Recent Developments in Agricultural Machinery

RECENT DEVELOPMENTS IN AGRlC ULTURAL MACHINERY

. .

. .

T W Edminster and H F Miller. Jr

.

United Stater Deparfmenf of Agriculture. Belfrville. Maryland

I . Introduction . . . . . . . . . . . . . . I1. Developments in Tillage and Seedbed Preparation . . . A. Conventional Equipment and Practices . . . . B . Special Tillage Equipment and Practices . . . . C. Seedbed Finishing Tools . . . . . . . . I11. Developments in Planting Equipment . . . . . . A. Row-Crop Equipment . . . . . . . . . B. Grain and Seed Drills . . . . . . . . . C Aerial Seeding and Fertilizing . . . . . . . IV Developments in Cultivating Equipment . . . . . . A . Mechanical Cultivation . . . . . . . . . B Flame Cultivation . . . . . . . . . . C. Equipment for Applying Chemical Herbicides . . D Thinning Equipment . . . . . . . . . V . Developments in Spraying and Dusting Equipment . . . A . General Developments . . . . . . . . . B . Spraying Equipment . . . . . . . . . . C . Dusting Equipment . . . . . . . . . . VI . Developments in Harvesting Equipment . . . . . . A. Forage Harvesting Equipment . . . . . . . B . Corn Harvesting Equipment . . . . . . . C. Grain, Legume. and Grass Seed Harvesting Equipment D . Cotton Harvesting Equipment . . . . . . . E . Dry Bean and Pea Harvesting Equipment . . . . F Vegetable Harvesting Equipment . . . . . . G. Root Crop Harvesting Equipment . . . . . . H . Tree Nut and Fruit Harvesting Equipment . . . I. Miscellaneous Crop Harvesting Equipment . . . VII . Conclusions . . . . . . . . . . . . . . References . . . . . . . . . . . . . .

.

.

. .

.

Page 171 173 173 176 . 182 . 182 . 183 . 187 . 189 . 190 . 190 . 192 . 192 . 192 . 193 . 193 . 194 . 195 . 196 . 197 . 202 . 204 . 207 . 209 . 211 . 214 . 218 . 223 . 226

. . . .

. . . .

. . . . . . . .

.

.

.

.

.

.

. .

. .

. . .

. . .

.

. .

. . . .

. . . . . . .

. . . . . . . . . .

.

.

.

.

.

. .

. .

. .

.

.

.

. .

. .

. .

.

.

.

.

.

.

. . . . . . . . . . . . .

226

.

1 Introduction

Development of agricultural machinery results from the joint efforts and activities of farmers. engineers. agricultural scientists and machinery 171

172

T. W. EDMINSTER AND H. F. MILLER, JR.

manufacturers. Most rapid progress is made when all disciplines combine their efforts into well-planned and executed programs. As new crop management ideas are developed through the research process, machines must be developed to meet the specific need. One new management practice may require only a minor modification of an existing machine, i.e., a different type of moldboard, a means of-placingfertilizer closer or farther away from the seed, or a gage wheel to give greater precision in the height of cut in a harvesting operation, Another new management practice may necessitate the development of an entirely new machine specifically designed to do a specific job. The constant-volume pump for liquid fertilizer application, the intercrop drill, and the castor bean harvester are examples of this type of evolution. Sometimes the machinery development process takes an opposite pattern. An improved mechanical linkage or a more rapid hydraulic control mechanism may make it feasible to step up drastically the operating speed of a certain machine. But, before the new speed can be safely utilized, new crop management practices must be developed-perhaps a simple land smoothing before planting, or use of a modified bed shape that will facilitate the use of this potential speed increase. Thus, progress in agricultural machinery development is closely interwoven with progress in the soil and plant management fields. When new scientific break-throughs are made in one field, new evidence of progress is certain to be seen in the related fields. There are few phases of agriculture that have seen such rapid growth and development as that of agricultural machinery. Tractor and machine development during the last fifty years has been the major key to the present high level of American agricultural production per unit of farm labor input. The history and romance of this development have been the subject of many excellent summaries. The works of Gray (1954, 1958) and Gray and Dieffenbach (1957) trace the history and development of the tractor. Fifty years of progress in farm machinery was reported by McColly (1957) and has also been summarized in a series of U.S. Department of Agriculture publications 1935a,b,c,d, 1949a,b). McKibben ( 1953) significantly points out that the absence of a serf or peasant class in American agriculture provided a major tribute to this technological advance. Much of the impetus to mechanization has been provided by certain economic and sociological trends in the course of the Nation’s development. Nutt (1950b) points out the factors guiding the mechanization of the Southeast, while Carreker (1950)illustrates the relation between the development of new conservation practices, such as terracing, strip cropping, mulch tillage, and grass-based rotations, and the parallel shifts in

RECENT DEVELOPMENTS I N AGRICULTURAL MACHINERY

173

the design and application of farm machines to meet this new trend. The over-all value of this technological development to the farmer was summed up by Walker (1952) in terms of increased workers efficiency, increased yields, and higher standards of living. Another important phase of early machinery development has been the splendid effort of engineers, industrial and public agencies alike, to foster a common goal for standardizing equipment. Our present-day ability to widely interchange parts, components, and whole machines, has been of tremendous importance. The intricate, but effective, network of committees and commissions that have made this possible are outlined by Tanquary ( 1957). These extensive publications reviewing early agricultural machine development have led the authors to limit their discussion to the more significant developments since 1950. Where there has been sufficient evidence of successful research progress on equipment not yet in production, the authors have suggested possible trends that might be anticipated through 1960 or shortly beyond. II. Developments in Tillage and Seedbed Preparation

A. CONVENTIONAL EQUIPMENTAND PRACTICES

The plow has been considered the basic implement for seedbed preparation for many centuries. The review of McColly (1957) stresses the drastic changes that took place as the walking plow was replaced by the sulky plow, and then progressed through various changes in general design until today’s modern lift-type tractor-mounted plows were developed. Another early and important break-through was the development of soft-centered steel for shares and moldboards providing a smooth effectively scouring surface on a tough shock-resistant base. Metallurgical developments continue to play an important part in the improvement of tillage equipment. Reed and Gordon (1951) and Mohsenin et al. (1956) have made important studies on the relative wear resistance of various metals for use in plows, disks, and other tillage tools. A number of workers are currently exploring the possibilities of coating tillage tools with various materials such as Teflon to improve scouring action and to reduce draft. Although there have been few startling changes in the basic design of tillage tools, there has been a growing comprehension of the soil physical and dynamic factors that must be considered in all attempted improvements of these basic tools. Agricultural engineers and soil physicists have teamed up in the research that has shown the relation between soil structure and consistency on implement design as reported by Nichols

174

T. W. EDMINSTER AND H. F. MILLER, JR.

and Reaves (1955).Soil reaction to plowshare design is described by Nichols et al. ( 1958),and its reaction to subsoiling equipment is shown by Nichols and Reaves (1958).The improved means of measuring this compaction factor have been made possible by the development of the straingage cell by Cooper et nl. (1957).More general concepts of the role of soil physics have been illustrated by Browning (1950). The effectiveness of various tillage implement forms and practices in achieving good mixing of soil was successfully evaluated through use of tracer techniques by Hulburt and Menzel ( 1953). Individually, none of these findings has resulted in radically new plow design; collectively, however, they have resulted in a new awareness of the specific criteria of design. With new understanding of the effects of adhesion, shear, and pressure translocation, designers have new means for improving the efficiency of plow design. The way a plow is mounted, adjusted, and controlled also contributes to its over-all effectiveness. In recent years there have been many advances in hitch and mounting design that give more effective results. Heitshu (1952) presents an exhaustive analysis of the kinematics of tractor hitches as they relate to mounted plows, disks, and subsoilers. The ability to provide weight transfer either to the tool for improved penetration or to the tractor for increased traction is a major advance. Collins (1951) and Tanquary and Clyde (1957) further describe the factors in hitch design that affect weight balance, side thrust, and suction control. The hydraulic capacity requirements for controlling these implements have been further analyzed by Worthington and Seiple ( 1952). These major developments in hitches and implement mounting and control systems are the cause for the growing popularity of mounted tillage tools. Integrally mounted on the tractor, these plows can be adjusted and controlled more effectively. This is particularly important in conservation farming where plows must be lifted to protect grassed waterways and terrace outlets and where implement position control is important in following the contour layouts in terraced and strip-cropped fields. With the added precision in control, plus the built-in safety devices, higher operating speeds, particularly in turning on headlands, is possible. The use of two-way or reversible plows that permit turning furrows in one direction, without leaving dead furrows or back furrows, has become increasingly important. They are particularly valuable in maintaining a uniform surface in irrigation borders and in maintaining uniform surface configurations under strip cropping and terracing practices. The higher cost of these plows is offset by the reduction in special smoothing and leveling steps that must be used to remove dead furrows made by

RECENT DEVELOPMENTS IN AGRICULTURAL MACHINERY

175

conventional equipment. The upslope plowing with this equipment compensates for the natural downslope soil movement, particularly on the steeper slopes. Where this has been practiced, more intensively cropped rotations can be more safely used than when downslope plowing is practiced. Similar advances have been made in the design of disk plows and harrows. Again metallurgy has played a significant role. Studies by Reed and McCreery (1954) showed that disk life was closely related not only to the type and hardness of steel used, but also to the directions that the steel blank was rolled during its fabrication. By cross rolling, its resistance to cracking and chipping could be greatly increased. The type of edge and the method of mounting on the hub also affected disk life. A review of recent commercial advertisements indicates that these findings have been quickly incorporated in nearly all industrial designs. Further improvements have been the result of new understanding of the relationship between soil reaction and disk geometry as reported by McCreery and Nichols (1956) and Thompson and Kemp ( 1958). These workers have shown the relation between disk penetration and weight, of pressure and forward motion on the shear forces acting on the soil, and of disk angle as it affects the speed of rotation. A very significant relationship between the design of the bevel on the disk edge and its effects on soil compaction was discovered. Each of these factors when incorporated into a new design will result in cleaner, more rapid, and more effective cutting by disk implements. Both Kramer (1955) and Clyde (1956) have made important contributions to a basic understanding of offset and conventional disk harrow design. Through an analysis of the dynamic forces involved in the operation of these implements, they have proposed means of providing for simpler construction and improved durability. Added flexibility and greater range in adjustment to meet soil variables have also been proposed. Another important aspect of harrow and disk plow design has been the tremendous improvements in bearing design. Howe and Raley (1958) stress the impact that prelubricated and “lifetime” lubricated bearings have on the life of equipment that must operate under severe dust and shock conditions. For example, a triple-sealed prelubricated bearing system on a harrow that had recently completed disking 2200 acres of Arizona sand was without appreciable wear. Other changes in design of the so-called conventional tillage equipment are imminent. For example, Brown (1957) reports on a design for individual spring release beams for tractor-mounted moldboard plows. Tests show that it takes at least 1 minute to rehitch a conventional breakaway plow as opposed to only 8 seconds to relatch a spring release

176

T. W. FDMINSTER AND H. F. MILLER, JR.

beam. Plows equipped with this type of beam are already commercially available. With the continuing trend to increased power and speed for tillage operations, this has an important economic aspect. Draft reduction is an objective of most mechanical designers. Gunn and Tramontini (1955) in preliminary studies have shown the possibility of reducing draft by oscillating the tillage implement. EQUIPMENT AND PRACTICES B. SPECIALTILLAGE In recent years there has been a growing interest and awareness, on the part of agronomists, engineers, and soil scientists, of the question of what is the optimum in tillage and seedbed preparation. The objectives of conventional tillage have been basically to stir and loosen the soil and to control the weeds. While this has generally been effective in creating a satisfactory medium for plant growth, it has also, in many instances, resulted in destruction of soil structure, reduced infiltration capacity, increased susceptibility to erosion, accelerated reduction of organic matter, and other evidences of soil decline. It is with this in mind that Melsted (1954) asks the question: “How should cultivated crops, especially row crops, be tilled and managed so that they will become soil conserving?” He goes on to establish the importance of studying new concepts in tillage practices that will (1) achieve erosion control, ( 2 ) maintain organic matter, (3) control weeds, and ( 4 ) provide optimum soil tilth for plant growth. During the period following World War I1 literally hundreds of studies have been conducted that compared various forms of mulch tillage, trash plowing, balk tillage, ridge planting, minimum tillage, plowplant techniques, and many others with conventional seedbed preparation methods. Summaries of many of these studies are to be found in such references as Cook and Peikert ( 1950), Jacks et al. (1955), Aldrich ( 1956), Baugh et aZ. ( 1950), Schaller and Evans (1954), Buchele et al. (1955a,b), McCalla (1958), U. S. Dept. Agr. (1958a), Moody et aZ. ( 1952), and Willard et al. (1956). These reports stress the many variables and problems that have been encountered in attempting to develop new and modified tillage practices. Further discussion of these practices will be limited to specific factors in implement design and development. Some of the early mulch tillage work in the Southeast is reported by Nutt (1950a), who used a tractor-mounted tool bar to carry a set of cut-away middlebusters with disk hillers attached to throw vegetation away from the planting furrow. This operation was preceded by heavy disking or ripping 2 or 3 weeks in advance to kill the vegetation. Regrowth in the row middle was further controlled at lay-by through use of broad, flat sweeps.

RECENT DEVEIXlPMENTS IN AGRICULTURAL MACHINERY

177

These same general principles were later incorporated in a commercially available Mulch-Till planter described by Poynor ( 1950). This heavily constructed machine utilized a series of sweeps and rotary hoe sections to prepare planting furrows in which the crop was planted by a set of rear-mounted planters. High power requirements and problems of maintaining adjustment were frequently encountered with this device. In many areas the preceding crop that furnished the desired mulch residue was made up largely of perennials. The conventional undercutting by sweeps that had been effective with annual grain stubbles, as reported by Duley (1948, 1954), did not adequately kill perennial crops when they were substituted in the rotation in place of annual stubble crops. The resulting regrowth of the sods and other perennials, together with the other nutritional, temperature, and weed-control problems, caused, in many cases, sharp declines in crop yield-too sharp to offset the advantages of increased infiltration capacity and reduced surface runoff and erosion. This problem of managing perennial residues led to the work of Lillard et al. (1950) in which the double-cut plow principle was developed. Through use of the commercially available Oliver T-N-T plow, adjustments were made in the plow to slice free and invert the top 2% to 3 inches of sod while rather thoroughly tilling the 3- to 4-inch depth zone of soil immediately below with the plow’s extra subbase. After drying out for a period of 10 days to 2 weeks, the ribbon of inverted sod could be broken up with a field cultivator, disk, or other implement that would not too deeply incorporate it in the soil. Essentially a 100 per cent kill of the perennial residue was thus achieved. This double-cut principle formed the basis for other work by Free (1953) in which standard plows were modified by attachments. In concurrent work in Ohio, Harrold and Dreibelbis (1950) found that disking alone, or the use of field cultivator alone, would not provide the necessary kill of the vegetation. Disking in combination with herbicides showed some promise. Preplowing followed by the field cultivator after a 2-week period also gave better weed control but resulted in less surface mulch. Hays and Taylor (1958) report on similar studies in the Upper Mississippi Valley. These are but a few examples of the great number of studies made throughout the Humid Region in which attempts have been made to utilize crop residues for mulches under cultivated crops. Nearly all of the studies involved the use of standard plows, disks, or field-type cultivators, in either a modified form or in new patterns of sequence or timing. Such studies prompted many important side studies regarding the effects of these desired mulches upon soil structure, soil temperature, nutritional

T. W. EDMINSTER AND H. F. MILLER, JR. 178 balance, moisture relations and on runoff and soil loss. None of them materially contributed to development or advancement in machinery design until some more radical or drastic approaches were taken in the mid-1950’s. With the advent of the “minimum tillage” concept new machine developments have rapidly taken place. The minimum tillage approach to seedbed preparation for cultivated crops has several objectives. The first, and most obvious, is to reduce the soil compaction caused by the extra implement traffic. This results in improved infiltration through the loose surface layers and a higher level of hydraulic conductivity through the soil layers immediately beneath the surface, Both of these factors contribute to general reduction in the soil erosion and runoff hazards that occur when the field becomes too firmly packed and smoothed. In some instances a reduction in the weed population is a by-product of the minimum tillage approach. Some of the earliest work on minimum tillage was conducted at the Ohio Agricultural Experiment Station in 1935, where seedbed preparation was limited to use of a light smoothing harrow on plowed ground prior to planting. Over a fourteen-year period crop yields were essentially the same under this practice as under conventional preparation. Cook et al. (1953) reported similar results when the plow was followed by various types of packers that would smooth and firm the surface enough to permit accurate planting. Out of preliminary studies of this type came the practice of tractor-track planting, as described by Peterson et al. (1958). In this practice the tractor wheels are set to the same spacing as the planter, thus crushing down and firming the plowed field just ahead of the conventional planter. This practice has been further modified to put the planting and plowing all into one operation. It is commonly referred to as the “plow-plant” method. To accomplish this, researchers developed several machine modifications ranging from a trailing-type planter towed behind the plow, to planting units mounted on the plow frames, as described by Musgrave et al. (1955) and Aldrich and Musgrave (1955). A further development in which the planter unit is mounted on the forward cultivator bar is illustrated by Winkelblech (no date) and by Hansen et al. (1958). With this approach, one row can be planted with each pass of a 3-bottom 14 inch plow, or two rows with a 5- or &bottom plow (Fig. 1). In the development of plow-plant devices it is important to mount the planter in such a way as to assure accurate tracking of the planter shoe so that the corn row will be placed directly in the middle of the furrow slice, thus giving greater uniformity to depth-of-seed placement and seed cover. Aldrich (1956) also points out that the degree of packing

RECENT DEVELOPMENTS IN AGRICULTURAL MACHINERY

179

FIG.1. Experimental “plow-plant” equipment. ( Courtesy of the Agricultural Engineering Department, Cornell University.)

that precedes the actual opening of the seed furrow can be adjusted by mounting an extra press wheel in front of the planter shoes or by the use of a specially designed planter shoe that will firm the seed bed (Fig. 2 ) . Minimum tillage can also be adapted to the use of 2-, 4-, or 6-row

FIG.2. Detail of special soil-firming shoe on furrow opener. (Courtesy of the Agricultural Engineering Department, Cornell, University.)

