The paper presents a research study on the effects of soybean seed impacting by a rotating steel arm of circumferential speed 21.46 ms-1. Three varieties of soybean (Aldana, Polan and Progres) were tested in relation to their moisture content variations. The sample seeds were evaluated in respect of the resulting mechanical damage, as well as the value of seed energy and capability of germination. On the basis of the results, it was found that the varieties differed greatly in their seed susceptibility to mechanical damage but only in the low moisture content range of 7 - 14 %. The optimum moisture content, at which the damage was below 5 % for specific varieties, varied from variety to variety (13.1 % for Aldana, 18.5 % for Polan and 15.3% for Progres). As the extent of mechanical damage increased, the seed energy and capability of germination decreased. The seeds disqualified in the germination test consisted mainly of seeds which germinated abnormally, especially in the low moisture content range.