Harvesting

• It is the operation of cutting, picking, plucking digging or a combination of these operations for removing the crop from under the ground or above the ground and removing the useful part of fruits from plants.

Harvesting action can be done by four ways

1. Slicing action with a sharp tool.
2. Tearing action with a rough serrated edge.
3. High velocity single element impact with sharp or dull edge.
4. Two elements scissors type action.

• Manual harvesting involves slicing and tearing action.

Harvesting can be done by

• Manually operated tool
• Animal drawn machine
• Mechanically operated machine.

There are a few related terms in connection with harvesting, which are as below

Mower	It is a machine to cut herb age crops and leave them in swath.
Reaper	It is a machine to cut grain crops.
Reaper binder	It is a reaper which cuts the crops and ties them into neat and uniform sheaves.
Swath	It is the material as left by the harvesting machine.
Sickle	It is curved steel blade having a hand grip used for harvesting by manual power.
Windrow	It is a row of material formed by combining two or more swaths.
Windrower	It is a machine to cut crops and deliver them in an uniform manner in a row.

Sickle

• Sickle is a simple harvesting tool.
• It is used for harvesting crops and cutting other vegetations (Fig. 31).
• It essentially consists of a metallic blade and a wooden handle.
• Sickles are classified into two classes: (i) Plain and (ii) Serrated.
• Blade is the main metallic part of the sickle.
• It is desirable to make the blade made of carbon steel.
• The blade is made in a curved shape.
• The teeth of serrated sickle is made sharp for efficient working in the field.
• The handle of the sickle is made of well seasoned wood.
• The forged end of the blade for fixing the handle is called tang.
• The plain or serrated edge in the inner side of the blade is called tang.
• The plain or serrated edge in the inner side of the blade is called cutting edge.
• Protective metallic bush fitted at the junction of the blade and the handle to keep the tang tight in the handle is called ferrule.
• Harvesting by sickle is a very slow and labour consuming device.

• Paddy thresher is the thresher used for threshing paddy.
• The threshing cylinder is of spike tooth type and the top cover has louvers to guide the crop axially.
• In the end of the cylinder there is a thrower for the paddy stalks.
• The thresher has also the cleaning mechanism and bagging attachments.
• It can be operated by a tractor, diesel engine o electric motor.
• The capacity may be 250-1000 kg/hr.

Paddy thresher (Pedal operated)

• It consists mainly of a well balanced cylinder with a series of threshing teeth fixed on wooden slats.
• It has got gear drive mechanism to transmit power. While he cylinder is kept in rotary motion at high speed, the paddy bundles of suitable sizes are applied to the teeth (Fig. 32).
• The grains are separated by the combing as well as by hammering action of the threshing teeth.
• This thresher mainly consists of: (i) Body frame (ii) Cylinder (iii) Drive mechanism (iv) Axle.

Combine –Harvester– Thresher

• It is machine designed for harvesting threshing, separating, cleaning and collecting grains while moving through the standing crops.
• Bagging arrangement may be provided with a pick up attachment, it may be self propelled or tractor operated.

The main function of a combine are:

• Cutting the standing crops
• Feeding the cut crops to threshing unit
• Threshing the crops
• Cleaning the grains from straw
• Collecting the grains in a container.

The whole machine is composed of the following components

• Header
• Reel
• Cutter bar
• Elevator canvas
• Feeder canvas
• Feeding drum
• Threshing drum
• Concave unit
• Fan
• Chauffer sieve
• Grain sieve
• Grain auger
• Tailing auger
• Tail board
• Straw spreader
• Return conveyor
• Shaker
• Grain elevator
• Grain container.
• Header is used to cut and gather the grain and deliver it to the threshing cylinder.
• The straw is pushed back on the platform by the reel.
• Small combines use scoop type headers, while large combines use T type headers with auger tables.
• Harvesting is done by a cutting unit, which uses a cutter bar similar to that of a mower.
• The knife has got serrated edge to prevent the straw from slipping while in operation.
• There is a suitable cutting platform which is provided with a reel and a canvas.
• The reel is made of wooden slats which help in feeding the crops to the cutting platform.
• The reel gets power through suitable gears and shafts.
• The reel revolves in front of the cutter bar, while working in the field.
• The reel pushes the standing crops towards the cutting bar, while working in the field.
• The reel pushes the standing crops towards the cutting unit.
• The reels are adjustable up and down as in or out.
• The cutter bar of the combine operates like a cutter bar of a mower (Fig. 33).
• It cuts the standing crops and pushes them towards the conveyor.
• The conveyor feeds the crop to the cylinder and concave unit.
• Canvas Table conveyors are mostly used with scoop type headers which have narrow cut.

