The results of studying of long-term fodder cul-ture of cup plant as the predecessor for spring wheat and barley in the conditions of forest-steppe of Omsk Region are presented in the study. Vari-ous terms of plowing of long-term herbage of awn-less brome (control) in spring and cup plant in spring, in summer and are analysed in the fall. It is revealed that on average for years of researches the optimum level of productive moisture in the lay-er of 0-20 cm was on all options of experiments, but at autumn terms of plowing of cup plant re-serves of moisture were 1.9-4.1 mm more. Density of an arable layer under the studied predecessors did not differ significantly and was optimum (1.11-1.14 g/cm3) for grain crops. At cup plant , as well as in brome, the most part of lateral roots (36,2-55,7%) settled down in a layer of earth of 0-10 cm, but more powerful lateral roots of cup plant got deeply therefore in layers of 10-20 and 20-30 cm the root mass of cup plant surpassed on 0,3- 0,6 t/hectare. In comparison with awnless brome cup plant by years on 1,2-1,5 t/hectare had a gain of roots above. Use of a cup plant as a siderat al-lows to plow from 49,4 to 63,9 t/hectare of green material that provides receipt to the soil from 7,9 to 12,1 t/hectare of dry organic substance and at de-composition of biomass of a siderat return to the soil of 185,2-282,1 kg/hectare of nitrogen, 21,4-32,4 phosphorus and 242,1-449,8 kg/hectare of potassium. Cup plant in spring term of plowing and summer term at a plowing of green material and the root remains (siderat) as the predecessor promotes increase in productivity of a spring-sown wheat by 25,0-27,9 % and barley for 24,6-30,0 % in compar-ison with awnless brome.