 
 head of the lateral. 
 
 Table 2 has been prepared as an aid in the determinations indi- 
 cated above. Certain hypothetical conditions of pressure requirements 
 and capacities of sprinkler heads have been assumed and possible 
 combinations of pipe sizes computed. The pressure required at the 
 intake of laterals made up of the indicated pipe lengths and carrying 
 a certain number of sprinkler heads is also given under the heading 
 ''Initial Pressure." 
 
 Table 2 can be used only as a rough guide to required pipe sizes, 
 and then only if the distance between sprinklers and the capacities 
 and pressure requirements are as given. 
 
 A main designed to supply sufficient pressure for the most remote 
 lateral is usually large enough to supply sufficient pressure for nearer 
 ones. Ordinarily smaller pipe sizes can be used in laterals close to 
 the source than in those more distant. Effort spent in a close deter- 
 mination of pipe sizes, so that every pound of available pressure is 
 utilized, is repaid by a smoothly operating system and low first cost. 
 
 The design of a system for the use of portable stands is less com- 
 plicated than that for a permanent installation. However, the same 
 principles apply and the same care should be used. The greatest 
 saving can be gained through the careful design of the main line, since 
 small reductions in diameters of large sizes are reflected in relatively 
 large reduction in costs per foot of pipe. The principles involved in 
 designing the underground distributing main are, of course, common 
 to all types of sprinkling installations. 
 
 DEVELOPMENT OF PRESSURE FOR SPRINKLER OPERATION 
 
 In some limited areas irrigation water is delivered through pipe 
 lines under such natural pressure that sprinkler installations can be 
 operated without the use of pumps. Such conditions, however, are 
 not often found. Growers receiving water from gravity ditches or 
 low pressure pipe lines, and those who secure water from private 
 wells must use pumps to supply the pressure necessary for sprinkler 
 
30 
 
 CALIFORNIA AGRICULTURAL EXTENSION SERVICE 
 
 [CiRC. 4 
 
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 CO 
 
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1926] IRRIGATION BY OVERHEAD SPRINKLING 31 
 
 operation. The cost of pumps, in such cases, must be charged against 
 the sprinkler installation, and the annual operation cost, including 
 interest and depreciation, charged against the maintenance of the 
 system. 
 
 When a pump is required one of the high pressure types should be 
 chosen, since the pressure at the intake must be sufficient to overcome 
 frictional resistance in the system in addition to the pressure required 
 for the operation of the sprinkler outlets. Two types of pumps are 
 in common use for this purpose, viz., displacement, or plunger, and 
 centrifugal pumps. 
 
 Displacement pumps are those which force water by means of a 
 piston or plunger traveling backward and forward in a close-fitting 
 cylinder. ■ Such pumps are divided into several classes, depending 
 upon the number of cylinders built into a single pump and upon the 
 action of the cylinders. A single acting plunger forces water only on 
 one stroke of the piston ; a double acting plunger forces water during 
 both the forward and the backward stroke. All displacement pumps 
 should be equipped with ample air chambers to act as cushions for 
 absorbing pulsations due to the action of the pistons. A relief valve 
 or by-pass should be placed in the discharge pipe to prevent damage 
 to the pump or motor, should the discharge be shut off during the 
 operation of the pump. 
 
 Displacement pumps for sprinkler operation should be chosen only 
 upon recommendation by reliable manufacturers of pumping machin- 
 ery. For certain conditions, such as an extremely high lift and 
 delivery at high pressures, displacement pumps are well suited. Dis- 
 placement pumps cannot be used wdth waters carrying sand. 
 
 Centrifugal pumps are rapidly gaining favor as sources of pres- 
 sure for sprinkler operation. When such a pump is used, the outlets 
 can be completely closed during the operation of the pump without 
 damage. Centrifugal pumps create pressure by forcing water into a 
 line by means of an impeller or vaned wheel which revolves at a high 
 speed in a closed shell or case. A single-stage centrifugal pump, that 
 is, a pump which carries but one impeller, may be used for instal- 
 lations where the required pressure at the intake need not exceed 
 50 pounds per square inch. In cases where a greater initial pressure 
 is required, a two-stage pump may be used. A two-stage pump con- 
 tains two impellers, each operating in a separate shell but rotated by 
 the same shaft. 
 
