Sunflowers do have a fire risk when drying in the bin, though that risk is not necessarily related to the drying temperature.
“Material within the sunflower can get held up in the dryer and we will end up with portions becoming over-dry and combustible,” said Ken Hellevang, North Dakota State University Extension Service agricultural engineer and grain drying expert.
In addition, there is lint that comes off of the sunflower seeds that can accumulate in the dryer.
“We need to be constantly monitoring when we are drying sunflowers for storage,” he said.
If a fire starts, shut off the fan and have fire extinguishers readily available.
“If you are there monitoring, using the fire extinguisher at the fire point should be enough to extinguish it,” he said.
Immediately after putting out the fire, empty the dryer completely.
To avoid fires, frequently clean the dryer.
“Fires used to be a huge issue, but as the amount of sunflower acreage decreased, we didn’t hear much of it,” Hellevang said.
However, in the fall of 2020, there were a lot of flowers that were at high moisture and needed to be dried down.
Hellevang has his own oil sunflower air drying chart that is based on drying in October.
If the moisture content is 17 percent, the airflow should be 1.00 cfm/bu (cubic feet per minute per bushel) with a fan time of 648 hours or 27 days.
“Over the years, however, I feel more comfortable with starting at 15 percent than 17 percent,” he said.
At 15 percent moisture, using airflow at 1.00 cfm/bu, the fan time is 20 days; using airflow at .75 cfm/bu, the fan time is 30 days; and using airflow at .50 cfm/bu, the fan time is 40 days.
At 13 percent moisture, using airflow at 1.00 cfm/bu, the fan time is 14 days; using airflow at .75 cfm/bu, the fan time is 21 days; and using airflow at .50 cfm/bu, the fan time is 28 days.
“The 30-degree drying times in November are roughly double,” he said. “If we had been looking at 27 days, typically, we are looking at 54 days. So we are not going to be able to completely air dry the sunflower.”
With cold November conditions, progress can be made by adding supplemental heat. That would depend on what the outside conditions are and how much supplemental heat is needed.
If flowers were taken off at too high of a moisture content, the crop would have to be held over in the bin and dried in the spring.
“Spring drying works excellent for sunflowers,” Hellevang said.
With adequate airflow at 1 cfm/bu, flowers can be dried in roughly one month of fan time.
There may be temptation to pile the grain because it is high moisture, but it is critical to have air going through that pile.
“I discourage doing that right from the beginning because a 1-inch rain will increase the moisture content of 1 foot of sunflowers by about 9 percentage points,” he said. “We can go from reasonably moist conditions to horribly wet conditions in very little time with rain or snow that gets into the pile.”
If someone still wants to pile the grain, it needs a cover and negative pressure to hold the cover in place. Designed and managed aeration is critical for the pile. A producer should examine the cover often for perforations.
“I have seen way too many piles turn to mush because we don’t follow these practices,” Hellevang said.