THE CEREAL CROP

Harvesting the last grain


..............almost!


Home FARMING ZONES IN WANA  >  Guide to cereals and pasture >   You Are Here 

Better cereal yields and lower cost production

CHAPTER HEADING

SUMMARY

This is a practical guide to the use of shallow cultivation for seed bed
preparation and seeding. Shallow cultivation is essential for cereals after
medic in order to ensure regeneration. It is a low cost means of seeding
for cereal, grain legumes and vetches.

This chapter provides the economic justification for shallow cultivation.

Deep plough and cultivation is entrenched in the WANA region. The
technology is wasteful and costly.

This is an overview of deep ploughing and shallow cultivation.

Once the decision has been made to use shallow cultivation it is absolutely
essential to have the proper implements. These are simple and cheap. Their basic design principles are described.

Cultivation, hay production and rotations are the main methods of
controlling weeds in the WANA region. Herbicides have a role. Practical
problems are discussed.

The response of cereals to nitrogen fertiliser in the WANA region is erratic. This is explained and strategies developed to overcome the problem. Phosphate placement can also increase yield responses.

YOU ARE HERE

Mechanical harvesting is the main method of harvesting cereals in the
WANA region. The machines imported from Europe and North America
perform badly as they are designed for high yielding, damp crops.
Australian adaptations will improve efficiency in low to medium yielding
crops with short, brittle straw.

Even a modified harvester will not work efficiently on small farms, around
olive trees and with many types of cereal crops. The stripper is a genuine small scale machine suited to these conditions.

Using shallow cultivation will often require more weight on tractors. Why
and how?

Small farmers often employ contractors to carry out cultivation, seeding and
harvesting. This is expensive and various forms of group ownership provide
a low-cost alternative.


FOUR COMMON ROTATION ON THE GROUND IN THE WANA REGION

SEASON

CEREAL - FALLOW

CEREAL - MEDIC

(Traditional rotation)

CEREAL - VETCH

CEREAL - GRAIN
LEGUME.

AUTUMN

Cereal crop sown

Cereal crop sown

Cereal crop sown

Cereal crop sown

WINTER

Cereal crop grows

Cereal crop grows

Cereal crop grows

Cereal crop grows

SPRING

Cereal crop matures

Cereal crop matures

Cereal crop matures

Cereal crop matures

SUMMER

Cereal crop harvested
Stubble grazed by livestock

Cereal crop harvested
Stubble grazed by livestock

Cereal crop harvested
Stubble grazed by livestock

Cereal crop harvested
Stubble grazed by livestock

AUTUMN

Weeds germinate naturally

Medic regenerates from seed
produced 18 months earlier.
No cultivation of the land
required.

Land cultivated and sown to
vetch or similar forage
legumes.

Land cultivated and sown to
grain legume such as lentils or
chick peas.

WINTER

Weeds grazed. Low stocking rate.

Medic pasture grazed. High stocking rate.

Grazed or more often left for
hay.

Grain legumes grow.

SPRING

Land cultivated for fallow

Medic grazed. Pods produced
for future regeneration.

Cut for hay.

Grain legumes mature.

SUMMER

Bare soil vulnerable to
erosion.

Pods and stubble grazed.

Stubble grazed.

Harvested.

Stubble grazed.

AUTUMN

Cereal cycle begins again.

Cereal cycle begins again

Cereal cycle begins again

Cereal cycle begins again

Harvest losses in the WANA region

    Harvest losses are very high in the WANA region.

Most cereal crops are harvested with large combine harvesters. The loss of grain before and during harvest is considerable.

    The loss is a significant amount and is a very large amount compared to the generally low yields in the region. Harvest losses of 150 to 200 kg per hectare are common or 10 to 20% of the total yield.

    The modifications outlined in the chapter below will reduce the harvest loss to less than 50 kg per ha.

The harvester in the background is just finishing the harvesting of this field in Tunisia. It is a standard machine as used in high yielding crops in Europe. It has not been modified for North African conditions. The women and children are gleaning the large quantity of heads missed by the harvester. Grain on the ground is eaten by sheep.

This cannot of course be totally guaranteed as unusual weather conditions may cause heavy pre-harvest losses.

    If we take a low figure of saving 10% of the yield through lower harvest losses and take the low figure of 202 tonnes of cereals harvested by each harvester recorded for Algeria (see below) we obtain a saving of 20 tonne of extra grain per harvester per year.

This saving of 20 tonnes of grain is pure profit as all the cost of production (including harvesting) have already been paid.

    The modifications outlined below vary in cost.

The profit outlined above of 20 tonnes would comfortably pay for the low cost package in the first season and make an additional return on investment.

    The complete package would cost a little more than this low estimate of profit in one year if fitted to an existing machine.

If fitted to the harvester at the factory the cost of modifications would be much less.

