Grain loss in combine harvesting: causes, measurement, and reduction in practice.

The harvest season is the crowning achievement of the year's work for every farmer. This is when it's decided what yield the energy and resources invested from sowing to harvest will result in. However, combine efficiency is a critical factor, and improper settings or lack of attention can cause significant, often unnoticed losses. In this article of the Agrider Knowledge Base, we deal in depth with the problem of combine grain loss: we reveal the causes, present methods for accurate measurement, and give practical tips for minimizing harvest loss. Our goal is to help you keep as little crop on the ground as possible, thereby maximizing profit and harvest efficiency.

Why is the issue of grain loss so critical?

Many farmers tend to underestimate the extent of harvest loss or accept a certain level as "natural." Yet every single kilogram of loss means lost revenue. Just think about it: with a 10-ton wheat yield, even a 1% loss means 100 kg/ha of crop, which means an expense of several thousand forints per hectare, and on a national level, it causes a loss of billions for Hungarian agriculture. Moreover, beyond economic aspects:

• Economic impact: Direct loss of revenue. The higher the market price of the commodity, the greater the weight of the loss.
• Agronomic impact: Grains left on the ground can sprout as volunteer plants the following year, weeding the field, competing with the main crop for nutrients and light. In addition, unharvested plant parts can provide a breeding ground for pests and diseases.
• Environmental impact: Waste of resources (seed, fertilizer, fuel, labor hours) that were spent on the produced but unharvested crop.

Main causes of grain loss on the combine

Grain loss cannot be traced back to a single cause but is the result of complex processes that can occur in different parts of the combine. It is important to understand where and why loss occurs so that we can intervene in a targeted way.

Header and adapter loss

This type of loss can account for up to 80% of the total harvest loss! It is mainly caused by improper setting of the adapter, cutting of plant stems, and detachment of grains. Typical causes:

• Cutting height: If the cut is too high, many plant parts remain on the ground. If the cut is too low, the machine can pick up soil and stones.
• Reel speed and position: The reel speed must be adjusted to the ground speed and the condition of the crop. A reel that is too fast can knock out the grains, and one that is too slow does not pull the plant in properly.
• Adapter type and condition: A damaged header, worn blades, and fingers in poor condition can all contribute to loss.
• Crop condition: Lodged, flattened, or weedy crops are more difficult to harvest, and shattering loss is increased.

Threshing system loss

The threshing setting is key. This is where it's decided whether the grains detach properly from the ear/cob without being damaged. Poor settings can result in:

• Unthreshed grains: If the gap between the threshing drum and the concave is too large, or if the drum speed is too low, many grains remain in the ear.
• Grain breakage: If the gap is too small or the drum speed is too high, the grains are damaged, causing a decrease in value.
• Overloading: Due to driving too fast, the threshing system cannot process the incoming material, which can result in unthreshed grains.

Cleaning system (sieves and wind) loss

The threshed crop is separated on the sieves and with the help of wind. The sieve setting and fan speed are critical here:

• Opening the sieves: If the sieves are too closed, some of the grains can end up on the straw walkers/rotors and be lost. If the sieves are too open, a lot of chaff enters the grain tank.
• Fan speed: Too strong wind can blow the lighter grains out of the machine. Too weak wind does not clean the crop properly, and too much chaff remains in the grain tank.
• Overloading the cleaning system: Due to driving too fast, the sieves and the wind cannot perform the cleaning task effectively.

Straw walker/rotor loss

This section is responsible for the final separation of the grains from the straw. Loss occurs here mainly if:

• Too much material: Excessive material flow does not allow for effective separation.
• Wet straw: Wetter, heavier straw is harder to shake, and grains can get stuck in it.
• Improper RPM: In rotary machines, the rotor speed, and in straw walker machines, the condition of the walkers and the intensity of the movement affect the loss.

Measuring grain loss in practice

Instead of assumptions, we need facts! Measuring loss is essential to know where we stand and whether our settings are truly effective. Do not rely solely on the combine's built-in sensors; they require calibration.

