Remember to check your grain in storage - often
Wednesday, October 6, 2010
Regardless of the year, it is critical that operators pay attention to temperature or moisture content increases in stored grains or oilseeds
by RALPH WINFIELD
Shortly after I went on staff at the then Western Ontario Agricultural School at Ridgetown in 1964, I started talking about grain drying and storage. My colleague Ralph Clayton and I actually started an elevator operator's course in 1967.
So what has changed? Primarily, my hair colour and the people who are operating elevators and on-farm grain drying/storage systems.
Unfortunately, the failure to remember the need to check on grain in storage has not changed. Grain – be it corn, wheat or soybeans – is still a living, respiring product. It produces heat and gives off moisture when the carbohydrates break down. In other words, the grain heats and sweats.
As a farm elevator operator told me almost 30 years ago, "If you had $20,000 in cash under your mattress, you would check it every night before you get into bed. Surely you can afford the time to check the same value of grain or oilseed product in your storage at least once a week."
My colleague Helmut Spieser and I have been holding grain-drying seminars again for about three years now. The major change I am seeing is a new, somewhat younger group of operators. Some of them do not remember the drying problems of 1992. That is the year the moisture content of corn increased during the drying season because the corn was not fully mature.
Fast forward to 2009, when we nearly had a repeat of 1992. Much of the Ontario corn had lower than ideal test weights. Coupled with that was the "moisture bounce" that was experienced by many dryer/storage operators.
Regardless of the year, it is critical that operators pay attention to temperature or moisture content increases in stored grains or oilseeds. Firstly, every storage bin should have good aeration systems in place. Most bins now have full aeration floors and a permanent aeration fan. But, just as importantly, the bin must have sufficient air outlets (vents) in the roof to permit air to get out without creating back pressure.
Some bins are equipped with temperature-sensing cables, which is a good use of technology but one that should not be relied upon as the only indicator of potential problems.
A nose is still the best sensing device. When the aeration fan is turned on to check grain condition, a nose at a bin vent is the best indicator available. It tells temperature or deterioration in condition. Frequently, aeration can correct most problems if they are detected early.
Aeration to control grain temperature is the best form of insurance available. First, you must know the aeration rate in cubic feet per minute per bushel (cfm/bu) of every storage bin you own or operate. Think of cfm/bu as a speedometer. It will tell you how long it will take to change the temperature of the grain in the bin.
Aeration rate can be established by knowing two things. One is the performance curve of the fan and the second is the static pressure that the fan is delivering in inches of water column (in. w.c.). A simple U-Tube manometer will provide a static pressure value. The fan performance curve or table should be available from all reliable fan manufacturers.
When to aerate. It is absolutely critical that the grain temperature be reduced to within 5 C or 10 F of average ambient temperature as quickly as possible after harvest or drying.
The grain mass temperature must be adjusted downward frequently as average ambient temperatures decrease during the fall and early winter time frame. Don't be in as great a rush to bring the temperature up in the spring, especially if grain is in concrete silos.
Watch out for concentrations of fines in bins. Unless you clean dried corn going into storage, it is critical that you core the bins after filling to minimize the risk of a fines concentration, usually at the center of the bin. Do remember that this is also the location of moisture concentration in the grain if it is not cooled down adequately by aeration during the fall.
How much do you have to remove to core a bin? It will depend on the size (capacity) of the bin. For small, 5,000-bushel bins, about 200 bushels is sufficient. For larger bins, watch for the size of the inverted cone at the top of the bin. The diameter of the cone should equal one-half the diameter of the bin.
If practical, clean or sell the cored sample. However, if the fines content is not excessive, the cored sample can be put back into a bin.How long to aerate. Included is a table of fan run times to move an aeration front through a bin "to change temperature" for various air flow rates from 1/20 to one cfm/bu. The fan should be run continuously for at least the number of hours shown. You should, of course, pick a time when rain or fog is not likely to occur.***chart goes here called BF_Oct10-76.gifAeration versus natural air dying. Aeration is intended to remove field heat from wheat or residual heat from corn coming from a high temperature dryer.
If you are planning to remove moisture, for example, from wheat harvested at 17 per cent moisture, or corn taken from the dryer at 16-17 per cent moisture, it is critical that you have an airflow rate of at least 1/2 cfm/bu. Do remember that the airflow rate can be increased by only partly filling a bin to reduce the static pressure.
Many operators have filled bins with 16-17 per cent moisture wheat and operated the aeration fan continuously for 30 days or more, only to find that the wheat was still at 16-17 per cent moisture. Please remember that wheat has about twice the airflow resistance of corn or soybeans. Therefore, the airflow rate will be reduced. The solution is simple. Reduce the fill height to one half.
Helmut Spieser and I continue to get panic calls as Labour Day approaches. They go like this. "I have been running my aeration fan for 30 days now and my wheat is still at 17 per cent moisture. How come?"
The response is: "Does it still smell good with no off-odour?" If the answer is yes, the next statement is predictable. "Move half of the wheat to another bin, whether it is one that you own or a neighbour's bin."
Good luck with your 2010 harvest season. BF
Agricultural engineer Ralph Winfield farms at Belmont in Elgin County