180

T. W. EDMINSTER AND H. F. MILLER, JR.

planting equipment by trailing some type of compaction tool behind the plow, i.e., a culti-packer, rotary hoe (pulled backward as a treader), a spiral roller, or other seedbed finishing tools that will do a minimum of smoothing and compaction. Conventional planting equipment can then follow as a separate operation. Adapting the conventional ridge planting long used in the Southeast, Buchele et al. (1955a,b) and Lovely (1956) have proposed the ridgeplanting of corn as a further modification of minimum tillage. In this practice two 14-inch furrows are turned to each other on top of a 28-inch unplowed strip. A disk furrow opener replaces the conventional runnertype opener to provide for better trash cutting and to stabilize the position of the planter on top of the ridge. A disk cultivator is used in cultivating and maintaining the high ridge upon which the crop is planted. Each of these minimum tillage practices, while still in the research and development stage, shows considerable promise of meeting the objectives of ( 1) lower-cost seedbed preparation, ( 2 ) improved infiltration and, with it, better erosion control, and ( 3 ) reduced cultivation needs. While present studies are dependent upon shop-built equipment to provide the desired test conditions €or detailed study by soil scientists and agronomists, these practices are providing the farm machinery industry with a challenge to develop “line” models for more extensive use. The development of special tillage practices has not been limited to those for Humid Region conditions. Throughout the more arid western states modified tillage practices have long been under development and used to provide a means of protecting the soil, both under crops and during fallow periods, from the ravages of wind erosion and, in some areas, water erosion caused by rapid spring snow melt and accompanying rains. Duckfoot cultivators, “stubby” moldboard plows, and early versions of the modem sweep cultivators paved the way for the present-day equipment. Zingg and Whitfield (1957) have summarized the research on stubblemulch practices in the West and provided the early history and data showing the effect of various practices on erosion control, wheat production, soil properties, and the problems of production management. A critical analysis of the machinery requirements for stubble-mulch tillage, particularly for the Pacific Northwest, was reported by Ryerson ( 1950). Analysis of the operating characteristics and requirements of implements for wind erosion control has been made by Woodruff and Chepil (1956); and Chepil and Woodruff (1955). Krall et al. ( 1958) and Aasheim (1949) have summarized the results of various tillage practices from the standpoint of soil and water conservation and crop production under summer fallow conditions.

RECENT DEVELOPMENTS I N AGRICULTURAL MACHINERY

181

The machinery-development problems for the western area are severe;

i.e., equipment must be able to handle straw residue from a few hundred

to over 12,000 pounds per acre, or residue standing over 2 feet in height, under hard dry soil conditions. The tillage job is essentially one of undercutting so as to provide (1) minimum of mixing of the soil and mulch except as needed to anchor the mulch in place, ( 2 ) minimum breakage of the mulch, and (3) minimum pulverization of the soil. Tools that are in the process of development include various types of mulch pulverizers that will beat the straw into 8- to 12-inch lengths that can be handled by the tillage implements’ rotary cutters, and hammer-mill type beaters of extra heavy design, all of which have high clearance. Sweep plows measuring 5 and 6 feet with 90- to 120-degree blade angles are being developed for undercutting. Rod weeders have also been effective, particularly when they are designed with a center drive which off sets clogging problems of conventional end-drive machines. Various types of field cultivators, particularly those equipped with coil shanks that will provide added vibration to assist in clearing the shanks, are finding adaptation. In areas where it is essential to break up hard soils to permit

FIG.3. Skew treader operating in heavy wheat stubble. Note straw-chopping effect and partial incorporation of straw to provide good wind and water erosion control. (Courtesy of the Agricultural Research Service, USDA, by T. R. Horning.)

182

T. W. EDMINSTER AND H. F. MILLER, JR.

improved infiltration of the limited moisture, the rotary subsoiler has been used. It creates a series of pits 8 to 10 inches deep that will serve as reservoirs and points of entry for moisture. Various types of treaders, frequently consisting of heavy-duty rotary hoes pulled backward, either straight or on a skew, are also used to break up surface crusts, cut and anchor mulch into the soil, and improve conditions for moisture penetration (Fig. 3 ) . Many of these specialized tillage implements have been produced by small, local, machinery companies, Each has added certain modifications to meet local real or assumed needs. This section discusses only some of the major tillage equipment. Of equal interest would be a review of developments in the special equipment lines such as the giant moldboard and disk plows capable of plowing 3 and 4 feet deep, the various developments in rotary tillage equipment, and recent trends in subsoiler design to reduce draft and increase effective soil shatter. Since each of these lines of equipment has a more limited area of application, their development will not be described here. C. SEEDBED FINISHING TOOLS The previous discussion has been chiefly devoted to the primary tillage operations of plowing and disking. Under conventional tillage management practices these operations are generally followed by various seedbed finishing operations, the nature and extent of which are dependent upon the fineness of seedbed desired. The precision seeding of fine, high-priced vegetable seed may dictate an extremely smooth, well-pulverized soil, while wheat might be drilled into a rough, cloddy, wind erosion-resistant soil on the High Plains. In recent years such conventional finishing tools as the disk and spiketooth harrows, spring-tooth harrows, floats, and drags have been supplemented by a series of specialty tools. These range from a Germandeveloped, flexible knitted-steel rod-spring-tooth harrow which, as described by Sack (1951), will conform to all surface irregularities, such as beds and furrows, to the more functional harrows, knives, packers, and rollers, each intended as a tool to break up clods and thus leave a smooth, uniform soil to accommodate the planter. 111. Developments in Planting Equipment

Recent trends in planting equipment are cumulative resultants of many separate advances in materials of construction, refinement of power controls, and improved metering-system design. Some of the trends seen in tillage equipment are also occurring in the planting lines, viz., the shift

RECENT DEVELOPMENTS IN AGRICULTURAL MACHINERY

183

from pull-behind units to flexible, high-speed, tractor-mounted units, greater interchangeability of parts, and improved adjustments and controls that permit more precise operation at higher speeds.

A. ROW-CROP EQUIPMENT The factor of precision is becoming increasingly important. Uniformity in the depth of seed placement is essential if uniform germination is to be achieved. Uniformity of plant spacing, while not a critical factor from the standpoint of crop yield, is important in mechanical harvesting to assure an even flow of crop material into the harvester. The effectiveness of mechanical thinners is also dependent upon uniform planting, just as high-speed mechanical, flame and chemical weed-control practices depend on such uniformity of plant position. There has been a significant trend toward the use of bigger multiple planting units. Four- and six-row units (Fig. 4 ) are rapidly replacing

FIG.4. A six-row planter equipped to apply liquid fertilizer and granular insect and weed-control chemicals. (Courtesy of the International Harvester Co. )

two-row equipment. Where land smoothing and conditioning is practiced this trend has been most rapid. Similar trends are occurring in grain drills, both through use of additional furrow openers and through the use of multiple units operating on one hitch. This increased use of multiple planting units has created several related machine-design problems. When planting is done in multiple units the cultivation equipment must

T. W. EDMINSTER AND H. F. MILLER, JR. 184 be designed on the same basis to insure proper alignment. Equipment for side dressing, weed and insect control sprays, and other follow-up management practices must be adapted to the same multiples as the planters. With the increased length to which the tool carriers must be extended to accommodate these multiple units a problem in suspension develops. Provision must be made to carry heavy seed and fertilizer hoppers without causing changes in the depth adjustment of the planter as the weight changes with dispersal of their contents. In four- and particularly six-row equipment, provision should be made for individual suspension of the planting units to permit them to follow irregularities in the contours without affecting the planting depths. Provision for folding or otherwise retracting these long tool carriers is essential to provide for roadability and to facilitate passing through gates and into storage sheds. Precision placement of seed in the planting furrow has been the goal of agronomists and engineers alike. During recent years the intensive cotton mechanization research program has focused major attention on cotton-planting equipment. Studies to determine the relative importance of various planting techniques and spacings have been reported by Corley et al. ( 1955),Hudspeth and Jones ( 1954), Miller ( 1955a,b), and Colwick (1955). The importance of using hill-drop cotton planters on heavy soils is stressed by Miller (1955a,b). His studies showed that, where several seeds germinated close together, they could, by combined effort, emerge under more serious crusting conditions than would be possible under single-drop plantings. Closer spacing, three to five plants per foot, gives better vegetative growth control, grass and weed control through shading and improves harvester efficiency. Autry and Schroeder (1953) have made detailed studies of the design factors for hill-drop planters resulting in new concepts on cell shape, plate speed, plate-to-ground speed ratio and in tube design. The simple matter of shortening the tube length has resulted in more accurate seed drop and placement, according to Porterfield et aZ. (1954). There has been a complete redesign of the planter shoe and seed-covering devices to achieve precise control of seed depth and depth of seed cover. The development of the seed press wheel has been traced by Miller (1955a). While this device was first used as early as 1925, it did not come into prominent use until the steel rim was replaced by the zero-pressure, hollow rubber tire in the early 1950's. Its use and application is described by Tavernetti and Miller ( 1954) ( see Fig. 5). The seed press wheel principle is becoming more important on a number of other planters where seed germination is critically dependent upon intimate seed-soil contact. This contact permits quicker moisture

RECENT DEVELOPMENTS IN AGRICULTURAL MACHINERY

185

pick-up giving earlier germination and emergence. This permits shallower planting and helps to combat crusting problems. Interchangeable hoppers, agitators, plates, and speed-control gears have made the modern planter extremely versatile; one basic planter meets all of the farmer’s needs. Each design improvement-sometimes insi@cant when viewed alone-has contributed to the present-day planter capable of accurate and reliable seed placement at speeds of over 4 miles per hour. Taken in total, this is a major break-through in improving farm operation efficiency.

FIG.5. Detail of planter-shoe equipped with soft rubber-tired seed press wheel.

( Courtesy of the International Harvester Co. )

The application of fertilizer as a part of the planting operation has become a universal practice. Here, as with planters, the progress in development has been the result of many minor steps. The engineering problems in fertilizer placement have been summarized by Walker (1957). He pointed out that on early models, placement of the fertilizer has been haphazard; the split boot roughly divided the application into two bands that were approximately level and theoretically to the side of the seed. As agronomists unraveled the feeding habits of seedlings and plants, the importance of precise fertilizer placement was established. Special fertilizer-disk openers, equipped with tapered prelubricated roller bearings, now give a positive furrow for fertilizer placement at any depth or distance relative to the seed that may be desired. Nearly all planters can be modified to use either dry or liquid fertilizer. Positive valves are designed to open and close automatically as the planter is raised and lowered from the carrying and planting positions. The fertilizer hoppers have changed. On early planters the fertilizer

186

T. W. EDMINSTER AND H. F. MILLER, JR.

hopper’s capacity was about equal to the capacity of the seed hopper. Higher rates of application, longer rows and higher speeds gradually forced redesign; hoppers of one and two hundred-pound capacity thus becoming common. Their sharp angular designs are being replaced by smooth one-piece construction. Glass-fiber reinforced plastic hoppers are rapidly replacing metal units. This is a major development in meeting the corrosion problem, Plastic coating of other portions of the fertilizerplacement equipment and use of reinforced cast plastic components, while still in the research and development stage, promise further advances. (Fig. 6 ) .

FIG.6. Multiple row planter equipped with large plastic hoppers for dry-fertilizer application and special hoppers for adding other soil treatment materials. (Courtesy of the International Harvester Co.)

The introduction of many new forms of fertilizer has forced other developments. Merrill (1956) and Guelle (1954) have provided a general review of these developments. The safe and accurate transfer and metering of materials such as anhydrous ammonia has necessitated the development of a whole array of transfer systems, metering devices, and injection equipment. Hedman and Turner (1954) reported on the early developments in direct-injection metering systems, variable orifices, and on the use of the ratometer to indicate rate of flow for anhydrous ammonia. After several additional years of research, Hansen (1958) made an exhaustive report on the engineering principles involved in handling liquid materials. The multiple-discharge hose-type fertilizer pump, described by Gantt (1956) and Gantt et al. (1956), was made possible by the introduction of improved bearing designs and the development of plastic hose material that could stand up against constant flexing. Devices and schemes for actual placement of fertilizer in the soil with minimum waste and loss continues to be a challenge, A unique suggestion has been made by Arya and Pickard (1958). They suggest

RECENT DEVELOPMENTS IN AGRICULTURAL MACHINERY

187

direct injection in which the kinetic energy of the material is substituted for the tractor energy now used to force the injection knives through the soil. This is an example of how far reaching the application of sound engineering principles may be in the design of agricultural machinery. In the continuing trend toward unitized operations the applications of insecticides, fungicides, nematicides, and herbicides are rapidly being combined with the planting operation. An array of tanks, pumps, valves, sprays, and injectors are being added to planting units. While each item added requires additional power, it does reduce the number of trips over a field and thus reduces labor output.

B. GRAINAND SEEDDRILLS Equipment for planting and fertilizing those crops commonly grown in narrow-spaced rows or drills has been modernized in the same way that row planters have been changed, Seed-metering devices have been improved to give positive seed spacing. Both single and double-disk openers, equipped with dust-tight prelubricated bearings, cut through trash and clods to give precise depth placement. Fertilizer, formerly loosely broadcast on the surface, is now drilled into the soil at an exact distance to the side and at a predetermined depth below the seed. Carefully designed covering blades have replaced the chain-type covers, and press wheels firm the soil around the seed. Both the grain and fertilizer hoppers have been enlarged, treated to prevent corrosion, and equipped with positive-action agitators. There is a strong trend toward the use of tractor-mounted drill equipment. Buhr (1955) notes that a mounted drill can plant a daily acreage equivalent to that of a 25 per cent larger drill towed on wheels. This increased production is due to faster field travel, more rapid turns on headlands, easier loading since the drill can be readily backed up to a truck, and smoother fields due to self-elimination of tractor wheel tracks. Each small change has had a significant bearing on the improvement of farm efficiency. More rapid and timely planting with improved percentages of germination is vital in modern farm operations. Aside from these general machine changes there have been some significant changes in the uses being made of drill equipment. The interseeding of legumes and grasses in corn at the last cultivation, as reported by Van Doren and Hays (1958) has been an important conservation and crop-management development. When interseeding is practiced the corn rows are generally spaced 60 to 80 inches apart to reduce shading and moisture competition for the interseeded crop. Since moisture may be limited at time of seeding, it is important that the soil be firmly packed around the seed. Two machines that have been found

188

T. W. EDMINSTER AND H. F. MILLER, JR.

successful are a conventional grain drill with packer wheels attached and the cultipacker seeder. Drills have been modified by removing one or two openers to permit straddling the corn rows or by cutting off part of the machine to reduce the drill width. Specifically designed drills for interseeding are appearing on the market. Johnson (1955) and Peterson ( 1955) describe many of the machine modifications in detail (Fig. 7).

