Don't Fully Trust Mother Nature to Dry Your 'Flowers
Saturday, September 1, 2001
filed under: Harvest/Storage
Don’t Fully Trust Mother Nature to Dry Your ‘Flowers
While Natural Drydown Is Preferable, There’s Also Something To Be Said About Harvesting Good Quality Sunflower On Your Own Timing, And Avoiding An Early Arrival Of Old Man Winter
The rise in energy costs has resulted in a good share of ink the last few years advising producers on how to save money on fuel. However, while efficient spending on farm inputs is critical, it also doesn’t make sense (or cents) to avoid some practices if that may result in more expense later.
Like grain drying, for instance. Some producers seem hesitant to spend money on grain drying, but while natural drydown is preferable, using a grain dryer can also be viewed as a good management tool to help avoid even higher costs and more uncomfortable working conditions that are possible late in the season with the early arrival of old man winter.
Think of it as an investment in harvesting good quality grain on your schedule, making sure you avoid drying in poorer conditions, says Ken Hellevang, North Dakota State University extension ag engineer.
“The earlier we can start the drying process, the more energy efficient it’s going to be. Last year we had a nice fall and everybody was happy with letting mother nature do the drying for them. Then the latter part of October we got rain, then it got cold after the beginning of November and we had a horrible mess,” he says. “At some point we need to look at from the standpoint that, ‘yes, it’s costing me to dry, but it’ll allow me to get it off in good condition.’ The later we wait, the more risks we face. So many times we have people who gamble and then pay dearly for it.”
Hellevang says that the efficiency and speed of drying is much greater in October, when the average temperature in the Northern Plains is around 50 degrees, compared to November, when the average temperature is around 30 degrees. The 20-degree difference effectively doubles drying time for natural air or low temperature drying, and requires an additional 9 gallons of propane per hour based on 20,000 cubic feet per minute (cfm) of airflow in a high temperature dryer. “So when we’re talking about natural air drying, the ability to get started a little earlier will make a world of difference. The same thing goes with high temperature drying,” he says.
From the standpoint of energy efficiency, it’s best to use the highest drying temperature possible without damaging the sunflower between 180 and 200 degrees is sufficient for continuous flow dryers, says Hellevang. Temperatures over 110 degrees should not be used to dry sunflower for seed purposes. Drying temperatures up to 220 degrees do not appear to have an adverse effect on oil percentage or fatty acid composition, according to past NDSU research, although high drying temperatures can damage confection sunflower.
Obstruction to the flow of sunflower seed in the dryer can lead to overdrying, and overdrying can cause sunflower or debris in the sunflower to become very combustible. However, contrary to what some believe, there is no correlation between dryer temperatures and dryer fires. “Some have tried backing off dryer temperatures, turning the heat down from 200 degrees to 180 degrees, for instance, thinking it will minimize the hazard of dryer fires. That’s probably not going to happen, however. What we’ve found is that the biggest correlation between fires comes from housekeeping. Clean your dryer in between batches so there’s no accumulation of fines or debris. That’s what tends to be linked most with fires,” says Hellevang.
If using a heater to warm air for low temperature drying, be sure not to overdry. The additional heat that warms the air by 20 degrees will cut the relative humidity roughly in half. Thus, instead of drying oil sunflower to around 8 or 9% moisture, it will dry to 5 or 6%, which is too dry. Sunflower that is over-dried tends to shell more, and if it’s confection, the market might not accept them. Overdrying sunflower also leads to more shrink, meaning you’ll have less to haul to market. For example, if you have 100 pounds of oil sunflower at 10% moisture and you dry it down to 6% moisture, you’ll have only 95 pounds left you lost 5% of the weight by overdrying.
Note that more horsepower is needed for drying sunflower, and less for aeration. A 20-horse fan would be needed to dry oil sunflower in a 36-ft. diameter, 25-ft. deep bin, but a 1.5 horse fan would be more than adequate for aeration.