Table 1.

        This shows the level of mechanical harvesting in the WANA region.

Algeria has been counted separately as the investment in mechanical harvesting in Algeria has been much high than any other country in the WANA region.

In fact Algeria accounts for 9,300 harvesters out of a regional total of 26,881.

The Australian figures demonstrate the higher yield for dryland cereal crops in that country.

The Australians also use smaller PTO driven harvesters that do not exist in the WANA region where all the harvesters are large self-propelled machines imported from Europe or North America.
 

Country or  Region

Area of cereal crop harvested by each machine. Ha

 Output of each harvester Tonnes

Algeria

304

202

The WANA region excluding Algeria

787

848

Australia

202

412

Reasons for harvest loss

   Pre-harvest loss.

    Cereal grain is lost on the ground before harvest.

Losses have been reduced over the years particularly with barley due to plant breeding. New varieties have a better retention of grains in the head.

Losses still occur due to the hot dry conditions in the WANA region. Hot winds can still cause considerable loss of grain on the ground before harvest.

The obvious solution is to reduce the exposure of the crop to these winds. If the crop is harvested as soon as it is ripe with more harvesters there is less risk of pre-harvest loss.

This solution may seem obvious but is not economically sound. 

Harvesting the crop more quickly under present conditions requires more harvesters. These are extremely expensive. The crops in the WANA region are low yielding. It is doubtful whether the returns would justify an even larger expenditure on harvesters.

The figures in Table 1 already show that in Algeria the area per harvester is approaching the level in Australia but the output of each harvester is only half.

The existing harvesters need to be made more efficient.

Greater output per harvester rather than more harvesters is the solution. At present their output is low because the ground is rough after years of deep ploughing. They cannot operate at full speed or with wide fronts due to this rough ground.

For small farms with small fields and many crop types a totally different harvester is required.

    Harvest loss

    The harvesters used in the region have been imported from the northern temperate regions.

They are designed for harvesting high yielding crops with large amounts of straw. The northern crops have a high moisture content. Their straw is tough and comparatively long.

The conditions in the WANA region are totally the reverse.

Yields of grain and straw are low. The straw is dry, brittle and short.

It is not surprising that the harvesters do not work efficiently.

They are well outside their specifications and the conditions for which they were designed.

This is not how it is perceived in the WANA region. Operators are blamed for harvest loss.

Both the manufacturers and the extension agents claim that the operators fail to adjust their machines properly.

We will show that the machines cannot be adjusted. They are designed for the northern crop conditions. They must be modified for WANA not adjusted.

    Post-harvest loss

    Poor grain handling from harvester to store reduces the effective output of the harvesters and increases grain losses.
 

Does harvest loss matter?
 

    Lower harvest losses required for profitability.

    If we take a typical harvest loss for the WANA region of 200 kg per ha. this will represent a significant 10 to 20% of the yield of the cereal crop.

The loss of this amount of grain will seriously affect the profitability of the crop.

If the same amount were lost in southern Europe where yields are 5 tonne per ha. the 2% to 4% loss would not be so important.

In northern Europe where yields are even higher 1% or 2% loss would not be significant at all.

    Recovery by sheep.

    Much of the grain lost on the ground is eaten by sheep.

This certainly reduces the economic impact but sheep do not recover all the grain.

Only a half to three quarters is recovered (depending on soil type).

The recovery of the grain is not an ideal means of feeding sheep. The grain goes mainly to the adult sheep. They graze at the front of the flock and have more experience in finding grain. The young sheep should receive priority in summer as their low body weight and lack of fat reserves can result in death.

The grain is recovered quickly in early summer.

It would be better to feed grain over a more prolonged period - even into autumn after the first rain.

    Price differentials for grain.

    There are considerable price differentials between different grains.

Durum wheat is worth more than soft wheat.

Soft wheat is worth more than barley.

It is more profitable to recover all the grain and feed sheep on low cost barley rather than high priced durum wheat.
 

Measuring the loss.  

    This requires three separate measurements:-

    The crop before harvest.

    The measurement of the harvest loss in the crop before the harvester is used will indicate the loss due to hot winds.

If these measurements are made over a period of weeks it should possible to build up a picture of the risks of harvest loss at this stage.

    For example: Harvest loss before harvest may be = 25 kg/ha.

    The stubble after harvest excluding the zone behind the thresher.

    The harvest loss due to the front of the harvester is measured at this stage.

    Harvest loss in front = (total harvest loss)  - (harvest loss before harvester)

    For example:   Harvest loss may be 100 kg/ha = 125 kg total loss - 25 kg pre-harvest loss.

    Loss in the stubble and straw behind the thresher.

    This will indicate the amount of grain lost because it passes right through the harvester.

    Harvest loss through machine = (total harvest loss behind thresher) - (pre-harvest loss) - (harvest loss in front.)