Why is measurement important?

• Quantification: We know exactly how much crop we are losing.
• Targeted intervention: Measurement helps identify which part of the combine the greatest loss is occurring.
• Checking settings: It provides feedback on whether changes have improved the situation.

Measurement step by step

The most reliable method is manual measurement with a collection tray. For this, we will need one or more standard-sized (e.g., 0.5 m²) collection trays or an Agrider loss measuring vessel.

1. Choose a representative area: Perform the measurement on an average part of the field, avoiding edges and headlands.
2. Stop the combine: Drive the combine for a short distance at a steady speed, then stop suddenly.
3. Reverse: Back up the combine 5-10 meters to take a sample from the area left by the machine.
4. Place the trays: Place the collection trays according to the width of the header under the material left by the straw walkers and the cleaning system. One tray under the straw, one under the chaff, and if available, one in front of the header.
5. Collect the grains: Carefully collect all the grains from the trays and separate them from plant residues.
6. Weigh the grains: Weigh the collected grains (in grams).
7. Calculate the loss: Use a simple formula to determine the kg/ha value of the loss. (e.g., for a 0.5 m² tray, the value measured in grams multiplied by 20 gives the kg/ha if you only measure the loss behind the machine.)
8. Repeat: Repeat the measurement in several places and after several setting changes!

Acceptable loss levels: For wheat and barley, it is around 0.5-1.5%, for corn 1-2%, and for sunflower 2-3%. However, the goal is always to approach zero!

Built-in combine loss measurement systems

Modern combines often have built-in loss measurement sensors that show loss in real-time. These can be useful tools, but regular calibration with manual measurements is important, as their accuracy can vary depending on the crop and conditions.

Practical tips for reducing grain loss

The goal is to minimize harvest loss. This requires continuous attention and precise setting of the machine.

Pre-harvest checks

• Machine inspection: Check every part of the combine! Worn rasp bars, damaged sieves, and clogged straw walkers all increase loss. Agrider experts help with preparation.
• Crop maturity stage: Choosing the harvest time is critical. Too dry, overripe crop is more prone to shattering, and too wet crop is harder to thresh and clean.
• Weather conditions: Harvest in calm, dry weather if you can.

Correct setting of the combine

This is the most important step. Different settings are optimal for every crop type and every condition. Don't be afraid to experiment!

• Factory settings: Always start with the basic settings suggested in the manual.
• Gradual fine-tuning: Perform one setting at a time (e.g., drum speed), then measure its effect before moving on to the next one.
• Ground speed: Optimize ground speed for the amount of crop and the machine's capacity. Driving too fast overloads the system, driving too slow wastes time and fuel.
• Threshing setting: Adjust the drum speed and concave gap so that the grains are threshed but not broken. Check the grain tank for broken grains and unthreshed ears.
• Sieve setting: Gradually open or close the top and bottom sieves until you achieve optimal cleanliness and minimum loss.
• Fan speed: Adjust the wind strength to blow out lighter chaff but not the grains.

Regular checks during harvest

• Checking straw walkers/rotors: Regularly check the exit point of straw and chaff to see if there are threshed grains in it.
• Checking the grain tank: Examine the cleanliness of the crop in the grain tank. A lot of chaff or broken grain may indicate a bad setting.
• Monitoring the header: Pay attention to shattering in front of the header, especially when harvesting sunflower and rapeseed.

Summary: The key to profit lies in the details

Minimizing combine grain loss is not a one-time task, but a process that requires continuous attention and precision. Regular measurements taken during the harvest season, careful maintenance of the machine, and settings adjusted to conditions make the difference between average and excellent results. Every kilogram of crop saved on every single hectare directly increases the profitability of the farm and harvest efficiency.

Remember, the Agrider Knowledge Base is always at your disposal to help Hungarian farmers work more successfully with the latest and most practical knowledge. Apply the tips described above and maximize your harvest results!