 Centrifugal pumps must be installed close to the source of water. 
 Long suction pipes should be avoided whenever possible. In cases 
 where a centrifugal pump must be placed directly over a water 
 
32 
 
 CALIFORNIA AGRIOULTURAL EXTENSION SERVICE 
 
 [CiRC. 4 
 
 supply, as in a well, the distance from the water level during the 
 period of greatest draw-down, to the center line of the pump must not 
 exceed 22 feet. All centrifugal pumps must be primed before start- 
 ing. This can best be accomplished by filling the suction pipe and 
 pump shell by means of a priming pump located at the highest point 
 on the pump's shell. Figure 12 shows a direct connected single-stage 
 centrifugal pump used for the development of pressure for sprinkler 
 operation. 
 
 Fig. 12. — A typical pumping plant for sprinkler operation. Such pumping 
 plants are necessary when the water supply is not under pressure or when available 
 pressure is inadequate. 
 
 Centrifugal pumps are simple in design. They are inexpensive in 
 first cost, as compared with displacement pumps of the same capaci- 
 ties. They have few^ wearing parts and are usually equipped with 
 adequate oiling facilities. The better pumps are so assembled that 
 replacements may easily be made. 
 
 The selection of the proper type of centrifugal pump and the 
 proper size for a particular installation demands expert advice. The 
 efficiency to be gained by a centrifugal pump under any set of con- 
 ditions depends greatly upon the speed at which it is operated. 
 Recommendations with regard to the speed of operation should be 
 carefully observed. 
 
1926] IRRIGATION BY OVERHEAD SPRINKLING 33 
 
 POWER REQUIREMENTS FOR SPRINKLER OPERATION 
 
 The power required by any pumping- plant depends upon the 
 quantity of water lifted in a given time, the height to which it must 
 be lifted, or the pressure required at the discharge, and the efficiency 
 of the plant. 
 
 A simple formula for determining the horsepower required for 
 lifting certain quantities of water to given heights is : 
 
 G.P.M X g X 100 .. 
 
 3960 XJ^ ^^ 
 
 where G.P.M. = quantity of water lifted in gallons per minute. 
 H == vertical lift effected, in feet. 
 
 E = expected combined efficiency of pump and motor. 
 (About 65 per cent for well designed centrifugal 
 plants driven by electric motors.) 
 HP. = horsepower required. 
 
 Since causing a stream of water to flow under a pressure of one 
 pound per square inch requires as much power as would be expended 
 in lifting the same stream to a height of 2.31 feet, the equation may 
 also be written : 
 
 G.PJL X f X 100 ,„. 
 
 ^■^■~ 1714 X E ^^> 
 
 where P = pressure in pounds per square inch which must be 
 
 effected at the discharge end of the pump. 
 
 In cases where the same pump is used to lift water through 
 appreciable distances, as from a well, and to subject the discharge to 
 a pressure sufficient to operate a sprinkler system, the motor must be 
 large enough to satisfy both these demands for power. Such compu- 
 tations can best be made by changing the pressure requirements into 
 the equivalent feet of vertical lift (by multiplying by 2.31) and adding 
 the vertical lift to the point to which pressure requirements are com- 
 puted. The relation stated in equation (1) can then be used. In 
 cases where a long suction pipe is necessary, allowances should be 
 made for losses in efficiency due to the resistance to flow in the suction 
 pipe. 
 
