If you are storing more grain on farm this spring than usual, you are not alone. Over the last few weeks, we have heard from more producers who are considering holding grain longer into summer months than they normally would. We have also heard a few reports of spoiled grain as producers fill April contracts. Carrying graining into summer has been done for many years successfully but requires much more intensive management than winter grain storage.
Key advice for long-term grain storage
- If bins were not cored in early winter, core bins now.
- Verify the moisture content of stored grain is at or below recommended levels.
- Monitor grain temperature every 3 or 4 weeks throughout storage paying special attention to insect activity and mold.
- Monitor the roof area for signs of condensation.
- Cover fans to keep the chimney effect from warming the grain.
- Provide roof ventilation at two levels above the surface of the grain, one vent should be close to the peak of the bin.
- Aerate bins on cool mornings every couple weeks as grain at the top of the bin becomes warm.
The first management consideration is the moisture of your stored grain. If you plan to store grain into the warmer summer months, it is important to know the moisture content of your stored grain. Last fall some grain went into storage at a higher than ideal moisture content. If crop development was impacted by the unusual weather conditions in 2019, moisture tester readings can be off by up to 2 points. The recommended maximum storage moisture content for summer are 13% to 14% for corn, 11% for soybeans and 13.5% for wheat. If your stored grain is currently at a higher moisture content, you should consider moving it to market or drying to these recommended storage moistures using natural drying, if possible. Using high temperature drying now is not recommended because re-cooling the grain for summer storage will be challenging.
The second consideration for maintaining stored grain into the summer is temperature. Historically, it was recommended to warm grain in the summer as ambient air temperatures increase, but this is no longer considered a best management practice. It is now recommended to keep grain as cool as possible for spring and summer grain storage. Warming grain to average outdoor summer temperatures can lead to increased potential for insect infestation and mold growth. Keeping grain temperature below 70 degrees F lessens insect reproductive activity compared to 80 degrees F but keeping this temperature below 60 degrees F will greatly reduce insect activity. When grain temperatures are below 50 degrees F, most insects are dormant.
Monitoring stored grain temperature through the summer will allow you catch potential problems. Grain is an excellent insulator, so it can be challenging to detect pockets of warm grain. If summer grain storage will be common on your farm, using multiple temperature monitoring cables throughout the bin is recommended. Since the grain at the top of the bin is often the warmest, a 2-foot thermometer can be used to check temperatures if monitoring cables are not installed. Grain temperature should be checked every couple of weeks in the center and around the edges of the bin. Often the south side of the bin warms up before other sections. Increased temperature may be a sign of mold growth or insect activity.
Proper ventilation is also important when keeping grain in summer months. Solar radiation warms the roof of the bin and the air below. Natural convection air currents within the bin cause air to rise along the walls and be drawn into the center of the bin, warming the grain. Natural ventilation of the air space above the grain can be used to help keep this space cool. Having vents in two areas above the grain with either a vent or fan at the peak assists with this ventilation. This works similar to attic vents in a home. Air enters at the bin eave openings and leaves at the peak vent helping to keep the area above the grain cool.
The bottom positive pressure ventilation fans can also be used to help keep the grain at the top of the bin cool. Running fans every three or four weeks on a cool morning for a couple days in a row can cool the grain at the top of the bin. The air entering the bottom of the bin is cooled by the cold grain and then cools the grain at the top. It is very important to select mornings when air is cool and dry. While we often do not cover bottom ventilation fans during winter grain storage, this is much more important for summer storage. Openings at the bottom of the bin create a chimney effect throughout the entire grain mass. Warm air enters the bottom of the bin and as wind blows past the top of the bin the air is drawn up through the grain mass warming it up. Fan covers can be as simple as a tarp fastened over the fan or there are more durable fan covers available.
Keeping stored grain in condition during summer months will take more management than winter storage and the risk of spoilage is higher. Remember that stored grain cannot be kept in condition indefinitely. We strongly recommend you have a grain marketing plan for any grain you are keeping in storage.