The following is provided by Canadian Grain Commission
The test weight conversion charts are based on accumulated data over crop years, representing changes in growing environment and crop varieties. The data is limited only by the number of samples available for inclusion. The test weight conversion charts are updated to reflect changes in dominant crop varieties and environmental conditions affecting crop quality. Conversion charts for some crops such as triticale are not available due to a lack of data, or where official inspection does not include test weight as a grade-determining factor, such as for peas and lentils.