Modern agriculture is based on highly efficient equipment, especially high-speed, powerful tractors and agricultural machines. Tractors with mounted and trailed implements allow the mechanization of many agricultural operations.

Use of tractors allows farmers to accomplish the main tillage and care of plants in the optimum time without major manual labour. Permanent enlargement of farms, extension of land under cultivation and intensification of crop rotation promotes more efficient agriculture as well. Widespread use of high-speed assemblies is hampered by two factors: existing agricultural methods based mainly on machines and implements with passive tools; and difficulties in ensuring safe working conditions for the high-speed tractor assembly operator.

Mechanization can accomplish approximately 70% of planting and growing operations. It is used at all stages of crop cultivation and harvesting as well. Nevertheless, each stage of planting and growing has its own requisite set of machines, tools and environmental conditions, and this variability of the production and environmental factors has an influence upon the tractor driver.

Cultivation of the Land

Cultivation of the land (ploughing, harrowing, scuffing, disk harrowing, entire cultivation, rolling-down) is important and the most labour-intensive preliminary stage of crop production. These operations involve 30% of planting and growing operations.

As a rule, loosening of the soil results in the formation of dust. The nature of the dust in the air is variable, and depends on meteorological conditions, season, kind of work, type of soil and so on. Dust concentration in tractor cabs can vary from a few mg/m³ to hundreds of mg/m³, depending essentially on the cab enclosure. Approximately 60 to 65% of cases exceed the permissible total dust concentration level; permissible levels of respirable (less than or equal to 5 microns) dust are exceeded 60 to 80% of the time (see figure 1). Silica content in the dust varies from 0.5 to 20% (Kundiev 1983).

Figure 1. Tractor driver exposures to dust during land cultivation

Cultivation consists of power-consuming operations, especially during ploughing, and it demands a considerable mobilization of the power resources of machines, generating considerable levels of noise where tractor drivers sit. These noise levels amount to 86 to 90 dBA and higher, creating a considerable risk of hearing disorders for these workers.

As a rule, whole-body vibration levels where the tractor driver is seated can be very high, exceeding levels established by the International Organization for Standardization (ISO 1985) for fatigue-decreased proficiency boundary and frequently for exposure limit.

Ground preparation is conducted mainly in early spring and autumn, so the microclimate of cabs in temperate zones for machines without air conditioners is not a health problem except on occasional hot days.

Sowing and Growing

Ensuring that sowing attachments or ploughing implements move in a straight line and that tractors follow marker tracks or the middle of the row are characteristic features of the sowing and care of crops.

In general, these activities require the driver to work in uncomfortable positions and involve considerable nervous and emotional tension due to restricted working-zone visibility, resulting in rapid development of operator fatigue.

The layout of sowing machines and their preparation for use, as well as the necessity of manual auxiliary work, especially materials handling, may involve considerable physical loads.

A wide geographical distribution of grain varieties results in a diversity of meteorological conditions when sowing. Winter crop sowing for different climate zones can be performed, for example, when the outdoor temperature ranges from 3–10 °C to 30–35 °C. Spring crop sowings are performed when the outdoor temperature ranges from 0 °C to 15–20 °C. The temperatures in tractor cabs without air conditioners can be very high in regions where climate is mild and hot.

Microclimate conditions in tractor cabs are favourable as a rule during tilled crops sowing (sugar beet, maize, sunflower) in temperate zones. Cultivation of crops is performed when the outdoor temperature is high and solar radiation is intense. The air temperature in cabs without microclimate control can rise to 40 °C and more. Tractor drivers can work under uncomfortable conditions about 40 to 70% of the total time involved in the care of crops.

Working operations for tilled crops cultivation involve considerable moving of earth, causing formation of dust. Maximum ground dust concentrations in the breathing zone air do not exceed 10 to 20 mg/m³. The dust is 90% inorganic, containing a large amount of free silica. Noise and vibration levels where the driver sits are a little lower than those existing during cultivation.

During sowing and cultivation, workers can be exposed to manures, chemical fertilizers and pesticides. When safety regulations for handling these materials are not followed, and if machines are not working properly, the breathing zone concentration of hazardous materials can exceed permissible values.

Harvesting

As a rule, harvesting lasts from 25 to 40 days. Dust, microclimate conditions and noise can be hazards during harvesting.

Breathing zone dust concentrations depend chiefly on outside concentration and the airtightness of the harvesting machine’s cab. Older machines without cabs leave drivers exposed to the dust. Dust formation is most intensive during the harvesting of dry corn, when the dust concentration at non-enclosed combines’ cabs can be as much as 60 to 90 mg/m³. Dust consists mainly of plant scraps, pollen and mushroom spores, mostly in large, nonrespirable particles (larger than 10 microns). Free silica content is less than 5.5%.

Formation of dust during sugar beet harvesting is lower. Maximum dust concentration at the cab does not exceed 30 mg/m³.

Harvesting of grain is generally performed in the hottest season. Temperature in the cab can rise to 36 to 40 °C. The flux level of direct solar radiation is 500 W/m² and more when ordinary glass is used for cab windows. Tinted glass lowers the temperature of air in the cab by 1 to 1.6 °C. A mechanical forced ventilation system with a flow rate of 350 m³/h can create a temperature difference between inside and outside air of 5 to 7 °C. If the combine is equipped with adjustable louvers, this difference drops to 4 to 6 °C.

Tilled crops are harvested in the autumn months. As a rule conditions of the microclimate in cabs in this time are not a great health problem.

Experience in developed countries points to the fact that agriculture at small farms can be profitable with the use of small-scale mechanization (minitractors—motorized units with a capacity of up to 18 horsepower, with different kinds of auxiliary equipment).

Use of such equipment gives rise to a number of specific health problems. These problems include: intensification of workload in certain seasons, the use of child labour and the labour of elderly persons, absence of the means of protection against intensive noise, whole-body and local vibration, harmful meteorological conditions, dust, pesticides, and exhaust gases. The effort necessary to move the control levers of motorized units can amount to 60 to 80 N (newtons).

Some kinds of work are performed with the help of draught animals or done manually due to insufficient equipment or because of the impossibility of using machinery for some reason. Manual labour demands as a rule considerable physical effort. Power requirements during ploughing, horse-drawn sowing and manual mowing can amount to 5,000 to 6,000 cal/day and more.

Injuries are common during manual work, especially among inexperienced workers, and cases of plant burns, insect and reptile stings and dermatitis from the sap of some plants are frequent.

Prevention

One of the main trends in tractor construction is the improvement of working conditions of tractor operators. Side by side with perfection of the design of protective cabs is the search for ways of coordinating technical parameters of various tractor units with the functional abilities of operators. The aim of this research consists of ensuring the effectiveness of control and driving functions as well as necessary ergonomic parameters of the workplace environment.

Effectiveness of control and driving of tractor assemblies is ensured by good visibility of the working zone, by optimizing assemblies and control panel design and by proper ergonomic design of tractor seats.

Common ways of increasing visibility are increasing the viewing area of the cab using panoramic glass, improved layout of auxiliary equipment (e.g., fuel tank), rationalization of seat location, use of rear view mirrors and so on.