    Of course this harvest loss through the machine is not over the whole field.

The loss has to be adjusted on a per ha basis.

    For example:

Harvest loss measured behind thresher = 300 kg per ha.

    Deduct other harvest losses that is 300 kg -  125 kg  = 175 kg

    The 175 kg is adjusted for the width of the thresher.

    Width of front = 4 metres

    Width of thresher = 1 metre

    175 kg behind thresher = 44 kg per ha. which passes through the harvester.

   Summary

    Pre harvest loss = 25 kg /ha. over whole field.

    Loss at front   = 100 kg /ha over whole field.

    Loss through harvest = 175 kg/ha behind thresher and 44 kg / ha over whole field.

    Total loss = 169 kg / ha. over whole field.

Diagram 1

    The above diagram illustrates the losses as they are built up on each other, layer by layer.

    The pre-harvest loss covers all the above diagram.

    The area behind the front = (the pre-harvest loss) + (the loss at the front)

    The area behind the thresher = (the pre harvest loss) + (the loss at the front) + (the grain that passes through the machine)
 

   How to measure the loss on the ground
 

    The loss of grain can be measured using the sampling method outlined for medic pasture Measuring medic pods  Using the same sampling disc it is possible to count the number of grains on the ground. These should be converted to grains per square metre.

Table 2 

Shows the weights of some common crop grains and the conversion factors required to convert the grain numbers into kg per ha.
 
 

CROP

Range of grain weights

gm. per 1000 grains

Average grain weight

gm. per 1000 grains

Conversion factor grain numbers to kg per ha.

WHEAT

28 to 44

35

2.8

BARLEY

34 to 47

40

2.5

OATS

34 to 40

35

2.8

LUPINS

100 to 180

140

0.71

PEAS

180 to 250

210

0.47


 

Let us say that the Measuring Disc is used 10 times in a crop = 10 X 0.01 sq. m. = 0.1 sq. m.

    Each time the 11 cm disc (= 0.01 sq. metre)  is thrown the number of grains is counted. The numbers are added together and the total X 10 = grains per square metre.

The grains per square metre are divided by the conversion factor = kg per ha.

    For example:

    Sample shows 280 wheat grains per sq. m. Divide by 2.8  = 100 kg per ha.

Table 3

    Shows the grain loss in another way.

The number of grains per sq. metre = 100 kg/ha are calculate.
 

CROP

Number of grains per sq. metre = 100 kg per ha.

WHEAT

280 or about 5 or 6 heads of wheat

BARLEY

250

OATS

280

LUPINS

70

PEAS

50

    It can be seen from the above that a figure of 200 kg/ha grain loss for wheat that is common in the WANA region amounts to only 10 or 12 heads of wheat per sq. metre.
 
 

Definitions
 

Diagram 2

    Diagram 2 shows the main elements of the cereal crop. Before harvest the stem or stalk supports the head. The head contains grain and chaff.

    After harvest the stems and other material left on the ground is called the stubble.
 
 

Diagram 3

    Diagram 3 shows the main parts of the modern combine cereal harvester.

The REEL has FINGERS which feed the crop onto the KNIFE.

The KNIFE runs between FINGERS and cuts off the crop.

The SPIRAL moves the cut material to the centre of the front.

The REEL, the KNIFE and the SPIRAL form the FRONT which can be removed for transport.


    The crop material is picked up by the ELEVATOR and fed into the THRESHER

    The THRESHER separates the GRAIN from the STRAW and the CHAFF.

    The material is thrown back onto the STRAW WALKERS

    The STRAW remains on the STRAW WALKERS and is worked back through the machine and falls out the back.

    The GRAIN and CHAFF fall through the STRAW WALKERS onto the SIEVES

    Air is blown over the sieves. The CHAFF is blown out the back. The GRAIN is fed into the storage tank.


HOW TO REDUCE HARVEST LOSSES

A PRACTICAL GUIDE.


Reducing pre-harvest losses.

    The problem of pre-harvest loss is exposure.

The longer the crop is exposed to adverse weather conditions after it is mature the greater the risk of pre-harvest loss.

Exposure is an economic decision. Trying to harvest all the crop at the optimum time is impossible.

       More harvesters.

    As we have already explained the option of more harvester is costly and unlikely to be profitable given the low cereal yield in the WANA region.

        Greater speed.

    The harvesters used in the WANA region have been imported from Europe and North America.

They are designed to harvest high yielding crops and are currently under-utilised.

Different makes and models have different capacities but a typical machine would harvest a 10 tonne per ha. crop at a speed of 3 km per hour with a standard width of front of about 6 m.

In theory such a machine could be used in a 1 tonne per ha crop at a speed of 30 km per hour.

This would harvest the straw and grain at the same rate. The harvester would in theory cope with this level of through put.