FIG.7. Interseeding alfalfa in corn up to 40 inches in height. Fenders protect corn plants. Fertilizer is applied in bands directly in front of tubes delivering legume seeds to the soil surface. Legume seed is broadcast directly in the corn row. Pressure on packer wheels may be adjusted to suit soil conditions. A mounted grain drill may be modified to provide a similar unit. (Courtesy of the Allis Chalmers Manufacturing Company.)

The seeding of small grains in permanent pasture to provide supplementary winter grazing has become another important new management practice, particularly in the South. This practice resulted in the development of a number of multiple-use drills designed to operate in heavy pasture sods where conventional drills would have been unable to provide an adequate seed furrow and proper fertilization and seed coverage. Early studies on the design of the machines are reported by

RECENT DEVELOPMENTS I N AGRICULTURAL MACHINERY

189

Jones et al. (1951), Dudley and Wise (1953), and Howell and Jones (1954). Particular attention has been given to the development of this machine by Hulburt (1956), Wagner and Hulburt (1953), and U. S. Dept. Agr. ( 1956a). With growing use of rough, cloddy, and trashy fallows for wind and water-erosion protection throughout the West, new drills have been developed to operate under these severe conditions. Many of these machines are essentially standard drills that have been made heavier and equipped with larger disk openers, One unique machine that has been developed at several western locations is the blade-type drill. A hollow horizontal blade (similar to a blade weeder) is drawn through the soil at planting depth, a moving chain conveys the seed down a tube and meters it out along the trailing edge of the blade. Krall (1951) reports that while many refinements are needed to improve uniformity of seed metering and to reduce seed damage, this drill operates very well under extreme trash conditions (over 2000 pounds per acre) where conventional drills will clog. C. AERIAL SEEDINGAND FERTILIZING The use of aircraft for seeding and fertilizing rough hilly areas and wet areas has advanced tremendously in recent years. The first rice seeding by plane was reported in California in 1929, when it was necessary to replant areas that had already been flooded. Most of the rice acreage in this country is now seeded by plane, Southwell (1951) describes the use of planes for seeding burned and cut-over pasture and range land that is too rough for conventional drills. Pelleted seed has been found effective in this work. Much attention has been given to the development of special planes for this work. High payload capacity with maximum maneuverability is a major objective. Weick (1952) and Anonymous (1956a) trace the development of specialized airplane equipment both here and in England. With further refinements in seed-pelleting techniques and in improved equipment, this type of seeding and fertilization will gain in importance. The spreading of over 450,000 tons of fertilizer on approximately 4 million acres by plane during 1957-1958 in New Zealand (Anonymous, 1958) is an important indication of this trend. A comprehensive discussion of planting and fertilizer-placement equipment would be too extensive for this report. Each specialty crop has certain planter requirements that result in the development of special equipment. For example, Futral and Allen (1951) describe a special high-speed peanut planter that uses a perforated belt with sized holes to pick up, convey, and then “throw” the seeds to the ground. The

190

T. W. FDMINSTER AND H. F. MILLER, JR.

development of graded and later monosperm sugar beet seeds required the design of special planting equipment in this industry. Burgesser (1950)points out that the use of coated and pelleted seeds will require a complete new study of planter design to assure proper metering, placement, and covering. Descriptions of these special planter developments can best be found in the literature pertaining to the individual crop under study. IV. Developments in Cultivating Equipment

Cultivation of crops generally refers to those tillage operations that are carried out after the seed has been planted. Weed control is the major objective of cultivation but in some areas, particularly where irrigation is practiced, it is intended to loosen the soil, thus improving infiltration. While the actual cultivators themselves have changed little, the ways in which they are mounted, powered, adjusted, and managed have been modified. The chemical and flame control of weeds have further modified the entire cultivation program.

A. MECHANICAL CULTIVATION It is pointed out by Bainer et al. (1955) that nearly all present-day cultivators are tractor mounted. The tricycle-type tractor with high clearance and adjustable rear-wheel tread has become the primary base for cultivating equipment. Small tractors with rear-mounted engines to provide maximum visibility have been adopted to carry cultivators for vegetable crops where extremely close and precise tillage is required. Some improvements have been made in the methods of mounting cultivators on the tractor frame. While front-mounted units are preferred because of better visibility and more responsive control from steering, rear-mounted units still have certain advantages. Quick coupling on the drawbar links and the fact that they may be set to partially remove the compaction effects of the tractor wheels, are important considerations. There is still serious need for simplification in mountings and in adjustment. This becomes more important as the number of row units increases to four-, six-, and even eight-row outfits. Quick interchange is desired for the many different cultivator tooth designs. The advances in metallurgy and in heat treatment have made possible the development of cultivator teeth that have much longer life through resistance to shock and abrasion. Williamson (1955)points out that sweeps of thin, broad-angle, low-crown design provide excellent weed cutting with a minimum of soil throwing even at high speeds. Only

RECENT DEVELOPMENTS IN AGRICULTURAL MACHINERY

191

3/16 inch thick, they are self-sharpening and can be used without other care until worn out. Hydraulic controls have replaced nearly all of the mechanical lift equipment. Double-acting cylinders permit positive penetration under hard-ground conditions. In some instances the units on each side of the tractor can be lifted or lowered independently. This provides a great advantage when cultivating along grass waterways, variable-width contour strips, and terraces. In tractors equipped with both front- and rearmounted units, delayed-action valves are being used to permit the rear gang to stay in the soil until they have moved forward to the field edge, where the front gang was raised. There have been many modifications in plant-shield design. Rotary shields and floating self-adjusting stationary shields permit much closer operation to the row. To improve this further, one company has developed an electronic control mechanism that automatically senses the position of the cultivator in relation to the plant and then transmits this to an automatic power-steering mechanism. This system virtually eliminates the hazards of human error in guiding the tractor in close-cultivation work. The rotary hoe, and a number of its modifications, has been in use for many years, Recent improvements in design and construction has placed new emphasis upon its use. A major design change has been the sectional and individual suspension of the spiders in place of the single, rigid axle mounting. This has resulted in maximum flexibility, allowing the unit to conform to surface irregularities, and thus doing away with the problem of excessive depth of penetration on high spots and weeds left in depressions. Rea (1954) has shown that excellent results can be obtained with such equipment at speeds up to 18 miles per hour. R. W. Wilson (1956b) has also shown that this equipment has considerable promise in early cultivation of tobacco. Sectional units consisting of three or four rotary-hoe wheels have been mounted on conventional planters directly over the crop row in order to break crusts and dislodge small weeds that could not be reached with conventional cultivating attachments. Rotary cultivating units, in which the row middles are stirred by units driven from the power takeoff that have various-shaped knives and blades mounted parallel to the axis of rotation, have been developed for cultivating special crops. The degree of soil pulverization can be controlled by adjusting the relative speed of rotation to the rate of forward travel. There is continued effort to find better ways of controlling weed growth in the row where it is difficult to reach without injuring the crop.

192

T. W. EDMINSTER AND H. F. MILLER, JR.

Liljedahl et n2. (1956) proposes the use of heat, ultrasonic and impact energy to damage weed seeds in the soil before planting. They developed experimental equipment for picking up the soil in the immediate area in which the seeds are to be planted, treating it, and then replacing it immediately in front of the planter. Initial results indicate that such an approach should be given thorough study, particularly where special high-value crops are to be seeded.

B. FLAMECULTIVATION Flame control of weeds on ditch banks and rights-of-way has become a standard practice. Its application to weed control between plants under cultivation was first considered in the early 1940’s. Major attention has been given to the use of flame cultivators in cotton growing. Stanton ( 1954) and Stanton and Tavernetti (1956) have outlined in detail the development of more precise and uniform seedbeds, This, together with uniform seed depth, results in a plant uniformity that permits close adjustment of the flame with minimum plant damage. Several burner designs involving various shapes, slopes, and types of flame deflectors have been developed. Staggered mounting prevents the flames from striking each other and thus being deflected up the plant. In some areas, particularly California, there is growing interest in this equipment. FOR APPLYINGCHEMICAL HERBICIDES C. EQUIPMENT Weed control specialists have made tremendous strides in the development of chemicals for the control of weeds in cultivated crops. Equipment for the application of these chemicals has passed through many stages of development. Basically, it consists of standard assemblies of tanks, pumps, pressure-control regulators, and application nozzles. Engineers have been challenged to develop units that can be used in conjunction with planting and mechanical cultivation equipment. Nozzle designs that will give a uniform, precisely placed application with a minimum gallonage have been the major objective. Most of this equipment is rather standard in design and application, and hence will not be discussed in detail. Excellent discussions of its development, design, and use are to be found in the reports of Akesson and Harvey (1948), Fairbanks (1951), Page (1952), and Yeo (1955).

D. THINNING EQUIPMENT Many crops such as sugar beets, cotton, and vegetables have low and unreliable emergence rates. To assure a good stand, these crops are planted thick and then thinned to desired spacing and stand. AS

RECENT DEVELOPMENTS IN AGRICULTURAL MACHINERY

193

hand-labor costs have increased, many types of mechanical blockers and thinners have been developed. The simplest device is the cross-blocker with a series of rotating knives or sweeps of selected length that is driven across the row to cut out unwanted plants. Down-the-row thinners follow the direction of the row but have rotary knives that are geared to the rate of forward movement in such a way as to remove the unneeded plants. This latter type has received much attention from design engineers. Blade speed, design, and orientation have been carefully worked out to provide a high degree of precision and uniformity in the thinning operation. A detailed analysis of the design factors included is given by Richardson (1958). British studies are reviewed by Maughan et al. (1959). Flame and chemical thinners have been developed but have not been extensively used. Baggette ( 1949) describes equipment that suspends a cover over one or more plants at the selected plant-spacing interval; the remaining plants are then burned out by a flame or sprayed with a direct contact-type herbicide. The thinners discussed above are all of the random selection type. One selective-type thinner uses an “electric eye” to locate and examine the plants. A windowed box containing the phototube is passed over the row. Light reflected from the first plant actuates the tube. This, in turn, puts a thinning knife into operation until the tube has located the next plant at the required distance. The knife then moves aside until it has passed this “selected” plant. Holmes (1950) indicates that by adjusting the phototube it can be made to select only the larger crop plants, thus duplicating, to a’degree, the selective ability of a human thinner. This is a costly device; however, it indicates the unlimited possibilities that exist for further automation in the field of farm equipment, V. Developments in Spraying and Dusting Equipment

A. GENERAL DEVELOPMENTS The increased use of both ground machines and aircraft for the application of agricultural chemicals has been phemonenal in the past decade, with an estimated use of approximately 260 million dollars worth of these chemicals on United States farms annually. Major uses are for insect, disease, weed and brush control, and defoliation. The type of chemical used has changed in the past ten years from predominantly dust to spray. An example of the phenomenal growth in spray equipment is shown by the fact that in 1947 approximately 3000 tractor power-take-off sprayers were manufactured, whereas in 1957 about 60,000 were manufactured. An average of approximately 50,000

T. W. EDMINSTER AND H. F. MILLER, JR. 194 were manufactured during each of the intervening years. In 1947 one buyers’ guide listed only five manufacturers of tractor-mounted powertake-off sprayers, but a hundred manufacturers were listed in 1957. The airplane is considered an agricultural machine for applying spray and dust materials, since an estimated 5000 planes treat over 60 million acres annually for pest control, A U. S. Department of Agriculture (1958~)report on the pesticide situation for 1957-1958 stated: “The acreage treated by aircraft for pest control in California rose from 296,059 in 1946 to 5,611,000 in 1956, with the area in 1956 almost twice that in 1951.” The U. S. Department of Commerce (1957) gives a breakdown of aviation application uses for agriculture. The U. S. Department of Agriculture (1958d) also gives a selected list of references on aircraft in agriculture. Much progress has been made in the manufacture of spray equipment for both ground machines and aircraft by the use of better materials and manufacturing techniques. Improved nozzles, pumps, valves, as well as longer-lasting tanks and lines, have come about by the use of higher-grade metals or newly developed synthetic materials. For instance, as many as six different types of stainless steel are used in the manufacture of present-day spray equipment. Detailed discussion of the use and development of spray and dusting equipment is given by Smith (1955) and Bainer et al. (1955). Considerable work has been done on the effect of particle and droplet size when using different chemicals for various purposes. However, researchers are still working for a method to control droplet size and to produce sprays with a large percentage of droplets in a narrow range of sizes. Other problems concern methods of increasing the percentage of material which actually sticks to the plant stem and leaf surfaces, and ways of measuring these amounts quickly and accurately. A new photographic and electronic counting method of measuring spray droplet size has been reported by Farnham (1958) to be a hundred times faster than presently used methods. Brittain et al. (1955) discuss a relatively simple method of evaluating the deposit on plants, and Kromer (1949) relates the engineering challenge of spray application. Black (1956) reports on the corrosion and abrasion effects of pesticides on application equipment.

B. SPRAYINGEQUIPMENT Sprayers for field crops are primarily of three types-tractor-mounted, tractor-trailed, and high-clearance self-propelled. Orchard sprayers are generally classified as high pressure or blower (mist) types. Recent developments have been the increased use of self-propelled sprayers for

RECENT DEVELOPMENTS I N AGRICULTURAL MACHINERY

195

ficld crops and blower (mist) typc sprayers for orchards. The introduction of blower (mist) sprayers for use on field crops, primarily vegetable crops, has been for disease control. Williamson ( 1958) discusses recent increased use of self-propelled high-clearance sprayers in cotton, Black et al. (1954) describe the de-

FIG. 8. New m i s t blower sprayer maneuverable for spraying in any direction. (Courtesy Food Machinery and Chemical COT.)

