Soybean Quality with Rotary and Conventional Threshing

ABSTRACT COMBINES with a conventional rasp bar cylinder or with a single- or double-rotor threshing mechanism were field tested in Amsoy-71 soybeans at three moisture contents to determine the effect of threshing mechanism on soybean quality. Each threshing mechanism was operated at four peripheral velocities. Composite threshing and separating losses were also determined. A separate field experiment was conducted at one harvest moisture and one peripheral velocity to determine the ef-fect of concave clearance on threshing quality. Percentages of splits were statistically significantly higher for the conventional cylinder than for either rotary threshing mechanism. However, when the conventional cylinder was operated within the manufacturer's recom-mended cylinder speed range, the splits from threshing did not exceed the allowable limits for USD A No. 1 soy-beans. Samples collected from the grain-tank auger con-tained 0.6 to 1.5 percent more splits than those from the clean-grain auger. Composite threshing and separating losses ranged from 5.8 to 18.2 kg/ha, and, for both rotary combines losses at the slowest threshing speed were significantly higher than at the two highest threshing speeds.