Travelling at 30 km per hour is obviously impractical. The machine would be unsafe at that speed. There would be considerable damage to the machine. It would be impossible to control the cutting height effectively.

Having said that 30 km per hour is an impractical harvesting speed there is an opportunity to increase the speed of harvesting.

The limiting factor is the uneven ground. The ground is uneven due to years of deep ploughing.

If shallow cultivation with scarifier and harrows is used over a number of years the ground will become level and smooth. Harvester speeds can be increased substantially.

Greater speed under test

The Kondinin Group (a group of Australian farmers who test farm machinery and services) have conducted an experiment on modern harvesters to test their performance and capacity. The results are reported in their magazine "Kondinin Group Farming Ahead" May 2007 No 184 pp 16 - 32 ("Tests thresh out harvester performance" by Tim Andrew and Josh Giumelli.) I would strongly recommend that anyone buying a harvester should first read this issue of the Kondinin Group Farming Ahead magazine as it contains many interesting articles on harvesters, their use and ownership.

The four harvesters tested were:

Case IH Axial flow 8010 costing $AUS 464,750

Claas Lexion 580R costing $AUS 496,100

John Deere 9860 STS costing $AUS 479,410

New Holland CR 970 costing $AUS 400,512

All the harvesters were fitted with a a front of more than 12 metres or about 40 feet. This is much wider than fronts commonly used in the WANA region (I have never seen a harvester in the region with a front wider than 6 m) where the ground is too uneven to allow such a wide front to operate efficiently.

Key test results from the Kondinin experiment.

Harvester make and model
Maximum machine harvested yield of cereal - see below
Yield at a speed of 12 km/h
Yield qx/ha
Speed km/h
Area ha/h
Throughput of harvester qx/h
Yield qx/ha
Throughput of harvester qx/h
Case IH Axial flow 8010
31.2
6.47
7.89
246.2
25.3
389.3
Claas Lexion 580R
32.4
5.34
6.84
221.6
23.9
366.6
John Deere 9860 STS
30.4
4.72
6.04
183
21.8
335.2
New Holland CR 970
31.5
6.34
8.12
255.8
26.9
412.9

"Maximum machine harvested yield" come from a series of experiment that were conducted on each machine. They found that revovery was reduced at low speed and and at high speeds. Each machine had a different recovery / machine speed curve. The speed shown in the table is the speed that achieved the maximum recovery of grain. It can be seen that both the speed and the recovery was different for each machine.

The experiment also shows very clearly that high operating speeds with high throughput for the harvester are not compatible with achieving the maximum yield of cereals.

The above table shows that the maximum yields were obtained at different speeds for each make of harvester but in general they were considably lower speeds (roughly half) than those used to achieve a high throughput for the machine.

For example the John Deere produced the lowest efficiency of harvesting (30.4 qx) even at the slow speed of 4.74 km/h but when the speed was increased to a more normal 12 km/h the yield dropped away considerably to only 21.8 qx/ha - that is a 28% reduction in yield resulted from the higher speed. Machine throughput increased 83% but it was a high price to pay for a loss of 8.6 qx per ha of grain.

The Claas Lexion produced the highest absolute yield of grain but the New Holland produced a better combination of yield efficiency and speed and the highest grain yield at 12 km/h. The New Holland was also considerably cheaper than all the other machines.

While the comparison between the machines tested is most significant the general point that higher speed and higher throughput reduce the yield harvested is applicable to all harvesters.

       Wider front.

    Harvesters in the WANA region are imported with standard fronts of about 6 m.

These are designed for high yielding crops.

With the light yields of the WANA region it is theoretically possible to have a front at least double the width (see experiment above).

Again the barrier is the uneven ground.

The diagrams below demonstrate the problem.

Diagram 4


    Diagram 4 show the front of the harvester passing over the waves left by deep ploughing.

The front needs to be adjusted constantly to avoid hitting the ground or missing parts of the crop but with the standard width and moderate to slow speeds most of the crop will be harvested.

The throughput will however be low and only a tiny fraction of the capacity of the machine.

Diagram 5



    Diagram 5 shows how  difficult it is to use a wide front over waves.

This front is only 25% wider than the standard front in Diagram 4 not double. 

In the above diagram it could be operated lower but there is a constant danger of damage if operated too low over rough ground.

        Nomadic harvesters.

    The movement of harvesters from regions with early maturing crops to later regions is well organised in the USA and Canada.

The same system could be used in the WANA region.

It would mean that harvesters were utilised over a longer period. More harvesters would be available in each region at the critical time and then move on to later maturing districts.

         Windrowers.

    A windrower is essentially the front of a harvester.

It cuts the crop. It concentrates the heads and straw into a central strip and leaves it on the stubble.