34 CALIFORNIA AGRICULTURAL EXTENSION SERVICE [CiRC. 4 
 
 THE EFFECTIVENESS OF IRRIGATION BY SPRINKLING 
 
 PENETEATION AND SOIL MOISTUEE CONSIDERATIONS 
 
 The value of overhead sprinkling as a means of irrigation depends 
 upon the effectiveness of this method in creating and maintaining 
 a satisfactory soil moisture content. Soils vary in water holding 
 capacity and permeability, fine-textured soils holding more moisture 
 than coarser soils but '' taking" water less readily. Plants suffer for 
 water when the moisture content within the rooting zone drops below 
 a point known as the wilting coefficient. The wilting coefficient for 
 most soils may be determined in the laboratory with a fair degree of 
 accuracy. If it can be assumed that the major concentration of feed- 
 ing roots occurs in a definite soil stratum, a satisfactory^ method of 
 irrigation would permit the application of water by such a means 
 and in such an amount that the soil moisture content in* that stratum 
 of soil may be maintained between these limits. 
 
 Six sprinkled citrus groves in Los Angeles and Orange counties 
 were sampled intensively for depth of penetration of irrigation water 
 and soil moisture content during the irrigation season of 1925 to 
 determine the effectiveness of irrigation by the sprinkling method. 
 Three of these groves were on decomposed granite soils of low water 
 holding capacity and easy permeability, while three were on soils of 
 finer texture into which water penetrates less readily. In most cases 
 the groves were sampled immediately before and after each irrigation. 
 In every case samples were taken from the same limited areas at each 
 time of sampling. Although this method of sampling did not neces- 
 sarily indicate the average moisture content in the entire grove at the 
 time of the sampling, it did give a fairly accurate idea of the soil 
 moisture history in the small plots under consideration. 
 
 In the case of the three groves on decomposed granite soils, the 
 sampling indicated that satisfactory irrigations had been accom- 
 plished. In none of these groves did the soil moisture content in the 
 principal rooting zone fall below the wilting coefficient between March 
 and November. Adequate penetration of moisture at each irrigation 
 was, in most cases, indicated by an increase in soil moisture content 
 in the fourth foot of soil. The effect of irrigation was sometimes 
 evident in the fifth and sixth foot. It is to be noted that these groves 
 were managed by men experienced in sprinkler operation. Sprinkler 
 heads were well adapted to conditions, and factors determining the 
 required period of operation were well understood. A great measure 
 
1926] IRRIGATION BY OVERHEAD SPRINKLING 35 
 
 of the success of overhead sprinkling in these groves can probably be 
 attributed to the experience of the operators. 
 
 Inadequate penetration of irrigation water was noted in each of 
 the three sampled groves on the heavier soil. In most cases irrigation 
 resulted in an increase in the moisture content of the surface foot 
 alone, the greater depths being at, or dangerously near, the wilting 
 coefficient when the residual soil moisture from winter rains had been 
 depleted by plant withdrawals. In one case, however, sprinklers were 
 operated for a period four times as long as usual and an increase in 
 the soil moisture content was noted to a depth of six feet. This fact 
 together with scattered observations upon the penetration secured in 
 difficult soils by overhead sprinklers in other areas seems to indicate 
 that adequate penetration in such soils can be obtained with experi- 
 ence, patience, and proper care in the selection and use of equipment. 
 
 DUTY OF WATEE 
 
 Observations on the amount of water used per acre in the irri- 
 gation of citrus trees by overhead sprinkling as compared with the 
 amount used by other methods show no significant difference which 
 can be attributed to the method of application. These observations 
 were localized in three areas. In these areas the amount of water used 
 in 1925 on groves under good sprinkler management were compared 
 with neighboring groves of comparable age, variety, and thrift, which 
 were irrigated by means of furrows. The results of these observations 
 are summarized in table 3. Although it is impossible to draw con- 
 clusions from such a small number of fields, it is probable that in 
 practice, such factors as the cost of water used, the skill of the 
 irrigator — and in the case of surface irrigation, the preparation of 
 the land — are of more importance in determining the amount of 
 w^ater to be used per acre than is the method of application. 
 
 EVAPOEATION LOSSES 
 
 Losses by evaporation from overhead sprinkling, especially during 
 periods of high temperatures and low humidity, are doubtlessly 
 significant in areas where water costs are high. As yet, no workable 
 means of measuring this loss has been devised. Irrigating by 
 sprinklers at night seems to reduce the losses from evaporation. 
 