196

T. W. EDMINSTER AND H. F. MILLER, JR.

velopment of a high-clearance, self-propelled sprayer for sweet corn. These sprayers have recently been equipped with attachments such a s topping devices for cutting tops from crops, flame cultivators for use in flaming rank-growing cotton for weed control, and granular insecticide distributors for corn borer control. The new development of blower-type sprayers, sometimes referred to as air-blast or mist-concentrate sprayers, is significant and their use is rapidly expanding. These sprayers use less water, thereby applying more concentrated spray while also obtaining equal or better coverage than hydraulic sprayers using large volumes of water. The use of this type sprayer for row crops and vegetables is discussed by J. D. Wilson ( 1956) (Fig. 8 ) . Recent developments and methodology in the use of airplanes for forest and row-crop spraying are discussed by Isler and Thornton (1955), Young et al. (1957), Chamberlin et aZ. (1955), U. S . Department of Agriculture ( 1954), and Anonymous ( 1956~). Helicopters are being used to a small but increasing extent. Their use is limited to spraying of high-value specialty crops, such as cranberries, which are difficult to get to with either ground equipment or winged-type aircraft. C. DUSTING EQUIPMENT Although the use of dusting equipment has rapidly declined owing to increased use of sprays in the past decade, there has been some improvement in application equipment. This is particularly true with respect to modification of dusting equipment for use of granules. Improved hopper and metering equipment design has resulted in more uniform distribution of dust across the swath for both ground machines and aircraft. For aircraft, an additional small airfoil has been closely coupled to numerous discharge points to aid in promoting rapid spreading of the materials. This new equipment dispenses liquid, dust, or granules with only minor adjustments being necessary for dispensing the different types of materials. VI. Developments in Harvesting Equipment

Quality changes through improved design and manufacturing processes have produced harvesting machines which do a better job in less time, last longer, and require less labor for operation. The number of machines has increased, although the number of farms has decreased. During the period 1950 through 1958, the number of grain combines increased by 46 per cent, corn pickers by 63 per cent, pickup balers by

RECXNT DEVELOPMENTS I N AGRICULTURAL MACHINERY

197

201 per cent, and field forage harvesters by 215 per cent. Percentage increase of machines on specialized crops is even greater, depending upon the number needed and the degree of success in perfecting the equipment. The harvesting of specialized crops is rapidly changing from hand to mechanical methods. Scarcity of labor and tightening of the economic situation is expediting this change-over. Increase of mechanized harvesting contributed primarily to the 21 per cent reduction in man-hours used on farms in the past ten years. There has been very little reduction in man-hours used for those crops in which the harvesting has not been mechanized. The general trend has been toward harvesting equipment that can be operated by one man with the least expenditure of his energy. The trend in design is toward more automatic operation, increased use of hydraulic systems, V-belt drives, self-aligning prepacked bearings, and lighter materials for construction where possible. Less vibration is experienced owing to better balancing of moving parts. The use of large harvester-mounted bulk bins unloaded by gravity dumping or auger conveyors is becoming standard practice. There is a trend toward larger self-propelled machines for the bigger farms. Smaller machines are being designed to mount on tractors or other power units which can accommodate several types of equipment. Harvesting machines are being designed to operate under a wider range of crops and cropping conditions. HARVESTING EQUIPMENT A. FORAGE Forage crop production of over 100 million tons (excluding that used for silage) constitutes approximately one-fifth of all harvested crop acreage in the United States. S t r i d e r and Phillips (1956) report that while only 29 per cent of all hay was baled in 1944, 73 per cent was baled in 1954. This trend was due primarily to the introduction of automatic-tie pickup balers, reduction of storage space requirements, and ease of handling as compared with loose hay. Chopped hay for curing and dehydration increased from approximately 2 to 7 per cent during the same period. Long, loose hay has steadily declined during these same years to a low of 20 per cent in 1954. Although hay crops in general have a relatively low cash value per acre, much progress has been made in equipment for mechanizing the crop. Improvements in hay crushers have decreased the hazard of crop loss under changing weather conditions. Automatic one-man-operated balers with a second man loading the trailer has been a common practice for the past ten years. Recently, one-man hay balers have been designed to kick or throw the bale into the trailer, thereby eliminating one man

198

T. W. EDMINSTER AND H. F. MILLER, JR.

FIG.9. One-man baler throws bales from machine to trailer. (Courtesy Deere and C o . )

(Fig. 9). It appears that hay pelleting or wafering by field machines may further reduce the handling costs in the field, in storage, and in feeding. 1. Mowing With over 75 per cent of the mowers equipped with power drive in lieu of ground drive, 6- and 7-foot cutter bars have become standard. Elfes (1954) reports on the design and development of a new highspeed mower having a reduced stroke length and a dynamically counterbalanced reciprocating blade so designed that its operation is not affected by the raising and lowering of the bar. It is equipped with special sealed antifriction bearings throughout, and a V-belt replaces the pitman rod.

2. Hay C w h e r s The general use of field hay crushers has increased from only a few hundred to several thousand between 1955 and 1958. Consisting primarily of a pair of steel rollers held together under pressure by adjustable springs, the crusher is driven by the power-takeoff of the tractor. A pickup unit lifts the hay from the swath and feeds it between the rolls. The crushed hay is dropped back onto the stubble in a swath. Crushers are made as separate units or in combination with mowers.

RECENT DEVELOPMENTS IN AGRICULTURAL MACHINERY

199

Ramser and Kleis (1952) and Butt et al. (1956) report that crushed hay generally dries to a safe storage moisture content in one-third to two-thirds of the time required for uncrushed hay. Although the reduction in drying time is seldom sufficient to allow cutting and storing in the same day, it often allows the hay to be picked up on the second day when normally it would take 3 or 4 days for it to reach a safe moisture content. Earlier models of the hay crushers generally had smooth crushing rolls, whereas some recent models are equipped with fluted rolls which tend to crimp the hay. 3. Raking

Agricultural statistics indicate that side-delivery rakes on farms have become the predominant type, with approximately 1.3 million in use in 1957. Bainer et al. (1955) classify side-delivery rakes as ( 1 ) cylindricalreel, ( 2 ) oblique reel-head, ( 3 ) finger wheel, and (4)drag-type. Each of these rakes, owing to differences in design, imparts a different velocity and movement to the hay in the raking process. Giles and Routh (1951) in comparative tests on the three side-delivery-type rakes found that the leaf loss with the finger-wheel rake was considerably less than with the other two types. The increased mobility of tractor-mounted rakes facilitates their use on grassed waterways, terraced outlets, and in odd-shaped land areas that may occur in conservation layouts. 4. Baling

Improvements in equipment for baling have increased the popularity of this method of harvesting and handling hay. Outstanding changes have been the development of the automatic baler and the use of twine for tying. There has been a threefold increase in the number of automatic pickup balers since 1950. Of the approximately 600,OOO in 1958, approximately 80 per cent used twine. In addition to the shift toward more twine-tied balers, there has been a trend toward smaller bales. These bales are easier to handle and are particularly adapted to the one-man balers equipped to eject the bale into the trailer. At least one company is proposing a control which permits the tractor driver to change the direction in which the bale is thrown. The two main types of balers are the plunger type (rectangular bale) and the round-bale type. Hay buyers have generally demanded denser bales. Burrough and Graham (1954) developed a method employing strain gages and a sensing unit for measuring the power input to various drives of plunger-type forage balers which show the effects of varying moisture content, bale density, baling rate, and plunger speed. The maximum

T. W. EDMINSTER A N D H. F. MILLER, JR. 200 force required for an increase in bale density of 8 to 10 pounds per cubic foot increased from 4500 to 10,OOO pounds, and the baling energy increased from 1.2 to 2.2 horsepower-hour per ton. For only a 14-pomd increase in a 7-cubic foot bale, almost twice as much energy is required. Automatic twine-tying devices have been refined and improved. Baler twine is heavier than binder twine, having a tensile strength of approximately 275 pounds. The normal rectangular twine-type bales use slightly over 3 pounds of baler twine per ton, while round bales require slightly over 2%pounds of binder twine per ton. Bainer et al. (1955) describe the need and present-day use of safety devices or shear pins in such places as (1)between the flywheel and the plunger, ( 2) in the drive ahead of the baler flywheel on power-take-off driven balers, (3) in needle drive should it strike an obstruction, (4) in the drive to the tying mechanism, ( 5 ) in the pickup and conveying drive, and (6) in the feed-mechanism drive to prevent overloading.

5, Chopping With different attachments, field forage harvesters can be used to harvest row crops for silage, grass from a standing crop or windrow for silage, straw and other kinds of forage, and green chopped hay for direct feeding or dehydration. Field forage harvesters, developed first about 1936, have increased rapidly in recent years from approximately 80,000 in 1950 to 240,000 in 1957. These machines took the place of the row-crop binder. Field forage harvesters are of two major types, cIassified as to placement of cutting knives into a flywheel or cylinder arrangement. The flail-type forage harvester developed from the swinging-blade stalk shredders since World War I1 has recently increased in importance Fig. 10) Bockhop and Barnes (1955) ran tests on power distribution and requirements of a flail-type forage harvester, reporting the power requirements as relatively high when compared with conventional-type forage harvesters but having comparable capacity. The flail-type machine is of simple design with relatively few working parts and can be utilized as an ensilage harvester, hay and straw chopper, stalk shredder, weed cutter, beet topper, and for other purposes. The authors further state that it can probably be used economically by a farmer who uses an ensilage harvester an average number of hours per year and who already has a three- or four-plow tractor. The economy-model flail harvester results in a product with somewhat longer length of cut, and when this is not objectable, farmers should find it acceptable, especially where green-feeding practices are used. I

RECENT DEVELOPMENTS I N AGRICULTURAL MACHINERY

201

King and Elliott (1955) report on the development of a semi-selfpropelled baler and forage harvester, both pickup and direct cut. The tractor is used as a prime mover, with mounting hitches so designed and arranged that the tractor may be hitched to the harvester in a matter of 2 or 3 minutes. A separate power unit when needed may be mounted on the three-point hitch behind the tractor and beside the harvester. Cykler (1950) tells of harvesting Napier grass in Hawaii with a harvester developed and used for harvesting green feed the year around.

FIG. 10. Flail-type harvester cuts, chops, and loads forage by direct-cut or from windrow. (Courtesy Lundell Manufacturing Co., Inc. )

It was mounted on a track-type tractor for use on small, rough, rocky, and irregularly shaped fields. A commercial machine for field hay pelleting was announced during 1958. While not yet in wide commercial use, it should have great potential if present experimental harvesting and feeding trials continue to be successful. It will greatly reduce the cost of handling forage both from the field to storage and from storage to feeding. Dobie (1959) reports that by far the greatest activity is being exerted in the field of producing large wafer-type pellets. He states that numerous manufacturers are

202

T. W. EDMINSTER AND H. F.

MILLER,

JR.

making pellets 3 to 4?iinches in diameter and % to 1%inches thick. Most of these machines are plunger-type machines with the application of the high pressure necessary to make the wafer of suitable density resulting in terrific impact pressure at the forward end of the stroke. A heavy frame plus the heavy flywheel needed to move the pulsating load, results in a fairly heavy machine per ton per hour output. The principal advantage of the plunger machine for wafering is that it will handle either long or chopped hay; this reduces the cost of processing prior to pelleting and places field pelleting in a more favorable position because less auxiliary equipment is needed. Wafers made from chopped hay are usually more uniform in shape and thickness than long hay wafers. The present field machines for making wafers have the capacity of about one-half that of a conventional baler and make wafers best from hay containing from 12 to 20 per cent moisture. 6. Mbcelluneous Equipment

Windrowers, hay tedders, and various types of buck rakes and hay loaders are passing through a period of redesign and modernization. Hydraulic-operated, tractor-mounted units of many types are available for putting up loose hay. B. CORNHARVESTING EQUIPMENT Corn is the largest acreage field crop in the United States and the most important source of feed, with 90 per cent of the total corn acreage harvested for grain. Ninety per cent of the total annual production of corn, 3%billion bushels, is from the twelve North Central States. There are approximately 745,000 corn pickers in the United States, an increase of about 42 per cent since 1950. According to Scoville (1956) over onehalf of these are in the Corn Belt, but the most rapid rates of increase in the past few years have been in the South, Northeast, and Far West. A new type of picker-sheller unit, introduced since 1953, is a modified grain combine for picking and field shelling of corn. According to the best estimates, there were slightly over 5000 picker-sheller units in use in 1957 and approximately 9OOO grain combine attachments for picking and field shelling. Corn harvesters may be classified as snappers, picker-huskers, or picker-shellers. Bainer et al. (1955) report a fourth type, introduced commercially in 1954 as a combination picker-chopper. This machine picks the ears and delivers them into a wagon while the stalks are cut and fed into a conventional forage-chopper and either discharged on the ground or delivered into a truck or moving wagon beside the harvester.

RECENT DEVELOPMENTS IN AGRICULTURAL MACHINERY

203

Safety is one of the greatest problems to consider in the use of a mechanical corn picker. Scranton (1952) reports that in a survey it was found that nearly all accidents with corn pickers were caused by carelessness. There is a major educational task in teaching users of such machines to be careful. There are some twenty-one rules listed for normal and safe operation of corn pickers by the Farm Division of the National Safety Council. 1. Snappers and Picker-Huskers A snapper-type corn harvester is essentially the same as a pickerhusker except that there is no provision for removing the husks. The snapped ears are conveyed directly into a wagon. The snapping rolls are generally operated at about 500 to 600 f.p.m. (peripheral speeds). The rolls are ordinarily made of cast iron or cast steel, with spiral ribs or lugs on their surfaces. On a picker-husker, the husking rolls may be on a separate bed, incorporated in the snapping-roll elevator, or may be a direct extension of the snapping rolls. Most husking units have one roll of each set made of rubber; the other roll may be of steel, wood, rubber, or cast iron. Field losses generally run in the range of 5 to 10 per cent. Field losses may be kept to a minimum by proper adjustment of the machine, careful driving, and avoiding high speeds. Under most conditions, speed should not exceed 3 to 3%m.p.h. Richey et al. (1956) report a new design for corn-snapping rolls. The new principle varies from the conventional in that the stalk is bent sideways and passes through the snapping rolls at about a 45-degree angle. This action clears the ears from the rolls and reduces the shelling losses. The side-snapping action tends to spread the rolls in a 45-degree plane and is referred to as the side-snapping principle. 2. Picker-Shellers and Combine Attachments

Picker-sheller corn harvesters may be of the same general design as the picker-huskers, except for the addition of the shelling unit and a grain bin or elevator to elevate the shelled corn into a trailing wagon or one pulled beside the harvester. Corn may be harvested with pickershellers with a moisture content ranging from 14 per cent (dry enough to store) up to 30 per cent or higher. When the early-harvest method is practiced, the corn will be too high in moisture content to store and must be artificially dried down to approximately 14 per cent moisture. Ear corn will keep in storage up to moisture contents of around 20 per cent. Hurlbut (1955) and Pickard (1955) tell of experimental work between 1950 and 1954 on an experimental ear-corn harvesting attachment which mounts on the front of a combine, and also compare differ-

T. W. EDMINSTER AND H. F. MILLER, JR. 204 ent types of cylinders and concaves for efficiency in shelling of corn. Morrison (1955) reports on the commercial adaptation in 1953 of a com-harvesting attachment on a self-propelled combine. He lists fourteen different advantages of combining corn, including more economical and efficient harvest, an earlier harvest, crop residues left in the field, and less storage space required. Goss et al. (1955) reported on tests, conducted in California during the 1954 harvest season with corn-harvesting attachments, which indicated that the ordinary grain combine equipped with a rasp-bar cylinder is well suited for shelling corn under California conditions. The major problem in harvesting corn with adapted combines was the delivery of the unshelled corn to the cylinder without loss of corn, primarily ear corn on down or lodged stalks. The combine attachments for corn are relatively simple, and fast change-overs from grain to corn are possible on most machines because both front ends attach to the same bearing points and use common drives and the same lifting system. There is no wagon to pull and the machines operate better in soggy fields.

C. GRAIN,LEGUME,AND GRASSSEED HARVESTING EQUIPMENT Although grain combines are used primarily to harvest small grains and soybeans, they are used for many other crops, such as rice and various legume and grass seeds. In the United States, combines have almost completely taken over the job of threshing grain, either by direct cutting or combining from a windrow. Brodell et al. (1952) reported that 85 to 95 per cent of the barley, wheat, and soybean crops in the United States were harvested with combines in 1950. There were approximately 1,040,OOO combines in the United States in 1957, compared to approximately 700,000 in 1950. Approximately 20 per cent of the combines on farms today are the self-propelled type, and this trend is rapidly increasing, since approximately one-half of the combines manufactured during 1956 and 1957 were of the self-propelled type. The main advantages of self-propelled combines over the trailingtype machines are that they have greater flexibility and maneuverability, save more grain in opening up fields, and permit the driver to have better control of his machine and a better view. Gray (1955) gives the function, operation, and care of the combine, as well as details with respect to adjustments for twenty different crops, Witzel and Vogelaar (1955) report that the first self-propelled combines on rolling ground did not gain widespread popularity, probably because during the period from 1910 to 1930 the track-type tractor came into being as the primary answer to pulling the large hillside combines.

RECENT DEVEMPMENTS IN AGRICULTURAL MACHINERY

205

During the period from 1910 to 1949, hillside combine development was marked by general design improvements, such as universal adoption of steel frame and body, antifriction bearings, V-belt drives, rubber tires, and weight reduction. Another advance during this period which helped to reduce manpower requirements was the adoption of bulk handling of threshed grain, thereby eliminating the sack sewer and sack “jigger.” In addition, several ingenious automatic leveling-control devices had been developed, making possible a two-man crew in place of the original five-man crew. They further report that the relatively recent development and widespread adoption of level-land, self-propelled, pusher-type combines was watched with a great deal of interest by the hillside area farmers. At least two hillside self-propelled pusher combines went into the field in 1949. A limited number of hillside self-propelled combines were put in the field by one manufacturer in 19%. Inventors converted several hillside combines to the self-propelled type. Several makes of hillside combines were available by 1954. This year also marked the introduction of the first hillside combines with factoryinstalled automatic leveling controls. The main difference between a hillside combine and a conventional combine is that the separator body is kept level in the lateral direction regardless of the ground slope. Some combines have a part of, or the entire, separator kept level to some degree in the longitudinal direction. The need for and advantage of longitudinal leveling depends somewhat on the separator design. The two main types of sensing devices for automatic controls are those in which the force of gravity acts on a solid mass and those in which it acts on a liquid. The first of these is primarily the pendulum type which controls hydraulic valves directly and is also used to control electric switches which energize hydraulic-valve solenoids. The second type depends on the force of gravity acting on a liquid, such as a mercury switch. Safety is important in the use of hillside combines. They are designed with a wide wheel base so that the center of gravity falls well within the wheel base at extreme hillside conditions. Each individual wheel also has a brake. Power steering used on models produced during the last few years is itself a good safety device. Automatic controls also assist in safety since they guard against the operator leveling the wrong way. Heitshu (1956a) describes the chain of events leading to the development of one manufacturer’s self-propelled hillside combine. The complete drive-axle assembly and a schematic drawing of the automatic leveling circuit is given. Many of the operating characteristics and safety features of the hillside combine are described in detail.