Optimization of construction control elements is connected with the construction of the control mechanism’s drive. Along with hydraulic and electric drives, a new improvement is suspended control pedals. This allows improved access and increased driving comfort. Functional coding (by means of form, colour and/or symbolic signs) plays an important part in recognition of the control elements.

Rational layout of instrumentation (which comprises 15 to 20 units in modern tractors) requires taking into account further increases in indicators due to remote control of technological process conditions, automation of the driving and operating of the technological equipment.

The operator’s seat is designed to guarantee a comfortable position and effective driving of the machine and tractor assembly. Design of modern tractor seats takes into account anthropometric data of the human body. Seats have adjustable back and arms and can be adjusted according to the operator’s size, in both horizontal and vertical dimensions (figure 2).

Figure 2. Angle parameters of optimal work posture of a tractor driver

Precautions against harmful working conditions for tractor drivers include means of protection against noise and vibration, microclimate normalization and airtight sealing of cabs.

Besides special engineering of the engine to reduce noise at its source, considerable effect is achieved by mounting the engine on vibration isolators, isolating the cab from the tractor body with the help of shock absorbers and a number of measures designed for absorption of noise in the cab. Flaky, sound-absorbing lagging with a decorative surface is applied for this purpose to cab wall panels, and rugs made of rubber and porolon are laid on the cab floor. Hard perforated panelling with an air gap of 30 to 50 mm is applied to the ceiling. These measures have reduced noise levels in cabs to 80–83 dBA.

The main means of damping low-frequency vibration in the cab is use of an effective seat suspension. Nevertheless, the effect of whole-body vibration damping achieved this way does not exceed 20 to 30%.

Agricultural ground levelling gives considerable opportunities for decreasing vibration.

Improvement of the microclimate conditions in tractor cabs is reached with the help of both standard equipment (e.g., fans with filter elements, thermo-insulating tinted glass, sun-proof cap peaks, adjustable louvers) and special devices (e.g., air conditioners). Modern tractor heating systems are designed as an autonomous assembly attached to the engine’s cooling system and using warmed water to heat the air. Combined air conditioners and air heaters are also available.

Complex solutions of the problem of noise, vibration and heat isolation and sealing of cabs can be reached with the help of sealed cab capsules designed with suspended control pedals and wire rope systems of drives.

Ease of access to tractor engines and assemblies for their maintenance and repairs, as well as obtaining timely information about technical condition of certain units of the assembly, are important indices of the level of tractor operator working conditions. Eliminating the cab bonnet, forward inclination of the cab, detachable panels of the engine’s bonnet and so on are available in certain types of tractors.

In the future, tractor cabs are likely to be equipped with automatic control units, with television screens for observation of implements that are out of the operator’s field of vision and with units for conditioning of microclimate. Cabs will be mounted on outside rotary rods so they can be moved to a required position.

Rational organization of work and rest is of great importance for the prevention of fatigue and diseases of agricultural workers. In the hot season, daily routine ought to provide for working mainly in the morning and evening hours, reserving the hottest time for rest. During exhausting work (moving, hoeing), short regular breaks are necessary. Special attention has to be devoted to the rational, balanced nourishment of workers with due regard for the energy requirements of the tasks. Drinking regularly during the heat is of great importance. As a rule, workers drink traditional beverages (tea, coffee, fruit juices, infusions, broths and so on) in addition to water. Availability of sufficient amounts of wholesome liquids of high quality is very important.

Availability of comfortable overalls and personal protection equipment (PPE) (respirators, hearing protectors), especially during contact with dust and chemicals, is very important as well.

Medical control of the agricultural workers’ health has to be oriented to prevention of common occupational diseases, such as infectious diseases, chemical exposures, injuries, ergonomic problems and so forth. Teaching safe working methods, information about matters of hygiene and sanitation are of great importance.

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The gathering in of agricultural crops upon maturity, or the practice of harvesting, signals the end of the production cycle prior to storage and processing. The size and quality of the crop removed from the field, orchard or vineyard represents the most significant measure of a farmer’s productivity and success. The value that has been placed on the outcome of the harvest is reflected in the terms used almost universally to measure and compare agricultural productivity, such as kilograms per hectare (kg/ha), bales per hectare, bushels per acre (bu/a) and tons per acre or hectare. From an agronomic perspective, it is actually the inputs that determine the yield; however, it is the harvest that becomes the primary determinant of whether or not there will be sufficient seed and resources to ensure the sustainability of the farm and those it supports. Because of the significance of harvest and all of its related activities, this part of the agricultural cycle has taken on an almost spiritual role in the lives of farmers throughout the world.

Few agricultural practices illustrate more clearly the scope and diversity of technology- and work-related hazards found in agricultural production than harvesting. Crop harvesting is carried out under a wide variety of conditions, over various types of terrain, utilizing machines from simple to complex that must handle a diversity of crops; it involves considerable physical effort from the farmer (Snyder and Bobick 1995). For these reasons, any attempt to briefly generalize the characteristics or nature of harvest practices and harvest-related hazards is extremely difficult. Small grains (rice, wheat, barley, oats and so on), for example, which dominate much of the planted cropland in the world, represent not only some of the most highly mechanized crops, but in large regions of Africa and Asia are harvested in a manner that would be familiar to farmers 2,500 years ago. The use of hand sickles to harvest a few stalks at a time, hard-packed clay threshing floors and simple threshing devices remain the primary tools of harvest for far too many producers.

The primary hazards associated with the more labour-intensive harvesting practices have changed little with time and are often overshadowed by the perceived increased risks associated with greater mechanization. Long hours of exposure to the elements, the physical demands resulting from lifting heavy loads, repetitive motion and awkward or stooped posture, along with natural hazards such as poisonous insects and snakes, have historically taken, and continue to take, a significant toll (see figure 1). Harvesting grain or sugar cane with a sickle or machete, picking fruit or vegetables by hand and manually removing peanuts from the vine are dirty, uncomfortable and exhausting tasks that in many communities frequently are completed by large numbers of children and women. One of the strongest motivating forces that has shaped modern harvesting practices has been the desire to remove the physical drudgery associated with manual harvesting.

Figure 1. Hand-harvesting millet

Even if the resources were available to mechanize harvesting and reduce its risks (and for many small farmers in many areas of the world, they are not), investments to improve the safety and health aspects of harvesting would likely have smaller returns than would comparable investments to improve housing, water quality or health care. This is especially true if farmers have access to large numbers of unemployed or underemployed workers. High levels of unemployment and limited job opportunities, for example, place large numbers of younger workers at risk of injury during harvest because they are cheaper to use than machines. Even in many countries with highly mechanized agricultural practices, child labour laws frequently exempt children involved in agricultural activities. For example, special provisions of the US Department of Labor child labour laws continue to exempt children under 16 during harvest and allow them to operate agricultural equipment under certain conditions (DOL 1968).