• Numerous Biblical references tell how grain has harvested and threshed by hand.
• The hand reaper was used in Europe and America until horse-drawn machinery was adopted.
• The long-handled scythe was developed toward the end of the Colonial period.
• The cradle was introduced between 1776 and 1800. Obed Hussey obtained a patent on a reaper in 1833.
• McCormick claimed to have demonstrated his first horse-drawn reaper in 1831 but did not obtain a patent until 1884. NcCormick built fifty machines in 1845 and about 800 in 1848.
• A platform for manual binding was introduced about 1850 and the self-raking reaper appeared about 1854.
• The first mechanical wiro-tying mechanism was introduced in 1873.
• Twine binders were introduced in 1880, but it was not until 1892 that
• Apple by obtained a patent on a twine knotter.
• The horse-drawn grain binders were ground driven.
• Auxiliary engines were mounted on some binders about 1920 and the power-take-off-driven binder was introduced in the late 1920s.

Development of the Thresher

• One historian records that in Bedford Conty, Pennsylvania, grain was still generally threshed with the flail in 1829.
• Much grain was trodden out by horses in the late 1830s.
• The patent granted to Hiram A. and John A. Pitts, December 29, 1837, was the beginning of the thresher. It was horse-operated.
• In 1844, the manufacture of the Case thresher was begun at Racine, Wisconsin.
• By 1900, threshers were equipped with self-feeders, band cutter knives, weighers, and wind strawstackers.

Development of the Combine

• A patent on what was termed a combined harvester-thresher was granted to Samuel Lane in 1828.
• The real beginning of the combine for harvesting, threshing, and cleaning was when A.Y. Moore et al. of Kalamazoo, Michign, obtained a patent in 1835.
• By 1854, 600 acres of wheat were combined in Alameda County, California, but the method was not truly initiated in California until about 1880.
• One of the earliest manufacturers of horse-drawn traction-driven combines was the Stockton Combined Harvester and Agricultural Works of California.
• Steam-tractor drawn combines were introduced in the 1890s. Some of these machines were equipped with a 42-foot header and harvested, it was claimed, from 90 to 125 acres in a day.
• Gasoline-tractor drawn combines were introduced on a large scale in the wheat areas of the Middle West as the result of labor shortages during the First World War or about 1916.
• Combines were first introduced in northwest Texas in 1919, when seven machines were used.
• The self-propelled combine was commercially introduced about 1938.

Harvesting and threshing methods

• The systems followed in mechanically harvesting grain (and other seed crops) include (a) direct combining, (b) windrowing and combining, (c) binding or heading and stacking, followed by threshing in a stationary machine, and (d) windrowing, picking up the windrows with a field chopper, and threshing in a stationary machine.
• Direct combining and windrow combining require the least amount of labour, and in the United States, have largely replaced stationary threshing methods.
• The windrow-combine method involves an extra operation as compared with direct combining but is advantageous under certain conditions. Windrowing permits the curing of green weeds and unevenly ripened crops before threshing.
• The weather hazard to the standing crop is reduced because windrowing can be started several days earlier than direct combining.
• Windwors on grain stubble 9 to 12 inches tall cure more rapidly than standing or shocked grain, regardless of whether or not rain occurs.
• Heavy vegetative crops, such as alfalfa grown for seed, are often harvested by the windrow-combine method.
• Stationary threshers are still used to some extent where the fields are small and the conditions not well suited to combine operation.
• Binding or heading the grain prior to threshing provides the advantages of curing green material and reduction of weather hazards (as with windrowing) but involves a considerable amount of labour.
• The stationary thresher accumulates the straw in a stack, which is an advantage if the straw is to be saved for future use.
• Table 104 given a comparison of the labour to harvest wheat with various methods.

History

• Stationary choppers for corn silage date back to the latter part of the nineteenth century, whereas field choppers, commonly known as forage harvesters, appeared in the late 1930's.
• The development of machinery for collecting green crops in the 20 years from the late 1940's to the late 1960's shows how machines can become obsolete.
• Green-crop loaders which delivered long crops on the front or rear of a trailer and needed a couple of men with hand forks to build a load were superseded in some countries by "one man" loaders and self-emptying trailers; but it was not long before both of these were replaced by forage harvesters.
• Of course these are advanced techniques being used in some countries, but the older ones are also being used in many places in the world, as a result of different labor and machinery availability.