36 
 
 CALIFORNIA AGRICULTURAL EXTENSION SERVICE 
 
 [CiRC. 4 
 
 TABLE 3 
 
 Duty of Water in Acre-Feet per Acre on Sprinkled and Furroay Irrigated 
 Orange Groves, Season 1925 
 
 Area 
 
 Soil type 
 
 h 
 ■11 
 
 
 
 II 
 I- 
 
 I > 
 
 n 
 II 
 
 < 
 
 .Hfe 
 
 1 
 Weighted 
 average 
 
 Sunnyslope . 
 
 Hanford gravelly 
 sandy loam. 
 
 1 
 
 8.5 
 
 1.13 
 
 1 13 
 
 1 
 2 
 3 
 4 
 5 
 6 
 
 4 5 
 4 5 
 4 5 
 10.0 
 10 
 10 
 
 1.14 
 1 54 
 1 75 
 1.92 
 1 64 
 1 71 
 
 1.67 
 
 Sierra Madre 
 
 Hanford gravelly 
 sandy loam. 
 
 1 
 2 
 3 
 
 8.7 
 
 5 
 
 23.0 
 
 1 88 
 1 26 
 1 05 
 
 1.28 
 
 1 
 2 
 3 
 
 5.50 
 4 00 
 3,90 
 
 1.42 
 1,31 
 1.40 
 
 1.38 
 
 La Canada 
 
 Hanford gravelly 
 sandy loam. 
 
 1 
 
 8.5 
 
 1.11 
 
 1.11 
 
 1 
 
 10.0 
 
 1.00 
 
 1 00 
 
 FERTILIZER DISTRIBUTION 
 
 Although conclusive experimental work is lacking, it can probably 
 be assumed that the distribution of fertilizing materials through the 
 soil after a surface application may be accomplished more speedily 
 and more effectively by sprinkling immediately after the distribution 
 of fertilizer than by any other means except a natural rain of proper 
 intensity and duration. 
 
 PEST AND DISEASE CONTROL 
 
 Experimental evidence as to effectiveness of overhead sprinkling 
 upon pest and disease control is not available. 
 
 TEMPERATURE AMELIORATION 
 
 In areas affected by hot dry winds, relief from excessive drying 
 out can probably be attained by sprinkling during the hours of 
 greatest danger, since exaporating water absorbs heat. An additional 
 benefit would accrue from the increased humidity in the area under 
 the sprinklers. In areas endangered by low temperatures, sprinkling 
 as a means of frost protection is of doubtful value. In freezes of long 
 duration, the ice load carried by delicate trees, when sprinkling is 
 unwisely attempted, may, and often does, cause damage to the trees. 
 
1926] IRRIGATION BY OVERHEAD SPRINKLING 37 
 
 FEUIT QUALITY 
 
 Experienced packing house managers claim that fruit of a higher 
 quality comes from sprinkled groves than from groves irrigated by 
 other means. It has never been proved, however, that the increased 
 quality is due to the method of irrigation. 
 
 SUMMARY 
 
 1. Irrigation by overhead sprinkling is costly. At present this 
 method of irrigating is limited to the production of high-priced crops 
 on land of high value. 
 
 2. Intensive soil-moisture sampling during the irrigation season 
 of 1925 indicated that adequate soil-moisture penetration can be 
 secured by the sprinkling of decomposed granite and sandy loam soils 
 if the sprinkling equipment is w^isely selected and intelligently 
 operated. Experimental evidence as to the adaptability of sprinkling 
 to heavy soils is not as conclusive. 
 
 3. The type of installation to be adopted for a particular location 
 depends upon the crops to be irrigated, the money available for 
 investment in such equipment, and the labor available during the 
 irrigation. 
 
 4. The detailed design of a sprinkler layout requires considerable 
 skill and care. 
 
 5. Except in favored localities where natural pressure is available, 
 pumps must be installed to create pressure for the operation of the 
 system. 
 
 6. Sprinkler systems, if used, should be, installed because of their 
 ability to distribute irrigation water uniformly and effectively, and 
 not because of claims for other advantages. 
 
