The following list shows the kinds of work done by machines and some examples of each type: 1. Tractors 2. Ploughs 3. Cultivators and Harrows 4. Deep Penetrators 5. Compactors 6. Drills 7. Harvesters 8. Crop Handlers 9. Fertiliser Spreaders 10. Earth Movers.
Machinery # 1. Tractors:
The most important item of farm machinery is the tractor. Tractors have displaced draught horses because they move faster and because they can be kept working day and night if necessary. The first tractors began to appear on Australian farms after World War I, but it was not until after World War II that they were widely used. The first tractors were not very popular because they were very hard to start, unreliable, uncomfortable, and they were hard to turn when drawing implements.
Modern tractors are very efficient, easy to start, and the rubber tyres and springs make them comfortable. Little effort is required to attach or change implements on modern tractors. The farmer of today can choose from a wide range of tractors, from small garden machines to the huge units of 335 kW power or more, but the rising cost of fuel is a problem.
Two inventions have greatly increased the usefulness of modern tractors. First, the use of hydraulic rams has made it possible for a tractor driver to lift and move very heavy loads and implements with fingertip control. Secondly, as a tractor pulls an implement through the soil, the implement may tend to ride out of the ground and move upwards in hard soil.
The three-point linkage system transfers this upward pressure into a downward thrust on the back axle, and this results in the back tyres taking a firmer grip. Because of three-point linkage, quite small tractors can now do the work for which more powerful tractors were once needed.
Despite the improvements made in the design of tractors, unfortunately it is still true that tractors are dangerous machines. Tractor accidents are among the most common of all accidents on the farm, and great care is needed when using a tractor on steep hillsides or sloping land.
Machinery # 2. Ploughs:
Ploughs are the most widely used farm implements, and have a long history. Ploughs do the same kind of work as a man using a garden spade—that is, they dig and turn the soil over.
The first crop growers used pointed sticks which merely scratched and loosened the soil surface. The ancient Egyptians and Sumerians used heavy wooden ploughs drawn by oxen. These implements are still used in many parts of the world such as India, but they only break up the surface and do not turn the soil over.
In the middle Ages, English farmers used a plough fitted with a knife or coulter to cut the soil, and an iron share to penetrate the soil. There was also a wooden board which pushed the soil to one side. These ploughs were followed by a person using a wooden mallet to break up the clods. At the end of the eighteenth century in England and Holland, ploughs were made with a curved iron mould-board which turned the earth over as it went along.
The modern mould-board ploughs have developed from these early implements. Provided that the soil is reasonably moist, a mould-board plough is the best implement for killing and burying weeds, and for digging without destroying soil structure. If you watch a mould-board plough being used well, you will see that the slice of soil is first lifted up the shin where large cross-wise cracks appear in it.
Then the slice is gently turned over and this breaks the soil mass into little crumbs without shattering it completely. Special kinds of mould-board ploughs have been developed for different soil conditions. Ploughs with long sloping mould-boards are suited to heavy grassland soils. Ploughs with short steep mould-boards are used to break up harder soils.
In very sticky clay soils, a plough with a skeletal mould-board is sometimes used. Stump-jump ploughs were developed in Australia to prevent breakage caused by tree roots. Orchard ploughs are usually mounted on an offset frame so that they can be worked close to fruit trees.
In Australian wheat lands the soil is usually too hard and dry to use mould-board ploughs, and disc ploughs are more useful. The rotating steel discs cut into the soil and loosen it, but they have two disadvantages. Weeds are cut off by the discs, but they are not buried as well as by a mould-board. Also the discs destroy the soil structure by shattering and pulverising. For this reason farmers in some areas have begun to use cultivating implements with wide-cutting tines rather than damage their soil with disc ploughs.
Machinery # 3. Cultivators and Harrows:
The main purpose of these implements is to kill weeds and loosen the surface soil. They also have the effect of smoothing out a rough ploughed surface. The difference between cultivators and harrows is that the latter are lighter and do not penetrate so deeply. Rigid tine cultivators are very strong and work the soil deeply. Spring tine cultivators work less deeply and are popular in the wheat belt. Tillers are light tined implements which are often carried at the rear of tractors. Disc cultivators can be used to cut up trash and stubble as well as to cultivate the soil surface.
