Optimizing combine settings: How to reduce grain loss

Optimizing Combine Settings: How to Reduce Grain Loss

Harvest is the pinnacle of the agricultural year, where the fruits—or failures—of months of work are decided. The combine, as the most important tool for harvesting, plays a key role in ensuring the crop reaches the grain tank with the lowest possible loss and in the best quality. However, a poorly adjusted machine not only leaves part of the yield on the stubble but also unnecessarily increases fuel consumption and machine wear. Imagine if you could eliminate just 1-2% of grain loss per hectare; in a larger farm, this could represent savings of several million forints! In our article, we provide practical advice to help you get the most out of your combine and minimize grain loss.

Why is Combine Adjustment Critical?

Grain loss is not just a minor error, but a serious economic factor. In an area with an average wheat yield of 5 tons, a 1% loss means 50 kg/ha of grain. If we multiply this by current grain prices and the farm's total harvested area, it quickly becomes clear how much money a poor setting leaves on the ground. Moreover, loss can affect not only quantitative but also qualitative parameters, such as purity or the proportion of broken kernels.

The complexity of settings is increased by the fact that there are no universal "perfect" values. Optimal parameters can vary on every plot, in every crop stand, and even at different times of the day. The crop variety, moisture content of the yield, straw condition, weediness, and stubble height all influence which setting is most appropriate.

Measuring Grain Loss: The First and Most Important Step

To know what needs to be optimized, we must first measure the initial state. Measurement is essential for successful adjustment.

How to Measure Accurately?

• Tray method: This is the most common and reliable method. Place at least 2-3 trays with a known surface area (e.g., 0.25 m²) behind the combine, in the chopper area. After harvesting, collect the grains that fell into the trays, pick out the clean kernels, and weigh them. Multiply the resulting weight (in grams) by 4 to get the kg/ha value. It is important to repeat the measurement several times and calculate an average.
• Square meter sampling: Similar to the tray method, but here we place a 1 m² frame on the stubble and collect all the grains from within the frame. This method can be used even if no tray is available.
• Built-in combine loss sensors: Modern combines are already equipped with such sensors. These are useful for continuous monitoring, but it is important to calibrate them manually from time to time using the methods above, as their accuracy depends heavily on the crop type and the settings. Remember, the sensor only shows what it measures; without calibration, it can be misleading!

When to Measure?

Perform a new measurement every time you switch plots or if conditions (e.g., moisture, straw volume) change significantly. It is worth checking at the beginning, middle, and end of the day, as dew or heat also affects harvesting conditions.

Main Combine Adjustment Points and Their Impact on Loss

Now let's look at the critical points where most losses occur and how they can be optimized.

Header Settings

• Cutting height: If the cut is too high, part of the crop remains on the stubble; if it's too low, contamination picked up from the ground (soil, stones) can damage the machine and impair threshing efficiency.
• Reel speed and position: The reel speed should be adjusted to the ground speed. A general rule of thumb is that the peripheral speed of the reel should be 1.2-1.3 times the combine's ground speed. If the reel is too slow, it pushes the crop away from the header; if it's too fast, it knocks the grains out of the ear. Set the reel position so that the tines reach in slightly above the ears, yet still between the plants, to guide the crop into the cutting mechanism.
• Side cutters (sunflower, rapeseed): When harvesting sunflower and rapeseed, using side cutters can significantly reduce losses caused by heads or pods falling out to the side.

Threshing System Settings

This is the heart of the combine; this is where grain loss and the broken kernel ratio are determined. There are two main types: drum and rotor systems.

• Drum speed (for drum machines): The drum speed must be adjusted to the threshability of the crop. A speed that is too high causes broken kernels, while one that is too low does not thresh the grains completely. Start with the value suggested in the manual, then fine-tune it.
• Concave clearance (front and rear): The distance between the drum and the concave. It is closely related to the drum speed. Generally speaking, the smaller the gap, the more intense the threshing. Here, too, a balance must be found between broken kernels and unthreshed grains.
• Rotor machines: Here, the rotor speed and the rotor concave clearance are critical. Rotor machines are generally gentler on the grain, but manufacturer specifications and fine-tuning adjusted to the crop must still be followed.

Sieves and Airflow Control

From the threshed material, the grain is separated from the chaff and straw with the help of sieves and wind. The goal is a clean grain tank with minimal loss.

• Sieve opening (upper, lower): Set the opening of the upper sieve so that the grains fall through, but larger pieces of straw and chaff remain. The opening of the lower sieve is even smaller; this separates the grain from smaller contaminants and sends unthreshed parts to the returns elevator. If the opening is too large, a lot of contamination enters the grain tank; if it's too small, grains also remain on top, and loss increases.
• Air pressure (fan speed): The airflow generated by the fan blows the lighter parts (chaff, dust) off the sieves. Wind that is too strong blows out the grains as well; wind that is too weak does not clean the grain enough, which puts a load on the returns system.

Straw Walkers / Rotary Separator

The task of the straw walkers is to remove the grains remaining in the straw after threshing. If they receive too much straw or too high a load, they cannot perform their job effectively, and significant loss can occur.

• Even feeding: It is important that the combine is fed evenly. A sudden large amount of material overloads the straw walkers, which increases loss.
• Straw flow: Ensure that the straw passes through the straw walkers without obstruction. Blockages or excessively wet, clumped straw can cause significant loss.

Specific Crops and Adjustment Tips

Every crop requires a different setting:

• Wheat/Barley: General, medium speed and clearance. Pay attention to moisture content; drier crops may need lower drum speed, while wetter ones may need higher.
• Corn (Maize): Low drum speed (often with a corn concave), large drum clearance (to avoid breaking kernels). Correct adjustment of the corn head (header) is crucial. Use of large, specialized corn sieves.
• Sunflower: Very low drum speed, large drum clearance (extremely sensitive to breakage!). Special sunflower header that cuts off the heads and brings in minimal straw. Sieves and wind should also be adjusted carefully.
• Rapeseed (Canola): Medium-high drum speed, but smaller drum clearance than for wheat (pods are difficult to open). Use of a specialized rapeseed header to minimize seeds falling out to the side.

Practical Tips

• Read the manual! Although it seems basic, manufacturer instructions contain the starting values you can build upon.
• Even speed: The ground speed of the combine must be uniform. Sudden accelerations or decelerations disrupt the internal material flow and increase loss.
• Regular checks: Do not just check the grain loss, but also regularly check the cleanliness of the grain tank, the load on the returns, and the condition of the straw.
• Weather factors: Morning dew or evening humidity changes crop properties, which requires adjusting the settings.
• Machine cleanliness: A clean combine works more efficiently. Deposited dust and chaff can block airflow and the operation of the sieves.
• Software optimization: Modern combines often offer software assistance for adjustment. Take advantage of these functions, but remember that manual checking is still fundamental.

Summary

Optimizing combine settings is a continuous process of learning and fine-tuning. There is no single "magic" setting that is perfect under all circumstances. The key is continuous monitoring, measurement, and adaptation. The time and energy invested during harvest to precisely adjust the machine pays off many times over in the form of less grain loss, better quality crop, and more efficient fuel consumption. Don't leave the crop on the ground, optimize wisely!