Proper Storage: Protecting the Value of Your Harvested Grain
Sep 04, 2019
You may have heard a time or two this harvest that “the safest place for the crop is in the bin”. Although the bin is generally safer than the field, just because grain has been stored does not mean that it should be “out of sight and out of mind”. In order to keep stored grain safe it needs to be closely monitored and carefully managed. Understanding the potential risks facing grain once it is in the bin, and the measures that can be taken to prevent them, will help you avoid many costly headaches when it comes time to ship your grain.
Potential problems with storing grain
Because of its insulation properties, grain is able to hold its original harvest temperature quite steadily. This means that when warm grain is put in the bin and left unaltered, it retains its warmth and is at risk of spoiling and insect infestation. Furthermore, when the temperature outside the bin is quite different than the temperature inside the bin it creates a convection like current (Figure 1) that can lead to condensation and create hot spots within the bin. These hot spots will be worse if the grain is not dry and can become hot enough to spoil. This warm humid air will attract insects that can either feed on the grain or feed on the fungi that are produced in this type of climate.
Figure 1. Air flow in grain bin when outside air temperature is cooler then inside temperature (Canadian Grains Commission, 2013).
Preventing spoiled grain
Each crop is classified dry at different moisture contents (Table 1). Ensuring that grain is put into the bin at a moisture suitable to make straight grade is a critical step to maintaining its quality during storage. However, the spoilage chart (Figure 2) shows how important it is to monitor the temperatures in the bin because even in dry, or close to dry, situations the crop may still be at risk of spoilage.
Table 1. Maximum moisture content for straight-grade seeds (Canadian Grains Commission, 2013).
|Maximum Moisture Content (%)||Grain(s)|
|9.5||Domestic mustard seed|
|14.0||Lentils, Rye, Triticale, Soybeans|
|16.0||Peas, Faba beans|
Figure 2. Guidelines for safe storage for four different crops. Adapted from Canadian Grains Commission (2013).
How to avoid spoilage when grain comes off tough?
Aeration or drying are the primary means of bringing high moisture grain into a safe storage range, but how to choose between the two?
Drying uses higher airflow rates with added heat and has several advantages including: allowing for the harvest of tough grain (and all the harvest perks that come with that), reducing or eliminating spoilage, and potentially eliminating the need for swathing. However, drying also comes with disadvantages including: heighted risk of rejection of artificially dried grain from maltsters, elevated cost, and the requirement of labour by an experienced operator in order to be done correctly.
Aeration uses lower airflow rates and is dependent on the air temperature and relative humidity in order to dry down grain. Aeration can provide some similar benefits if fans are ran at strategic times based on air temperature and relative humidity. The process of aeration ventilates the stored grain and creates a fairly even temperature throughout the bin. If targeting a malting grain, aeration is the best bet for drying it down to the desired moisture level. Below are a few general tips to keep in mind when running aeration fans:
- Warm air + warm grain = drier grain
- Warm air + cool grain = wet grain
- Cool air + warm grain = wet grain in short term, but up to 2% drying in long term
- Cool air + cool grain = essentially no change
- Minimal fan hours with slightly tough grain (1-2% over) = run fans at night only
- Minimal fan hours with very tough grain (more than 2%) = run fans during the day only
- For a uniform moisture content over the whole bin without over drying any, run fans during the day only until moisture is 1-2% above dry then run fans at night to cool and finish drying (PAMI)
Preventing insect infestations
Keeping your grain bug free starts with a clean bin. This means removing ALL grain and dockage left in the bin that will serve as a food source for the bugs. Cleaning all augers, combines, and trucks is also important to keep the grain insect free. Treating grain with an insecticide such as Protect It or Malathion Dust may also help to keep out the bugs, but be sure to check product labels before treating any grain as some cannot be treated with certain insecticides (i.e. canola and malathion). Getting the stored grain’s temperature below 18°C as soon as possible is also very crucial to reduce reproduction of storage pests.
Importance of monitoring
There are many tools available to help monitor the temperature inside the bin and detect the beginning of any storage problems. Temperature cables that are closely monitored and tracked can help save tens of thousands of dollars in just one year. Other ways to monitor insects, moisture and temperature of the grain inside the bin is probing into the bin and also taking out a sample. Be sure to monitor the difference in temperature of the grain in the middle of the bin to the top and bottom, as well as if there is any insect damage (chewing) or live insects in the sample.
Another great way to get the picture of what is going on inside that bin is actually taking the grain out of the bin and either moving to a new CLEAN bin or just turning it back into the same bin. This helps cool the grain if done in winter, which helps reduce spoilage and minimize hot spots. It can also kill some insects in the grain if the temperature is below freezing. Turning bins can be an important management strategy for any type of grain, but is especially important in oilseeds. Oilseeds, because of their high oil content, are more prone to spoilage and hot spots, so mixing up these hot spots helps to reduce spoilage. Frequency for monitoring can never be too much, but once every 7-10 days is recommended for the first 60 days.
Having the grain off the combine and in the bin is not a guarantee for its safety. However, with careful management and regular monitoring, the bin truly can be the safest place for your crop to be. This will not only help keep the grain in tip top shape for filling contracts, but will also help keep that number on the bottom line as high as it can be!
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