The heads are much safer in the windrow than standing in the crop. They do not shake in the hot wind. The grain remains in the head. The material in the windrow (heads and straw) is then picked up with the harvesters. The harvester has the front removed and a special pick-up attached instead.

The windrower is cheaper and faster than the combined harvester.

It is used to extend the season for harvesting.

For example let us say the optimum period for harvesting without serious pre-harvest loss is three weeks.

The combined harvester is used during the three weeks to harvest the crops directly.

The windrower is used at the same time. During the three weeks the windrower will cut and windrow another area greater than that harvested by the harvester.

The harvester will then move on to harvest the windrowed crop.

This will be safe from wind damage. If the crop was all harvested by the harvester it would be at least six weeks before the last part of the crop was harvested.

Purchasing a harvester and a windrower is cheaper than two harvesters. Two operations with two operators will add fractionally to the cost.

The use of the windrower in the WANA region is severely limited until the ground is more even.

The windrower is wider and faster than the harvester. On rough ground it would be impossible to operate a wide front at greater speed without damage.

The full advantages of the windrower will only be available once the land is level.

        The grain handling bottleneck.

    Once the land has been levelled after a few years of cultivation and seeding with a scarifier and seeder, harvesters can be fitted with wider fronts.

They can be operated at higher speeds.

Windrowers can be used.

The harvesters in the WANA region are fitted with bagging platforms. A couple of workers bag off the grain as it is separated by the harvester. The bags slide down a shoot onto the ground. They are then picked up and moved to the store.

This may prove to be a bottleneck that prevents a higher throughput.

In any case the use of this type of mobile bagging station is not efficient.

Later in this chapter we will describe an alternative system which will overcome this bottle neck.

Instead of bagging on the machine where only two operators have space to work the grain is transferred to a stationary tank with many more bagging off points.

   The stripper.

    The stripper is an alternative means of harvesting suited to small farms.

    * What is a stripper?

    The stripper is a harvesting machine used in Australia for over 100 years. More details:  Stripper

    The combine harvester carries out three functions:-

    + It cuts and collects the crop.

    + It threshes the grain from the straw and the chaff.

    + It separates the grain from the straw and the chaff.

    The end product is the grain. The straw and chaff is waste and dumped on the ground.

    The stripper carries out two functions and is therefore between a combine harvester and a windrower:-

    + It cuts and collects the crop.

    + It threshes the grain from the straw and the chaff.

    The end product is the grain, and chaff with some straw.

The crop material is then dumped and the separation takes place afterwards. Once the crop has been placed in these dumps it is safe from loss due to hot winds. The separation can be done over the whole of the summer with no time pressure.

    * The stripper and the combined harvester compared.

    The stripper is not only different from the combined harvester in the way it operates (two stages of harvesting instead of three) it is a different scale of machine.

It has only five or six moving parts and can therefore be made as a small machine at low cost.

The stripper has a front of only two metres.

It is ideal for small fields and will handle uneven ground.

    Example 1.  50 ha. of cereals. All wheat. In one field. Reasonably level.

    + A combined harvester is the obvious choice. It has one operator. It can harvester the area quickly and efficiently.

    + For the same investment as one combine harvester one could buy 10 or perhaps 15 strippers. Using them on the 50 ha field would take more time. There would be 10 to 15 operators to pay. The whole idea is ridiculous.

    Example 2.  50 ha of cereals. On 10 small farms of 5 ha each. Some durum wheat. Some soft wheat. Some barley. Average field size less than 2 ha.

    + The combined harvester is no longer the obvious choice. It is difficult to manoeuvre in small fields. Pieces of the crop are missed at the corners and around obstacles. The machine has to be constantly cleaned between different fields with different crops and different owners.

    + The strippers are operated by the farmers. 10 operators is no longer an additional cost but in fact a saving of contractors' fees. The strippers will handle small fields better. Corners will not be missed.

    + The stripper is also a chaff cart. Chaff is important for small farmers and the stripper will carry out the task more efficiently than a chaff cart fitted behind the combine harvester. See  Stripper

 

This is typical of many cereal crops grown on small farms. Trying to harvest the cereals with a conventional harvester is hopeless. A stripper would be ideal.

    * Harvesting efficiency with the stripper.

    The stripper has a proven record of high efficiency.

The small front is more efficient than that on the large combine harvester.

There is no grain lost through the machine as by definition all the material is collected together.

    The stripper also combines the chaff cart. This will be discussed later.
 
 

Reducing the losses at the front of  the combine harvester
  

  The problem with reel.

    The purpose of the reel is to feed the crop onto the knife and the spiral.

It has a series of thin fingers which grip the crop, push it back onto the knife and then move up so they do not become entangled in the straw.

    + The dry brittle crops in the WANA region are delicate. The action of the reel can break heads off. They fall straight onto the ground. They do not enter the knife. Remember that only a few heads per sq. m. will add up to a loss of 100 kg per ha,

    + The crop is low yielding and thin. The fingers are not effective in griping the crop and moving it back onto the knife.

