Harvesting is the last step in the production process cycle of an agricultural system. At this stage, all the investments and efforts to achieve a good crop yield have already been carried out, with only the removal of the product remaining.
Grain harvesters have a very important role in the execution of this task, and in this operation, in addition to adequate and careful planning, correct knowledge of the characteristics of the product to be harvested and the machine to be used is essential.
Grain harvesters
Grain harvesters have the function of removing the product from the crop, leaving the grain clean, without straw or crop residues and with minimal quantitative and qualitative losses (mechanical damage).
In its constructive structure, the main components of a combine are:
• cutting and collecting system;
• trail system;
• separation system;
• cleaning system;
• transport and storage system
Given the current scenario, where the lack of water affected the growth and productivity of crops, especially in the southern regions of the country, I share some initial adjustments to be used as a basis for the 2021/2022 grain harvest.
Main factors that must be observed:
Harvester advance speed
The forward speed largely depends on the volume of crop mass and terrain conditions, in addition to weather conditions, humidity, acceptable loss limit, combine operating capacity and header cutting width.
We can suggest that the combine is operated with constant speed, maximum engine speed, in order to keep the rotation of the axles at maximum speed and make the harvested crop is correctly directed in all the main assemblies of the machine.
It is important to point out that for the harvester with a conventional threshing unit (straw bag), when there are grain losses from the rear of the machine, its travel speed must be reduced. This happens because the existing mass on the straw bag system that works with alternating movement and fixed rotation can be overloaded, preventing the separation of the harvested material.
In the case of a harvester with a threshing unit and longitudinal flow separation (rotor), the orientation is opposite to that indicated for a straw extractor harvester. In rotor harvesters, with grain losses, the speed must be increased gradually until the entire threshing and separation system of the rotor is completely filled, involved and compressed by the harvested mass. In addition, other features added to the displacement speed can be easily performed, as the rotation system and adjustments of these mechanical sets are variable.
cutting height
Cutting height adjustment is important for combine performance. When using a low cut in the straw, it is easier to plant, but the amount of straw that enters the harvester is greater, requiring greater attention from the operator to avoid losses and bushing on the platform.
Reel Position
Flexible Snail Deck: Reel works in a low and backward position to pull product up the cutterbar and into the snail.
Draper Header: The reel only needs to pull the product onto the cutterbar, and it should work high and ahead. The reel position recommendation for the Draper is directly above the cutterbar and low enough that the reel fingers can touch and pick up the product.
The position of the reel varies according to the position of the plant:
Standing plant: the reel should be positioned in such a way that the bars support the plants in their mid-section.
Lying plant: The height and feed of the reel should be adjusted so that the fingers lift the crop so that the bars can support it for cutting.
Reel Speed
The optimum reel speed dictates that the crop when cut falls immediately into the cutting deck.
With the plant standing, the reel speed may be equal to or a little higher than the harvester's advance speed;
With the plant lying down, the reel speed must be greater than the forward speed of the combine.
Incorrect adjustment of reel speed and its consequences:
Low speed: Losses due to crop tipping in front of the cutterbar and crop winding on the reel;
High speed: Threshing losses due to impact and losses due to the hurling of the cut crop.
Worm position (snail platform)
The auger is intended to transport the material evenly to the cylinder feeder.
It should be positioned right at the bottom of the platform housing - down and back (Figure 1), making its scrapers very close to the auger helical system.
Improper height adjustments of the auger in relation to the platform bottom can result in:
Excessive height: Uneven feeding; Small height: Early threshing; Grains thrown to the ground; and Crushing the stalks.
Retractable finger position
Its function is to drive the material fully to the feeder without breaks or early threshing. Improper adjustment of the retractable fingers can cause losses:
Excessive advance: Loss from crop damage; Loss from breakages; and Early threshing loss.
Excessive retraction: feeding deficiency.
Float pressure adjustment
Be careful to use different cutterbar pressure ranges for different soil types and conditions. On dry and firm soils, it is necessary to work with low and medium pressure, while wet soil requires greater pressure on the soil.
Conveyor speed (Draper Platforms)
For machines that have platform side belt speed adjustment capabilities, use speeds in the range of 160rpm to 180rpm.
Platform attack angle adjustment
Angle of attack adjustment is performed by the header or cylinder feeder (when equipped). The platform angle should preferably be adjusted on a level floor, so that the cutting system is close to the floor, forming an angle of 10 degrees in relation to the cylinder feeder (machine neck), so that the sliding plates act correctly in contact with the ground. Incorrect slopes affect grain loss, material flow, height control function, and reduced material ingress into the header.