206

T. W. EDMINSTER AND H. F. MILLER, JR.

Pool (1958) describes controls for full-leveling of hillside combines.

This article is the partial history and gives details of engineering developments leading to the manufacture of a hillside combine by another

major company. The pendulum system with direct-acting valves was used to activate the mechanism for leveling this particular combine. Bigsby (1958) describes power requirements of a combine cylinder when threshing solid and hollow-stemmed varieties of wheat. By the use of strain gage equipment, he determined that 20 to 25 per cent more power is required on the cylinder when threshing solid-stemmed wheat than is required to thresh hollow-stemmed wheat at the same rate. This problem became one of major interest when severe losses in wheat yield in western Canada caused by the wheat stem sawfly resulted in the development of solid-stem varieties of hard spring wheat. Self-propelled combines are now being offered with 18-foot-wide cutter bars, both for the level and the hillside types. Many features are now being built in the combines, such as lifetime lubricated bearings, improved V-belt and pulley drives with mechanisms for easy adjustment or changes in speed, as the case may be. Many combines are also offered with windrow pickup attachments for combining grain and other crops from the windrow if desired. Many companies are offering attachments for corn harvesting, as previously discussed. Air-conditioned cabs are now available for self-propelled combines which give year-round heating or cooling. The compressor for cooling is belt-driven from the combine engine. Full-view windows with tinted safety glass are featured for greater comfort for the operators, Although soybeans are harvested primarily by conventional-type combines, problems of germination in connection with cracking of seed during harvest are common, as discussed by Moore ( 1957). Heitshu ( 1956b) discusses the problems of ridging and low pods as being serious to contend with in combining and the necessity of keeping the ridges low so that the height of beans on the ridge and those in the middles will not be too different. He also points out the important contribution which could be made by plant breeders and agronomists with respect to soybeans, as has been the case with many other crops. He feels that, through the cooperation of plant breeders and engineers, soybeans which have higher fruiting characteristics and a more desirable row profile can be grown, and that machines can be made which will do a more efficient job of harvesting and reduce cracking. Bunnelle et al. (1954) say that successful harvesting of small-seeded legumes depends as much on the cultural practices used to produce the crop as on the operation of the harvester. Combines, when properly adjusted, are capable of doing a good job of harvesting these crops,

RECENT DEVELOPMENTS IN AGRICULTURAL MACHINERY

207

although most machines require some modification for the best performance. They further conclude that at normal load rates, the factors affecting combine performance in small-seed legume harvesting are cylinder speed, loss of free seed over the straw walkers, and the cleaning shoe adjustment. Park and Webb (1958), reporting on southeastern seed harvest studies, give several conclusions for different crops. They conclude that angle-bar cylinders threshed more crimson clover seed with less seed damage than rasp-bar cylinders. Supplemental angle bars are available for most combines with rasp-bar cylinders for use on hard-to-thresh crops. Rubber on angle bars significantly reduced seed damage. Low ground speed was necessary to minimize seed losses in crimson clover. In small grains tests, when comparing the angle-bar and rasp-bar cylinders and comparing open and closed grates, Park and Webb found no appreciable differences in threshing performance. The most serious losses in rescue, fescue, and lespedeza seed were due to weather and cutter-bar shattering, often amounting to over 50 per cent. Cutter-bar loss was reduced and cutting performance was improved by use of a tined pickup reel. Klein and Harmond (1959) give the development of a suction-type field reclaimer for shattered seed which was mounted on a combine and used as a once-over operation. The attachment for picking up shattered seed used revolving swinging chains to loosen the seed at the ground surface within the suction head mounted behind the combine. The seed, straw, and soil are conveyed back into the combine separating mechanism where the seed is saved. Tests show an increase in recovery of pure live seed from 46 per cent to 68 per cent in crimson clover and from 24 per cent to 62 per cent in sub clover when compared with combining without the benefit of the suction seed reclaimer.

D. COTTONHARVESTING EQUIPMENT Mechanical cotton harvesters available today are of two basic types, commonly referred to as pickers and strippers. Picking machines remove seed cotton from the open bolls, the unopen bolls being left on the plant. Stripper-type harvesters strip the entire plant of the cotton, including the open or closed bolls and many leaves and stems. It was 1946 before mechanical cotton harvesters were manufactured in any appreciable number; by 1957 about 20,400 pickers harvested 19 per cent of the crop and 26,500 stripper-type machines were used on farms to harvest 13 per cent of the crop, making a total of one-third or less of the cotton crop in the United States machine-harvested. Colwick and Regional Technical Committee members (1953) describe the Beltwide harvesting results from several phases of regional

208

T. W. EDMINSTER AND H. F. MILLER, JR.

work. A U. S. Department of Agriculture Special Report (1956b) describes the impact of mechanization on cotton production. Less than 2 per cent of the cotton in the Southeast is mechanically harvested, while 70 per cent or more of the crop in the irrigated West is harvested with mechanical pickers. Smith (1955) gives a detailed description of both picking and stripping machines as to types, construction, and use.

1. Picking Machines Fairbank and Smith (1950) divided the operating cost of mechanical picking as follows: operating, 25 per cent; overhead, 20 per cent; field losses, 20 per cent; and grade reduction, 35 per cent. It was concluded that even with field losses and losses due to grade reduction, mechanical cotton harvesting was definitely profitable under the existing price and labor conditions. These conditions have continued to exist up to the present time with a gradual increase in the percentage of the crop harvested, Harrison (1951) states that conformation of the boll largely determines how well spindles will perform the task of harvesting cotton. Good recovery was from bolls having relatively smooth inner surfaces when dry,the burs straight, approximately equidistant one from the other with the cotton protruding far enough to afford good contact by the spindles but set deeply enough into the carpels to provide reasonable storm resistance. Unfavorable environment, particularly lack of moisture, causing a gnarled opening of burs of any variety tends to produce difEicult machine- or hand-picking conditions. Harrison has been successful in breeding in California a variety of cotton well adapted to spindle picking. Tavernetti and Miller (1954) report on the importance of properly managing all growing practices for most efficient harvesting. With good management, machine-picking efficiencies in California run 95 per cent or better. Williamson et al. (1954) describe factors affecting the efficiency of mechanical pickers for picking quality cotton in the Yazoo-Mississippi Delta as varieties, field layout and water control, stalk disposal and seedbed preparation, seed preparation and planting, weed and grass control, insect control, defoliation, and machine performance. Wooten and Montgomery (1956) give the effects of relative humidity and spindle moisture on machine-picked cotton, showing that cotton should not be machine picked early in the morning when the humidity is high. Relative humidity has more effect on moisture content of machine-picked cotton than the water which is added to the picking spindles. Powers (1949) concludes that weeds, lack of good defoliation, lack

RECENT DEVELOPMENTS IN AGRICULTURAL MACHINERY

209

of good gins in the area for machine-picked cotton, small farms, and no particular shortage of hand labor are the main reasons why inechanical pickers are not used more in the Southeast. Important recent developments in spindle pickers include improved wearing quality of spindles, improved spindle grease seals, reduction in spindle twist left in cotton through improved spindle design and adjustment, and introduction of low-drum, single-row pickers for smaller acreages.

2. Stripping Machines Harvesting of cotton with stripping machines is limited primarily to the High Plains of Texas and Oklahoma, but it is beginning to expand into other areas as varieties and gins are made available for this type of harvest. Oates et nl. (1952) report on the development of a new, brush stripper-type cotton harvester. While this machine proved to give good efficiency of gathering most varieties, difficulty was encountered with problems of quality because of the mixing of excessive soil and trash with the lint. Both the brush gatherer and air-conveying system are reported to be major contributors to quality difficulties. There have also been numerous trials in the use of rubber paddles for stripping, according to Smith (1955), but neither the brush nor rubber paddles have come into any extensive use up to the present time. A recent development in the stripper-type harvester has been the use of extremely long brush-type stripping rolls to harvest taller, highyielding cotton of the open-boll type. After being stripped from the plants, the cotton with burs and trash is conveyed into a combination stick-and-bur-remover-type cleaner, mounted on the tractor, which takes most of the burs and sticks out of the cotton before putting the partially cleaned seed cotton into the harvester basket. With further improvements this type of operation may prove to be economically feasible. It no doubt can be successfully used for the second picking operation. One advantage of this type of stripper is that it leaves the burs and most of the trash in the field rather than carrying them to the gin. It can be expected that stripper-type machines of conventional or improved types will be used more and more as cotton is mechanized, primarily because of their low cost of operation.

E. DRYBEANAND PEA HARVESTING EQUIPMENT On almost 1%million acres, dry edible beans and peas are grown in the United States each year. Most of the production is in the states of California, Michigan, Idaho, Colorado, New Yak, Nebraska, and Wyoming. During the past ten years, the older method of cutting, windrow-

210

T. W. EDMINSTER AND H. F. MILLER, JR.

ing, stacking or baling, and stationary threshing of beans has declined sharply. McColly (1958) reports that a number of threshing machines were converted to a combined harvester-thresher, either pull type or self-propelled, and fitted with a special pickup device and feeder. The most common method employed in harvesting navy beans in Michigan is the combine pickup from a windrow. Many growers have special bean combines which usually have two cylinders designed especially for this crop; however, the trend in edible bean harvesting is to utilize the grain combine with attachments which include cylinder speed-reduction drives, screens, and other parts varying somewhat with manufacturers ( McColly, 1958). A few manufacturers have rubber-covered bars available to replace grain-threshing bars on the cylinder, and a bean grate can be placed under or back of the cylinder. There have been recent developments of a torsion spring-tooth cylinder and concaves for combines which have proved very effective in threshing edible beans. Cracking of beans can be eliminated and there is not as much delay waiting for the heavy bean root to dry out enough to go through the cylinder. This spring-tooth equipment is not as effective in threshing small grains, however, as are other types of cylinders and concaves. A blade-type bean harvesting cultivator attachment fitted with vine turners, row dividers, and windrowing rods is very commonly used to push dry beans from the soil and to form them into windrows. A rotary crop cutter is under development in Michigan and has proved successful in harvesting tests. The machine consists of hydraulic motor-driven notched disks horizontally rotating toward each other so that each, in cutting a row, forms a windrow from two rows. McColly further states that farmers would prefer direct-combining beans in order to avoid the possible loss in the windrowing in case of inclement weather. Therefore, crop scientists are working on a new variety of navy bean which grows as an upright plant rather than a vine. In direct combining, a power-driven six-bat finger-type reel is employed with an eccentric mechanism to vary the pitch of the tines during reel rotation. The finger-type reel is more efficient than the standard bat-type reel because the tines can be adjusted so that they lift the bean plant toward the cutter bar. This action saves many bean pods from being severed by the sickle and results in decreasing cutter-bar shatter loss by as much as 50 per cent. When a grain combine is used, the cylinder speed should be reduced to about one-half to one-third that required for threshing wheat, according to McColly. Defoliation of the crop when the beans are harvested standing is necessary for best harvesting and to help reduce quicMy the moisture content in the bean. Harvesting efficiency depends very much

RECENT DEVELOPMENTS I N AGRICULTURAL MACEXINERY

211

upon correct combine adjustment. The machine should be so designed that these adjustments can be made easily and in a reasonable time. Unfortunately, in many cases this is not done and there is a need for improvement in combine design so that these adjustments can be made more easily. Combine adjustments required for harvesting peas are essentially the same as described for soybeans. Gray (1955) describes these adjustments in detail. Peas may be combined direct as well as from the windrow. F. VEGETABLE HARVESTING EQUIPMENT Mechanizing the harvest of many vegetable crops is proving to be one of the most difficult equipment problems to solve. However, tremendous progress has been made in the past five years primarily because of the necessity of reducing the labor requirements for harvesting these crops. For instance, the man-hours required for harvesting asparagus, carrots, cherries, celery, and strawberries by hand are two to eight times greater than for all other growing operations. This contributes to a critical peak seasonal labor demand. Mechanized harvest can largely eliminate this problem. Because of the generally smaller acreage of vegetable crops as compared with other field crops, development work on harvesting equipment for vegetables has been done primarily by individual growers, smallequipment manufacturers, and in many cases, public research.

I. Asparagus Several different types of harvest-aid machines of the type which carry the person at a slow rate of speed through the field so that his handcutting efficiency is increased have been developed by asparagus growers. Miller (1957) describes a machine developed by one grower at a cost of approximately $750. By utilizing foot-actuated controls, both hands of the operator are free to cut the asparagus passing directly in front of and below him. With three harvesters, this one grower has reduced the number of hired hands from 24 to 3. Several years of work on a completely mechanical asparagus harvester is described by Kepner (1957). The machine has a bandsaw type of blade which cuts all the spears from a band 30 to 36 inches wide at or just below the ground surface immediately after they have been caught by the gripping units. This machine cuts all spears regardless of their length; thus, spears that have just emerged are not long enough to save. Spears shorter than 3%inches are below the normal gripping level and are not recovered. Kepner states that the machine-harvested yield was considered to be 55 per cent of hand-cut yields due to loss of the short spears. Under certain assumed conditions and estimated cost, mechanical

212

T. W. EDMINSTER AND H. F. MILLER, JR.

harvesting and hand cutting would yield the same net return per acre if the machine-harvested yield were 65 per cent of hand-cut yield. By further modification of cultural and management practices, such as bed height and shape and harvest timing, further improvement in the percentage of harvested yield can be expected. 2. Green (snap) Beans

Outstanding progress has been made recently in the development and use of mechanical harvesting equipment for snap beans. Work (1958) reports that some 200 mechanical bean harvesters were used during that year, The two-row machine takes the leaves and stems between rollers, pulls the beans, and drops the refuse on the ground. The field is picked only once. Some growers pick their beans first by hand and then follow with the machine for the second and last harvest, Breeders are working on strains of beans which are well adapted for machine harvest. The stage of maturity and other factors make a great difference; however, growers are willing to sacrifice total yield in favor of low harvesting costs. 3. Pole and Lima Beans Kubik (1957) reports that an experimental pole bean harvester is under development. Operated by one man, it picks up to 4 acres per day. Straddling the row, a pair of picker heads work simultaneously on both sides, snapping beans from the vine and dropping them into a container. Kubik also reports that an experimental machine picks lima bean pods from the vines with less than 5 per cent loss of beans. By mounting a regular stationary lima bean huller onto a trailer and equipping it with a pickup attachment, lima beans can be hulled directly from windrows, 4. Lettuce, Cabbage, and Celery Several different types of labor-saving devices have been developed for aiding in the harvesting and packing of vegetable crops, such as lettuce, cabbage, and celery. The most common type harvest-aid, laborsaving device is one mounted on a large trailer or tractor chassis, incorporating a packing unit and conveyor belts extending out on either side to bring the hand-cut vegetables into the packing line on the machine. There have been several attempts to develop a mechanical harvester for celery. The main difficulty has been the proper gaging of a cutting device for removing the roots from the stalk. Been (1957) reports on a conveyor belt harvester-loader for cabbage. This machine is towed by a row crop tractor and loads the cabbage into a trailer.

RECENT DEVEMPMENTS IN AGRICULTURAL MACHINERY

213

5. Sweet Corn During the past ten years, the mechanical harvesting of sweet corn for processing has come into widespread use. The tractor-mounted, tworow harvester which is produced commercially, automatically strips the ears from the stalk and conveys them to trucks or wagons in the field. This type harvester reduces the picking costs approximately 60 per cent and replaces ten to fifteen hand pickers.