The most popular disc harrows consist of four gangs angled in such a way as to give the surface a thorough cultivation. However these implements may produce a seed bed which is too fine for some crops. Spike harrows can be used to smooth over a roughly cultivated surface, but they will not deal properly with some weeds. Chain harrows are useful for breaking up and spreading animal manures, and they also have some smoothing effect.
At present there is much interest in machines which will not only kill weeds, but will leave the trash lying on the soil surface where it may act as a mulch and act to reduce wind erosion. One of the most interesting of such machines is the blade plough which consists of wide flat “V” shaped blades preceded by a disc coulter. Each blade has a cutting width of about 150 cm. The rod weeders also leave trash on the surface.
Machinery # 4. Deep Penetrators:
After using a mould-board plough or a rotary hoe for some time a hard layer called a plough pan may be left beneath the surface. Whenever it is necessary to break up these “plough pans” and loosen the deeper layers of the soil, very strong implements must be used. Subsoil ploughs and chisel ploughs may be used at depths of 30 cm or more, whereas scarifiers and deep tillers work at shallower depths.
Machinery # 5. Compactors:
Plain steel or log rollers have the effect of bringing moisture to the surface by compressing the surface soil. In heavy black clay soils where the dry surface clods are very hard, a steel culti-packer gives a better compacting result.
Machinery # 6. Drills:
A drill is an implement for sowing seeds, and special seed drills are designed for many crops. By far the commonest drill used in Australia is the combine, which can be used for sowing any of the cereals. The combine is mounted on wheels, and has a seed box and a fertiliser box across the top.
It is called a combine because it combines the work of a light cultivator and a seed drill. It not only sows the seed and drills fertiliser into the seed furrows, but also has a number of cultivating tines in front of and behind the drills. The combine is often used without seed as a cultivator.
The most modern combines used for sowing wheat make use of flexible hoses along which seed and fertiliser can be blown down into the drill shoes. Since some of these machines are very wide they can cover the ground very quickly. They can also do away with the need for bags, as they can be loaded by augers.
Maize is usually sown with a special corn dropper, and potatoes are planted with a potato planter. Sugar cane sets are planted by special machine, while small seeders are available for sowing a wide variety of vegetable seeds.
Sometimes it is desirable to sow seeds into the surface soil without disturbing the plants already growing there or the layer of leaf litter and other organic matter at the surface. New seeders have been invented to do this work. The sod seeders sow seeds of plants such as vetches straight into a grass pasture, while minimal tillage machines sow seeds into stubble or old cultivation paddocks without disturbing the surface litter.
Machinery # 7. Harvesters:
Of all the wonderful inventions in farm machinery, some of the modern crop harvesters are the most striking. Some modern harvesters almost appear to think as they gather and sort and handle crops of various kinds. Harvesting machinery includes balers, pick-up balers, potato spinners, potato harvesters, reaper and binders, headers, auto-headers, maize harvesters, cane harvesters, cotton harvesters, vegetable pickers and many others.
The wheat header is a remarkable machine which cuts off the heads of grain, thrashes out the grain, and then separates the grain from the straw and the chaff. Figure 23.2 is a cross-section of a header showing some of the main parts. A cutter first cuts off the heads as they come between the fingers of the comb.
A spiral then moves the heads across to one side to the foot of an elevator. The elevator lifts the heads upwards to a place where a rotating beater throws the heads downwards into the small space between the fast-spinning drum and the bars of the concave, and it is here that the grain is beaten out of the heads. Straw walkers pick up the broken straw and drop it out the back of the header.
The grain and chaff fall through a strong stream of air made by a fan, and the lighter chaff is blown away from the grain. The grain falls onto the riddles where it is sieved and then collected by the grain auger. Elevators or augers then take the grain up to the grain box.
The moving parts of a header may be operated by a power take-off shaft which is coupled to the tractor, but the auto-header is completely driven by an engine built into the implement. All-crop harvesters are able to harvest seeds of varying sizes such as Phalaris, wheat, oats, barley, linseed and grain sorghum.
The harvesters for sugar cane “top” the stalks, removing the upper leaves, cut the stalks at ground level and cut the cane into short manageable lengths. Cotton harvesters are efficient machines which literally do the work of hundreds of hand pickers.