So far, the main focus has been on the harvester's cutting and feeding area, as studies indicate that the cutting platform can be responsible for up to 85% of grain losses and harvest operational yield.
cylinder feeder
The feeder belt chains must always be sufficiently tensioned so that the crossbars lightly touch the bottom of the feeder (figure 2). This allows the chain to sag to admit varying volumes of product, ensuring a uniform feed to the threshing. If the machine has an adjustable and/or floating roller, leave it in the low position for harvesting soybeans.
Power module
Some combines have the feed module before the rotor. If the combine being adjusted has the module and speed adjustments, choose low rpm for seeds and high speed for others.
The feed module has a very important function, being responsible for providing a uniform, continuous and smooth feed to the combine rotor. This system has no threshing function, only feeding. If it is observed that the performance is compromised by jerks or bushings, mainly in green or wet masses, look for alternatives in the aftermarket market for systems that direct the harvested product to the same direction of rotation of the rotor (not in the center). If you opt for this feature, ensure that the chosen system does not alter the machine's original characteristics and/or nullify some important function, such as the stone box (when equipped).
Concave leveling and selection
The adjustment of the cylinder or rotor with the concave is one of the most important for the quality of the grain. If the rotation speed is too high and with a small opening of the concave, the grain will be crushed and it will break, however, if the rotation speed is low and the opening of the concave is too large, the product will not be threshed, in this case the perception and operator sensitivity is critical.
For straw bag or rotor harvesters, we must check the parallelism between cylinder and concave and or rotor and concave, so that the adjustment and adjustment of these are as accurate as possible.
Harvester removes straw after leveling the cylinder with the concave, it is necessary to perform the clearance of the concave in relation to the cylinder, this must have an initial clearance 2x (X1) greater than the final (X1/2), as shown in figure 3.
On a rotor harvester, the clearance between the concaves and the rotor must be equal at the front and rear. The concave leveling should be done in such a way that the concave bar interferes with the rotor track elements at the front and rear, when this happens, relieve as little as possible both sides in the same proportion, ensuring that the rotor turns freely without interference with the concaves. For rotor combine, start leveling adjustment with the concave fully closed.
Another important point is the correct selection of concaves. Many agricultural machinery manufacturers offer different concave models for different crops with the harvester, leaving the operator to choose the correct sets to be used according to the needs and conditions of the crop throughout the harvest. This year, opt for concave with a thick frame and/or intersperse with a concave with a round bar. It is worth remembering that there are practical alternatives in the aftermarket market that eliminate machine downtime for changing and choosing concaves. This ensures more aggressiveness, compression and flow required for the main crops, without the need to change.
The use of correct concaves and standard crop adjustments are critical for conventional and axial threshing systems as they are responsible for threshing and removing beans from the pods. More than 90% of the grain is separated in the threshing unit and the remaining 10% is separated by the other units of the combine.
Sieve and fan system
Correct adjustment of the sieves is very important to avoid losses. If the upper sieve is too open, it will overload the spool, if it is too closed, it will cause grain losses. If the lower sieves are too open, they generate impurities in the grain tank, if they are too closed, they generate too many grains in the track and, consequently, breakages. The opening of the lower sieve must be slightly larger than the grain being harvested, while in the upper sieve the opening must be twice as large as the lower one.
Adjusting the direction and intensity of the air must be with an even direction of the air to the screens. The flow rate should be adjusted so that it just blows the straw out. In the vast majority of rotor harvesters, the screen area is larger than straw harvesters, which requires 20% more wind for its cleaning area.
Suggestion of initial adjustments for harvesting soybean crop 21/22, with unit for mechanical soybean threshing from 12 to 15%:
These settings were developed as an initial harvest reference, starting with the lowest values of each indicator, and slightly different settings can be used.
*To adjust the Concave, increase it 2 by 2 until there are no broken grains.
*Fan: if you have fan losses, reduce it from 50 to 50 until wind losses are over.
* Rotor: the rotation suggestion is indicated so that the crop stays longer in the threshing and separation system.
Up to three adjustments may be required throughout the day. Therefore, operator sensitivity is essential at this stage, avoiding damages and losses in the harvested crop.
Rotor machines have a higher operating capacity than a drum and straw machine, as they allow the material to remain in the threshing section for a longer period and have the advantage of significantly reducing mechanical damage to the grains. Therefore, machines equipped with this system are suitable for harvesting seeds or grains that are more susceptible to mechanical damage.
Some studies report that there may be an increase of 5% to 15% in the germination power of seeds harvested with machines equipped with an axial flow threshing mechanism (rotor), when compared to those with a conventional threshing system (straw bag). However, both require careful adjustments to ensure satisfactory operating capacity, with good grain quality and low volume of losses. These are some tips that can help you to have a safe and more efficient harvest.
