Evaluating the accuracy and efficiency of test weight instruments for soybean (Glycine max L.) research

The United States official soybean (Glycine max L.) test weight (TW) is 75.7 kg hL(-1) (60 lb bu(-1)). This standard is used to convert the weight of a load of soybean into bushels. Typically, when TW falls below 68.4 kg hL(-1), (54 lb bu(-1)), growers may receive discounted payments. In recent years, the average TW of soybean appears to have declined in certain regions. There is currently no literature on the relative merits of common instruments used to measure TW. Therefore, we compared three instruments: a Mini GAC Plus, a Perten Aquamatic 5200, and a volumetric instrument, for accuracy and speed of sample processing in a lab setting. The TW of 517 plots generated from 11 soybean field trials grown in Tallassee, Alabama, over 2 years was measured to compare the performance of these instruments. The median value per instrument was used to determine variation and bias among the machines, and the speed of processing 100 samples was used as a measure of efficiency. For accuracy, the Perten had better agreement with the volumetric than the GAC and contained less bias compared to the GAC. All three TW instruments differed significantly from each other in processing speed. The volumetric instrument had the fastest processing speed, but its utility was limited due to a lack of moisture measurement. Otherwise, the Perten Aquamatic 5200 is more efficient. Future experiments should examine seed quality parameters and how they may influence the measurements of samples.

Automated summary

The official soybean test weight standard in the United States is 75.7 kg/hL (60 lb/bu), with discounts given when the weight falls below 68.4 kg/hL (54 lb/bu). There is a lack of literature on the comparison of instruments used to measure test weight. This study compared three instruments and found that the Perten Aquamatic 5200 had better accuracy and faster processing speed, while the volumetric instrument had the fastest processing speed but lacked moisture measurement.