Effects of mechanicalty sizing soybean seed on plantability and seed quality. The effects of mechanically sizing on soybean seeding precison and seed quality investigated. The performance of two seed distribution mechanisms were evaluated (JM ? 11 - fluted wheel, JM-2.100 e JM-2.000 plates) concerning mechanical injury imparted to the seeds and plantability. Sizing of soybean seed, with commercially available size grading equipment according to recommended technology for seeds, did not adversely affect seed quality related to viability, vigor and mechanical damage. The two seed distribution mechanisms caused significant increments, the level of mechanical damage to the seed. This fact resulted in reduction on seed quality. Sizing of soybean seed at different wreens improved the precision of seed distribution only for the fluted wheel seed distribution mechanism.