A row crop planter has a pneumatic system for conveying seeds to individual row units employing three-way splitters above certain master row units for supplying seed to each master row unit and a pair of associated slave row units. Each three-row splitter has an upper inlet chamber of annular shape with an offset inlet coupled to a conveying hose for receiving an air entrained seed flow, and an annular passageway extending downwardly from the inlet chamber to an outlet for delivering seeds to the master unit below. A pair of laterally extending slave outlet conduits extend obliquely upward and each has a jumper hose connecting with an adjacent slave unit. The flow circulating within the annular region allows seeds to fall downwardly and air to spiral upwardly into a supplemental air conduit. An air bypass passageway conveys air flow from the supplemental air conduit toward the slave outlet conduits.