Contrary to a general perception that greater mechanization in agriculture has increased the risks associated with agricultural production, with respect to harvesting, nothing could be further from the truth. Through the introduction of intensive mechanization in major grain- and forage-producing regions, the amount of time required to produce a bushel of grain, for example, has dropped from over an hour to under a minute (Griffin 1973). This accomplishment, though heavily dependent upon fossil fuels, has released tens of millions of people from the drudgery and unsafe working conditions associated with hand harvesting. Mechanization has resulted in not only tremendous increases in productivity and yields, but also the near elimination of the most historically significant harvest-related injuries, such as those involving livestock.

The intensive mechanization of the harvesting process, however, has introduced new hazards, which have required periods of adjustment and in some cases the replacement of machines with improved practices and designs that were either more productive or less hazardous. An example of this technological evolution was experienced with the transition that took place in corn harvesting in North America between the 1930s and 1970s. Up through the 1930s, the corn crop was almost entirely harvested by hand and transported to on-farm storage sites by horse-drawn wagons. The primary cause of harvest-related injuries was related to working with horses (NSC 1942). With the introduction and widespread use of the mechanical, tractor-drawn corn picker in the 1940s, horse- and livestock-related deaths and injuries rapidly declined during the harvest period, and there was a corresponding growth in the number of corn picker-related injuries. This was not because corn pickers were inherently more dangerous, but because the injuries reflected a rapid transition to a new practice that had not been fully refined and that farmers were unfamiliar with. As farmers adjusted to the technology and manufacturers improved the performance of the corn picker, and as more uniform varieties of corn were planted that were better suited to machine harvesting, the number of deaths and injuries quickly declined. In other words, the introduction of the corn picker ultimately resulted in a decline in harvest- related injuries due to exposure to traditional hazards.

With the introduction in the 1960s of the self-propelled combine, which could harvest higher-yielding corn varieties at rates ten or more times faster than the corn picker, corn picker injuries almost disappeared. But, once again, as with the corn picker, the combine introduced a new set of hazards that required a period of adjustment. For example, the ability to gather, cut, separate and clean the grain in the field using one machine changed the handling of grain from a lumpy flow process in the form of ear corn to shelled corn, which was almost fluid-like. Consequently, in the 1970s, there was a dramatic increase in the number of auger-related injuries, and of engulfments and suffocations in flowing grain that took place in storage structures and grain transport vehicles (Kelley 1996). In addition, there were new categories of injuries being reported that were related to the sheer size and weight of the combine, such as falls from the operator platform and ladders, which can place the operator as much as 4 m off the ground, and operators being crushed beneath the multi-row gathering unit.

The mechanization of the corn harvest directly contributed to one of the most dramatic shifts in rural population ever experienced in North America. The farm population, in less than 75 years after the introduction of hybrid varieties of corn and the mechanical corn picker, went from over 50% to less than 5% of the total population. Through this period of increased productivity and greatly reduced labour demands, the overall exposure to agricultural workplace hazards was substantially reduced, contributing to a drop in reported farm-related deaths from over 14,000 in 1942 to fewer than 900 in 1995 (NSC 1995).

Injuries associated with modern harvesting operations typically relate to tractors, machinery, grain-handling equipment and grain-storage structures. Since the 1950s, tractors have contributed to approximately one-half of all farm-related fatalities, with overturns being the single most important contributing factor. The utilization of rollover protective structures (ROPS) has proven to be the single most important intervention strategy in reducing the number of tractor-related fatalities (Deere & Co. 1994). Other design features that improved the safety and health of tractor operators included wider wheel bases and designs that lowered the centre of gravity to improve stability, all-weather operator enclosures to reduce exposure to the elements and dust, ergonomically designed seating and controls and reduced noise levels.

The problem of tractor-related injuries, however, remains significant and is a growing concern in areas that are being rapidly mechanized, such as China and India. In many areas of the world it is more likely to see the tractor being used as a vehicle of highway transport or a stationary power source than being used in the field to produce crops, as it was designed to do. In these areas, tractors are typically introduced with minimal operator training and are used widely as a means of transporting multiple passengers, another use for which the tractor was not designed. The result has been that runovers of extra riders who have fallen from the tractors during operation has become the second leading cause of tractor-related fatalities. If the trend towards greater utilization of ROPS continues, runovers may eventually become the leading cause of tractor-related fatalities worldwide.

Though used fewer hours during the year than tractors, harvesting equipment such as combines are involved in about twice as many injuries per 1,000 machines (Etherton et al. 1991). These injuries often take place during servicing, repairing or adjusting the machine when the power to machine components is still engaged (NSC 1986). Recent design changes have been made to incorporate more passive and active operator warnings and interlocks, such as safety switches in the operator seat to prevent machine operation when no one is in the seat, and to reduce the number of maintenance points to reduce operator exposure to operating machinery. Many of these design concepts, however, remain voluntary, are frequently by-passed by the operator and are not universally found on all harvesting machines.

Hay and forage harvesting equipment exposes workers to hazards similar to those found on combines. This equipment contains components that cut, crush, grind, chop and blow crop material at high speed, leaving little room for human error. As with grain harvesting, hay and forage harvesting must take place in a timely fashion in order to prevent damage to the crop from the elements. This added stress to complete tasks rapidly, in conjunction with machine hazards, frequently leads to injuries (Murphy and Williams 1983).

Traditionally, the hay baler has been identified as a frequent source of serious injuries. These machines are used under some of the most harsh conditions found in any type of harvesting. High temperature, rough terrain, dusty conditions and the need for frequent adjustments contribute to a high rate of injury. The conversion to large packages or bales of hay and mechanical handling systems has improved safety with a few exceptions, as was the case with the introduction of the early designs of the round baler. The aggressive compression rolls on the front of these machines resulted in a large number of hand and arm amputations. This design was later replaced with a less aggressive gathering unit, which nearly eliminated the problem.

Fire is a potential problem for many types of harvesting operations. Crops that are required to be dried to less than 15% moisture content for proper storage make excellent fuel if ignited. Combines and cotton harvesters are especially vulnerable to fires during field operation. Design features such as the use of diesel engines and protected electrical systems, proper equipment maintenance and operator access to fire extinguishers have been shown to reduce the risk of fire-related damage or injury (Shutske et al. 1991).

Noise and dust are two other hazards that are typically intrinsic to harvesting operations. Both pose serious long-term health risks to the operator of harvesting equipment. The inclusion of environmentally controlled operator enclosures in the design of modern harvesting equipment has done much to reduce operator exposure to excessive noise pressures and dust levels. However, most farmers have yet to benefit from this safety feature. The use of PPE such as ear plugs and disposable dust masks provides an alternative, but less effective, means of protection from these hazards.

As harvesting operations around the world become increasingly mechanized, there will be a continuing shift from environmental-, animal- and hand tool-related injuries to those caused by machines. Drawing upon the experiences of farmers and manufacturers of harvesting equipment who have completed this transition should prove useful in reducing the adjustment period and preventing injuries caused by lack of familiarity and poor design. The experience of farmers with even the most highly mechanized harvesting operations, however, suggests that the injury problem will not be totally eliminated. Contributions of operator error and machine design will continue to play a significant role in injury causation. But there is no question that in addition to greater productivity, the process of mechanization has significantly reduced the risks associated with harvesting.

