Transitional storage periods call for active grain management

From CO₂ monitoring to equilibrium moisture content, operators have more tools than ever to protect stored grain quality.

Elise Schafer

July 8, 2026

Typical warming from spring to summer is one of the most consistent triggers of stored grain quality loss. During colder months, grain quality stabilizes. But as outside temperatures climb, stored grain becomes increasingly vulnerable. The grain mass inside bins warms unevenly, and that temperature differential drives moisture migration — particularly if grain was stored at elevated moisture levels or without proper cooling. The result can be hot spots, crusting, mold growth and quality losses that develop quietly before they become visible.

Now is the time to take a methodical approach to preserving grain quality and profitability through the warmer months ahead.

Start with bin sanitation

Iowa State University Extension and Outreach recommends completing the following steps before filling a bin with new grain:

Clean walls and floors by sweeping, vacuuming or washing
Remove dust around doors, seams, vents and false floors
Repair cracks or holes in bins
Remove old grain around storage areas
Eliminate grass and weeds around bins

Operators also should confirm that aeration fans, temperature cables, probes and automated monitoring systems are functioning correctly. Spoilage detected early is easier to manage than issues discovered later in the storage season.

Check moisture content

Stored grain should be checked for moisture content before high summer temperatures increase spoilage risk. North Dakota State University (NDSU) Extension recommends the following benchmarks for safe summer storage:

Corn: 13% to 14% moisture
Soybeans: 11% to 12% moisture
Wheat: 13% moisture

Ken Hellevang, professor emeritus and agricultural engineer at NDSU, noted that allowable storage time for soybeans at 13% moisture drops below 100 days at 70 F, meaning summer heat quickly compresses the safe storage window.

Storage life depends heavily on grain moisture and temperature. Beginning at harvest, corn at 20% moisture has a safe storage period of roughly 28 days at 60 F, up to 90 days at 40 F and about 115 days at 35 F.

In-bin drying systems can gradually reduce moisture while grain remains in storage. Delaying drying until summer risks heating grain and accelerating spoilage. If in-bin drying capacity is insufficient, high-temperature drying may be necessary for rapid turnaround.

Monitor temperature and CO₂

Rob Proulx, NDSU Extension ag technology and grain systems specialist, advises checking grain temperature every two weeks during spring and summer. A temperature increase may indicate a developing storage problem.

CO₂ monitoring provides another early warning layer, according to research from Purdue University. Respiration from insects, mold and fungi produces CO₂ as grain deteriorates, and elevated CO₂ levels can signal spoilage days or weeks before temperature cables detect a problem.

Permanently installed CO₂ monitoring devices and automated systems can identify changes in CO₂ levels and trigger aeration fan response without requiring constant manual attention.

Use aeration fans strategically

A common mistake is treating aeration as a set-and-forget operation. As outside temperatures rise, large temperature differences between grain and ambient air can create condensation inside bins. Industry recommendations generally call for maintaining a temperature differential of no more than 10 to 15 F by slowly warming grain with outdoor temperatures.

Oklahoma State University Extension notes that airflow rate is critical for uniform cooling. Airflow is expressed as CFM per bushel, or cubic feet of air per minute per bushel of stored grain. Bins should have at least 0.10 CFM per bushel for aeration of already dried grain.

Operators also should watch for fines and broken kernels concentrated in the core of a bin. Excessive fines can restrict airflow, create temperature gradients and accelerate moisture migration.

Automated fan controls eliminate guesswork by operating fans only when ambient air conditions provide meaningful cooling potential. This reduces energy consumption and minimizes over-drying shrink loss.

Stay alert through summer

The 2026 season carries additional weather-driven storage risk. Moderate to exceptional drought across much of the U.S. increases the likelihood of stressed, lower-test-weight grain entering storage from this year’s harvest. Late-spring temperature swings, including frost events in parts of the Midwest as recently as mid-May, followed by forecasts for above-normal temperatures across much of the country, mean some grain already has been exposed to thermal stress.

DTN Meteorologist John Baranick noted that a developing El Niño is beginning to influence U.S. weather patterns. Historically, developing Super El Niño years have produced increased humidity and precipitation across portions of the Corn Belt through summer and fall. For grain storage managers, that translates into more opportunities for moisture migration and condensation events — and a greater need for active, automated monitoring.

Equilibrium moisture content drives grain conditioning

While spring and summer grain management focuses on cooling grain and preventing spoilage, conditioning overly dry grain also can preserve quality and maximize profitability. According to Dirk Maier of Iowa State University, successful conditioning depends on understanding equilibrium moisture content, or EMC, and using the right automation tools.

EMC describes the relationship between grain moisture, air temperature and relative humidity. Grain naturally gains or loses moisture until it reaches equilibrium with surrounding air conditions.

Maier explained that air between 45 F and 70 F with relative humidity levels of roughly 60% to 70% can gradually raise soybean moisture content into the preferred 12% to 13% range.

Understanding EMC becomes especially important when operators attempt to recover value from overly dry grain. Soybean processors typically prefer soybeans around 10.5% moisture for flaking and oil extraction, while overly dry corn becomes more susceptible to cracked kernels, fines and dust.

Maier stressed that grain conditioning must rely on controlled aeration rather than direct water application, which federal regulators consider illegal adulteration. Instead, operators should use ambient air and automated fan controls that activate only when temperature and humidity conditions support safe moisture addition.

Commercially available systems from companies including AGI, GSI, OPI Systems, Sukup, Amber Ag, Centaur, Shivers Technology and Innovation Group (STIG), and Tri-States Grain Conditioning can monitor grain conditions and automate fan operation.

Research conducted at Iowa State found that airflow rates of at least 0.5 CFM per bushel are generally needed to gain even a half-point of moisture content efficiently. Higher humidity regions such as the eastern Corn Belt and south-central U.S. provide greater opportunities for profitable conditioning because fans can operate more often under favorable EMC conditions.

“Reconditioning grains using aeration fans and automatic controllers is technically feasible and economically desirable,” Maier said.