6. Cucumbers Hall (1956) and Farrow ( 1956) describe self-propelled, home-built cucumber harvester-type mechanical aids that utilize the principle of a moving platform upon which pickers are carried in the prone position. A conveyor belt takes the cucumbers to containers. A completely mechanical experimental cucumber harvester is described by Chisholm (1955). This machine will harvest 1 to 1%acres per hour, replacing forty harvest hands. The machine leaves the vine practically undamaged. This machine is still under development.

7. Spinach and Peas Spinach and green pea harvesters are in general use. A sickle-bar cutting device cuts the entire plant which is then hauled to the processing or shelling plant. These machines are generally referred to as “greencrop harvesters.” 8. Tomatoes

Tomatoes harvest has been expedited through the use of self-propelled field conveyors. Hofmeister (1955) reports the development of a field conveyor for harvesting tomatoes and other vegetables which increases harvest rate 30 to 100 per cent. This particular conveyor is propelled by a 4-horsepower gasoline engine which also drives the conveyor belt. Lorenzen ( 1956) describes an experimental tomato harvester designed primarily for use with pear-type processing tomatoes. The harvester cuts the vines and then separates the fruit from the vine. The development of a successful tomato harvester depends in part upon the plant breeder developing a variety which ripens uniformly. 9. Other Vegetables

Many crops, such as broccoli, melons, and peppers may also be more efficiently harvested by the use of field conveyors and mechanical aids. Kubik (1957) discusses several types of field conveyors ranging from small self-propelled types to large tractor-mounted units which have

214

T. W. EDMINSTER AND H. F.

n, JR.

conveyor belts as long as 70 feet. This type of equipment will continue to assist in the harvesting of vegetable crops until mechanical harvesters can be developed to do the complete job. G . ROOTCROPHARVESTING EQUIPMENT Much progress has been made in the development and use of root harvesting equipment for the approximately 5 million acres of root crops grown in the United States, The principal root crops include peanuts, potatoes, sugar beets, sweet potatoes, and onions. Crops such as sugar beets are completely mechanized insofar as harvesting, while some edible crops such as sweet potatoes are dug mechanically, but virtually the entire crop is still picked up by hand.

1. Peanuts Mechanization of producing and harvesting the Spanish-type peanuts grown in the Southwest is practically 100 per cent complete. Anonymous (1950) describes many of these early developments. The harvesting trend in the Southeast has been toward the use of commercially available or modified peanut combines designed specifically for combining peanuts from the windrow. Approximately one-half the crop in the Alabama-Georgia-Florida area was mechanically harvested in 1958. Machines designed principally on the raddle or carding principle have been most popular, but indications at present point toward the possible use of a combination cylinder and carding principle on the same machine to increase capacity and efficiency. Combination equipment incorporating tractor-mounted digger blades with a pulled-behind shaker-windrower has been developed in recent years. This has largely replaced the need for side-delivery rakes for windrowing peanuts. Mechanical harvesting in the Virginia-Carolina area has been nonexistent up to the present time. However, peanut combines were used by a few growers in 1957 with considerable increase in the number used in the 1958 harvest season. Duke (1957) describes the development of an experimental peanut digger-shaker-windrower for use on Virginia-type peanuts. For minimum shelling damage and foreign material during combining from the windrow, careful adjustments must be made in rate of forward speeds, picking cylinder and raddle clearances, and in the air baffles. Mills and Dickens (1958) explain that windrow harvesting method for peanuts offer many peanut growers the opportunity to eliminate the need for keeping a large labor force for peak harvest seasons. For instance, over 22 man-hours of labor per acre can be saved with the windrow method. They further state that the savings on labor costs alone can

RECENT DEVELOPMENTS I N AGRICULTURAL MACHINERY

215

justify the cost of the equipment needed for the windrow method if over 30 acres of peanuts are grown. Windrow combined peanuts in the Virginia-Carolina area are seldom dry enough for storage and must be artificially dried. Teter and Givens (1957) discuss curing and mechanical drying of peanuts and give recommendations for these operations in connection with mechanical harvesting and windrowing in the VirginiaCarolina area.

2. Irish Potatoes Approximately 5000 mechanical potato harvesters were used on farms during 1958. Martin and Humphrey (1951) report on the early development of Idaho potato harvesters. Most of these first harvesters were equipped with sacking attachments and have since been converted to load directly into a truck with a bulk box conveying or dumping attachment for unloading. Norton et al. (1956) tell of modern equipment types that were first used to any extent in Florida in 1953 and 1954. Bartlett and Huntington (1956) tell of early concepts and present status of potato harvesting in Maine where stones in the soil are the greatest limitation to the satisfactory performance of mechanical harvesters. However, they state that during 1955 several commercial machinery manufacturers had harvesters working successfully in Maine and many growers plan to use the new-type harvester on their crops as soon as their farming operations can be adapted to bulk handling methods. The potato-growing areas of northern California, southern Oregon, and Washington are using commercially manufactured harvesters to good advantage. However, mechanical harvesting has developed slowly in the central California San Joaquin Valley area, primarily owing to the difficulty of clod separation. Glaves and French (1958) describe certain developments with respect to mechanical potato harvesting, including general harvester design and its evolution, de-vining accessories, clod and stone separation, and transfer into the hauling container. Hopkins (1956) gives the results of an investigation of potato injury during digging and the influence of digger blade and elevator chain design on these injuries. 3. Sweet Potatoes

At present sweet potatoes are harvested with some type of plow or digging blade that lifts them from the ground. This is followed by hand picking. Park et aZ. (1953) give an extensive account of machinery for growing and harvesting sweet potatoes. Although equipment has been improved in recent years, complete mechanical harvesting without excessive bruising is not possible at present.

216

T. W. EDMINSTER AND H. F. MILLER, JR.

4. Sugar Beets A resume of sixteen years of research in sugar beet mechanization is given by Walker (1948). He explains that in 1942 there were four companies with experimental machines in the field and in 1947 approximately 4000 harvesters were used to harvest 30 per cent of the United States crop. In 1958 approximately 20,000 harvesters gathered essentially 100 per cent of the crop. Barmington and McBirney (1952) describe sugar beet mechanization in Colorado, while Armer (1953) describes the development of a harvester for Ireland's sugar beets, Bainer et al. (1955) describe the principles used in topping, gaging, cutting, lifting, and loading sugar beets with presentday machines. Several different principles of harvesting are in use. One is in-place topping followed by two rotating converging wheels that loosen and lift the beets; another method lifts the untopped beets by means of a spiked wheel and the tops are cut by two rotating disks just before they are placed in the carrying container. 5. Table Beets, Carrots, and Turnips Mahoney (1953) and Boswell (1953) discuss the necessity and progress of mechanizing such crops as red beets, carrots, and other vegetable crops. The first mechanical harvesters for these crops were developed for vegetables used in commercial processing and canning where bruising and cutting is not nearly as serious as when the crop is used for the fresh market. However, in many cases these machines are now being used for harvesting fresh market products. The latest machines dig, top, and load in one operation. Specially designed plow points lift the beets or carrots as guide rods lift the leaves which are firmly engaged between two rubber belts. After the topping mechanism has removed tops which fall onto the ground, the vegetables are conveyed into a side-delivery elevator and thence to a truck or trailer alongside the machine. 6. Onions

Lorenzen (1950) describes the development of an experimental mechanical onion harvester capable of digging, lifting, topping, and sacking the onions in one operation. Under normal field operations the machine handled about 2 acres in a 10-hour day. Since 1950, at least four individuals or small manufacturers have developed and offered onion harvesters for sale. Johnson (1957) describes one harvester which picks up onions after a machine has cut underneath the bulbs so that the tops will dry. The harvester picks the onions up, then a fan blows the tops up

RECENT DEVELOPMENTS IN AGRICULTURAL MACHINERY

217

while the cutter bar clips them from the bulbs. An air blast blows the cut tops onto the field while the bulbs are caught in a box. Onion harvester development has been encouraging, and it can be expected that within the next few years a large percentage of the commercially grown crop will be mechanically harvested.

7. Radishes Small one-row, as well as three- and five-rowmounted radish harvesters have recently been put into use in several of the radish-growing areas. The multiple-row mounted harvester is capable of pulling and topping 10 acres of radishes in a 10-hour day, while traveling at a speed of about 3 miles per hour. It is most commonly adjusted to harvest five rows planted 9 inches apart, although it can be adjusted to different bed widths and numbers of rows per bed. The radishes are pulled by the tops between pairs of moving V-belts and are carried to revolving knives for topping. Conveyors take them to a trailer or truck which moves along-

FIG.11. Radish harvesting is completely mechanized with small one-row or large tractor-mounted machines as shown in this photo. (Courtesy Tawco Pruducts, Inc.)

218

T. W. EDMINSTER AND H. F. MILLER, JR.

side the harvester. The small one-row harvesters are available for operation in small fields and are operated by a person walking behind them. A small gasoline motor powers the unit and a platform is carried on the machine for placing boxes or crates to receive the harvested radishes (Fig. 11 ).

H. TREENUT AND FRUITHARVESTING EQUIPMENT The harvesting of fruit and nuts by hand is a costly operation and much work is being done in an effort to provide harvest aids which will partially mechanize the harvesting operation. For both fruit and nut removal various mechanical shaking methods are being used. In some cases, the product is allowed to fall on the ground where it is picked up mechanically or by hand; in other cases, catching frames are provided for receiving it and conveying into some type of container.

1. Walnut, Pecan, Filbert, and Almond Walnuts are the most completely mechanized of the tree nut crops. Growers of a large percentage of the crop use mechanical shakers to remove the crop from the trees. Special tractor-mounted pickup machines windrow and pick up the walnuts and put them into trailers pulled either beside or behind the harvester. Closely spaced steel fingers act as a brush, raking and throwing the nuts into a drag elevator which in turn dumps them into a screen conveyor. Soil falls through the screen while leaves and trash are blown upward and away by a fan. It is necessary for fields to be prepared to a very smooth surface so that this type of equipment may be used for picking up the nuts. Mechanical shaking devices are becoming more popular each year for pecans although the crop is still practically all picked up by hand. Approximately 35 per cent of the 1958 filbert crop was harvested with some type of mechanical harvesting device. The nuts are allowed to fall when ripe so they will be free of the husks, they are picked up with either a brush or sweeper device, or they are raked into piles by hand and then scooped into a cleaning or sacking machine which is pulled through the orchard. It is estimated that 40 to 45 per cent of the 1958 almond crop was harvested mechanically with new harvesters similar to those used for picking up walnuts. Mechanical shakers are not used extensively for almonds at present because they do not clean the tree without additional poling or knocking. It is estimated that some type of mechanical shaker was used for 5 per cent or less of the almonds harvested in 1958, but shakers will likely be accepted rapidly once they have been sufficiently developed to clean the trees.

RECENT DEVELOPMENTS I N AGRICULTURAL MACHINERY

219

2. Primes niul Figs Prunes are harvested by hand before they fall or from the ground after they fall. A machine which efficiently picks prunes up off the ground has recently been developed by Adrian and associates, U. S. Dept. of Agriculture ( 1958b) (Fig. 13).The machine is self-propelled similar to a lawn mower and is operated by one man. It is approximately 20 inches

FIG.12. Experimental prune harvester picks prunes from ground after they have been shaken from the tree. Adaptations of this principle are being used for machines to pick up other tree fruit and nut crops. (Courtesy of Agricultural Research Service, USDA.)

wide and will pick up approximately 1000 pounds of prunes per hour. Two small rollers rotate to pass objects between them as the machine moves over the ground. The fallen fruit is pulled into the space between the two rollers and passed back between two conveyor belts that carry the prunes to a box at the rear of the machine. For most efficient operation, the orchard ground must be level and free of stones, broken branches, and other debris. It is expected that a considerable number of machines

220

T. W. EDMINSTER A N D H. F. MILLER, JR.

using this principle will be in commercial manufacture and available for prune growers during 1959. Experimental results in picking figs up off the ground by use of the same type of equipment as described above for prunes are encouraging. It is quite possible that the same type of machine can be adapted for efficiently picking up figs. 3. Grapes Lamouria et al. (1958)report on the development of an experimental grape-harvesting machine that not only reduces hand-labor requirements but approaches hand-picking efficiency, provided the vines are trained so that the clusters of grapes hang uniformly underneath the wires holding them. The machine, mounted on a four-wheel tractor, clips the bunches of grapes with a moving knife and loads them into a trailer pulled by another tractor between the adjoining grape rows. The performance of the harvester during 1957 trials proved that it was capable of commercial harvests provided the vines are properly trained; however, it is expected that several years will be required for properly training vines. 4. Fruit Harvest Aids Lamouria et al. (1957) describe exploratory trials to evaluate the feasibility of shaking peaches and Bartlett pears onto a catching frame. Over 75 per cent of the peaches shaken onto a frame were free of visible injury, while at two other locations approximately 79 and 59 per cent of mechanically harvested pears were free from visible injury. Measurements show that more fruit was damaged in the fall through the tree than was injured in falling onto and then over the catching-handling apparatus. Tests showed that the taller the trees, the more the injury that can be expected from the fruit falling through the various branches and onto the catching container. Adrian and Fridley (1958) report on the effects of frequency and stroke of mechanical shakers on fruit removal and power requirements, as analyzed in a study of reciprocating-type shakers. The force and power requirement tests were carried out with the use of an oscilloscope and strain gages. Fruit removal was found to be affected primarily by four variables: ( 1) the frequency of the shake; (2 ) the length of stroke; (3) the force ( F ) required to remove the fruit divided by the weight ( W ) of the fruit ( F / W ) ; and ( 4 ) the number of fruit-bearing branches in any given tree. A number of years of observation will be needed before final judgment on possible tree damage caused by shaking can be made. Adrian and Fridley further states that visual observations made in these studies

RECENT DEVELOPMENTS I N AGRICULTURAL MACHINERY

221

indicate that boom shakers may cause less tree damage than cable shakers. Hill and Brazelton (1955)have developed a machine called the “steel squirrel” which makes it possible for one man to do one and one-half to two times as much work in the orchard operations which require ladders. The machine is operated with an air-cooled, gasoline engine which also runs an air compressor. The compressed air is used to operate pneumatic tools and a lift cylinder. All controls are mounted to enable the operator to maneuver the machine by hand- or foot-operated controls so that both hands are left free to work. Other machines somewhat similar to the one described have recently been developed and placed on the market. This type of machine is becoming quite popular for pruning and thinning work, but has not been used to any large extent for picking. The cost of such machines at present is too high for use by one person in the picking operation. It is also difEcult to maneuver such machines in apple orchards and for similar crops where props are needed to hold up the limbs until the fruit is removed. Gaston and Levin (1953) made time and motion studies of apple picking to determine the possibilities of mechanizing harvesting operations. They studied existing equipment, such as mobile platform, mobile ladders, hydraulic booms, and picking tubes. They concluded that it is unlikely that apple picking will be completely mechanized in the near future, but that apple picking could be made easier and per-man production could be increased by the use of mechanical aids which would carry the weight of the harvested fruit and transfer it to the ground automatically. Gaston and Levin (1956)further studied and helped develop equipment for handling apples in bulk boxes, Their studies indicated that if an extensive amount of bruising is to be avoided, considerable care must be taken in filling and emptying bulk boxes. However, actual counts showed that the amount of bruising that occurred when bulk boxes were filled does not exceed that which occurred when field crates were used. Levin and Gaston (1958)describe in detail the equipment used by deciduousfruit growers in handling bulk boxes. They estimate that in 1957 over 4 million bushels of fruit were moved in bulk boxes in the United States. This was a considerable increase over previous years and indications are that this trend will continue. McBirney (1957)reports that the use for bulk harvesting and handling of apples for the fresh-fruit market is a new development in the Pacific Northwest. He stated that approximately 750,000 bushels of apples and 2000 bushels of pears were harvested in the

222

T. W. EDMINSTER AND H. F. MILLER, JR.

bulk bins in the Pacific Northwest in 1957. Considerable research work is being carried on in the Northwest by private and public research agencies in studying suitable bin sizes, height, capacities, types, designs, and materials, and the merits of each. Levin and Gaston (1956) developed a method of handling red cherries in water from the orchard to the processing plant. Their studies show that handling red cherries in water from the time they are harvested in the orchard until they reached the processing plant helps to maintain the quality, provides a means of improving grade by orchard sorting, reduces cost of handling, eliminates lugs and lug storage (as well as maintenance, distribution, and accounting problems connected with lugs ) , simplifies management, and is commercially feasible. In 1958, almost all the red cherry crop in Michigan was handled and transported from the orchard to the processing plant in water. Gaston and Levin (1957) developed a ventilated picking lug for strawberries. The new lug is used both for picking and transportation to the processing plant. The term “ventilated is used because the sides are lower than the ends thereby permitting air to move freely through the stack of lugs. The container is fitted with a metal handle which is easily removed and makes it possible for the picker to use the container in much the same way as the older type. Gaston et al. (1958) also developed a detachable lug carrier for harvesting raspberries to be processed. The lug is similar to that described above for use in picking strawberries, but the carrier is different in that it consists of a metal frame made from %-inch iron rod that holds the lug approximately 10 inches off the ground and at the same time provides a means of carrying it. Unpublished data further indicate that Levin, Gaston, and Hedden have made progress in blueberry harvesting by the development of a self-propelled catching frame and the use of a specially designed shaking device attached to an electric drill for removal of the blueberries which fall onto the catching frame before being further delivered into boxes at the end of the frame. This development may soon further revolutionize the harvesting of this crop so that considerable reduction in harvesting costs is realized. U.S. Department of Agriculture ( 1959) report that Adrian and Fridley in cooperation with a commercial manufacturer have developed a new self-propelled catching conveyor which will soon be available for the harvesting of such fruit as prunes, plums, and other small tree fruits where it is not desirable to shake the fruit onto the ground. With three men operating a pair of the self-propelled catcher-conveyors and a tractormounted tree shaker, it will be possible to harvest 30 to 50 trees in an

RECENT DEVELOPMENTS I N AGRICULTURAL MACHINERY

223

hour. Each catcher-conveyor is 18 feet long, with a 6-foot wide conveyor belt the length of the machine. In addition, it has a 4-foot tilted but flexible flap on one side and a 1%-foot-wideflap on the other cut in the center so as to fit halfway around a tree, With two catcher-conveyors in use, the short treeside flaps would be adjusted so as to lap over the treeside flaps of the other catcher-conveyor. As the fruit falls, the 6-foot belt carries the fruit to one end of the machine into bulk boxes. Additional personnel are required to remove full containers and place empty ones on the rack as the units move from tree to tree.