 7. Judgment and care are essential in the intelligent operation of 
 a sprinkler system. There is no substitute for a soil auger in deter- 
 mining the effectiveness of an irrigation. 
 
PUBLICATIONS AVAILABLE FOE FREE DISTRIBUTION 
 
 BULLETINS 
 
 No. No. 
 
 253. Irrigation and Soil Conditions in the 366. 
 
 Sierra Nevada Foothills, California. 
 2G1. Melaxuma of the Walnut, "Juglans 367. 
 
 regia." 
 
 262. Citrus Diseases of Florida and Cuba 368. 
 
 Compared with Those of California. 
 
 263. Size Grades for Ripe Olives. 369. 
 268. Grovring and Grafting Olive Seedlings. 
 
 273. Preliminary Report on Kearney Vine- 370. 
 
 yard Experimental Drain. 371. 
 
 275. The Cultivation of Belladonna in 
 
 California. 372. 
 
 276. The Pomegranate. 
 
 277. Sudan Grass. 373. 
 
 278. Grain Sorghums. 374. 
 
 279. Irrigation of Rice in California. 
 283. The Olive Insects of California. 
 
 294. Bean Culture in California. 375. 
 
 304. A Study of the Effects of Freezes on 
 
 Citrus in California. 376. 
 
 310. Plum Pollination. 
 
 312. Mariout Barley. 377. 
 
 813. Pruning Young Deciduous Fruit 379. 
 
 Trees. 380. 
 
 319. Caprifigs and Caprification. 
 
 324. Storage of Perishable Fruit at Freez- 381. 
 
 ing Temperatures. 
 
 325. Rice Irrigation Measurements and 382. 
 
 Experiments in Sacramento Valley, 
 1914-1919. 383. 
 
 328. Prune Growing in California. 
 
 331. Phylloxera-Resistant Stocks. 385. 
 
 335. Cocoanut Meal as a Feed for Dairy 386. 
 
 Cows and Other Livestock. 
 
 339. The Relative Cost of Making Logs 387. 
 
 from Small and Large Timber. 388. 
 
 340. Control of the Pocket Gopher in 
 
 California. 389. 
 
 343. Cheese Pests and Their Control. 390. 
 
 344. Cold Storage as an Aid to the Mar- 
 
 keting of Plums. 391. 
 
 346. Almond Pollination. 
 
 347. The Control of Red Spiders in Decid- 392. 
 
 uous Orchards. 393. 
 
 348. Pruning Young Olive Trees. 394. 
 
 349. A Study of Sidedraft and Tractor 
 
 Hitches. 395. 
 
 350. Agriculture in Cut-over Redwood 396. 
 
 Lands. 
 
 352. Further Experiments in Plum Pollina- 397. 
 
 tion. 
 
 353. Bovine Infectious Abortion. 398. 
 
 354. Results of Rice Experiments in 1922. 399. 
 
 357. A Self-mixing Dusting Machine for 
 
 Applying Dry Insecticides and 
 Fungicides. 400. 
 
 358. Black Measles, Water Berries, and 401. 
 
 Related Vine Troubles. 
 
 361. Preliminary Yield Tables for Second 402. 
 
 Growth Redwood. 403, 
 
 362. Dust and the Tractor Engine. 404 
 
 363. The Pruning of Citrus Trees in Cali- 405! 
 
 fornia. 495 
 
 364. Fungicidal Dusts for the Control of 
 
 Bunt. 
 
 365. Avocado Culture in California. 
 
 Turkish Tobacco Culture, Curing and 
 Marketing. 
 
 Methods of Harvesting and Irrigation 
 in Relation of Mouldy Walnuts. 
 
 Bacterial Decomposition of Olives dur- 
 ing Pickling. 
 
 Comparison of Woods for Butter 
 Boxes. 
 
 Browning of Yellow Newtown Apples. 
 
 The Relative Cost of Yarding Small 
 and Large Timber. 
 
 The Cost of Producing Market Milk and 
 Butterfat on 246 California Dairies. 
 
 Pear Pollination. 
 