    + A few heads are caught in the reel. These are brittle and have broken off from the straw. They move round with the reel and are blown off.

The effect is more severe when operating into a strong hot wind and with barley where the long awns catch the wind.

When the heads are blown off the reel at the top of its rotation they pass over the top of the front not into it. Again we need to remember how few heads are needed to create a significant loss.
 

    The solution to the reel problem.
 

    + Replacing the reel.

    The reel can be replaced with a blower.

The blower is much better suited to low yielding, brittle crops as found in the WANA region.

The blower has a fan which drives air into a tube. The tube is placed across the front in a similar position to the reel. Below the tube are series of nozzles that blow jets of compressed air onto the crop at an angle. They blow the crop onto the knife and into the spiral.

It is obvious that such a blower would be totally ineffective in Europe, most of the USA and Canada.

It would not have the strength to blow crops of 5 to 10 tonnes onto the knife or to have any impact on tangled and damp crops.

In the WANA region it is most effective with crops yielding less than 3 tonne per ha. that are dry and upright.

    The major problem is the cost.

Replacing the reel with a blower will be expensive. Most farmers and contractors will be reluctant to make such an expensive modification.

Part of the cost is the low value for the reel that is replaced. If the blower is fitted in the factory as original equipment or if the harvester can be purchased without a reel the cost is not high and worthwhile.
 

    + Catching the heads that fall.

    The heads that break off and drop on the ground can be caught using long concave fingers.

These will be described below in the problems of the knife. The cost of adding the long concave fingers is not great and improves the efficiency of the knife also.
 

    + Catching the heads that blow in the wind.

    The heads that break off and are flicked upwards into the wind by the reel can be caught and dropped back into the front by fitting a screen.

The screens are usually made locally.

They are mounted over the front at an angle so the heads drop back into the front. They are usually made from mesh. The cost of this modification is small. 

    The problem of the knife.

    The first point to make is that light thin crops are harder to cut than thick ones.

This is can be demonstrated if one takes a piece of string and holds it in one hand. Then attempt to cut it with a scissors. Unless the string is held taught at both ends or unless the scissors are extremely sharp the string will not be cut.

    Exactly the same problem occurs with the combine harvester.

The light crop is more difficult to cut cleanly and efficiently than the heavy crop.

The knife is not always sharp.

Diagram 6

    Diagram 6 shows a combine harvester operating in a cereal crop with a yield of 5 tonne per ha.

This is not an exceptional yield in Europe or North America and is well within the capacity of this type of harvester.

Of course in the WANA region yields are much lower.

A 5 tonne crop would not be found on dryland farms in the cereal zone. Occasional it would be found under irrigation which in not the topic of this web site.
 
 

    It can be seen that the fingers and knife enter a dense forest of stems.

They are easy to cut off.

The large number of stems means that most of the knife is exposed.

There is two or three times as much open knife as finger. This type is called an OPEN FRONT.

Diagram 7

    Diagram 7 shows the same OPEN FRONT being used on a crop of 1 tonne per ha.

This is a typical yield in the WANA region. Most countries in the WANA region have national averages between 1 and 2 tonne per ha.

There are obviously many crops that are 1 tonne per ha. There are a significant number that yield less than 1 tonne.

    There is sparse number of stems and heads entering the knife and they are difficult to cut off.

Solution to the knife problem.

    The solution to the problem of the knife is to change the ratio of exposed knife to finger to reflect the light yielding crop.

    Diagram 8
 

    Diagram 8 shows the modified fingers for low yielding crops.


    The main features of these fingers (called a COMB FRONT) are:-

    + The stems and heads are fed into a much narrower gap between the fingers. This provides dense bundle of stems for the knife to cut.

    + The fingers are much longer and more pointed to feed the stems into the gap gently. A blunt or abrupt finger would push the heads under rather than into the gap.

    + The fingers are longer and concave (see below) to catch any grain that falls out of the heads or any heads that break off due to the action of the reel.

    + The gap is adjustable for different crop yields.

This does not mean that adjustments are made for each crop.

That would be time consuming and tedious.

If crops are generally below 1.5 tonne the gaps will be less.

Between 1.5 tonne and 3 tonne a medium gap.

Above 3 tonne the gap is wider still.

Once the yield is in the range 3 to 4 tonne both types (OPEN FRONT and COMB FRONT) can be used with equal effect.

Higher yielding crops are harvested with an OPEN FRONT

Having operated a COMB FRONT harvester for many years the adjustment is not critical. Using a gap for a low yielding crop in a crop slightly above 1.5 will work. The only disadvantage will be a few blockages. If all the crops are above 1.5 it is more efficient to adjust the gap.