I. MISCELLANEOUS CROPHARVESTING EQUIPMENT

1. Sugar cane Although the sugar cane harvesting method used at present in Louisiana is mechanized, it is not accomplished in a once-over cutting and loading operation. The present harvesters cut the cane at the ground, remove the tops and lay the cane back on the ground in windrows. The dry leaves are burned from the cane in the windrow, after which it is picked up by tractor-mounted grab forks and loaded into trailers for delivery either to the mill or a central loading point. Ramp (1956) reports on the development of an experimental sugar cane harvester for Louisiana. The machine is a once-over type harvester consisting of gathering, cutting, topping, stripping, and loading attachments mounted on a four-wheel chassis which pulls the trailer behind for receiving the harvested cane. The machine has both a lower and upper stripping device made of revolving cylinders with rubber stripping fingers which remove all of the dry leaves and most of the green leaves from the cane. The machine is provided with a cable and winch-type trailer hitch which makes the unhitching and hitching of trailers to the harvester simple and quick. Unpublished 1958 test results from the experimental harvest show that the ground loss is less than 5 per cent, depending upon the condition of the cane and the extent of cane borer damage. The average trash content of the cane after harvesting varies between 2 and 6 per cent, depending upon such factors as variety and condition of the cane and the speed at which the machine and stripper finger mechanism are operated. Field machinery for cutting, bulk loading, and hauling of sugar cane in Hawaii is described pictorially in Anonymous ( 1956b). Duncan ( 1950) describes the development of an experimental harvester for Hawaii consisting of a machine for cutting the entire cane stalks at the ground level and loading them into transport equipment.

224

T. W. EDMINSTER AND H. F. MILLER, JR.

2. Tobacco

Production of flue-cured tobacco is just over 1 million acres. Most recent harvest-aid machine developments for tobacco vary all the way from very small one-man operated machines to large machines which carry several workers. The tobacco is primed by workers riding on the lower part of machines and is elevated by endless conveyors to the upper part of the carrier, where it is speared and placed in racks until unloaded at the end of the rows or curing shed. Winn and Burkhardt ( 1054) describe a two-man harvesting and spearing machine, operated by a foot control, with one man priming and a second man operating the spearing machine. Wilson (1056a)reports on studies comparing different types of mechanical priming devices. A careful analysis was made of the operations involved in leaf selection and removal, damage to the leaves, and the handling of leaves after priming, Wilson concludes that the design of a machine should be based upon its weekly capacity for each acre, as each acre must be harvested weekly for up to 6 weeks. A machine capable of harvesting 3 acres per day (one barn of tobacco) could handle approximately 18 acres per year. It is conceivable that a machine of this capacity could be used cooperatively by more than one grower, according to Wilson. Development work on a completely mechanical tobacco harvester is known to be in progress by at least one university.

3. Castor Beans A r m s and Hurlbut (1052) and Schroeder and Reed (1952)describe early models of experimental castor bean harvesters. Schoenleber et aZ. ( 1057) describe the development of a two-row, tractor-mounted, complete combine-type castor bean harvester which gathers, hulls, and places the beans in a bin provided for dumping them into truck transport at the end of the rows. Field tests during 1956 in dwarf castor beans yielding 2700 pounds per acre and ranging in height from 30 to 48 inches resulted in the machine having less than 5 per cent harvesting loss when traveling at a speed at 25 miles per hour. Coppock and Schoenleber (1057) describe the development of a castor bean harvester for California in cooperation with growers and industry, using basic principles described above but designed to harvest beans 10 to 15 feet tall, a height often attained with present varieties under Western irrigated conditions. The machine harvested beans yielding 3000 pounds per acre at a speed of 2% miles per hour. The main new

RECENT DEVELOPMENTS IN AGRICULTURAL MACHINERY

225

features of the Schoenleber and Coppock machines are oscillating brush seals at the lower part of the gathering device which prevent seed loss, rotating knockers which hit the plant and knock the beans from the stalks, and the huller which removes the hulls from beans before placing them into the bin. Commercial machines patterned after the SchoenleberCoppock design were used to harvest approximately 25,000 acres of castor beans in the United States in 1958. 4. Tung

Kilby and Jezek (1957) describe the development of harvesting principles used experimentally to harvest tung nuts. The machine being tested at present consists of a rotating brush-type windrower which places the nuts in a windrow which is straddled by the tractor. A pickup device, pulled behind the tractor, using steel fingers operating on an endless flexible metal belt, picks the nuts up from the windrow, a fan separates some of the foreign matter, and conveyors deposit the nuts into the trailer pulled behind the harvester. One of the main obstacles encountered in mechanizing the harvest of this crop has been the difficulty of smoothing the ground in presently established orchards and the large amount of dead stems, leaves, and trash which are gathered with the nuts. Nuts harvested in this manner generally contain too much moisture, particularly during a wet season, and must be dried, which further complicates the harvest problem. 5. Kenaf Whittemore and Cocke (1954) tell of the mechanization of kenaf, a plant which produces fiber that can be used as a substitute for jute. Although there is no commercial kenaf production in the United States at this time, considerable work has been conducted toward mechanization of this crop. Byrom (1958) describes the development of a kenaf harvesting machine known as a harvester-ribboner which cuts the tall kenaf plants and passes them through a decorticating device mounted on the harvester. The decorticator removes all of the extraneous matter from the stalks, leaving the long kenaf ribbons which are loaded onto a trailer and taken to the processing plant.

6. Fiber Flax Pulling machines for harvesting fiber flax are described by Harmond and Klein (1955). Several different foreign makes are described as well as the self-propelled push-type puller which was developed on the U. S. Department of Agriculture project in cooperation with Oregon.

226

T. W. EDMINSTER AND H. F. MILLER, JR.

VII. Conclusions

With the tremendous improvement, modernization, and development of agricultural machinery in recent years, it is obviously impossible to explore all of the changes that have taken place. It is equally impossible to present more than an introduction to the major trends that are discussed. The details of each new development must be found in the literature citations and through more intensive study of specific phases of agricultural progress. It should be recognized, however, that each new development and improvement in modern farm equipment is the result of joint contributions from many disciplines, This progress could not have been achieved without the rapid advances in metallurgy and bearing design, or the many improvements in hydraulic controls and electrical devices. New concepts in the fields of basic plant science from the standpoint of plant breeding, plant physiology, fertilization requirements, and over-all management needs have provided other clues and guides in the machine development process. The future holds much promise! The continued need for increased farm efficiency provides the stimulus for new developments. Automation, now reflected in new tractor torque converters and transmissions, the bale ejector-loader, the photoelectric thinners, and the electronic cultivator guides, will provide a whole new realm for machine development. The combining or “unitizing” of equipment and operations, well exemplified by planters that prepare the final seedbed, apply insecticides, fungicides, herbicides, fertilizers, and plant seeds all in one pass over the field, will become increasingly important. The reduction of seasonal peak labor loads through use of larger and more efficient tillage, planting, and harvesting equipment is inevitable. Machines will be developed to replace the high hand-labor requirements of many specialty crops just as the mechanical cucumber harvester replaced forty pickers on one farm. Farmers, engineers, and agricultural scientists alike have an unlimited challenge in the field of continued agricultural mechanization.

REFERENCES Aasheim, T. S. 1949.Montana Agr. Expt. Sta. Bull. 468. Adrian, P. A., and Fridley, R. B. 1958. California Agr. 12, 3, 15. Akesson, N. B., and Harvey, W. A. 1948.California Agr. Expt. Sta. C ~ T C 389. . Aldrich, S . R. 1956. What’s New in Crops and Soils 9, 3.

RECENT DEVELOPMENTS IN AGRICULTURAL MACHINERY

227

Aldrich, S. R., and Musgrave, R. B. 1955. New York Agr. Expt. Sta. Agron, Mimeo. 951.

Anonymous. 1950. Texas Agr. Expt. Sta. Bull.

727;

Oklahoma Agr. Expt. Sta. Bull.

6-361.

Anonymous. 1956a. Engineering 182,316. Anonymous. 1956b. Hawaiian Sugar Planters’ Assoc. Engr. Bull. 73. Anonymous. 1956~.“Texas A & M College System Handbook on Aerial Application in Agriculture.” College Station, Texas. Anonymous. 1958. Ann. Rept. The Aviation Industry of N e w Zealand, Inc., Wellington, N e w Zealand. Armer, A. A. 1953. Agr. Eng. 34,312,314. Arms, M. F., and Hurlbut, L. W. 1952. Agr. Eng. 33,784-786. Arya, S. V., and Pickard, G.E. 1958. Agr. Eng. 39, 16, 19,23. Autry, J. W., and Schroeder, E. W. 1953. Agr. Eng. 34,525,527,531. Baggette, T. L. 1949. Agr. Eng. 30,489,495. Bainer, R., Kepner, R. A., and Barger, E. L. 1955. “Principles of Farm Machinery.” Wiley, New York and Chapman and Hall, London. Barmington, R. D., and McBirney, S. W. 1952. Colorado Agr. Expt. Sta. Bull. 420-A. Bartlett, H. D., and Huntington, D. H. 1956. Maine Agr. Expt. Sta. Bull. 549. Baugh, E. R., Hickock, R. B., Kohnke, H., and Mayer, I. D. 1950. Agr. Eng. 31, 399. Been, W. G. 1957. Market Growers J. 06, 17. Bigsby, F. W. 1958. Am. SOC. Agr. Engr. Mimeo. Paper. 58-61. Black, D. T. 1956. U. S. Dept. Agr. ARS 42-6. Black, D. T., Ditman, L. P., and Burkhardt, G. J. 1954. U. S. Dept. Agr. Circ. 946. Bockhop, C. W., and Barnes, K. K. 1955. Agr. Eng. 36, 453-457. Boswell, V. R. 1953. Am. Vegetable Grower 1, 7, 20. Brittain, R. W., Brazee, R. D., and Carleton, W. M. 1955. Agr. Eng. 36, 319320, 323. Brodell, A. P., Strickler, P. W., and Pittman, D. D. 1952. U. S. Dept. Agr. Bur. Agr. Econ. Pub. FM91. Brown, R. T. 1957. Agr. Eng. 38, 804-805. Browning, G.M. 1950. Agr. Eng. 31, 341344. Buchele, W. F., Collins, E. V., and Lovely, W. G. 1955a. Agr. Eng. 36, 324-329, 331. Buchele, W. F., Collins. E. V., and Lovely, W. G. 195%. Iowa Farm Sci. 9, 3-5. Buhr, A. G. 1955. Agr. Eng. 36, 649, 650, 653. Bunnelle, P. R., Jones, L. G., and Goss, J. R. 1954. Agr. Eng. 35, 554-558. Burgesser, F. W. 1950. Proc. 6th Meeting Am. SOC. Sugar Beet Technologists pp. 79-84.

Burrough, D. E., and Graham, J. A. 1954. Agr. Eng. 35, 221-229, 232. Butt, J. L., Kelley, W. B., Martin, C. M., and Smith, L. A. 1956. Alabama Agr. Expt. Sta. L e a f i t 49. Byrom, M. H. 1958. Proc. Kenaf Conf. Hauana, Cuba. Carreker, J. R. 1950. Agr. Eng. 31, 445-447. Chamberlin, J. C., Getzendaner, C. W., Hessig. H. H., and Young, V. D. 1955. U.S. Dept. Agr. Tech. Bull. 1110. Chepil, W. S., and Woodruff, N. P. 1955. Kansas Agr. Expt. Sta. Circ. 318. Chisholm, J. A. 1955. Market Growers 1. 84, 8. Clyde, A. W. 1956. Agr. Eng. 37, 173-176. Collins, E. V. 1951. Agr. Eng. 32, 216-217. Colwick, R. F. 1955. Cotton Gin 6 Oil Mill Press 56, 11-12. Colwick, R. F., and Regional Technical Committee Members. 1953. Southern Coop. Ser. Bull. 33.

228

T. W. EDMINSTER AND H. F. MILLER, JR.

Cook, R. L., and Peikert, F. W. 1950. Agr. Eng. 31, 211-214. Cook, R. L., Turk, L. M., and McColly, H. F. 1953. Soil Sci. SOC.Am. Proc. 17, 410414.

Cooper, A. W., Vanden Berg, G. E., McCoUy, H. F., and Erickson, A. E. 1957. Agr. Eng. 30,232-235. Coppock, G. E., and Schoenleber, L. G. 1957. U.S. Dept. Agr. ARS 42-8. Corley, T. E., Stokes, C. M., and Kummer, F. A. 1955. Highlights Agr. Research Alabama Polytechnic Inst. 2, 1. Cykler, J. F. 1950. Agr. Eng. 31,78-77,79. Dobie, J. B. 1959. Agr. Eng. 40,78-77,92-93. Dudley, R. F., and Wise, L. N. 1953. Mlsstssippi Agr. Expt. Sta. Bull. 505. Duke, G. B. 1957. U.S . Dept. Agr. ARS 42-1 1. Duley, F. L. 1948. U.S. Dept. Agr. Farmers’ Bull. 1997. Duley, F. L. 1954. Nebraska Agr. Ext. Seru. Ext. Circ. EC 54-100. Duncan, R. A. 1950. Agr. Eng. 31, 85-88, 70. Elfes, L. E. 1954. Agr. Eng. 35, 147-153. Fairbank, J. P., and Smith, K. 0. 1950. Agr. Eng. 31, 219-222. Fairbanks, G. E. 1951. Karwm Engr. Expi?. Sta. Bull. 66. Farnham, S. E. 1958. Ind. Lab. 9, 5758, 80. Farrow, R. 1958. Market Growers 1. 05, 33. Free, G. R. 1953. Soil Sd.SOC.Am. Proc. 17,185-170. Futral, J. G., and Allen, R. L. 1951. Agr. Eng. 32, 215-218. Gantt, C. W., Jr. 1958. Agr. Eng. 37, 537439, 542. Gantt, C. W., Jr., Hulburt, W. C., and Bowen, H. D. 1958. U.S. Dept. Agr. Farmers’ Bull. 2096. Gaston, H. P., and Levin, J. H. 1953. Michigun Agr. Expt. Sta. Quart. Bull. 36, 18-23.