 A Survey of Orchard Practices in the 
 Citrus Industry of Southern Cali- 
 fornia. 
 
 Results of Rice Experiments at Cor- 
 tena, 1923. 
 
 Sun-Drying and Dehydration of Wal- 
 nuts. 
 
 The Cold Storage of Pears. 
 
 Walnut Culture in California. 
 
 Growth of Eucalyptus in California 
 Plantations. 
 
 Growing and Handling Asparagus 
 Crowns. 
 
 Pumping for Drainage in the San 
 Joaquin Valley, California. 
 
 Monilia Blossom Blight (Brown Rot) 
 of Apricot. 
 
 Pollination of the Sweet Cherry. 
 
 Pruning Bearing Deciduous Fruit 
 Trees. 
 
 Fig Smut. 
 
 The Principles and Practice of Sun- 
 drying Fruit. 
 
 Berseem or Egyptian Clover. 
 
 Harvesting and Packing Grapes in 
 California. 
 
 Machines for Coating Seed Wheat with 
 Copper Carbonate Dust. 
 
 Fruit Juice Concentrates. 
 
 Crop Sequences at Davis. 
 
 Cereal Hay Production in California. 
 Feeding Trials with Cereal Hay. 
 
 Bark Diseases of Citrus Trees. 
 
 The Mat Bean (Phaseolus aconilifo- 
 lius). 
 
 Manufacture of Roquefort Type Cheese 
 from Goat's Milk. 
 
 Orchard Heating in California. 
 
 The Blackberry Mite, the Cause of 
 Redberry Disease of the Himalaya 
 Blackberry, and its Control. 
 
 The Utilization of Surplus Plums. 
 
 Cost of Work Horses on California 
 Farms. 
 
 The Codling Moth in Walnuts. 
 
 Farm-Accounting Associations. 
 
 The Dehydration of Prunes. 
 
 Citrus Culture in Central California. 
 
 Stationary Spray Plants in California. 
 
 No. 
 
 87. Alfalfa. 
 117. The Selection and Cost of a Small 
 
 Pumping Plant. 
 127. House Fumigation. 
 129. The Control of Citrus Insects. 
 136. MeUlotus indica as a Green-Manure 
 
 Crop for California. 
 144. Oidium or Powdery Mildew of the 
 
 Vine. 
 
 CIRCULARS 
 No. 
 
 157. Control of the Pear Scab. 
 
 Lettuce Growing in California. 
 Small Fruit Culture in California. 
 The County Farm Bureau. 
 170. Fertilizing California Soils for the 
 
 1918 Crop. 
 173. The Construction of the Wood-Hoop 
 
 Silo. 
 178. The Packing of Apples in California. 
 
 160 
 164 
 166 
 
CIRCULARS— (Conhnw^d) 
 
 No. 
 
 179. Factors of Importance in Producing 
 
 Milk of Low Bacterial Count. 
 190. Agriculture Clubs in California. 
 199. Onion Growing in California. 
 
 202. County Organizations for Rural Fire 
 
 Control. 
 
 203. Peat as a Manure Substitute. 
 
 209. The Function of the Farm Bureau. 
 
 210. Suggestions to the Settler in California. 
 212. Salvaging Rain-Damaged Prunes. 
 215. Feeding Dairy Cows in California. 
 217. Methods for Marketing Vegetables in 
 
 California. 
 220. Unfermented Fruit Juices. 
 228. Vineyard Irrigation in Arid Climates. 
 
 230. Testing Milk, Cream, and Skim Milk 
 
 for Butterfat. 
 
 231. The Home Vineyard. 
 
 232. Harvesting and Handling California 
 
 Cherries for Eastern Shipment. 
 
 234. Winter Injury to Young Walnut Trees 
 
 during 1921-22. 
 
 235. Soil Analysis and Soil and Plant 
 
 Inter-relations. 
 
 236. The Common Hawks and Owls of 
 
 California from the Standpoint of 
 the Rancher. 
 
 237. Directions for the Tanning and Dress- 
 
 ing of Furs. 
 
