Bulk Compressibility Behavior for Select Crops

Highlights The pressure dependent bulk density relationship was evaluated for nine crops. Two compressibility models were proposed, with RMSE ranging from 1.7 to 7.1 kg m-3, depending on the crop. Differences between compressibility equations had minimal influence on packing predictions in full size bins. Combined test weight and packing correction factors are shown for each crop in bins of different sizes and construction. Abstract. Knowledge of the pressure-dependent bulk density increase observed in stored grains and oil seeds, commonly referred to as packing or compressibility, is important for maintaining accurate grain inventory, evaluating wall loads, and other applications that require estimating density at specific depths in a bin. This study presents compressibility equation parameters determined utilizing a compilation of the best data available, including previously published and new datasets. In all, confined uniaxial compression tests for nine crops (barley, canola, corn, oats, rice, sorghum, soybeans, hard red winter wheat, and soft red winter wheat) were included. The data was fit using two candidate compressibility equations, both of which generally fit well and resulted in root mean squared errors ranging from 1.7 to 7.1 kg m-3, depending on the model and crop. For crops with full scale bin data available from previous research, the resulting equations were applied to estimate inventory and were compared with the measured mass of grain in the bin. Results from both equations were similar, and apart from oats, median errors were less than 2.5%. Keywords: Bulk density, Compressibility, Pack factor, Grain storage, Test weight, Stored grain inventory.