Moisture content for Canadian grains

The Canadian Grain Commission monitors and maintains Canadian calibrations for two common types of moisture meter: Unified Grain Moisture Algorithm (UGMA) moisture meters and model 919/3.5” or equivalent moisture meters. Our calibrations are applicable to the 21 grains regulated under the Canada Grain Act. We also provide guidance on the use of these two types of moisture meter.

Calibrations on moisture instruments focuses on the normal trading moisture range for that particular commodity in order to be as accurate as possible to the reference result. Once outside that range, such as for wet or dry samples, the measurement variation increases.

Calibration development for both model 919/3.5” and UGMA-type moisture meters are based on a wide range of samples and moisture levels. They are not based on individual samples.

The Canadian Grain Commission does not endorse, certify, or approve the use of specific moisture meters.

We use UGMA moisture meters (specifically, the Perten AM5200A model) to determine the moisture content of grain. We also monitor and maintain calibrations for the GAC2500 (DICKEY-john) moisture meter at the Canadian Grain Commission office in Winnipeg.

Our research shows that UGMA meters produce less variable results than the model 919/3.5” meters, when compared to the reference method (the oven drying method). For example, in the CWRS plot of samples tested between 2015 and 2019 as seen in the graph below, we can see that overall the difference between the moisture meter calculated result and the reference oven result are similar for both types of moisture meters. However, the standard deviation, or variability, is larger for the model 919/3.5”.

Moisture meter results for Canada Western Red Spring Wheat from 2015 to 2019

Both 919/3.5” and UGMA moisture meters are accepted for use as long as they are properly calibrated and maintained.

The Canadian Grain Commission monitors two different types of instrument to measure moisture in grain:

• Unified Grain Moisture Algorithm (UGMA) moisture meters
• model 919/3.5” or equivalent moisture meters

These two types of moisture meter use different technologies and measurement frequencies. Both types of moisture meter are accepted for use as long as they are properly calibrated and maintained.

Every year, we check the accuracy of both types of moisture meter against the reference method (oven drying method). Our research confirms that, when properly calibrated and maintained, both types of moisture meter predict similar moisture results. Our research has also shown that moisture predictions are not consistently higher or lower using one technology compared to another.

However, results indicate more variance with the 919/3.5” meters, with more frequent outlier results both on the tough and damp moisture ranges. The higher level of consistency in UGMA test results is one of the reasons we continue to use this instrument as our standard moisture meter.

There are four main factors that may influence moisture measurement.

• environmental conditions (growing conditions, seed spoilage, insecticides, herbicides, fertilizers, etc.)
• kernel properties (kernel geometry, chemical composition, new varieties, etc.)
• sample preparation (amount and type of dockage, sample temperature, grain drying, etc.)
• instrumental properties (measurement frequency, density-compensation, measurement cell shape, etc.)

The first two cannot be controlled because they are determined by the very nature of the grain being tested. The remaining two sources can be managed by utilizing correct sample preparation processes and correct testing procedures.

If you do not agree with a licensed primary elevator’s assessment of your grain’s moisture, you have the right to ask for a Final Quality Determination from the Canadian Grain Commission. Your grain’s moisture will be assessed by a Canadian Grain Commission inspector. The elevator operator may issue you an interim primary elevator receipt after you request a Final Quality Determination. If they do not, keep the primary elevator receipt you were issued when you delivered your grain.

You have 7 calendar days from the date of delivery to request a Final Quality Determination.

Producers also have the option to submit samples to the Canadian Grain Commission for moisture assessment via rapid method test or reference oven test. These tests are offered for a fee. With these tests, producers will receive a certificate based on the sample provided. It’s important that producers submit a representative sample when requesting a test from the Canadian Grain Commission.

If you are using a model 919/3.5” or equivalent moisture meter, make sure you’re following the moisture determination guidelines for Canadian grains.

You can improve the accuracy of on-farm moisture testing by carefully managing two common sources of error: sample preparation and instrumental properties. When preparing the sample, we recommend that you:

• ensure the sample is representative of the entire lot of grain
• ensure the sample is free of dockage
• ensure the temperature of the sample is appropriate for the meter you’re using (see next question for more details)
• ensure moisture is more uniformly distributed between kernels by waiting one day after artificially drying the sample

To confirm proper calibration and maintenance of your instruments, we recommend that you:

• ensure your scale is calibrated and verified regularly
• regularly bring in your moisture meter for maintenance and calibration
• follow the moisture determination guidelines for Canadian grains and the manufacturer’s directions on the use and maintenance of the moisture meter

Take three readings for each sample and use the average of all three to get the most accurate reading for your sample.

For UGMA moisture meters, manufacturers state that samples can be tested at temperatures between -20° and 45°C. However, the possibility of ice crystal interference in test measurements is higher when samples are below 0°C. This is why the Canadian Grain Commission uses samples above 0°C when performing moisture meter tests.

For 919/3.5” moisture meters, all Canadian Grain Commission calibrations are valid between 11° and 30°C.

Samples being tested at the extreme ends of these temperature ranges may cause more variation in measurement results.

There are many factors that can influence moisture measurement, including environmental conditions and kernel properties. The crop protection products and varieties currently used by Canadian grain producers are different than the ones used 10 years ago, and these changes can have an impact on the way the instrument reads the moisture of a sample.

For example, when a new variety of grain is developed, some changes can affect the kernel’s composition, shape and size. The size and shape of the kernels influence how the seeds pack into the measurement cell, which can affect test results. Larger, rounder kernels pack differently, and will introduce more variation, than smaller, flatter kernels.

To make sure these types of changes don’t affect the accuracy of moisture test results, we check our calibrations for both types of moisture meter against our reference method (the oven drying method) every year and update our calibrations as needed. Our reference methods for moisture testing have remained unchanged for over 15 years.

When comparing results from different meters, it is also important to note that the 919/3.5” meters can produce more variable results than UGMA meters, so this may be a factor in differences that are observed.

If you have questions about moisture meters and getting an accurate reading, please contact one of our Moisture Technicians.