The article presents a theoretical justification for sorting corn ears on the developed plant and proposes a solution in the form of a working surface of varying curvature consisting of descending and ascending surfaces. The conditions under which the sparing mode is created for reloading the cobs are determined, the dynamic parameters for moving the cobs along the descending and ascending surfaces and by the grapho-analytical method are determined by intervals of their values corresponding to the sparing regime. The obtained theoretical dependences take into account the physical and mechanical properties of corn cobs.