By Geoff Geddes
While the practice of “out of sight, out of mind” might work with that dreaded “to-do” list, it could leave you out of luck when applied to soybean storage. Harvesting may be half the battle, but what you do afterwards is key to giving soybeans a fighting chance.
“Soybeans are a relatively new crop in Western Canada, so some farmers may not know just how different they are,” says Jitendra Paliwal, a professor in the Department of Biosystems Engineering at the University of Manitoba.
Needing their space
Because soybean kernels are much larger than crops like canola, you’re left with bigger intergranular spaces when you pack them in a bin. This makes a huge difference to movement of moisture in the bin as air travels quickly when drying and aerating the beans.
“Consequently, soybeans tend to dry quite rapidly compared to canola or corn,” says Paliwal. “If you’re not paying attention, you may over-dry your crop which can lead to shattering of the beans and a drop in value when you market them.”
Storage success begins with a clean bin. It’s crucial to ensure that everything is disinfected, no bugs or grain are left over from the previous crop and all crevices are properly sealed.
From there, the focus should be on moisture and temperature.
“If your moisture level is under 13 percent, you shouldn’t have storage issues,” says Dennis Lange, industry development specialist – Pulses in the Primary Agriculture Branch of Manitoba Agriculture.
Where you get into trouble is at levels of 16-17 percent.
“Last fall, some growers had trouble finishing certain fields and had to take crops off at higher moisture levels,” says Lange. “Normally you might turn the aeration fans on to extract some moisture, but since soybeans are usually harvested in September or October, there aren’t a lot of good drying days at that point.”
Forgetting can be unforgiving
With high moisture content, the worst thing you can do is put the beans in the bin and forget about them, as you could have crusting problems at the top of the bin.
“You could end up sealing off the top of the pile so moisture can’t migrate out of the bin, leading to crusting issues and heated beans,” says Lange.
“When dealing with excessive moisture, you need to pull a load out of the bin within two to three weeks and circulate it through the bin if you haven’t had much drying by then.”
Temperature is another aspect that could leave you hot under the collar if left unchecked.
“Aim for below 10°C,” says Paliwal. “Insects won’t grow at less than 20°C and not many insects infest soybeans, so most spoilage is from mould growth that can happen at over 8°C.”
Assuming moisture is not a problem, you can turn the fan on and cool the beans; however, if you have high moisture you may want to use heated air for drying.
A game of inches
Given that spoilage is the biggest storage problem for soybeans, a new solution is drawing some interest. A research project at the University of Manitoba is using electromagnetic imaging (EMI) – normally employed for cancer screening – to create a three-dimensional profile of a bin, showing pockets of moisture that can overheat and spoil.
“The old method of sampling with a probe is almost impossible now as most bins are 15 metres in diameter,” says Paliwal, who is one of the principals on the project.
“Now, the normal approach is via a hanging cable with sensors. The problem is, the sensors are about four feet apart and spoilage pockets are only a couple of inches wide, so you could easily miss them with the cable system.”
As Paliwal points out, it only takes one hot spot to lose an entire bin that could be worth hundreds of thousands of dollars. That’s a good reminder of why keeping an eye on your beans in storage is so important. To paraphrase the old saying: out of sight, out of mind, out of business.