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Storing

The growing and gathering of crops and production of livestock has long been recognized as one of the world’s oldest and most important occupations. Farming and ranching today is as diverse as the many crops, fibres and livestock which are produced. At one extreme, the farming unit may consist of a single family that cultivates the soil and plants and harvests the crop, all by hand over a limited area. The opposite extreme includes large corporate farms spanning vast areas that are highly mechanized, using sophisticated machinery, equipment and facilities. The same is true for the storage of food and fibre. Storage of agricultural products may be as rudimentary as simple huts and hand-dug pits, and as complex as towering silos, bunkers, bins and refrigerated units.

Hazards and their prevention

Agricultural products such as grains, hays, fruit, nuts, vegetables and plant fibre are often stored for later human and livestock consumption or sale to the general populace or to manufacturers. The storage of agricultural products prior to shipment to market may occur in a variety of structures—pits, bunkers, bins, silos, refrigerated units, carts, wagons, barns and railroad cars, to mention a few. Despite the diversity of products being stored and of storage facilities, there are hazards which are common to the storage process:

Falls and falling objects

Falls may occur from heights or at the same level. In the case of bins, silos, barns and other storage structures, falls from heights most often occur from and in storage structures. Most often the cause is unguarded roofs, floor openings, stairways, lofts and shafts, and climbing ladders or standing on raised work areas such as an unprotected platform. Falls from height may also result from climbing on or off the transportation unit (e.g., wagons, carts and tractors). Falls from the same level occur from slippery surfaces, tripping over objects or being pushed by a moving object. Protection against falls includes such measures as:

• provision of safety belts, harnesses, lifelines and safety boots

• installation of guard rails, toeboards, cat-ladders or crawling boards on sloped roofs

• guarded floor openings, lofts and shafts

• use of the standard rise and run of stairways, provision of handrails on both sides, and application non-skid strips where necessary

• maintaining floors in good condition, free from uneven surfaces, holes and accumulations of waste or slippery substances

• provision of handholds on permanent ladders, guard platforms and landings

• maintaining extension or step ladders in good condition and training employees on their use.

Agricultural products may be stored loose in a facility or bundled, bagged, crated or bailed. Loose storage is often associated with grains such as wheat, corn or soybeans. Bundled, bagged, crated or bailed products include hay, straw, vegetables, grains and feeds. Falls of materials occur in all types of storage. Collapse of unsecured stacked foodstuffs, overhead materials and piles of goods are often causes of injury. Employees should be trained in the correct stacking of goods to prevent their collapse. Employers and managers must monitor the workplace for compliance.

Confined spaces

Agricultural products may be stored in two types of facilities—those that contain enough oxygen to sustain life, such as barns, open carts and wagons, and those that do not, such as some silos, tanks and refrigeration units. The latter are confined spaces, and should be treated with appropriate precautions. The oxygen level should be monitored prior to entry and a supplied air or self-contained breathing unit used if necessary; someone else should be on hand. Suffocation may also occur in either type of facility if the goods which it contains have the characteristics of a fluid. This is commonly associated with grains and similar foodstuffs. The worker dies as a result of drowning. In grain bins it is a common practice for an agricultural worker to enter the bin due to difficulties in loading or unloading, often caused by a condition of the grain resulting in bridging. Workers attempting to alleviate the situation by unbridging the grain may voluntarily walk on the bridged grain. They may fall in and be covered with the grain or be sucked under if the loading or unloading equipment is operational. Bridging also may occur to the sides of such structures, in which case a worker may enter to knock down the material sticking to the sides and become engulfed when the material fails. A lockout/tagout system and fall protection such as a safety belt and rope are essential if workers are to enter this type of structure. Children’s safety is of special concern. Often inquisitive, playful and wanting to do adult chores, they are attracted to such structures, and the results are all-too-often fatal.

Fruit and vegetables are often kept in cold storage prior to shipping to market. As indicated in the above paragraph, depending on the type of unit, cold storage may be considered a confined space and should be monitored for oxygen content. Other hazards include frostbite and cold-induced injury or death from body temperature loss following prolonged exposure to cold. Personal protective clothing should be worn appropriate to the temperature within the cold-storage unit.

Gases and poisons

Depending on the moisture content of the product when it is placed in storage and atmospheric and other conditions, feeds, grains and fibres may produce dangerous gases. Such gases include carbon monoxide (CO), carbon dioxide (CO₂) and oxides of nitrogen (NO_x), some of which may cause death in a matter of minutes. This is also especially important if the goods are stored in a facility in which nonlethal gases may be allowed to accumulate to dangerous levels, displacing oxygen. If the potential for gas production exists, then monitoring for gases should be done. In addition, foods and feeds may have been sprayed or treated with a pesticide during the growing period to kill weeds, insects or disease, or during the storage process to reduce spoilage or mould, spore or insect damage. This may add to the hazards of gas production, inhalation of dusts and handling of the product. Special care should be taken by workers to wear PPE depending on the nature and longevity of the treatment, the product used and the label directions.

Machine hazards

Storage facilities may contain a variety of machinery for conveying the product. These range from belt and roller conveyors to blowers, augers, slides and other such product-handling devices, each with its own power source. Hazards and suitable precautions include:

• Nip points formed by belts, pulleys and gears. Agricultural workers should be protected from nip and shear points by an appropriate guarding around the point of potential contact.

• Protruding belt fasteners, setscrews, keys, bolts and grooves. Protruding setscrews, keys or bolts on revolving shafts should be countersunk, encased or shrouded. Belt fasteners should be inspected and repaired.

• Shear points caused by flywheel arms, augers and their housing, pulley spokes, crank and lever mechanisms. These should be guarded or enclosed.

• Contact with moving transmission or electrical elements. These should be guarded or enclosed.

• Inadvertent starting of machinery or equipment. A system for locking out or tagging out equipment prior to maintenance or repair should be implemented and enforced.

• Loose clothing or hair getting wound on or caught by shafts. Clothing that is loose, frayed or that has hanging threads should never be worn. Other personal protective apparel and shoes appropriate to the job task should be worn.

• Excessive noise. Noise exposure should be monitored and administrative, engineering and/or personal protective controls should be taken if necessary.

Employees should be trained and aware of the hazards, basic safety rules and safe working methods.

Health outcomes

Agricultural workers who are involved in the handling of agricultural products for storage are at risk for respiratory disorders. Exposures to a variety of dusts, gases, chemicals, silica, fungal spores and endotoxins can result in damage to the lungs. Recent studies link lung disorders caused by these substances to workers who handle grain, cotton, flax, hemp, hay and tobacco. Therefore the populations at risk are worldwide. Agricultural lung disorders have many common names, some of which include: occupational asthma, farmer’s lung, green tobacco sickness, brown lung, organic dust toxic syndrome, silo filler’s or unloader’s disease, bronchitis and airway obstruction. Symptoms may first manifest themselves as being characteristic of influenza (chills, fever, coughing, headaches, myalgias and breathing difficulty). This is especially true for organic dusts. Prevention of lung dysfunction should include an assessment of the worker’s environment, health promotion programmes targeted at primary prevention and the use of personal protective respirators and other protective devices based on the environmental assessment.

