As mentioned above, aeration objectives are to keep grain within 10 F of the average monthly ambient air temperature and to maintain relatively uniform temperature within the grain mass — preferably no more than a 10 F temperature difference from one part of the bin to another.
Grain temperature should be controlled throughout the year: cooled in the fall; held at 35 to 40 F through the winter; warmed in the spring; and held at about 50 to 60 F through the summer. According to Hellevang, North Dakota State University, recent research indicates that it is beneficial to keep grain as cool as possible during the summer.
A cooling or warming zone moves through your grain in the same direction as the flow of air. Rate of zone movement depends on both airflow rate (cfm/bushel) and the hours of fan operation. For example, with an airflow of 0.1 cfm/bushel, it takes about a week to completely move a cooling or warming zone through the grain mass, whereas with an airflow of 0.75 cfm/bushel, it takes approximately a day.
A common question, as stated by Jones and Shelton from Nebraska State, is whether airflow should be upward or downward through the grain mass. With aeration system performance, the effect of direction is negligible; however, upward airflow is preferred. With upward air movement, the top of the grain mass is the last area to change temperature, and it is easier to determine if the zone has completely moved through the grain at the top of the bin.
Insects and mold
Insects are not usually a problem in grain stored less than a year; however, if discovered, insect infestations should be treated since they will lead to other storage problems. Insects give off moisture that can create a mold problem. Mold activity will in turn raise temperatures and result in increased insect reproduction.
Monitoring grain condition
Grain condition should be monitored frequently to verify temperature. Regular examinations also ensure detection of mold and insect activity can be detected and treated. Generally, grain should be inspected at least once a month during the winter and every two weeks during the rest of the year. Grain temperatures should be checked and recorded at each inspection. Without records, it is difficult to tell whether elevated temperatures are caused by normally occurring outside temperatures or by heating due to mold.
Some additional areas and conditions to check when monitoring grain quality include: grain surface for condensation, crusting, wet areas, molds and insects, and exhaust air for any off-odors. If problems are detected, you should evaluate and mitigate as soon as possible. This may include cooling with aeration, additional drying or fumigation for insect control.
Safety is of the essence when checking grain, and caution is the watchword. Bridged grain is dangerous, and the collapse of bridged areas can result in suffocation. Employees should always use a safety harness, lifeline and grab rope and have a second person outside the bin to assist if an emergency arises.
Develop and implement a grain quality management plan
A key to maintaining good grain quality in your operation is the development and implementation of a good management plan. The first step is to set the time aside where you and your operations managers sit down and commit the plan to paper. Make sure that your plan includes the necessary details (e.g., what levels of moisture you will maintain in grain bins, etc.). As part of the plan, generate a timeline or table that includes specific dates throughout the year. The dates that all key maintenance operations will be completed are part of this, as well as the dates where you will test and monitor key factors in your grain operation.
As part of this system, establish a reporting system that works for everyone — from the employees who are cleaning the bins and reporting the results of moisture tests up through everyone on the management team. Having this information readily accessible will be important for regular monitoring and then making necessary changes.