    Diagram 9

    Diagram 9 shows the knife and fingers of an OPEN FRONT harvester from the front of the machine. It can be seen that any grain or heads that are knocked off by the reel before being cut by the knife fall directly on the ground and add to the harvest loss

    Diagram 10

    Diagram 10 shows the knife and fingers of a COMB FRONT harvester from the front of the machine. Fallen grains or heads fall into the concave on the top of the fingers and are swept back into the machine.


Fingers for a comb front conversion.

    Fitting a comb front.
 

    It is certainly worth fitting a COMB FRONT to the harvester if yields are consistently below 3 tonne per ha.

The lower the yield the greater the comparative advantage.

    + Original equipment.

    The COMB FRONT can be fitted as standard equipment on the harvester.

This is becoming increasingly difficult as European and North American manufacturers dominate the market for harvesters.

They have no concept of harvesting crops below 1 tonne and do not provide COMB FRONTS as an alternative on their machines.

COMB FRONTS can be purchased in Australia but the difficulty in finding and importing the front separately from the harvester is considerable.

The great advantage is that if the COMB FRONT is fitted as the original equipment it will cost the same as the OPEN FRONT.
 

    + Modification of the OPEN FRONT.

    This is more expensive but more practical.

It is possible to purchase the long concave fingers as bolt on extras.

A set for a standard harvester will cost Euro 500 to Euro 1000. plus freight.

The cost is not great considering the total cost of the harvester (€200,000 and more) and the saving in grain lost.

The bolt on fingers are not pieces of advanced technology. In fact the whole idea of the COMB FRONT is simplicity itself and dates back to the first half of the 19th century when these principles were developed by farmers harvesting crops that yielded less than 1 tonne per ha - often less than 0.5 tonne per ha.

Once a few sets have been purchased from Australia it should be possible to make cheaper local copies in the WANA region.

    Problems feeding the material into the spirals.

    Again the problems are greater for a low yielding crop compared to heavy yielding one.

In a heavy yielding crop for which the combine harvester is designed there is a great flow of material coming into the front.

It is cut off by the knife and swept into the spiral.

Everything is caught in the flow and losses are small.

With a low yielding crop there is no river of material - more a small stream.

Grains and heads can linger behind the knife for a few seconds until they are caught up with more material and swept into the spiral.

If at this point the harvester is passing over rough ground and the front bounces the grains and heads will bounce out the front rather than back into the spiral.

Obviously the problem can be reduced with a COMB FRONT as there is little opportunity for this material to fall through the small gaps.

Not only are the gaps small but they are full of stems being pushed together.

The problem becomes more acute on hilly country when the harvester is operating down hill and the slope back to the spiral is less.

   Solution to feeding problems.

    The solution to the feed problem is a vibrating mat.

It is fitted to the back of the knife.

It vibrates back and forth.

Any grain or heads on it are quickly vibrated back to the spiral. The other advantage of the mat is that the flow is more even.

If material accumulates behind the knife and does not fall forward it can form a lump that is pushed back by the incoming crop.

The lump can cause uneven threshing.
 

Reducing losses from the separation process.
 

    What is the problem?

    The crop enters the spiral.

It is taken to the centre of the machine.

It feeds into the elevator.

From the elevator it goes into the thresher.

The thresher separates the grain from the straw and the chaff.

The straw and some chaff and grain are thrown onto the straw walkers. The bulk of the grain and chaff falls directly onto the sieves.

The combine harvester is designed to handle large quantities of tough straw.

The straw walkers are wide and their action is vigourous This is essential for crops yielding 5 to 10 tonne per ha.

    In the WANA region the crops are short and the straw is dry and brittle.

The thresher will smash the short straw into even smaller pieces.

The straw is thrown onto the straw walkers and many of the short pieces of straw work their way through the gaps designed to let the grain and chaff through.

The short straw then moves with the grain and chaff onto the sieves below.

    The straw works its way onto the sieves and blocks them

The sieves are designed to handle grain (which is heavy and passes through) and chaff (which is light and is blown out the back).

The straw is not blown out the back by the blast of air needed to move the chaff.

It lodges in the holes in the sieve and blocks them.

The grain cannot pass through the sieve (nor can the chaff) it bounces to the back and out of the machine.

The normal response to blocked sieves is to increase the blast of air. This can blow out the straw but also some of the grain.

 The straw problem is a classic example of the combine harvester being designed for a different set of crop conditions.

The failure is usually blamed on the operator. It is obvious the operator cannot win.

Too little air blast blocks the sieves.

Too much blows the grain out the back.

There is no happy medium in between because the sieves were not designed to handle straw. Straw should remain on the straw walkers.

    Solutions to the straw problem.

    The problem must be tackled at its source which is the straw walkers.

    It would be good to think that the manufacturers would make a combine harvester for the region with less straw walker capacity that could handle the short brittle crops of the WANA region.