Transportation Operations

Although it may seem simple, the transportation of goods to market is often as complex and hazardous as growing and storing the crop. The transportation of products to market is as diversified as the types of farming operations. Transportation may range from goods being carried by humans and livestock, to being transported by simple mechanical devices such as bicycles and animal-drawn carts, being hauled by complex mechanical equipment such as large carts and wagons pulled by tractors, to the use of commercial transportation systems, which include large trucks, buses, trains and airplanes. As the world’s population increases and urban areas grow, road travel of agricultural equipment and implements of husbandry has increased. In the US, according to the National Safety Council (NSC), 8,000 farm tractors and other agricultural vehicles were involved in highway accidents in 1992 (NSC 1993). Many farming operations are consolidating and expanding by acquiring or renting a number of smaller farms which are typically scattered and not adjoining. A 1991 study in Ohio showed that 79% of the farms surveyed operated in multiple locations (Bean and Lawrence 1992).

Hazards and their prevention

Although each of the modes of transportation mentioned above will have its own unique hazards, it is the intermix of civilian traffic with agricultural transport machinery and equipment that is of major concern. The increase in road travel of agricultural equipment has resulted in a greater number of collisions between motor vehicles and slower moving agricultural equipment. Farm equipment and implements of husbandry may be wider than the width of the road. Due to pressure of planting at the right time to assure a crop or harvesting and getting the crop to a market or storage location as quickly as possible, agricultural machinery must often travel on the roadways during periods of darkness, early morning or evening.

An in-depth study of all 50 states’ codes in the United States revealed that the lighting and marking requirements vary greatly from state to state. This diversity in requirements does not communicate a consistent message to motor vehicle drivers (Eicher 1993). Faster speeds of other vehicles combined with inadequate lighting or marking of agricultural equipment is often a deadly combination. A recent study in the United States found that the common accident types are rear end, sideswipe-meeting, sideswipe-passing, angle, head-on, backing and other. In 20% of the 803 two-vehicle crashes studied, the farm vehicle was struck from an angle. In 28% of the crashes, the farm vehicle was sideswiped (15% meeting and 13% passing). Twenty-two per cent of the accidents consisted of rear-end (15%), head-on (4%) and backing (3%) collisions. The remaining 25% were crashes which were caused by something other than a moving vehicle (i.e., a parked vehicle, pedestrian, animal and so on) (Glascock et al. 1993).

Livestock are used in many parts of the world as the “horsepower” to transport agricultural products. Although beasts of burden are generally reliable, most are colourblind, have territorial and maternal instincts, react independently and unexpectedly, and are of great strength. Such animals have caused vehicle crashes. Falls from agricultural machinery and implements of husbandry are common.

The following general safety principles apply to transportation operations:

• Local traffic rules, regulations or laws should be learned and obeyed.

• No riders or passengers other than those that are necessary to accomplish the transport and unloading duties should be permitted.

• Vehicles should stay as close to the shoulder of the road as road conditions will allow.

• Passing other vehicles (moving or parked) and pedestrians must be done with caution.

• Broken-down vehicles should be moved off the road if possible.

• All marking and lighting on machinery and equipment should be maintained and clean.

• Driving should never be done under the influence of alcohol or drugs.

Laws and regulations may dictate the state of acceptable lighting and marking. However, many such regulations only describe the minimal acceptable standards. Unless such regulations specifically prohibit retrofitting and adding additional lighting and marking, farmers should consider adding such devices. It is important that such lighting and marking devices be installed not only on self-propelled implements but also on pieces of equipment that they may be pulling or trailing.

Lights are especially critical for dusk, dawn and night-time movement of agricultural equipment. If the agricultural vehicle has a power source, consideration should be given to having, at a minimum: two headlights, two tail-lights, two turn signals and two brake lights.

Tail-lights, turn signals and brake lights may be incorporated into single units or can be attached as separate entities. Standards for such devices may be found through standard-setting organizations such as the American Society of Agricultural Engineers (ASAE), the American National Standards Institute (ANSI), the European Committee for Standardization (CEN) and the International Organization for Standardization (ISO).

If the agricultural vehicle does not have a power source, battery-powered lights, although not as effective, may be used. Many such lights are commercially available in a variety of types (flood, blinking, rotating and strobe) and sizes. If it is impossible to obtain these devices, then reflectors, flags and other alternative materials discussed below may be used.

Many new retroreflective fluorescent materials are available today to aid in marking agricultural vehicles for enhanced visibility. They are manufactured in patches or strips in a variety of colours. Local regulations should be consulted for acceptable colours or colour combinations.

Fluorescent materials provide excellent daytime visibility by relying on solar radiation for their light-emitting properties. A complex photochemical reaction takes place when the fluorescent pigments absorb non-visible solar radiation and re-emit the energy as a longer wavelength of light. In a sense, fluorescent materials appear to “glow” in the daytime and appear brighter than the conventional colours in the same light conditions. The primary disadvantage of fluorescent materials is their deterioration with prolonged exposure to solar radiation.

Reflection is an element of sight. Wavelengths of light strike an object and are either absorbed or bounced back in all directions (diffused reflection) or at an angle exactly opposite to the angle at which the light struck the object (specular reflection). Retroreflectivity is very similar to specular reflection; however, the light is reflected directly back toward the light source. There are three primary forms of retroreflective materials, each having a different degree of retroreflectivity based on how they were manufactured. They are presented here in increasing order of retroreflectivity: enclosed lens (often called engineering grade or Type ID), encapsulated lens (high intensity) and cube corner (diamond grade, prismatic, DOT C2 or Type IIIB). These retroreflective materials are excellent for night-time visual identification. These materials are also of great assistance in defining the extremities of agricultural implements. In this application, strips of retroreflective and fluorescent material across the width of the machinery, front and back, best communicate to drivers of other, nonagricultural vehicles the actual width of the equipment.

The distinctive red triangle with a yellow-orange centre is used in the United States, Canada and many other parts of the world to designate a class of vehicles as “slow moving”. This means the vehicle travels less than 40 km per hour on the roadway. Typically, other vehicles travel much faster, and the difference in speed may result in a misjudgement on the part of the faster vehicle driver, affecting the driver’s ability to stop in time to avoid an accident. This emblem or an acceptable substitute should always be used.

Health outcomes

Agricultural workers who are involved in the transportation of agricultural products may be at risk for respiratory disorders. Exposures to a variety of dusts, chemicals, silica, fungal spores and endotoxins may result in damage to the lungs. This is somewhat dependent on whether the transport vehicle has an enclosed cab and whether the operator engages in the loading and unloading process. If the transport vehicle has been used in the process of pesticide application, pesticides could be present and trapped inside the cab unless it has an air filtration system. Nevertheless, symptoms may first manifest themselves as being characteristic of influenza. This is especially true for organic dusts. Prevention of lung dysfunction should include an assessment of the worker’s environment, health promotion programmes targeted at primary prevention and the use of personal protective masks, respirators and other protective devices.

