Harvesting instructions

Upright plant stand

High stubble

Straw and chaff evenly spread across whole area

Wide setting of chaff winnower and chaff spreader, sharp cutters

 

Nro 1/2004
Mika Peltonen, Seppo Pentti
Työtehoseura




"Circular pattern harvesting - an interesting option. Shall we start from the side or do we drive crosswise?"

Jussi Knaapi wrote recently (see KV 17/02) about optional drive patterns during harvesting. Based partly on his article and partly on work-studies implemented at the TTS Institute in 2003, we continue the thinking about how we could gain more of the optional drive patterns. The work-studies are related to a project dealing with optimisation of the drive patterns.

Learned drive patterns systematically tend to become a habit. Sometimes - for example in connection with some major change - we need to think over our drive patterns.
This applies not only to direct seeding but also to other cultivation work. For example, the harrowing patterns may be changed every year. It is no longer customary to plan the drive patterns in detail but sometimes doing so would make sense.




Circular-pattern harvesting with crosswise start: The harvesting is commenced by driving diagonally to and fro between the corners of the plot. After the diagonal stage, the harvesting is continued by applying a circular pattern. The turns are made in corners on finished swath.





Spiral-pattern harvesting proceeds so that on the first round the corners are not harvested and on the next rounds "pikes" are left in the corners. The job is completed by harvesting the "pikes" and corners crosswise.


Table 1

Most farmers apply the traditional method

The common, so-called traditional, harvesting method is suitable for all kinds of plots. By traditional harvesting is understood the method in which the harvesting commenced by driving around the plot and reverse turn is made in the corners. Driving around the plot is continued as long as it makes sense, and finally, the job will be completed as swath harvesting. Swath harvesting involves either drive or reverse turns.
If the plot is large, it is also possible to harvest the headlands open to sufficient width and after that continue the harvesting along the long sides. A large plot must be divided into smaller areas, because if the round is too long, the hopper gets full too early.
As the harvesting is continually carried out along the long side, the number of turns per harvested metre does not increase, even at the final stage. A prerequisite for rapid harvesting is that a "wide swath is cut" and the in-feed rate is smooth. The progress of harvesting is greatly affected by how long the emptying and turns take - harvesting is supposed to proceed straight ahead at a constant speed.
If we wish to speed up the harvesting, the easiest way is to cut down the time required for emptying and turns.
One reason for harvest losses is the uneven in-feed rate. By even in-feed rate is meant a fairly constant speed across a smooth plant stand and the change of speed if the stand requires this. In all cases, as the in-feed is cut off at headlands, we must operate at lower capacity or without loading the machine at all. Thus the harvest losses increase - in the same manner as they increase at sharp turns - as the material under threshing moves towards the edge of the threshing machinery and to the rear.



Optional routest

Before harvesting of a new plot is commenced we should think over how the harvesting can be made to proceed as quickly as possible. Should we divide the field into several smaller areas based on, for example, differences in growth rate or uniformity of plant stand? Next we must see what can we do about the drive patterns. The choice of drive pattern is determined by, for example, steep slopes, properties of the plant stand, form of plot, emptying sites and direction of flattening. Sometimes, if we need to harvest high, wet and flattened rye, the job might proceed faster if we reverse while "idling" and only harvest in the direction of flattening. Also, the later use of the plot should affect the drive pattern, for example, will the straw be taken away.


Spiral track harvesting

The spiral method involves driving around the plot along a spiral track making only slight turns without proceeding all the way to the corners. On later rounds, crescent-shaped areas, "pikes", are left standing at the corners. The swaths are in a radial position with respect to the centre-point of the plot. As a strip of equal size is left standing in the corner on every round, the turns do not get sharper as the harvesting proceeds. During the job study we tried to leave the strips that were not harvested two swaths wide. The harvesting was continued until there was left in the middle of the plot an area only about four swaths wide. After that the crescent-shaped corner strips and the area in the middle, which was still standing were harvested.
Depending on the properties of the combine harvester and the shape of the field, the width of the swath which is left standing ("pike") may differ. Applying the spiral method, even plots of a polygon shape may be harvested. The harvesting of the "pikes" requires the least time if they can be harvested by only one forward-reverse movement, i.e. the width of the "pike" is two times the swath. If the corner of the field is narrow, the "pike" must be wider and deeper. Turning always flattens the stand somewhat. This does not matter as the flattened areas may be harvested at the same time as the "pikes".
If the swath dividers are not required, they can be left away, because they flatten the stand in turns.
Turning is easier if the plant stand is relatively upright (otherwise turning might not even be possible) and the stubble is left slightly higher than normal. This makes for example the direct seeding easier.