 238. The Apricot in California. 
 
 239. Harvesting and Handling Apricots 
 
 and Plums for Eastern Shipment. 
 
 240. Harvesting and Handling Pears for 
 
 Eastern Shipment. 
 
 241. Harvesting and Handling Peaches for 
 
 Eastern Shipment. 
 
 243. Marmalade Juice and Jelly Juice from 
 
 Citrus Fruits. 
 
 244. Central Wire Bracing for Fruit Trees. 
 
 245. Vine Pruning Systems. 
 
 247. Colonization and Rural Development. 
 
 248. Some Common Errors in Vine Prun- 
 
 ing and Their Remedies. 
 
 249. Replacing Missing Vines. 
 
 250. Measurement of Irrigation Water on 
 
 the Farm. 
 
 252. Supports for Vines. 
 
 253. Vineyard Plans. 
 
 254. The Use of Artificial Light to Increase 
 
 Winter Egg Production. 
 
 255. Leguminous Plants as Organic Fertil- 
 
 izer in California Agriculture. 
 
 256. The Control of Wild Morning Glory. 
 
 257. The Small-Seeded Horse Bean. 
 
 258. Thinning Deciduous Fruits. 
 
 259. Pear By-products. 
 
 261. Sewing Grain Sacks. 
 
 262. Cabbage Growing in California. 
 
 263. Tomato Production in California. 
 
 264. Preliminary Essentials to Bovine 
 
 Tuberculosis Control. 
 
 No. 
 
 265. Plant Disease and Pest Control. 
 
 266. Analyzing the Citrus Orchard by 
 
 Means of Simple Tree Records. 
 
 267. The Tendency of Tractors to Rise in 
 
 Front; Causes and Remedies. 
 
 269. An Orchard Brush Burner. 
 
 270. A Farm Septic Tank. 
 
 272. California Farm Tenancy and Methods 
 
 of Leasing. 
 
 273. Saving the Gophered Citrus Tree. 
 
 274. Fusarium Wilt of Tomato and its Con- 
 
 trol by Means of Resistant Varieties. 
 
 276. Home Canning. 
 
 277. Head, Cane, and Cordon Pruning of 
 
 Vines. 
 
 278. Olive Pickling in Mediterranean Coun- 
 
 tries. 
 
 279. The Preparation and Refining of Olive 
 
 Oil in Southern Europe. 
 
 281. The Results of a Survey to Determine 
 
 the Cost of Producing Beef in Cali- 
 fornia. 
 
 282. Prevention of Insect Attack on Stored 
 
 Grain. 
 
 283. Fertilizing Citrus Trees in California. 
 
 284. The Almond in California. 
 
 285. Sweet Potato Production in California. 
 
 286. Milk Houses for California Dairies. 
 
 287. Potato Production in California. 
 
 288. Phylloxera Resistant Vineyards. 
 
 289. Oak Fungus in Orchard Trees. 
 
 290. The Tangier Pea. 
 
 291. Blackhead and Other Causes of Loss 
 
 of Turkeys in California. 
 
 292. Alkali Soils. 
 
 293. The Basis of Grape Standardization. 
 
 294. Propagation of Deciduous Fruits. 
 
 295. The Growing and Handling of Head 
 
 Lettuce in California. 
 
 296. Control of the California Ground 
 
 Squirrel. 
 
 298. The Possibilities and Limitations of 
 
 Cooperative Marketing. 
 
 299. Poultry Breeding Records. 
 
 300. Coccidiosis of Chickens. 
 
 301. Buckeye Poisoning of the Honey Bee. 
 
 302. The Sugar Beet in California. 
 
 303. A Promising Remedy for Black Measles 
 
 of the Vine. 
 
 304. Drainage on the Farm. 
 
 305. Liming the Soil. 
 
 306. A General Purpose Soil Auger and its 
 
 Use on the Farm. 
 
 307. American Foulbrood and its Control. 
 
 The publications listed above may be had by addressing 
 
 College of Agriculture, 
 
 University of California, 
 
 Berkeley, California. 
 
 12to-11,'26