Five Steps to Reduce Loss, Improve Combine Performance and Prepare for Next Year

Corn and soybean harvest is when months of management decisions finally come together. While getting the crop out in a timely manner is important, harvest performance should be measured by more than acres per hour.

A properly adjusted combine can help reduce grain loss, maintain grain quality, collect better yield data and evenly distribute residue for next year’s crop. Today’s combines also offer more automation to help operators maintain performance as field conditions change.

These topics were highlighted during the 2026 Combine University, which was developed through a partnership between Iowa State University Extension and Outreach and the ISU Digital Ag Innovation Lab. Combine University provided farmers and agricultural professionals with hands-on learning focused on combine settings, harvest loss, automation, yield monitor calibration and residue management. 

The principles highlighted during Combine University reinforce an important point: small adjustments can have a big impact on harvest performance. As combines roll this fall, farmers can focus on five key areas to reduce losses, improve efficiency and protect profitability.

1. Know where your grain is going

Before changing combine settings, determine where grain is being lost.

Harvest loss can occur before the combine arrives, at the header, or during threshing, separating and cleaning. Identifying the source is important because changing combine settings won’t correct grain that was already on the ground before harvest or grain being lost at the header.

Start by checking pre-harvest loss. Then separate header loss from losses coming out the rear of the combine.

In corn, header loss can include dropped ears, missed ears and loose kernels caused by shelling at the corn head. Header loss is often one of the largest contributors to overall harvest loss.

For soybeans, pay close attention to reel speed and position. A good starting point is to operate the reel approximately 25% faster than ground speed. In standing soybeans, keep the reel in the upper one-third of the plants. Dry afternoon conditions can increase shatter loss, so recheck losses as conditions change. 

Determine where the loss is occurring before making combine adjustments

2. Measure harvest loss instead of guessing

It doesn’t take much grain on the ground to add up to significant loss across a field. Table 1 below is a useful rule of thumb can help put what you see behind the combine into perspective. Don’t rely on one spot. Check several representative locations across the harvest width to better understand the amount and source of loss.

HARVEST TIP: Check pre-harvest loss first, then header loss and finally loss behind the combine. This helps identify which part of the harvesting process needs attention.

3. Set the combine—and keep checking it

Regardless of combine brand or color, the fundamental processes remain feeding, threshing, separating and cleaning.

Feeding should provide a smooth and consistent crop flow into the threshing system. Threshing removes corn kernels from the cob or soybeans from the pod. For corn, measuring cob diameter can provide a starting point for concave clearance. Hand-threshing several ears or soybean pods can also indicate how difficult the crop will be to thresh. After threshing, the combine must separate free grain from crop residue and clean the sample using the chaffer, sieve and fan.

Start with the manufacturer’s recommended settings but remember they are a starting point. Settings need to match actual crop and field conditions. When troubleshooting, avoid changing several settings at once. Change one setting at a time, evaluate the result and then make another adjustment if necessary.

The correct settings at 10 a.m. may not be the correct settings at 4 p.m. Crop moisture, hybrid or variety, wind, lodging and other field conditions change throughout the day. Recheck losses after significant changes.

Let automation help—not replace the operator

Newer combine automation systems use sensors for grain loss, grain quality, machine load, speed and other factors. A simple way to think about the process is:

SENSE → EVALUATE → ACT → MONITOR

Depending on the machine, operators may prioritize balanced performance, grain quality, low grain loss, maximum throughput or consistent throughput. Automation doesn’t eliminate the need to check behind the combine. Periodically get out of the cab, inspect the grain sample and measure losses. Technology works best when combined with operator knowledge and field observations. Pre-season combine calibrations are key for the automation to work properly by making sure the numbers in the settings on the screen are correct.

4. Make your yield data worth collecting

Harvest is also one of the most important data-collection operations performed on the farm. Before relying on a yield map for future management decisions, make sure the yield monitoring system is maintained and properly calibrated.

Check clean-grain elevator chain tension, inspect sensors for dirt and debris, make sure the feeder house position switch operates properly and keep camera lenses clean on machines equipped with camera-based automation.

For most crops, multi-point yield calibration is preferred because it exposes the yield monitor to several grain-flow rates. Also verify the accuracy of the scale being used as the calibration reference. An improperly calibrated grain cart scale doesn’t provide good “ground truth” for calibrating the combine.

Accurate yield data can support future decisions involving fertility, hybrid or variety selection, variable-rate planting and other management practices. But understand the limitations. Grain takes time to travel through the combine before reaching the mass-flow sensor—about 13 seconds on average, depending on machine and header configuration. Even a two-second error in yield-monitor time delay can produce noticeable errors in a yield map.

A colorful yield map isn’t necessarily an accurate yield map. Good management decisions require good data.

5. Remember that next year’s crop starts at harvest

The combine’s job isn’t finished when grain reaches the tank. Residue distribution behind the combine can directly affect field conditions for the next crop. As combines and headers have become larger, spreading residue uniformly across the entire header width has become increasingly important.

Poor soybean residue distribution can create areas of thicker residue that remain cooler and wetter in the spring. Those conditions can affect tillage, planter ride quality, seed depth, seed-to-soil contact and emergence uniformity.

The primary goal should be to spread residue wide and evenly. Fine chopping can also be beneficial when conditions allow. However, if wind or dry residue makes it difficult to achieve both a fine cut and even distribution, prioritize even distribution across the full width of the header.

A simple routine for the 2026 harvest

A good harvest routine doesn’t need to be complicated:

Check pre-harvest loss → Check header loss → Check behind the combine → Inspect grain quality → Adjust one setting at a time → Recheck → Verify yield data → Check residue distribution.

These were some of the practical take-home messages shared during ISU Combine University this August. The goal isn’t simply to harvest the most acres per hour. It is to find the best balance among capacity, grain loss, grain quality, accurate data and residue management.

Additional harvest resources are available through the Iowa State University Digital Ag Innovation Lab’s Research to Rows (R2R) website. The site includes combine resources and step-by-step monitor guides organized by display manufacturers, providing another resource for operators preparing equipment and monitors for harvest.

A few minutes spent checking combine performance can help keep more corn and soybeans in the grain tank this fall. Just as importantly, accurate yield information and uniform residue distribution can provide a better foundation for management decisions and crop establishment in 2027.

Next year’s crop starts with the job your combine does this fall.