Machinery # 8. Crop Handlers:
Bulk handling of crops is quicker and more efficient than the older methods, and crop-handling machines are becoming more important. Mowers, rakes, loaders, augers, chaff cutters and hammer mills are examples of these machines. One of the most useful inventions is the widely used auger. This consists of a spirally twisted steel core very like the threads on a screw, which operates inside a tube.
Augers are able to pick up any material of small size and carry it upwards when it can be tipped into a bin, silo, or hopper-trailer. Another idea is that of using a stream of air to blow chaff and other similar material from one place to another. Streams of air are used in some modern seed drills to carry the seed down tubes to the drills.
Machinery # 9. Fertiliser Spreaders:
Fertilisers in powdered form such as superphosphate were once distributed from machines of the direct drop type. These have been largely replaced by rotary machines fitted with spinners which distribute the fertiliser more evenly and cover wider areas.
Machines are used for drilling ammonia in the gaseous or aqueous form straight into the sub-surface soil. Spreading fertiliser from aeroplanes is popular, especially for rough wooded country where ordinary spreaders cannot be used. In 1957, 45 000 tonnes, or one fifth of all fertiliser spread on pastures, was applied from the air; in 1963, 461 000 tonnes, or one quarter of all fertiliser spread on pastures, was applied from the air.
Later, the amount of fertiliser spread from the air increased still further, but then declined when prices for animal products fell. Now, the prices for cattle and sheep have risen, but the great rise in the price of aviation fuel and superphosphate is holding back the use of aircraft. Small and large aeroplanes have been used to carry loads of a few hundred kg to five or six tonnes. The most popular aircraft are those which carry from one half tonne to one tonne per trip.
Machinery # 10. Earth Movers:
The use of earth-moving equipment during World War II developed on a grand scale, and farmers were quick to see the value of such machines on the land. Bulldozers, graders, blades, scoops, front-end loaders, trench-diggers and post-hole diggers are able to do the work of dozens of men in a short time. The main work done by these machines on properties includes the construction of dams, drains, roads, contour banks, silage pits and the clearing of land.
Although this description of farm implements is not complete, we should know something about the changes which have taken place in the design of farm machinery. Machines are now made which cover a much wider strip as they move over the ground. For instance, some tined cultivators cover a strip of land 20 metres wide; and there are now some disc cultivators with as many as 88 discs.
Some disc harrows are made so that they can be used in gangs to cover a very wide strip. Many implements are now fitted with rubber tyres on the wheels. This makes them easier to pull and leads to less soil damage than steel tyres. Moreover, because there is less vibration, the life of the machines is extended. Many modern machines make use of rubber parts which do less damage to plant material being handled.
For instance, some potato harvesters use rubber-covered elevators and rubber-lined hoppers, while in some of the latest transplanters, seedlings are gently held between sponge-rubber pads. New and stronger materials are being used in modern farm machinery. This has made it possible to reduce the weight of machines and this in turn has made it less costly to pull them over the soil.
One trend is that cultivating implements fitted with tines are now more popular than those fitted with discs, and at the same time the soil is being worked at a shallower depth than previously. Another change in farm machinery is that machines are now being developed to do entirely new kinds of work.
For example machines for drilling liquid ammonia into the soil and machines for the rapid drying of newly-harvested grain. A most important change is the development of machines which perform many operations at one time. Good examples of such machines are the auto-header and the pick-up baler.
One of the great problems of all farm machinery is the wear which is caused by dust and grit working its way into the bearings and other moving parts. The only way to reduce this wear is to keep a layer of oil or grease between moving parts. There have been many improvements in methods of lubricating parts such as bearings.
Open oiling holes provided no protection from dust, but there were weaknesses in most of the other methods used. The most satisfactory bearings are those which are grease-packed and sealed in the factory and which require only occasional attention, but they are of course more expensive.
The main change in the use of farm machinery in recent years has been the reduction in the need for farm labour. For instance, some huge tractors can now do the work of two or three smaller ones, bulk handling of hay needs little labour, while travelling irrigators greatly reduce labour needs. Although machines such as these mean great savings in labour costs, their purchase means heavy costs to the owner.