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Agricultural methods and practices vary across national boundaries:

• industrial agriculture—industrialized countries of the West (temperate climate) and specialized sectors of the tropical countries

• green revolution agriculture—well endowed areas in the tropics, primarily irrigated plains and deltas of Asia, Latin America and North Africa

• resource-poor agriculture—hinterlands, dry lands, forests, mountains and hills, near deserts and swamps. About 1 billion people in Asia, 300 million in sub-Saharan Africa and 100 million in Latin America are dependent on this form of agriculture. Women comprise a large proportion of subsistence farmers—nearly 80% of the food for sub-Saharan Africa, 50 to 60% of Asia’s food, 46% of the Caribbean’s food, 31% of North Africa and the Middle East’s food and 30% of Latin America’s food is produced by women (Dankelman and Davidson 1988).

With distinct agro-climatic features, the farm crops are grouped as follows:

• Field crops (cereals, oilseeds, fibre, sugar and fodder crops) are rain-fed or cultivated through controlled irrigation.

• Upland and semi-upland cultivation (wheat, groundnuts, cotton and so on) are practised where irrigation or rain water is not abundantly available.

• Wetland cultivation (rice crops) is practised where the land is ploughed and puddled with 5 to 6 cm of standing water and seedlings are transplanted.

• Horticulture crops are fruit, vegetable and flower crops.

• Plantation or perennial crops include coconut, rubber, coffee, tea and so on.

• Pastures are anything nature grows without human intervention.

Farming Operations, Hand Tools and Machinery

Farming in the tropical countries is labour intensive. The ratio of rural population to arable land in Asia is twice as great as in Africa and three times that of Latin America. It is estimated that human effort provides more than 70% of the energy required for crop production tasks (FAO 1987). Improvement in the existing tools, equipment and methods of work has significant effects in minimizing human strain and fatigue and increasing farm productivity. For field crops, farm activities may be categorized based on the physiological demand of work with reference to an individual’s maximal working capacity (see table 1).

Table 1. Categorization of farm activities

Source: Based on data from Nag, Sebastian and Marlankar 1980; Nag and Chatterjee 1981.

Seed-bed preparation

A suitable seed-bed is one that is mellow yet compact and free from vegetation that would interfere with seeding. Seed-bed preparation involves use of different types of hand tools, shallow chisel desi or a mould board plough pulled by draft animals (figure 1) or tractor implements for ploughing, harrowing and so on. About 0.4 hectare (ha) of land can be tilled by a bullock-drawn plough in a day, and a pair of bullocks can provide power to the extent of 1 horsepower (hp).

Figure 1. Bullock-drawn shallow chisel desi plough

In using animal-drawn equipment, the worker acts as a controller of animals and guides the implement with a handle. In most cases, the operator walks behind the implement or sits on the equipment (e.g., disc harrows and puddlers). The operation of animal-drawn implements involves considerable human energy expenditure. For a 15 cm plough, a person may walk about 67 km to cover a 1-hectare area. At a walking speed of 1.5 km/h, the human energy expenditure amounts to 21 kJ/min (about 5.6 × 10⁴ kJ per ha). A handle on implements that is too long or too short results in physical discomfort. Gite (1991) and Gite and Yadav (1990) suggested that the optimum handle height of an implement may be adjusted between 64 and 84 cm (1.0 to 1.2 times the metacarpal III height of the operator).

Hand tools (spade, shovel, hoe and so on) are used for digging and loosening the soil. To minimize drudgery in shovelling work, Freivalds (1984) deduced the optimum rate of work (i.e., shovelling rate) (18 to 21 scoops/minute), shovel load (5 to 7 kg for 15 to 20 scoops/minute, and 8 kg for 6 to 8 scoops/minute), throw distance (1.2 m) and throw height (1 to 1.3 m). Recommendations also include a shovel lift angle of about 32°, a long tool handle, a large, square-pointed blade for shovelling, a round-pointed blade for digging and hollow back construction to reduce shovel weight.

Nag and Pradhan (1992) suggested low-lift and high-lift hoeing tasks (see figure 2), based on physiological and biomechanical studies. As a general guide, the method of work and the hoe design are the deciding factors in performance efficiency of hoeing tasks (Pradhan et al. 1986). The mode of striking the blade to the ground determines the angle at which it penetrates the soil. For low-lift work, the work output was optimized at 53 strokes/ minute, with a land area dug of 1.34 m²/minute, and a work-rest ratio of 10:7. For high-lift work, the optimal conditions were 21 strokes per minute and 0.33 m²/minute of land dug. The shape of the blade—rectangular, trapezoidal, triangular or circular—depends upon the purpose and preference of the local users. For different modes of hoeing, the recommended design dimensions are: weight 2 kg, angle between blade and handle 65 to 70° , handle length 70 to 75 cm, blade length 25 to 30 cm, blade width 22 to 24 cm and handle diameter 3 to 4 cm.

Figure 2. Hoeing tasks in bund trimming in paddy field

Pranab Kumar Nag

Sowing/planting and fertilizer application

The sowing of seeds and planting of seedlings involve the use of planters, seeders, drills and the manual broadcasting of seeds. About 8% of total person-hours are required for broadcasting of seeds and uprooting and transplanting of seedlings.

• In the broadcasting of seeds/fertilizer by hand, manually operated broadcasters allow uniform distribution with minimum drudgery.

• Seeding behind a plough consists of sowing of seeds in a furrow opened by a wooden plough.

• In drilling, seeds are placed in the soil by a seed drill or seed-cum-fertilizer drill. The push/pull force required for a worker to operate the drill (manual or animal-drawn units mounted on wheels) is an important design consideration.

• Dibbling is the placing of seeds by hand or with a small implement (a dibbler), at an average spacing of 15 x 15 cm or 25 x 25 cm. Abrasion of fingers and bodily discomfort due to bent and squat postures are common complaints.

• In planting, sugar cane sets are planted at 30 cm length in a furrow; potato seed tubers are planted flat and ridges are made.

• About 1/3 of the world’s rice is grown by the transplanting system. This is also done for tobacco and some vegetable crops. Usually, germinating seeds are broadcasted densely on a puddled field. The seedlings are uprooted and transplanted to a puddled field by hand or with manual or power-operated transplanters. The operator of a manually operated transplanter walks behind the unit to operate the handle mechanism to pick and transplant the seedlings.

For manual transplanting, the workers are required to be immersed knee deep in mud. The squatting posture used for planting on dry land, with one or two legs flexed at the knee, cannot be adopted in a watered field. About 85 person-hours are required to transplant seedlings for each hectare of land. The awkward posture and static load exert strain on the cardiovascular system and cause low-back pain (Nag and Dutt 1980). Manually operated seeders produce higher work output (i.e., a seeder is about eight times more efficient than transplanting by hand). However, maintaining the balance of the machine (see figure 3) in a puddled field requires about 2.5 times more energy than manual transplanting.

