Thursday, 10 March 2011 14:48

Harvesting Operations

Written By: Field, William
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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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