Test Equipment and Measurement Instrument Blog

3 Best Practices for Preventing Spoilage During Grain Storage

Posted by John Bogart on Wed, Aug 26, 2015 @ 09:08 AM

Wheat_moisture_sample-992282-editedMoisture content and fluctuating temperatures are one of the biggest challenges farmers face when it comes to safely storing their grains. In order to make sure stored grain doesn’t spoil during the warmer months, farmers must frequently analyze samples of their stored grain to make sure it’s able to handle the heat. The ideal temperature for storing grain and preventing mold and insect growth is anywhere between 25°F and 60°F, but these storage temperatures can be hard to maintain when outside temperatures are consistently over 80°F during the summer. Freshly harvested grain is particularly challenging to store because of its naturally higher moisture content and temperature. During storage, the grain changes both physically and chemically, and this warmer, wetter grain will respire in its storage bins, producing additional heat and moisture. Consequently, that additional heat and moisture generated during storage leads to hotspot development, mold growth, and mycotoxin development – all of which lead to grain spoilage.

By following the safe grain storage best practices outlined below, you can learn how to mitigate the risks and losses associated with storing grain, and ensure your supply will be stored safely for a long period of time.

Moisture Content and Temperature Monitoring

In order to ensure your grain isn’t losing its profitability, it’s critical that you monitor moisture content and temperature on a regular basis during storage to make sure your grain remains cool and dry. Every two weeks, evaluate a number of grain samples to obtain a representative snapshot of your overall grain health. Measure and track the temperature readings, and be sure to make note of any drastic increases in grain temperature (5.5°C or 10°F per week). Drastic changes in temperature are indicative of increased respiration due to spoilage or the development of mold and/or hotspots, and each 10 degrees the grain temperature increases will reduce the allowable storage time by about half. Insect reproduction is also reduced at temperatures below 65 to 70 degrees Fahrenheit, so you’ll also want to keep grain as cool as possible to limit insect activity.

In addition to regularly checking grain temperature, be sure to measure your grain’s moisture content. Checking your grain’s moisture content is important because measurements at harvest are likely to have changed due to moisture gradients in the freshly-harvested kernel, moisture entering storage bins, and grain temperature. It is crucial that moisture content decreases as the grain temperature increases in order to prevent mold growth and grain deterioration. When checking the moisture content of stored grain, make sure your measurement is accurate by warming the grain sample to room temperature in a sealed container or plastic bag before measuring the moisture content. Otherwise, you need to make sure your moisture tester automatically compensates for temperature. Letting the kernel sit for 6 to 12 hours in a sealed environment allows grain moisture to reach equilibrium across the kernels, providing a more consistent and reliable reading. When cross-referenced with temperature, these moisture values will help in determining the length of time the grain is able to be safely stored. Given these requirements, it’s important that you use a reliable grain moisture meter to provide the fast, accurate readings you need. Inaccurate moisture measurements can lead to serious consequences, including higher-than-necessary drying costs, excessive shrink, and grain spoilages. 

Adequate Aeration

Because wet grains are known to respire and give off heat, it’s important that you control your grain temperatures by moving cool air through your grain storage bins. As a matter of fact, you should start aerating your grains as soon as they’re placed into storage. Properly aerated grains can generally be stored safely about four times longer than non-aerated grains, so it’s important that you start the process right away when the grain is at its highest moisture content in order to maximize its longevity. As a general rule of thumb, aeration problems can be minimized by keeping grain temperatures within 10-15°F of the average outdoor air temperature, while also keeping grain temperatures below 60°F to control insect growth and activity

Safe Storage Charts

Need some help figuring out how long you can store your grains safely under their current conditions? Use the safe storage charts below to see recommendations based on grain temperature and moisture content for the length of time grain ought to be stored prior to suffering 0.5% dry matter loss. Dry matter loss (DML) refers to loss of weight due to molds, sprouting, insect damage, and/or respiration during storage. 

Table 1: Safe Storage Chart for Corn



Table 2: Safe Storage Chart for Canola



Table 3: Safe Storage Chart for Soybeans






Table 4: Safe Storage Chart for Cereals (Wheat and Rice)


Safe Storage Charts. Digital image. Learn Grain Management. OPI, n.d. Web. 25 Aug. 2015.

What if you’re doing everything “right,” but still having issues with grain spoilage?

Despite employing the proper grain management principles mentioned above, inaccurate moisture measurements can still negatively impact grain spoilage. In this case, it’s important to eliminate the testing issues that may be the root cause of a grain condition problem, such as:

  • Insufficient grain sampling
  • Improper tester use
  • Non-calibrated testing

Insufficient Grain Sampling

When you collect a sample of your grain, where do you collect it? If you’re just scooping your sample off the top layer, you aren’t sampling enough. Probe your storage in several locations and depths, going as deep as possible into the center. This will give you a better idea of the grain conditions throughout your bin. Make sure to test each sample separately so you can pinpoint the hotspots and mitigate spoilage problems.

Improper Tester Use

In order to get a reliable moisture meter reading, it’s important that you properly use the moisture tester. Make sure the battery is healthy, as low batteries can cause inaccurate readings. Follow the manufacturer’s instructions for testing with that moisture meter, and make sure you know whether your tester has automatic temperature compensation. Some testers require separate measurement of grain temperature with a thermometer, and the addition or subtraction of a correction factor to the moisture reading.

Calibrate Your Tester for Accuracy

Moisture meters should be inspected for accuracy on a regular basis. Most equipment dealers that sell and service moisture analyzers have a certified unit available for calibration, and it’s important that you compare at least three samples of your unit’s measurements against those from the certified unit at least once per year, before harvest. If the difference for any sample is greater than 1.0 percentage point, or if the average difference for all samples at one moisture level is greater than 0.5 point, then your tester needs to be recalibrated.

Proper preparation and aeration, frequent grain monitoring processes, and the application of safe grain storage timeliness are all key components of a successful safe grain storage program. Following these best practices will help you ensure continuous inventory levels, prevent spoilage, and maximize profitability for your business. To learn more about how Kett moisture meters can help you measure and track your stored grain moisture levels, fill out our online contact form or talk to one of our qualified engineers by clicking the button below:

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Topics: Grain Moisture Meter, Grain Moisture Tester, Single Grain Moisture Tester, Seed and Grain Moisture Meter