Figure 3. Operating an improved germinated seeder

Paranab Kumar Nag

Plant protection

Fertilizer, pesticide, herbicide and other chemical applicators are operated by pressure through nozzles or by centrifugal force. Large-scale spraying is based on the hydraulic nozzle spray atomizer, either manually operated or using tractor-mounted equipment. Knapsack sprayers are scaled-down models of vehicle-mounted sprayers (Bull 1982).

• A compression knapsack sprayer consists of a tank, a pump and a rod with nozzle and hose.

• A lever-operated knapsack sprayer (10 to 20 l) has an operating lever.

• A power knapsack sprayer consists of a chemical tank of about 10-litre capacity and an air-cooled engine of 1 to 3 hp. The sprayer and engine unit is mounted on a frame and carried on the operator’s back.

• A hand-operated bucket sprayer and foot-operated sprayer require two persons for operating the pump and spraying. A rocking sprayer is operated by the rocking (forward and backward) movement of the handle lever.

When carried on the shoulder for prolonged periods, the vibrations of knapsack sprayers/chemical applicators have detrimental effects on the human body. Spraying using a knapsack sprayer results in potential skin exposure (the legs experience 61% of the total contamination, the hands 33%, the torso 3%, the head 2%, and the arms 1%) (Bonsall 1985). Personal protective clothing (including gloves and boots) can reduce the dermal contamination of pesticides (Forget 1991, 1992). The work is quite strenuous, due to carrying of the load on the back as well as continuous operation of the sprayer handle (20 to 30 strokes/minute); in addition, there is the thermoregulatory load due to protective garments. The weight and height of the sprayer, shape of sprayer tank, mounting system and force required to operate the pump are important ergonomic aspects.

Irrigation

Irrigation is a prerequisite for intensive cropping in arid and semi-arid regions. Since time immemorial, various indigenous devices have been used for lifting water. Lifting water by different manual methods is physically strenuous. In spite of the availability of water pump sets (electrical or engine powered), manually operated devices are widely used (e.g., swing baskets, counterpoise water lifts, water wheels, chain and washer pumps, reciprocating pumps).

• A swing basket is used for lifting water from an irrigation channel (see figure 4). The capacity of the basket is about 4 to 6 l and the frequency of operation is about 15 to 20 swings/minute. Two operators work at right angles to the direction of basket motion. The work demands heavy physical activity, with adoption of awkward body movements and posture.

• A counterpoise water lift consists of a container attached to the end of a horizontal lever which is supported on a vertical pole. The worker exerts force on the counterweight to operate the device.

• Reciprocating pumps (piston-cylinder type hand pumps) are operated either by hand in reciprocating mode or by pedalling in rotary mode.

Figure 4.  Lifting water from irrigation channel using a swing basket

Pranab Kumar Nag

Weeding and intercultivation

Undesirable plants and weeds cause losses by impairing crop yields and quality, harbouring plant pests and increasing irrigation cost. Reduction in yield varies from 10 to 60% depending upon the thickness of growth and the kind of weeds. About 15% of human labour is spent in removing weeds during the cultivating season. Women typically comprise a large portion of the workforce engaged in weeding. In a typical situation, a worker spends about 190 to 220 hours weeding one hectare of land by hand or hand hoe. Spades are also used for weeding and intercultivation.

Of several methods (e.g., mechanical, chemical, biological, cultural), mechanical weeding, either by pulling out the weeds by hand or with hand tools like the hand hoe and simple weeders, is useful in both dry and wet land (Nag and Dutt 1979; Gite and Yadav 1990). In dry land, the workers squat on the ground with one or two legs flexed at the knee and remove weeds using a sickle or hand hoe. In watered land, the workers adopt a bent forward stooping posture to remove weeds manually or with the help of weeders.

The physiological demand in using weeders (e.g., blade and rake, projection finger, double sweep type weeders) is relatively higher than in manual weeding. However, the efficiency of work in terms of area covered is significantly better with the weeders than with manual weeding. The energy demand in manual weeding jobs is only about 27% of one’s working capacity, whereas for different weeders, the energy demand goes up to 56%. However, the strain is relatively less in the case of wheel hoe-type weeders, with which it takes about 110 to 140 person-hours to cover one hectare. A wheel hoe-type weeder (push/pull) consists of one or two wheels, a blade, a frame and a handle. A force (push or pull) of about 5 to 20 kilograms of force (1 kgf = 9.81 Newtons) is required, with a frequency of about 20 to 40 strokes per minute. The technical specifications of the wheel hoe-type weeders, however, need to be standardized for better operation.

Harvesting

In rice and wheat crops, harvesting requires 8 to 10% of the total person-hours used in crop production. Despite rapid mechanization in harvesting, large-scale dependence on manual methods (see figure 5) will continue for years to come. Hand tools (sickle, scythe and so on) are used in manual harvesting. The scythe is commonly used in some parts of the world, because of its large area of coverage. However, it requires more energy than harvesting with a sickle.

Figure 5. Harvesting wheat crop using a sickle

Pranab Kumar Nag

The popularity of the sickle is due to its simplicity in construction and operation. A sickle is a curved blade, with a smooth or serrated edge, attached to a wooden handle. Sickle design varies from region to region, and there is a difference in cardiorespiratory load with different types of sickles. The output varies from 110 to 165 m²/hour, values corresponding to 90 and 60 person-hours per hectare of land. Awkward work postures may lead to long-term clinical complications relating to the back and to the joints of the limbs. Harvesting in a bent posture has the advantage of mobility on both dry and wet land, and it is about 16% faster than squatting; however, a bent posture is 18% more energy demanding than squatting (Nag et al. 1988).

Harvesting accidents, lacerations and incised wounds are common in paddy, wheat and cane sugar fields. The hand tools are primarily designed for right-handed persons, but are often used by left-handed users, who are unaware of the possible safety implications. The important factors in a sickle design are the blade geometry, blade serration, handle shape and size. Based on an ergonomics study, suggested design dimensions of a sickle are: weight, 200 g; total length, 33 cm; handle length, 11 cm; handle diameter, 3 cm; radius of blade curvature, 15 cm; blade concavity, 5 cm. For a serrated sickle: tooth pitch, 0.2 cm; tooth angle, 60°; and ratio of the length of cutting surface to chord length, 1.2. Since the workers perform activities under extreme climatic conditions, health and safety issues are critically important in tropical farming. The cardiorespiratory strain accumulates over long hours of work. Extreme climatic conditions and heat disorders place added stress on the worker and diminish working capacity.

Harvesting machines include mowers, choppers, balers and so on. Power-operated or animal-drawn reapers are also used for harvesting field crops. Combine harvesters (self-propelled or tractor operated) are useful where intensive cultivation is practised and the labour shortage is acute.

Harvesting of sorghum is done by cutting the ear-head and then cutting the plant, or vice versa. The cotton crop is collected in 3 to 5 pickings by hand as the ball matures. Harvesting of potatoes and sugar beets is done manually (see figure 6) or by using a blade harrow or digger, which may be animal or tractor powered. In the case of groundnuts, the vines are either pulled manually or removed using diggers, and the pods separated.

