Grain Storage: Aeration Part III

After reviewing part I and part II on my series on aeration I realized that there was one important topic I had yet to cover. Should Stored Grains be Warmed in the Spring? Here is my take on that important question.

As spring approaches, grain producers and handlers face a critical decision: Should they warm their stored grains to prevent moisture migration, or maintain a cool storage environment to preserve quality? This topic probably has had as much debate through the years as updraft vs. downdraft aeration. This topic ignites a debate among producers, grain handlers, vendors, academia, and other sources with opinions divided. Proponents of warming point to the protective benefits against moisture migration that can lead to quality degradation, while others advocate for keeping grains cool to maintain their integrity for as long as possible. Regardless of the stance taken, it is essential to inspect and manage these valuable assets rigorously during the spring months.

A range of factors complicate this decision-making process, including geographic location and climate zone, spring weather conditions, moisture and temperature of grain when placed into storage, aeration effectiveness, current grain moisture and temperature levels. In addition, bin type, whether steel or concrete, and bin size are variables. A 10,000-bushel farm bin reacts differently than a one to two million bushels commercial bin. Expected storage time is also a factor, will the bin be unloaded soon or is it going to be carried into the summer or longer? Are there any current quality issues or evidence of insect activity? These, along with other questions, must be analyzed and once the facts are obtained then a decision can be made.

The physics of grain that has been properly cooled and cored placed into storage in the fall is that in the spring the core will be cold, and temperatures will increase as you move out to the bin walls. This phenomenon is more prevalent in steel bins than concrete as concrete bins make excellent insulators. Larger diameter steel bins will also not be impacted as much as smaller diameter bins.

So, what are people saying?

• Greg Traame – Director of Technology GSI

Warm up or keep cold? This is the first decision to make, Trame says. “Growers in certain parts of the country prefer to keep corn cold as temperatures warm up outside. We’ve seen that work well as long as you keep a couple principles in mind.”

o   First, be prepared for lots of condensation forming water droplets when you finally empty the bin during warm weather. Expect grain handling equipment to get wet when cold grain meets warm air. As long as you’re aware it will happen, you can handle it successfully.

o   “Second, once you break the seal and open a bin of cold corn, then the ideal thing is to haul out the whole bin,” Trame says. “If it’s a large bin and you can’t do that, then realize that you must aerate and manage corn remaining in the bin.” Temperature. Many people in the central Midwest choose to warm grain up as spring approaches rather than leave it cold. “A good goal is keeping grain temperature within 10 to 15 degrees of the average daily temperature,” he says. “If grain is at 40 and the temperature outside averages 60, that’s a wider gap than you would like.”

•   Purdue University AE-90 - G. H. Foster and B. A. McKenzie

 In March or April, warm the grain to about 50°F by aerating, If It is to be stored into late summer.

This is a controversial practice. Some operators prefer to leave the grain at 30-40° F as long as possible. However, if the grain is stored into late summer, reverse moisture migration may cause moisture to accumulate between the warm grain on the surface and the cold grain toward the center of the bin. The trouble spots usually develop 2-3 feet below the grain surface.

Moisture migration and accumulation in summer usually proceeds slower than that which occurs on the grain surface during cold weather. Thus, it may not cause molding and heating until July or early August. If the grain is likely to be stored beyond July 1, then it should be warmed in mid-spring to near outdoor temperatures. Once aeration in the spring is started, continue it until all the grain is warmed uniformly to near outdoor temperatures.

• Purdue University AED-20 - Bruce A. McKenzie and Larry Van Fossen

Yes, in many cases, you will need to consider warming stored grain in the spring, particularly if it's been cooled to lower temperatures during winter. Warming the grain can help prevent moisture migration and associated spoilage, especially when the ambient temperature rises. However, the decision to warm and the extent of warming depends on factors like storage duration, grain type, and moisture content.

Here's a more detailed explanation: Why warm grain?

Cooling grain in winter is a common practice to slow down spoilage and insect activity. However, as the ambient temperature rises in spring, a significant temperature difference between the grain and the outside air can lead to condensation and moisture migration within the bin, potentially causing spoilage.

When to warm?

If you plan to store grain into the summer months (May or later), you should aim to warm it to around 50-60°F by May 1st. If you only plan to store it for a shorter period (through late March or early April), you may not need to warm it as much, according to CropWatch.

• Farm Journal  AG WEB- SDSU Extension -Sara Bauder, Adam Varenhort

Periodically run bin fans throughout the spring to help keep grain cool and slow warm-up.

• NDSU – Ken Hellevang

o   As outdoor temperatures increase, stored grain requires attention to prevent losses, says Ken Hellevang, North Dakota State University Extension agricultural engineer and grain drying expert. The stored grain temperature increases in the spring not only due to an increase in outdoor temperatures but also due to solar heat gain on the bin. Solar energy produces more than twice as much heat gain on the south wall of a bin in spring as it does during the summer.

Hellevang recommends periodically running aeration fans to keep the grain temperature near or below 30 degrees until the grain is dried if it exceeds recommended storage moisture contents, and below 40 degrees as long as possible during spring and early summer if the grain is dry. Night air temperatures are near or below 30 degrees in April and 40 degrees in May. Soybean oil quality may be affected in less than four months if even 12% moisture soybeans are stored at 70 degrees.

• Iowa State – Shawn Shouse and Kristina TeBockhorst

Any grain that was stored wetter than the recommended moisture contents, above 15% for corn and 13% for soybeans, should be dried or moved when cool grain temperatures (30-40 degrees Fahrenheit) can no longer be maintained. Grain stored cool through the winter does not need to be warmed up in the spring. Instead, aerate grain to maintain cool and even temperatures in the bin. Run aeration fans to check grain or run aeration cycles for temperature control during cool weather rather than warm, sunny days.

So, is there a definitive answer to this question? Probably not. There are so many variables that impact the decision to do spring rewarming or not providing a universal recommendation is difficult.

From my personal experience, we generally chose to keep large diameter steel or concrete bins cool as long as possible. We capitalized on cool night air to run fans when necessary. We also employed exhaust fans on top to remove moist air accumulating at the grain surface to prevent crusting. In cases involving smaller diameter bins or those with previous quality issues, we occasionally opted to rewarm. This approach consistently helped maintain grain quality.

Ultimately, whatever course you decide to take regarding warming stored grain, springtime is critical. Ensure that you have adequate monitoring and management practices in place to protect your valuable assets.

This concludes my examination into aeration of stored grains. I hope this series provides some insights and things for you to investigate further. As always, I welcome any comments or feedback on the information provided.

Please feel free to reach out with questions or suggest subjects that interest you.

Regards,

Grain Guy Fifty