Gaston, H. P., and Levin, J. H. 1958. Michigan Agr. Expt. Sta. Bull. 409. Gaston, H. P., and Levin, J. H. 1957. Michigan Agr. Expt. Sta. Quart. Bull. 558.

39, 548-

Gaston, H. P., Levin, J. H., and Hedden, S . L. 1958. Michigan Agr. Expt. Sta. Quart. Bull. 41,118-121. Giles, G. W., and Routh, C. A. 1951. Agr. Eng. 32, 537440, 544. Glaves, A. H., and French, G. W. 1958. Potato Handbook 3,5348. Goss, J. R., Bainer, R., Curley, R. G., and Smeltzer, D. G. 1955. Agr. Eng. 36, 794-796.

Gray, R. B. 1954. “Development of the Agricultural Tractor in the U. S.,” Pt. I. Am. SOC. Agr. Engr., St. Joseph, Michigan. Gray, R. B. 1955. U.S. Dept. Agr. Farmers’ Bull. 1761. Gray, R. B. 1958. “Development of the Agricultural Tractor in the U. S.,” Pt. 11. Am. SOC.Agr. Engr., St. Joseph, Michigan. Gray, R. B., and Dieffenbach, E. M. 1957. Agr. Eng. 30, 388-397. Guelle, C. E. 1954. Agr. Eng. 35, 185-187. Gunn, J. T., and Tramontini, V. N. 1955. Agr. Eng. 36, 725-729. Hall, B. J. 1958. Am. Vegetable Grower 4,24-25. Hansen, C. M., 1958. Agr. Eng. 39, 548551. Hansen, C. M., Robertson, L. S., and Grigsby, B. H. 1958. Michigan Agr. Erpt. Sta. Quart. Bull. 40,549-554. Harmond, J. E., and Klein, L. M. 1955. U.S. Dept. Agr. C ~ T C955. . Harrison, G. J. 1951. Agr. Eng. 32, 488-488, 492.

RECENT DEVELOPMENTS IN AGRICULTURAL MACHINERY

229

Harrold, L. L., and Dreibelbis, F. R. 1950. Agr. Eng. 31,393-397. Hays, 0.E., and Taylor, R. E. 1958. U. S. Dept. Agr. Farmers’ Bull. 2116. Hedman, C. L., and Turner, J. R. 1954. Agr. Eng. 35,801-803. Heitshu, D. C. 1952. Agr. Eng. 33,343-346. Heitshu, D. C. 1956a. Agr. Eng. 37,182183,187. Heitshu, D. C. 1956b. Soybean Dig. 16,5042. Hill, F. L., and Brazelton, R. W. 1955. Agr. Eng. 36, 17-19. Hofmeister, H. J. 1955. Mayland Agr. Expt. Sta. Misc. Publ. 224. Holmes, L. J. 1950. Proc. 6th Meeting Am. SOC. Sugar Beet Technologists pp. 249254. Hopkins, R. B. 1956. Agr. Eng. 37,109-111. Howe, R. S., Jr., and Raley, G. H. 1958. Agr. Eng. 39, 152-155,171. Howell, W. C., and Jones, T. N. 1954. Mississippi Agr. Expt. Sta. Inform. Sheet 501. Hudspeth, E. B., and Jones, D. L. 1954. Texas Agr. Expt. Sta. PrOgT. Rept. 1673. Hulburt, W . C. 1956. PTOC.Am. Assoc. Aduance. Sci. Sect. 0. Hulburt, W. C., and Menzel, R. G. 1953. Agr. Eng. 34,702-704,706,708. Hurlbut, L. W. 1955. Agr. Eng. 36,791-792. Isler, D. A., and Thornton, D. G. 1955. Agr. Eng. 36, 600-601,604. Jacks, G. V., Brind, W. D.,and Smith, P. 1955. Commonwealth BUT. Soil S C ~ . (Gt. Brit. ) Tech. Commun. 49. Johnson, W. B. 1957. Market Growers I. 86,28-29. Johnson, W. H. 1955. Ohio Farm and Home Research 40,40-42,49. Jones, J. N., Jr,, Lillard, J. H., and Hines, R. C., Jr. 1951. Agr. Eng. 32,417419. Kepner, R. A. 1957. California Agr. 11,4-6, 13-14,20. Kilby, W. W., and Jezek, R. E. 1957. Mksissfppi Agr. Expt. Sta. Bull. 548. King, R. W., and Elliott, B. G. 1955. Agr. Eng. 36,235-238,241. Klein, L. M., and Harmond, J. E. 1959. U. S . Dept Agr. ARS 42-24. hall, J. L. 1951. Montana Agr. Expt. Sta. Circ. 194. hall, J. L., Power, J. F., and Massee, T. W. 1958. Montana Agr. Ezpt. Sta. BuU. 540. Kramer, R. W. 1955. Agr. Eng. 36,587590. Kromer, 0.W. 1949. Agr. Eng. 30,524527. Kubik, B. M. 1957. Am. Vegetable Grower 12,27-29. Lamouria, L. H., Harris, R. W., Abernathy, H. H., and Leonard, S. H. 1957. CaZif~rraiaAgr. 1 1,ll-12, 14. Lamouria, L. H., Winkler, A. J., Abernathy, G. H., and Kaupke, C. E. 1958. Agr. Eng. 39,218-221,286. Levin, J. H., and Gaston, H. P. 1956. U. S . Dept. Agr. C ~ T C 981. . Levin, J. H., and Gaston, H. P. 1958. U. S. Dept. Agr. ARS 42-20. Liljedahl, J. B., Carleton, W. M., and Kinch, D. M. 1956. Agr. Eng. 37, 550-552, 554. Lillard, J. H., Moody, J. E., and Edminster, T. W. 1950. Agr. Eng. 31,395. Lorenzen, C.. Jr. 1950. Agr. Eng. 31, 13-15. Lorenzen, C., Jr. 1956. Am. Vegetable Grower 4,20. Lovely, W . G. 1956. PTOC.loth Hybrid Corn I d . Research Conf. Iowa, pp. 59-67; Iowa Agr. Expt. Sta. 1. Paper 2055. McBirney, S. W. 1957. Proc. Washington State Hot?. Assoc. 53,139-143. McCalla, T. M. 1958.1. Soil and Water Comeru. 13,255-258. McColly, H. F. 1957. Agr. Eng. 38,398404. McColly, H. F. 1958. Tram. Agr. Eng. 1,68-71, 75. McCreery, W. F., and Nichols, M. L. 1956. Agr. Eng. 37,808-812.

230

T. W. EDMINSTER AND H. F. MILLER, JR.

McKibben, E. G. 1953.Agr. Eng. 34,91-93. Mahoney, C.H.1953.Am. Vegetabk Grower 1,15. Martin, J. W., and Humphrey, E. N. 1951.Idaho Agr. Expt. Sta. Bull. 283. Maughan, G. L., Wood, G. M., and Chittey, E. T. 1959. J. Agr. Eng. Research 4, 30-35. Melsted, S. W. 1954.Aduances in Agron. 6, 121-142. Merrill, R. M. 1956.Plant Food Reu. 2,4-7. Miller, H. F.,Jr. 1955a.Cotton Trade J. ( 1955-56) Intern. Yearbook 36,5657. Miller, H. F.,Jr. 195513.Cotton Gin G Oil Mill Press 56,56-59. Miller, J. B. 1957.Market Growers J. 86, 16. Mills, W. T.,and Dickens, J. W. 1958. North Carolina Agr. Expt. Sta. Bull. 405. Mohsenin, H., Womochel, H. L., Harvey, D. J., and Carleton, W. M. 1956.Agr. Eng. 37,815820. Moody, J. E., Lillard, J. H., and Edniinster, T. W. 1952. Soil. Sci. SOC.Am. Proc. 16, 190-194. Moore, R. P. 1957.Soybean Dig. 17,1616. Morrison, C. S. 1955.Agr. Eng. 36,796-799. Musgrave, R. B., Zwerman, P. J., and Aldrich, S. R. 1955. Agr. Eng. 36, 593-594. Nichols, M. L., and Reaves, C. A. 1955.Agr. Eng. 36,517-520. Nichols, M. L., and Reaves, C. A. 1958.Agr. Eng. 39,340443. Nichols, M. L., Reed, I. F., and Reaves, C. A. 1958.Agr. Eng. 39,336-339. Norton, J. S., Greene, R. E. L., and Kushman, L. J. 1956. Florida Agr. Ex@. Sta. Bull. 579. Nutt, G. B. 1950a.Agr. Eng. 31,391-392. Nutt, G. B. 1950b.Agr. Eng. 31,443-444. Oates, W. J., Witt, R. H., and Wood, W. S. 1952.Agr. Eng. 33, 135-136,142. Page, G.E.1952.Oregon Agr. Ezpt. Sta. Bull. 493. Park, J. K., and Webb, B. K. 1958.South Carolina Agr. Expt. Sta. Bull. 461. Park, J. K., Powers, M. R., and Garrison, 0. B. 1953. South Carolina Agr. Expt. Sta. Bull. 404. Peterson, A. E. 1955.Plant Food Reu. 1,1617,30,31. Peterson, A. E.,Gerge, 0. K., Murdock, S T., Peterson, D. R. 1958. Wisconsin Ext. Seru. Circ. 559. Pickard, G. E. 1955.Agr. Eng. 36,792-794. Pool, S. D.1956.Agr. Eng. 37,245-248. Porterfield, J. G., Schroeder, E. W., and Smith, E. M. 1954. Oklahoma Agr. Expt. Sta. Tech. Bull. TbO. Powers, M. R. 1949.Agr. Eng. 30,496. Poynor, R. R. 1950.Agr. Eng. 31,509510. Ramp, R. M. 1956.Agr. Eng. 37,821-824. Ramser, J. H.,and Kleis, R. W. 1952.Illinois Ext. Sera Circ. 693. Rea, H. E.1954.Texas Agr. Erpt. Sta. Progr. Rep. 1691. Reed, I. F.,and Gordon, E. D. 1951.Agr. Eng. 32,98-100. Reed, I. F.,and McCreery, W.F. 1954.Agr. Eng. 35,91-94,97. Richardson, R. D. 1958.J. Agr. Eng. Research 3,299323. Richey, C. B., O’Donnell, J. F., Ashton, J. T., and Groves, R. J. 1956. Agr. Eng. 37, 93-97. Ryerson, G. E. 1950.Agr. Eng. 31,506-508,510. Sack, W. 1951.Agr. Eng. 32,159-160. Schaller, F. W.,and Evans, D. D. 1954.Agr. Eng. 35,731-734,736.

RECENT DEVELOPMENT IN AGRICULTURAL MACHINERY

231

Schoenleber, L. G., Bouse, F., and Coppock, G. E. 1957. Oklahoma Agr. Expt. Sta. Bull. B-489. Schroeder, E. W., and Reed, I. F. 1952. Agr. Eng. 33,775-776,779. Scoville, 0. J. 1956. Proc. U.S. Dept. Agr. Conf. Field Shelling and Drying of Corn, pp. Rl-R2. Scranton, C. J . 1952. Agr. Eng. 33, 140-142, Smith, H. P. 1955. “Farm Machinery and Equipment,” 4th ed. McGraw-Hill, New York. Southwell, P. H. 1951. World Crops 3,464-468. Stanton, H. S. 1954. Arkansas Farm Research 3. [8]. Stanton, H. S., and Tavernetti, J. R. 1956. Proc. Western and California W e e d Control Conf. pp. 140-145. Strickler, P. W., and Phillips, H. C. 1956. U.S. Dept. Agr. ARS 43-27. Tanquary, E. W. 1957. Agr. Eng. 38,606-609. Tanquary, E. W., and Clyde, A. W. 1957. Agr. Eng. 38,88-93. Tavernetti, J. R., and Miller, H. F., Jr. 1954. California Agr. Expt. Sta. Bull. 747. Teter, N . C., and Givens, R. L. 1957. U . S. Dept. Agr. ARS 42-12. Thompson, J. L., and Kemp, J. G. 1958. Agr. Eng. 39,285-287. U . S . Dept. Agr. 1935a. U.S . Dept. Agr. Inform. Bur. Agr. Eng. Ser. 48. U. S . Dept. Agr. 1935b. U . S. Dept. Agr. Inform. Bur. Agr. Eng. Ser. 52. U . S . Dept. Agr. 1935c. U . S. Dept. Agr. Inform. Bur. Agr. Eng. Ser. 53. U . S . Dept. Agr. 1935d. U . S. Dept. Agr. Inform. Bur. Agr. Eng. Ser. 70. U. S.Dept. Agr. 1949a. U.S . Dept. Agr. Inform. Bur. Agr. Eng. Ser. 73. U . S. Dept. Agr. 1949b. U.S. Dept. Agr. Inform. Bur. Agr. Eng. Ser. 74. U. S . Dept. Agr. 1954. U.S. Dept. Agr. Farmers’ BuU. 2062. U . S. Dept. Agr. 1956a. U . S. Dept. Agr. ARS Spec. Rept. 22-21. U . S. Dept. Agr. 1956b. U. S. Dept. Agr. ARS 22-34. U . S. Dept. Agr. 1958a. U.S. Dept. Agr. Farmers’ Bull. 2118. U . S . Dept. Agr. 1958b. U S. Dept. Agr. Agr. Research 6,14. U. S. Dept. Agr. 1958c. U.S. Dept. Agr. T h e Pesticide Situation fw 195748. U . S. Dept. Agr. 1958d. U . S. Dept. Agr. Library List No. 65. U. S. Dept. Agr. 1959. U . S. Dept. Agr. Agr. Research 7. U . S. Dept. Commerce. 1957. U . S. Dept. Commerce C A A Statistical Handbook of Civil Aviation 42,47-52. Van Doren, C. A., and Hays, 0. E. 1958. U . S. Dept. Agr. Leafkt 435. Wagner, R. E., and Hulburt, W. C. 1953. What’s New I n Crops and Soils 6,8-9. Walker, H . B. 1948. Agr. Eng. 29,425-430. Walker, H. B. 1952. Agr. Eng. 33,698,701,704. Walker, H. B. 1957. Agr. Eng. 38,6584361,676. Weick, F. E. 1952. Agr. Eng. 33.361364. Whittemore, H . C., and Cocke. J. B. 1954. Agr. Eng. 35,488-491. Willard, C. J., Taylor, G. S., and Johnson, W. H. 1956. Ohio Agr. E r p t . Sta. Research Circ. 30. Williamson, E. B. 1955. Cotton Trade 1. (1955-56) Intern. Yearbook 36, 58, 61-62. Williamson, E. B. 19.58. Proc. 12th Ann. Cotton Mechanization Conf., Brownsoilk,

Texas.

Willimisoii, E. B., Wooten, 0. B., and Fulgliain, F. E. 1954. Mississippi Agr. Exlit. Sta. Bull. 515. Wilson, J. D. 1956. Am. Vegetable Grower 4,9, 32-33.

232

T. W. EDMINSTER A M ) € F. I. MILLER, JR.

Wilson, R. W . 1956a. Agr. Eng. 97,407410. Wilson, R. W. 1956b. North Carolina Agr. Expt. Sta. Bull. 397. Winkelblech, C. S. (no date) New York Agr. Engr. Elct. Bull. 331. Winn, P. N., and Burkhardt, G. J. 1954. Mayland Agr. Expt. Sta. Bull. 542. Witzel, H. D., and Vogelaar, B. F. 1955. Agr. Eng. 36,525,528. Woodruff, N. P., and Chepil, W. S. 1956. Agr. Eng. 37,751-754,758. Wooten, 0. B., and Montgomery, R. A. 1956. Mkdssippl Agr. Expt. Sta. Clrc. 204. Work, P. 1958. Am. Vegetubk Grower 6,13-15. Worthington, W. H., and Seiple, J. W. 1952. Agr. Eng. 33,273-276,278. Yeo, R. R. 1955. N e w Mexico Agr. Expt. Stu. BuU. 391. Young, V. D., Chamberlin, J. C., Getzendaner, C. W., and Doenier, C. E. 1957. U.S. Dept. Agr. ARS 42-10. Zingg, A. W., and Whitfield, C. J. 1957. U.S. Dept. Agr. Tech. Bull. 1166.