That is unlikely. The market is too small for them to bother. The combine harvester must be modified.

    The solution is to fit baffle plates on the straw walker and block the gaps that let the grain and chaff fall through.

Usually 60 to 75% of the gaps are blocked.

The remaining gaps are sufficient to obtain a good separation of grain and chaff from the straw. Little straw now falls through and blocks the sieves.

    As far as we know there are no commercially available baffle plates. They are made by farmers or local workshops.
 

Cost - benefit for modifications
 

    Level ground.

    One of the most effective means of improving the efficiency of harvesting is to level the ground.

We have already shown  in Cultivation and seeding that the scarifier, harrows and seeder will level the ground.

This is a most cost effective means of cultivation and seeding.

An added benefit is more efficient harvesting.

Harvesters can travel faster.

Wider fronts can be used.

Less crop is missed.

There is less damage to the harvester.

Less grain falls out of the front.

    Modifications to the front.

    The modifications to the front depend on the crop yield.

There will be lower harvest losses.

The traditional OPEN FRONT harvesters will work satisfactorily when the yield is above 3 tonnes per ha.

Below 3 tonnes or 30 qx. a COMB FRONT is more efficient. The cost of modification is less than Euro 1000.

    The addition of a screen above the front is another cheap modification that would cost only  Euro 200 or less.

    These modifications are most cost effective.

    Further modification should be based on acute observation and measurement.

    The replacement of the reel with a blower is more expensive - perhaps Euro 5,000 to 7,000.

    The fitting of a vibrating mat behind the knife will cost in the region of Euro 3,000.

    While these amounts are still tiny in comparison to the cost of a new combine harvester (€200,000 and more) they should not be fitted until the other modifications have been made and tested.

    Modifications to the straw walkers.

    The fitting of baffle plates to cover most of the gaps in the straw walkers is cheap.

An estimate of Euro 300 would be reasonable.

    Low cost package

    Let us say the above package costs Euro 1,500 and saves only 20 tonne of grain per year.

This is a cost of Euro 75 per tonne.

It can be seen that there will be a complete return on investment in the first year and some profit.

In future years there will be a considerable return.
 

Handling the grain
 

    The present system.

    + Bagged and closed on harvester.

    At present most harvesters in the region (almost all in Algeria) have a bagging platform on the harvester.

Two workers bag the grain and close the bags.

The bags slide down a shoot onto the ground.

    + Bags collected.

    The bags are dropped at random and are collected later.

    + All spilled grain lost.

    Any grain that is spilt on the harvester or if a bag bursts is lost.

    + Limited capacity.

    If the speed of the harvester is increased and a wider front fitted the bagging capacity will limit the efficiency of the machine.

    + Expensive operating team.

    The harvester is operated by a team of three. This is expensive for a small farmer employing a harvesting contractor.
 

    Bulk tanks on the harvester.

   + Bulk tank

    It is cheaper to purchase combine harvesters with the standard bulk grain tank on the machine.

The grain is stored in the bulk tank during harvest.

When the tank is full the harvester leaves the crop and discharges the grain into a stationary tank.

This is a small delay but the rate of discharge is high and the harvester will only need to wait a few minutes.

    + Bagging tanks

    The stationary tank can be fitted with a larger number of bagging outlets.

The capacity is much greater.

All the bags are in one place for easy collection.

Grain spilt can be recovered.
 

     + Small farmers could do own bagging

    Small farmers could buy or hire their own stationary tanks.

These could be filled by the contractor with the harvester and then bagged by the farmer when convenient.

The cost would be less than employing additional workers to carry out the task.
 
 

Collecting the chaff and straw.
 

    The purpose of the chaff cart.

    The chaff cart is becoming increasingly popular throughout the world.

The main reason is the harvesting of weed seed particularly those from herbicide resistant weeds.

    In the WANA region the harvesting of weed seeds will probably be secondary to the use of the straw, chaff and grain for animal feed.

The chaff cart collects any grain that passes through the machine.

Unlike the grain blown on the ground all of this can be used by livestock. It can also be fed at the time when it is most needed by livestock. It can be fed selectively to young sheep.

   Dumped behind harvester.

    The chaff cart collects all the material that passes through the harvester.

When the cart is full it is automatically dumped in a heap.

If the farmer wishes to use the material in the autumn or winter or if he wishes to keep it as a drought reserve it must be collected again and transported to the farm house.

     Control weed seeds.

    Most of the weed seeds will be removed or eaten but some will remain and should be controlled by the farmer during the winter.

    The stripper carts the chaff.

    The stripper ( Stripper) collects the chaff and straw.

There is no need for a separate cart.

The grain, straw and chaff is transported back to the farmer house without the need to reload the material. For a small farmer this can be a considerable additional benefit.