October 19, 2022
Sunflower harvest is nearly underway in the Dakotas, with the near term-forecast of warm temperatures expected to help sunflower crops reach maturity. According to USDA’s National Agricultural Statistics Service, as of Sept. 25, 35% of the sunflower crop had brown bracts indicating maturity, behind the 50% average.
“There is considerable variation this year due to the challenging spring, variation in rainfall, planting date, maturity rating and growing degree days, so it is important to check each field,” says Ken Hellevang, North Dakota State University ag engineer and grain drying specialist.
The current forecast for October is slightly above-normal temperatures and normal precipitation. October showers can have a major impact on crops drying in the field. The amount of drying in the field depends on parameters such as maturity, hybrid, moisture content, air temperature, relative humidity, solar radiation and wind speed.
Calculating drying rates
A predictor of the drying rate is potential evapotranspiration. PET is based on parameters similar to those that affect drying. Field drying normally is more economical until mid-to-late October in North Dakota, and mechanical high-temperature drying normally is more economical after that, Hellevang notes.
The amount of natural air drying in bins that will occur in Northern states in late October and early November is limited, since the moisture-holding capacity of air is reduced at lower air temperatures, he says.
As average air temperatures drop below 40 degrees F, natural air drying becomes less efficient and economical. Adding heat causes the grain on the bottom of the bin to dry to a lower moisture content and increases drying speed only slightly.
Sunflowers at 15% moisture can be dried some during late October and early November by heating the air about 5 degrees and using an airflow rate of 1 cubic feet per minute per bushel. Hellevang recommends cooling the sunflowers to between 20 and 30 degrees for winter storage, and completing the natural air drying in the spring. Start drying in the spring when outdoor temperatures are averaging 40 degrees.
Be careful of dryer fires
Sunflowers can be dried in a high-temperature dryer, but dryer fires are a concern. The fire hazard is not related to drying temperature, but rather to housekeeping and managing the dryer. Hellevang has this advice to reduce the risk of fire:
Make sure trash does not accumulate in the dryer or on the dryer.
Ensure crop continues to flow in all sections of the dryer.
Monitor the dryer continuously.
Clean the dryer frequently to reduce the potential for debris to combust.
If a fire occurs, shut off the fan, extinguish the fire and empty the dryer section with the fire.
Oil sunflowers should be dried to about 10% moisture for storage over winter and about 7% to 8% if being stored into next summer. Non-oil sunflowers can be stored at about 10% moisture during the summer. Cool the sunflower to 20 to 25 degrees for winter storage.
Hellevang supports using temperature cables to assist with monitoring the sunflower, but technology does not replace management. He still recommends monitoring the sunflower moisture content, inspecting for insects and observing the sunflower quality.
Remember safety when working around grain. Protect yourself from grain dust with an N95 mask. Do not go into a grain bin while the grain is moving. It only takes a couple seconds to become helpless in flowing grain. Use the lockout tag-out system to ensure you do not get hurt while working on grain drying and handling equipment.
For more information on high-moisture sunflower drying and storage, visit NDSU grain drying and storage.
Source: North Dakota State University
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