Grain moisture standards for storage in grain sleeves
Grain moisture is a factor that reflects the volume of nutrients and the potential storage duration of the grain mass. It is one of the key quality indicators; determining grain moisture is carried out immediately after receiving a new batch of the crop.
The primary method for determining grain moisture is using a laboratory drying oven. A weighed portion of ground material is dried for 40 minutes at a temperature of 130°C in specialized equipment—a Trinkler oven. The application of this method is mandatory when determining moisture content (drying to a constant mass).
The loss in weight of the portion resulting from drying is calculated as equal to the mass of moisture present in the grain. Moisture content is determined by expressing this weight loss as a percentage.
Methods for Determining Grain Moisture
Based on moisture levels, grain material can be classified as:
- raw;
- damp;
- medium-dry;
- dry.
Dry matter in uncooled raw grain mass is lost in volumes of up to 0.2% per day. By contrast, dry grain, for instance, “breathes” low-intensively. Medium-dry material, compared to dry, “breathes” two to three times more actively, but due to low gas exchange, it can be stored normally. A damp product, compared to dry, “breathes” five to eight times more intensively.
The Impact of Moisture on Grain Material Quality
Accurate determination of grain moisture is of immense importance, as this exact indicator dictates the volume of nutrients and the potential storage duration of the material. If the moisture volume in the crop is exceeded, the produce will spoil quickly and lose most of its beneficial components. Excess moisture triggers unfavorable chemical and physical processes, resulting in:
- the appearance and rapid proliferation of insects, mites, and microbes;
- loss of flowability and increased vulnerability of the grain to mechanical impact;
- activation of fermentation processes;
- reduction in test weight (the volume of grain material in one liter);
- breakdown of high-molecular biopolymers;
- sprouting and swelling of the produce.
Prolonged damp mass is completely unsuitable for further storage and processing.
Assessing Moisture Content
Given the importance of the issue, methods for determining grain moisture are regularly improved.
What is Critical Grain Moisture?
The moisture level at which free moisture forms within the grain material, causing the intensity of “respiration” to increase significantly, is called critical moisture. Each type of crop has its own critical grain moisture standard for storage in grain sleeves:
- high-oil sunflower—8%;
- corn—14%;
- wheat—15.5%;
- legumes—16%.
An acceptable moisture indicator for most cereals is up to 14%. At moisture levels a few percent below critical, the grain material retains its sowing properties for a long period (provided it is supplied with a sufficient volume of oxygen); under a shortage or total absence of oxygen, germination viability is lost within the first months of storage.
Grain with elevated moisture should not be stored in silage bags—storing grain in a dry state is optimal. Indeed, at warm temperatures, grain with elevated moisture creates an intercellular equilibrium of relative humidity above 65% to 70%, which promotes mold development. Therefore, it is best to store grain in sleeves while strictly observing the recommended moisture indicators for safe storage. The safe duration of storage in grain sleeves depends not only on the moisture of the loaded grain but also on the ambient outdoor temperature.
The higher the grain moisture and the warmer the outdoor temperature, the shorter the storage timeframe in grain sleeves will be.
For example, Ukrainian farmers have successful experience storing corn with a moisture content of 22% in grain sleeves for up to 30 days.
Grain Moisture Calculation. Recommended Grain Moisture Indicators for Storage in Grain Sleeves:
Safety Recommendations for Storage in Grain Sleeves
- Corn, soybeans, and wheat stored in silage bags should feature a moisture content of 15%, 13%, and 12% or lower, respectively. Sunflower and rapeseed should be stored with a moisture content below 10%. It is better to err on the conservative side and store drier rather than wetter grains, oilseeds, and legumes.
- Corn dried using a high-temperature dryer must be cooled down to ambient temperature before being packed into the sleeve so that heat is not trapped inside the bag during sealing. Otherwise, condensation on the upper inner side of the sleeve can lead to mold development and premature grain spoilage.
- Grain sleeves must not be overloaded; most bags stretch by approximately 10%, and overfilling can result in ruptured bags, particularly during their unloading. Control the sleeve stretching using the stretch-indicator ruler included with the Harwell TM grain sleeve kit. Furthermore, a sufficient length of free edge at the ends of the sleeve is necessary for proper sealing at the start and end of the filling process.
- Grain quality must be regularly monitored along each bag using CO2 sensing technology. Bags showing an increase in CO2 between bi-weekly readings should be scheduled for earlier unloading compared to bags with stable CO2 indicators.
- Before piercing the sleeve to measure grain temperature or extract a sample for testing, you must pre-tape the puncture site crosswise with tape. After taking the sample, seal the hole lengthwise using repair tape.
- Grain sleeves must be regularly inspected for rodent damage. Note that snow cover can conceal punctures, so snow should be cleared from the sleeves to effectively evaluate potential damage.
We discussed grain sleeves, the technology of storing grain, silage, and haylage in sleeves, and the pros and cons of using grain sleeves in greater detail in our article “Advantages and Disadvantages of Using Grain Sleeves.”
Wishing everyone a rich harvest!