A row unit for a high-speed agricultural seeder includes a leading system including an opener and a dispenser, a trailing system including a leveler and a packer, a primary force generator generating a primary force, and a packer force adjustment system generating a packer adjustment force. The primary force includes opener and trailing force portions that are transferred to the opener and trailing system, respectively. The trailing force portion includes a leveler force portion that is transferred to the leveler and a packer force portion that is transferred to the packer. The packer adjustment force is adjustable independently of the leveler force portion, such that a combined packer force equal to a sum of the packer force portion and the packer adjustment force is adjustable independent of the leveler force portion.