Circular pattern harvesting with crosswise start

The plot may also be harvested by first making a cross in the field to make the turning easier. This can be accomplished, as Knaapi writes, by at first driving and harvesting round the plot and driving diagonally only after that.
In a study by the TTS Institute, at the first stage, strips of two swaths in width were harvested diagonally from one corner of the plot to the other.
In two of the corners the time required for turning was longer than normal, because a special space had to be harvested for turning. After the phase of diagonal harvesting, the job was continued by circular-pattern harvesting and the turn was accomplished on the strips harvested in the corners.
The fastest way to harvest is to proceed from one corner of the plot to the centre at an angle of 45 degrees and, upon return to the corner, to continue along the side of the field to the next corner. If the field is rectangular, the driver should be skilful enough to drive straight ahead in the middle part of the field and then continue to the corner at an angle of 45 degrees. Thus the circular motion will proceed smoothly and the corner does not "escape". Small estimation errors are difficult to avoid when this method is applied.





Table 2

Clear differences in times required for work

The practical test revealed clear differences between the methods. We need, however, to keep in mind that the results were based on one measurement only. The results, however, are comparable.
All harvesting tests were carried out on rectangular plots. The plots were slightly less than one hectare in size. The work time does not include emptying of the grain hopper and the associated futile driving.
The work width of the combine harvester was 260 cm and the driving speed was on average 4 km/h. The results are presented in the table above. The spiral method brought about the best output.
The total work time required for one hectare was 62,3 minutes. 76 percent of the time was used for the harvesting itself. 22% of the time was used for harvesting of the crescent-shaped corner areas - the pikes.
Circular pattern harvesting with cross-start was slightly more efficient than traditional harvesting. In circular pattern harvesting the time required for crosswise harvesting of the corner areas was 9,83 min./ha, i.e. 13,4% of the work time.
The essential harvesting work took 55,5 min./ha. The turns took 11,2 min./ha, i.e. about 13% of the time. With this method the amount of time required for turns was relatively high, though it is question of round-pattern harvesting. Harvesting of the three triangle-shaped areas, left in the middle of the plot at the final stage of harvesting, takes time. The traditional harvesting took 75,5 min./ha, i.e. 13,2 minutes more than spiral-pattern harvesting.
The time required for turns was also considerable, i.e. 16,4%. Harvesting applying the traditional method required 28 turns per hectare, whereas the spiral-pattern harvesting only required four turns.



Circular-pattern harvesting requires practice

The test showed that the circular-pattern method is well worth thinking about and practising. In particular, leaving crescent-shaped strips of suitable size required practice. Crosswise harvesting also requires concentration so that the figures created are well balanced for circular pattern harvesting. Making a balanced cross-start based on the shape of the plot is difficult. The outcome can very easily be that in the end there are "pieces" of various sizes which were not harvested.
The same methods can also be applied for harrowing and seeding. The plot is sown "as spiral", making a gentle turn. As the seeding of the plot is completed, the "pikes" can be sown without applying any fertilizer. Thus no no free space for weeds will be left in the corners. If the farmer wants to prepare tracks for spraying in connection with seeding, the drive pattern shall be selected accordingly.
These optional methods with their variations can also be applied for other work. It pays to plan every turn. In particular the work proceeds faster if reversing can be avoided. To get an idea of how to make different methods suit one’s own farm, it is worth testing various optional drive patterns. The testing may bring about some astonishing savings in work.