Stored grain pack factor measurements for soybeans, grain sorghum, oats, barley, and wheat

Authors: BHADRA, RUMELA - Kansas Department Of Health And Environment; Casada, Mark; TURNER, AARON - University Of Kentucky; MONTROSS, MICHAEL - University Of Kentucky; THOMPSON, SIDNEY - University Of Georgia; MCNEILL, SAMUEL - University Of Kentucky; MAGHIRANG, RONALDO - Kansas State University; BOAC, JOSEPHINE - Kansas Department Of Health And Environment

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2018
Publication Date: 5/15/2018
Citation: Bhadra, R., Casada, M.E., Turner, A.P., Montross, M.D., Thompson, S.A., Mcneill, S.G., Maghirang, R.G., Boac, J.M. 2018. Stored grain pack factor measurements for soybeans, sorghum, oats,barley, and wheat. Transactions of the ASABE. 61(2):747-757. https://doi.org/10.13031/trans.12645.
DOI: https://doi.org/10.13031/trans.12645

Interpretive Summary: Grains and oilseeds stored in bins undergo packing due to overbearing pressure from the cumulative weight of the grain above, which increases the stored grain bulk density and, thus, storage capacity. To account for this increase in storage from packing, both the USDA Risk Management Agency (RMA), and the USDA Farm Service Agency warehouse group (FSA-W) use their own empirical packing factors when measuring bins. The American Society of Agricultural and Biological Engineers (ASABE) Standard EP413.2 provides another estimate of packing factors based on a computer model, WPACKING. We compared scale-measured mass of four grains and oilseeds in vertical storage bins to predicted mass based on these three methods of determining pack factor. WPACKING performed better than the other two methods for soybeans, sorghum, and barley and the FSA-W method performed better for oats. The RMA method had the least accurate predictions with all four crops. This was similar to previous data on hard red winter wheat and corn where WPACKING also usually gave better predictions of grain packing and of mass in the bins. For both the RMA method and the FSA-W method in barley bins and for the RMA method in oat bins, the predictions from those methods were especially poor with average absolute errors greater than 10%. This information will be highly beneficial to grain industry groups working with these methods for refining the methods to provide more accurate predictions of grain packing and inventory.

Technical Abstract: Grain and oilseed crops stored in bins undergo compaction due to overbearing pressure of the grain inside the structure. Thus, volume measurements of grain in bins need to be combined with the amount of compaction—usually called pack factor—in addition to the initial density so that the mass can be calculated in the structure. These pack factors are dependent on many parameters for the structure—such as size, shape, and sidewall material—and the grain—such as moisture, test weight, friction properties, and depth. Predictions from WPACKING, the program in ASABE standard EP413.2, and two standard USDA methods, the USDA Risk Management Agency (RMA) and USDA Farm Service Agency-Warehouse Licensing and Examination Division (FSA-W) methods, were compared to field measurements of 77 bins containing soybeans, sorghum, oats, or barley. Field data were collected on the grain profile, bin dimensions and material, and grain properties, along with the reported mass provided by the bin managers. The WPACKING predictions had the lowest absolute average error of predicted mass for soybeans, sorghum, and barley, while the FSA-W method had the lowest error for oats. The RMA method gave the largest prediction errors for all four crops and struggled especially with the low-density, high-compaction crops oats and barley, giving average absolute errors above 10% in both cases. Overall, WPACKING, the RMA method, and the FSA-W method had average absolute errors of 2.34%, 7.49%, and 3.21%, respectively, for the 77 bins. These results can be used to improve pack factor predictions for the grain industry.