A method of producing bimodal ethylene-based polymer includes reacting ethylene monomer and C3-C12 α-olefin comonomer in the presence of a first catalyst in an agitated reactor to produce a first polymer fraction, and outputting effluent from the agitated reactor. A second catalyst is added to the effluent downstream of the agitated reactor and upstream from a non-agitated reactor, the second catalyst facilitates production of a second polymer fraction having a density and melt index (I2) different from the first polymer fraction. The second catalyst and effluent are mixed in at least one mixer. The second catalyst, second polymer fraction, and the first polymer fraction are passed to the non-agitated reactor; and additional ethylene monomer, additional C3-C12 α-olefin comonomer, and solvent are passed to the non-agitated reactor to produce more second polymer fraction and thereby the bimodal ethylene-based polymer.