Abstract: An electrically adjusted and mechanically driven variable speed pulley transmission provides immediate and accurate changes to the seed dispensing rate of a planter. The variable speed pulley transmission is driven by a ground-engaging wheel and adjusted in response to electrically monitored variations between desired and actual seed plant densities. Adjustment to the sheaves of the transmission pulley is effected by an electric motor and tension springs which interconnect the movable pulley sheaves apply pressure to the sides of the pulley belt to assure torque transmission at low RPM's.