Tips on Drying, Storing Sunflower
A cooler growing season and later crop for many means a later fall harvest is possible, bringing greater challenges to sunflower drying and storage. Some tips to keep in mind, courtesy Ken Hellevang, extension ag engineer at North Dakota State University:
Storing wet ‘flowers short-term
Wet sunflower, over 17%, can be stored short-term as long as it can be kept cold. The allowable storage time (AST) for wheat can be used to estimate the AST for sunflower, by adding 5% to the sunflower moisture content. For example, 20% sunflower is equivalent to 25% moisture wheat.
The AST for 20% sunflower is about 110 days at 30 F, 37 days at 40 F, and 13 days at 50 F. Sunflower up to about 20% can be stored with continuous aeration to keep it cool, as long as capability is available to rapidly dry the sunflower. Storing sunflower above about 20% is discouraged, because there is a potential for the seeds to have enough surface moisture on them to freeze together and the bin could not be unloaded. Experience with corn is that this occurs in the mid-20% range, so it may be expected with sunflower at 20% or greater. The stored sunflower need to be monitored frequently to assure that they are staying cold.
An airflow rate of 1 cubic foot per minute per bushel will dry 15% moisture oil sunflower to about 10.2% in about 20 days, assuming average October conditions in North Dakota. The drying rate is much slower under colder November temperatures, taking nearly 40 days. Because drying rate is directly related to the airflow rate, increasing the airflow rate reduces the drying time.
Remember that fan horsepower requirements increase rapidly with increasing airflow rates, so sunflower depth in the bin may need to be reduced to achieve the desired airflow rate. Some heating of the air will occur as air passes through the fan. The amount will vary depending on the fan and operating static pressure, but a 4 or 5 degree increase is expected at about 6 inches of pressure. This needs to be considered when deciding how much heat to add.
Adding heat to natural air drying
Adding heat to a natural air drying system will slightly increase the speed of drying, but supplemental heat will also increase drying costs, and care needs to be taken to prevent over-drying.
The maximum recommended drying temperature of air used for drying varies by drying method, but it is typically 120 degrees for a bin batch dryer; 180 degrees for column batch; and 200 degrees for continuous flow/recirculating batch.
Drying temperatures up to 220 F do not appear to have an adverse effect on oil percentage or fatty acid composition. High drying temperatures for confection hybrids may cause the kernels to be steamed, wrinkled, or even scorched. Temperatures over 110 F should not be used to dry sunflower seed for seeding purposes.
Always remember that sunflower is an oil-based crop, and fine fibers from sunflower seeds pose a constant fire hazard. Debris that becomes very dry and combustible is the primary cause for fires while drying sunflower in a high temperature dryer. Obstruction to the flow of sunflower seed in the dryer also leads to overdrying. Thoroughly cleaning the dryer periodically will reduce the risk of dryer fires and dryer obstruction. It’s always a good idea to have a fire extinguisher on hand when harvesting and drying sunflower.
Estimate Cost for On-farm Storage
The Kansas State University Extension Service offers a free spreadsheet to help estimate on-farm storage costs, online at http://www.agmanager.info/crops/marketing/publications/stor_budget/On-farm%20storage.xls
More online resources for postharvest grain storage tips and information:
General guidelines for drying sunflower
•The area around the dryer and the plenum chamber should be thoroughly cleaned.
•The fan must be fed clean air without seed hairs.
•Overdrying sunflower must be avoided.
•A continuous flow for all sections of recirculating batch and continuous-flow dryers should be maintained. Uneven flow will cause overdried spots and increase fire hazard.
•Drying equipment must not be left unattended day or night.
•The dried sunflower should be cooled to air temperature before storing.
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