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December 16, 2004 NDSU Offers Winter Grain Storage Tips Natural-air and low-temperature grain drying is not effective during cold winter temperatures, according to a North Dakota State University Extension Service engineer and professor. “The cold air does not pick up much moisture, so the drying times become extremely long, months rather than weeks,” says Ken Hellevang, NDSU Agricultural and Biosystems Engineering Department. “The relative humidity is high, so the grain will only dry to about 20 percent moisture. When air temperatures are near or below freezing, the grain should be cooled to about 20 to 25 degrees and then the fans turned off.” Most grain moisture meters are not accurate at grain temperatures below 40 degrees. When the grain is cold, it should be placed in a sealed container, such as a plastic bag, and warmed to room temperature before checking the moisture content. At temperatures above 40 degrees, the meter reading must be adjusted based on the grain temperature, unless the meter measures the grain temperature and automatically adjusts the reading. Moisture meters are calibrated for mature grain with normal characteristics. Variations in grain maturity, growing conditions and test weight will affect the accuracy of the meter. Some deviations in meter accuracy might be expected for some of the grains this year. “High-moisture grain can be stored over the winter as long as the grain is kept cold,” Hellevang says. “Corn at 24 percent moisture can be stored for about 130 days if the grain temperature is below 30 degrees, but the allowable storage time decreases drastically at warmer grain temperatures. The estimated allowable storage time for 24 percent moisture corn is 40 days at 40 degrees, but only 15 days at 50 degrees.” Corn below 21 percent moisture can be natural-air dried in the spring using an airflow rate of at least 1 cubic foot of air per minute per bushel by starting the fans when the average temperature is about 40 degrees. Corn at moisture content exceeding 21 percent should be removed for high-temperature drying before temperatures rapidly warm during March. Solar heat gain will warm the top of the bin and the south wall to temperatures exceeding outdoor air temperatures. Grain will deteriorate even with the fan operating. Airflow keeps the grain cooled to near the air temperature, but the grain still will deteriorate at a rate based on the grain moisture content and temperature. Grain is more susceptible to deterioration if it is immature or the kernel integrity is damaged. Poor quality grain should be dried to a moisture content about 1 percentage point lower than good quality grain. Poor quality grain should be monitored more closely during the storage period. There will be a grain moisture content variation among kernels after drying in a high- temperature dryer if there was a moisture content variation before drying. For example, if the kernels vary in moisture between 20 percent and 30 percent before drying, the variation may be between 12 percent and 18 percent after drying. Due to the variations in maturity within fields and even on a single corncob, there is potential for variations in stored grain moisture content. Grain segregates based on size and density as it flows into a bin. If there is a variation in kernel size, pockets and variations should be expected. Some of these pockets may contain grain at higher moisture content. If a grain spreader has not been used to fill a bin, normally the smaller and denser material accumulates in the center of the bin. Grain germination may be damaged before visible mold is present on the kernels. This may happen when wet grain remains in a bin at moderate temperatures for an extended period before it is dried. Germination should be checked on malting barley and seed that was not dried within three weeks of being placed in the bin. There is the potential for bin vent screens to become iced over when operating fans near or below freezing temperatures. “There have been a few cases where vents iced over on bins of corn that were being cooled at freezing temperatures, which caused damage to the bin roof,” Hellevang says. “It is recommended to leave a bin fill-hole or manhole unlatched as a pressure relief valve if the air is being pushed up through the grain. If humid air is being pulled in through bin vents at temperatures near freezing, provide an unscreened opening, such as the manhole, for airflow.” Check the grain every couple of weeks until it has been cooled to 20 to 25 degrees. Check dry grain at least monthly during the winter and wet grain every couple of weeks. Measure and record the grain temperature. Check the grain moisture content and examine the grain in several locations. Search for small changes that are indicators of potential problems. High moisture grain is more likely to develop a crust, which may hide a cavity formed when the grain is unloaded. “The chance of suffocating is high if you fall into the cavity and are covered by the grain,” Hellevang says. “Grain stuck to the wall of a bin can also trap and suffocate a person attempting to break it loose. It is not healthy to breathe mold spores and suspended mold particles that may be in the air of a bin with deteriorating grain. Always wear at least an N-95 rated mask or respirator if in a bin with spoiled or moldy grain.” ### Source:
Kenneth J. Hellevang, (701) 231-7243, kjh-eng@ndsuext.nodak.edu |
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