Managing Soybean Harvest Timing

Soybean crops typically reach full maturity in late September as the seasons change. When the days get shorter and temperatures start to cool, leaves on soybean plants slowly turn yellow. By mid-October and November, these leaves turn brown and fall off, leaving the mature soybean pods behind, ready for harvest.

Although we can count on the seasons passing, leaves changing color, and farmers preparing their combines for soybean crop harvest, what we can't count on is exactly when this all should happen.

Weather fluctuations and changing planting times from year to year mean we know that sometime around the end of October or the beginning of November is probably the best time to harvest soybean crops, but we can't pinpoint the exact date or right time to do so without some investigation.

Because getting this timing right can impact your bottom line, let's discuss how moisture measurement protects soybean profits.

Soybean Crop Moisture Content Impacts Your Bottom Line

Monitoring the moisture content for soybean crops before harvest is crucial. This is because the moisture content directly impacts your overall yield and therefore, it also affects your revenue as well. Too much moisture and your sale price is penalized, while too little moisture can mean losing a large percentage of the total yield.

The ideal moisture content for soybean crops is 13 percent. Bean crops that test over 13 percent moisture content are assigned penalties on their scale ticket of sale, lowering the overall quality and sale price. Just as costly, though, is having too little moisture, which cuts into growers' profits. According to a study conducted by the University of Nebraska, a soybean crop harvest that measures at 9 percent moisture content correlates to losing 4.4 percent of the total yield.

At market, the moisture content changes the total number of soybean bushels sold. The same University of Nebraska analysis shows that a field producing 75 bushels per acre at 13 percent moisture will sell 3.3 fewer bushels per acre at 9 percent moisture. When soybeans drop to moisture levels that are too far below the optimal 13 percent, that amounts to lost revenue for growers who already operate at low profit margins.

Conversely, when moisture levels are too high, the risk of spoilage increases. At 13 percent moisture, soybeans can be safely stored at 60° Fahrenheit for about six months, but as moisture levels increase, the length of time they can be stored without spoilage starts to decline.

Managing Moisture Levels to Improve Yield

Clearly, harvest timing and moisture levels can have a huge impact on the quality of the harvest. Harvesting too early or too late can cause things like field losses, splits, and cracked seed coats, as well as limited storability, which is why it's so important to closely monitor the moisture content of soybean crops.

Shatter losses increase when seed moisture falls below 11 percent, which is also when seed coats are more likely to crack and foster a prime environment for mold growth. This is why a moisture content of about 13 percent is optimal to limit the risk of mechanical damage to the beans.

With soybean crops, moisture content can increase several points overnight or decrease during a hot, sunny afternoon, which is why it's recommended to avoid harvesting when beans are at their driest.

As soybeans start to dry down, growers need to begin regularly monitoring crop moisture levels to determine not just the best time to harvest the crop, but also the best field harvest order. To maximize grain weight and minimize potential yield losses, harvest should start as soon as the crop moisture content is somewhere between 13 and 15 percent.

Soybean Harvest Best Practices

Because it is nearly impossible to bring in a whole field at exactly 13 percent, the goal is to harvest as close to that target as conditions allow while limiting avoidable losses. University of Nebraska Extension offers several field-tested practices:

• Begin at 14-15% moisture. A field that looks wet from the road is often drier than it appears, and beans may be ready even with some leaves still on the plant. Soybeans are fully mature once about 95 percent of pods have turned their mature tan color.
• Adjust the combine to conditions. In tough or green stems, slow the ground speed and readjust several times a day as conditions shift from morning to afternoon.
• Mind the weather. Moisture can climb several points after an overnight dew and drop several points on a dry, windy afternoon. Because harvesting at the driest part of the day increases shattering, it is best avoided.
• Watch behind the combine. Four to five beans on the ground per square foot adds up to about one bushel per acre in lost yield.

Growers with bins equipped for drying can start as high as 16-18% moisture and aerate down toward 13%, capturing more yield before shatter and field losses set in.

Drying and Storing Soybeans After Harvest

Getting beans out of the field is only half the job. Holding them at the right moisture protects the yield you worked to capture. Target moisture levels depend on how long the crop will sit:

• For short-term winter storage in cool conditions, 13% is generally adequate for up to about six months.
• Beans held for roughly a year should be nearer 12%, and crops stored into the warmer spring and summer months should be dried to about 11% to limit mold growth and deterioration. Below 10%, on the other hand, beans become prone to splitting and quality loss.

In a normal year, natural, unheated air will dry soybeans down to about 13%. When cool, wet conditions call for supplemental heat, soybeans need a gentler touch than corn: limit drying air to 130 to 140° Fahrenheit for commercial beans and 100 to 110° Fahrenheit for seed beans, and keep retention time in the heated section under about 30 minutes.

Because soybeans are fragile, air that is too hot or too dry (along with rough handling) can crack seed coats and open the door to spoilage.

For accurate, instant, non-destructive moisture content readings at every stage, from the standing crop through the bin, the PM450 Advanced Grain and Seed Moisture Meter comes with 39 factory calibrations, including one designed specifically for soybeans.

This instrument is battery-powered, handheld, and can be adjusted for local conditions. The PM450 takes accurate readings of soybean samples straight from the field without any pre-processing, which shortens each test cycle and lets growers focus on product quality.

Frequently Asked Questions

What is the ideal moisture content for harvesting soybeans?
About 13% is the target. Beans delivered above 13% are docked on the scale ticket, while beans that come in too dry give up yield, roughly 4.4% at 9% moisture, according to University of Nebraska data. Most growers aim within a 13-15% window and get as close to 13% as conditions allow.

Can I measure soybean moisture in the field without preparing a sample?
Yes. The PM450 is non-destructive and needs no grinding or sample prep, so you can pour a whole sample and read the result on the spot. Its built-in soybean calibration makes it practical to check moisture repeatedly as a field dries down and to set the best field harvest order.

How accurate is the PM450, and what does it actually measure?
The PM450 measures moisture content across 39 factory calibrations, with accuracy of ±0.5 percent under 20 percent moisture referenced to standard loss-on-drying methods, and it compensates automatically for sample density and grain temperature during the pour. It is a moisture meter. It does not dry or store grain, but it delivers the readings growers need to make sound timing and storage decisions.

Since 1946, Kett has been creating high-performance, accurate instruments to measure moisture content, helping farmers optimize their crop yields, safely store harvested crops at proper moisture levels, and improve overall harvest quality. From seed to storage and beyond, we have the solutions growers need for abundant harvests year after year. To learn more about what we can do for you, contact us today.