Figure 6.  Manual harvesting of potatoes with a hand hoe

Threshing

Threshing includes separation of grains from the earheads. Age-old manual methods of threshing of grain from the paddy pinnacle are: rubbing the earheads with one’s feet, beating of the harvested crop on a plank, animal treading and so on. Threshing is classified as a moderately heavy task (Nag and Dutt 1980). In manual threshing by beating, (see figure 7) one separates about 1.6 to 1.8 kg of grain and 1.8 to 2.1 kg of straw per minute from medium sized paddy/wheat plants.

Figure 7. Threshing paddy pinnacle by beating

Pranab Kumar Nag

Mechanical threshers carry out threshing and winnowing operations simultaneously. The pedal thresher (oscillating or rotary mode) increases the output to 2.3 to 2.6 kg of grain (paddy/wheat) and 3.1 to 3.6 kg of straw per min. Pedal threshing (see figure 8) is a more strenuous activity than manual threshing by beating. The pedalling and holding of paddy plants on the rolling drum result in high muscular strains. Ergonomic improvements in the pedal thresher may allow a rhythmic pattern of leg work in alternate sitting and standing postures and minimize postural strains. The optimal momentum of the thresher may be reached at about 8 kg weight of the rolling drum.

Figure 8. A pedal thresher in operation

Pranab Krumar Nag

Power threshers are gradually being introduced in green revolution areas. Essentially they consist of a prime mover, a threshing unit, a winnowing unit, a feeding unit and a outlet for clean grain. Self-propelled combines are a combination of a harvester and a thresher unit for grain crops.

Fatal accidents have been reported in grain threshing using power threshers and fodder cutters. The incidence of moderate to severe thresher injuries was 13.1 per thousand threshers (Mohan and Patel 1992). Hands and feet can be injured by the rotor. The position of the feeding chute can result in awkward postures when feeding the crop into the thresher. The belt powering the thresher is also a common cause of injuries. With fodder cutters, the operators can sustain injury while feeding the fodder into the moving blades. Children sustain injury when playing with the machines.

The workers often stand on unstable platforms. In the event of a jerk or loss of balance, the torso weight pushes the hands into the threshing drum/fodder cutter. The thresher must be designed so that the feeding chute is at elbow level and the operators stand on a stable platform. The design of the fodder cutter may be improved for safety as follows (Mohan and Patel 1992):

• a warning roller placed on the chute before the feed rollers

• a locking pin to fix the flywheel when the cutter is not in use

• gear cover and blade guards to push limbs away and prevent clothes from getting entangled.

For threshing groundnuts, the traditional practice is to hold the plants by one hand and strike them against a rod or grill. For threshing maize, tubular maize shellers are used. The worker holds the equipment in his or her palm and inserts and rotates cobs through the equipment to separate the maize grains from the cobs. Output with this equipment is about 25 kg/hour. Hand-operated rotary type maize shellers have higher work output, about 50 to 120 kg/hour. The length of the handle, the force required to operate it and the speed of operation are the important considerations in hand-operated rotary maize shellers.

Winnowing

Winnowing is a process to separate grains from chaff by blowing air, using a hand fan or a pedal- or motor-driven fan. In manual methods (see figure 9), the whole content is thrown up in the air, and the grain and chaff get separated out by differential momentum. A mechanical winnower may, with considerable human exertion, be hand or pedal operated.

Figure 9. Manual winnowing

Pranab Kumar Nag

Other post-harvest operations include cleaning and grading of grains, shelling, decortication, hulling, peeling, slicing, fibre extraction and so on. Different types of manually operated equipment are used in post-harvest operations (e.g., potato peelers and slicers, coconut dehuskers). Decortication involves breaking of shells and removal of seeds (e.g., groundnuts, castor beans). A groundnut decorticator separates kernels from pods. Manual decortication has a very low output (about 2 kg of pod shelling per person-hour). Workers complain of bodily discomfort due to the continuous sitting or squatting posture. Oscillating or rotary-mode decorticators have an output of about 40 to 60 kg of pods per hour. Shelling and hulling refer to separation of seed coat or husk from the inner portion of the grain (e.g., paddy, soybean). Traditional rice hullers are manually (hand or foot) operated and are widely used in rural Asia. The maximum force which can be exerted by hand or foot determines the size and other characteristics of the device. Nowadays, motorized rice mills are used for hulling. In some grains, such as pigeonpea, the seed coat or husk is tightly attached. Removal of the husk in such cases is called dehusking.

For different hand tools and manually operated implements, the grip size and the force exerted on the handles are important considerations. In the case of shears, the force which can be applied by two hands is important. Although most injuries related to hand tools are classified as minor, their consequences are often painful and disabling because of delayed treatment. Design changes in hand tools should be limited to those that can be easily fabricated by village artisans. Safety aspects need to be given due consideration in powered equipment. Safety shoes and gloves available at present are far too expensive and are not suitable for farmers in the tropics.

Manual material-handling tasks

Most agricultural activities involve manual material-handling tasks (e.g., lifting, lowering, pulling, pushing and carrying of heavy loads), resulting in musculoskeletal strains, falls, spinal injuries and so on. The fall injury rate increases dramatically when the fall height is more than 2 m; impact forces are reduced manyfold if the victim falls on soft earth, hay or sand.

In rural areas, loads weighing 50 to 100 kg might be carried several miles on a daily basis (Sen and Nag 1975). In some countries, women and children have to fetch water in large quantities from a distance. These arduous tasks need to be minimized to the extent possible. Different methods of water carriage involve carrying on the head, on the hip, on the back and on the shoulder. These have been associated with a variety of biomechanical effects and spinal disorders (Dufaut 1988). Attempts have been made to improve shoulder load-carrying techniques, designs of wheelbarrows and so on. Load transportation using transverse yoke and head load are more efficient than the frontal yoke. The load optimization that can be carried by men may be obtained from the nomogram shown (figure 10). The nomogram is based on a multiple regression drawn between oxygen demand (the independent variable) and load carried and walking speed (the dependent variables). One may put a scale on the graph across the variables to identify the result. Two variables must be known to find the third. For example, with an oxygen demand of 1.4 l/min (approximate equivalent of 50% of one’s maximum working capacity) and walking speed of 30 m/min, the optimum load would be about 65 kg.

Figure 10. A nomogram to optimize load to be carried on head/yoke, with reference to walking speed and oxygen demand of work.

In view of the diversity of farm activities, certain organizational measures towards redesigning of tools and machinery, methods of work, installation of safety guards on machinery, optimization of human exposure to adverse work environment and so on may significantly improve conditions of work for farming populations (Christiani 1990). Extensive ergonomic research on farm methods and practices, tools and equipment may generate a great deal of knowledge for the betterment of health, safety and productivity of billions of agricultural workers. This being the world’s largest industry, the primitive image of the sector, particularly the resource-poor tropical agriculture, could be transformed as task-oriented. Thus rural workers can undergo systematic training on the hazards of jobs, and safe operational procedures can be developed.

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