A moisture meter can sometimes be fooled by sunflower with shells that are drier than the kernels inside, so watch for “moisture rebound” in sunflower. For example, the meter might indicate 10% moisture, and a subsequent reading indicates a jump up to 12% moisture. Thus, moisture testing is important, especially with sunflower. Test it, and then come back a day or two later to make sure it’s at the moisture you want. Hellevang notes that in a recent conversation with a federal grain inspection official, that a better way of testing sunflower for moisture is being developed. “So down the road we may have better equipment where we won’t have to deal with this problem,” he says.
Minimize Condensation
Make sure bin roof openings are adequate, says Hellevang. One square foot of bin vent opening for every 1,000 cfm of airflow is recommended. Also, be mindful of condensation that can form in the bin roof as warm grain cools. “A rule of thumb is that a 20-degree drop in temperature doubles its relative humidity. So if dry grain in the bin is sitting there at 50 degrees, the air coming off the grain will have a relative humidity of about 60% and be at 50 degrees. When the air comes in contact with the bin roof, cooled to 30 degrees by outside air, it will double with condensation starting when it reaches 100%.”
Get airflow going through stored sunflower as soon as possible, says Hellevang. “For every 10 degrees we can cool the grain, the allowable storage time is doubled,” he says. Put another way, the rate of grain deterioration doubles with every 10-degree increase in temperature. “Airflow is critical, and it doesn’t require a lot. A littler aeration can be of great benefit, and any is better than none,” says Hellevang. Because about a 20-degree temperature differential in the grain mass will cause moisture migration, aeration should start before the average outdoor temperature is 20 degrees cooler than the grain temperature, Hellevang recommends.
Cooling gradually in 10 to 15-degree steps to avoid a large difference between the bin and outside temperature, along with adequate bin vents, will help minimize condensation, he says. It will also help prevent pressure from building and possibly damaging the top of the bin roof due to ice blocking the vent screens. “If you have to run the fans when there’s a large temperature difference and outside it’s near or below freezing, I encourage producers to unlatch the opening at the top to prevent pressure in the head space of the bin from developing.” Just don’t forget to close it. – Tracy Sayler
Grain temperature key to grain storability
80 degrees: The ideal temperature for insect and mold growth in stored grain.
70 degrees: Cooling grain below this temperature reduces insect reproduction,
50 degrees: Cooling grain below this temperature causes insects to become dormant.
40 degrees: Mold growth is almost nil at temperatures below this.
20-25 degrees: Grain should be cooled to this range for winter storage.
Be Sure To Do Storage Checkups
Check the condition of stored grain about every two weeks while grain is cooling, then about monthly after grain has cooled. A check should include measurements of moisture content and temperature at several locations. Moisture measurement accuracy is dependant on the grain temperature, so it is best to collect a grain sample, let it warm to room temperature in a plastic bag or other sealed container, then check the moisture content. Also, be sure to cover fans and ducts after the grain has been cooled for winter storage to prevent snow from blowing into the bins.
Grain Drying And Storage Info Online
http://www.ext.colostate.edu/pubs/crops/00117.html
(Colorado State University, managing stored grain)
http://www.oznet.ksu.edu/library/ageng2/af158.pdf
(Kansas State University, drying and storing sunflower)
http://www.ext.nodak.edu/extpubs/plantsci/rowcrops/eb25w-10.htm
(North Dakota State University, sunflower drying and storage)
http://www.ag.ndsu.nodak.edu/aginfo/procrop/str/index.htm
(NDSU Pro Crop 2001 Storage Menu)
http://www.ext.nodak.edu/extpubs/grainsto.htm
(NDSU Online Grain Drying and Storage Publications)
http://www.ag.ndsu.nodak.edu/abeng/postharvest.htm
Extensive NDSU site on grain drying, handling and storage
http://www.extension.umn.edu/listing.html?topic=2&subcat=44
(University of Minnesota Grain Drying, Handling & Storage)
http://www.bae.umn.edu/extens/postharvest/tempstor.html
(U of M Grain Storage Issues)