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Oat Grain/Groat Size Ratios: A Physical Basis for Test Weight

¹USDA-ARS Wheat Quality Laboratory, Harris Hall, North Dakota State University, Fargo, ND 58105. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable. ²Corresponding author. Phone: 701-231-8069. Fax: 701-239-1377. E-mail: douglas.doehlert@ndsu.edu ³Department of Plant Sciences, North Dakota State University, Fargo, ND 58105. ⁴Agronomy Department, Iowa State University, Ames, IA 50011-1010.

Market value of oat grain is largely determined by test weight or bulk density, yet little is known of the physical basis for test weight in oats. We have hypothesized that a larger sized groat relative to the oat grain (the kernel with the hull) would generate higher test weight oats because the groat is the densest structure in the oat grain. We tested this by measuring oat grain size and oat groat size by digital image analysis for 10 genotypes grown in 10 environments. We also measured other physical characteristics of the oats grains and groats including mean grain and groat mass, test weight, and groat percentage. We found that the groat/ grain size ratio was highly correlated with test weight. Because the oat grain image area was nearly twice that of the groat, we suggest that there are significant amounts of empty space within the oat hull, which detracts from test weight. We also found that oat groat size distributions, like oat grains, fit bimodal distributions better than normal distributions.