A metering and mixing system of solid particulates for a rotary seed dispenser in agricultural equipment for sowing, wherein the rotary seed dispenser is mounted under a seed feeder. The rotary seed dispenser is driven at the bottom by a planter drive system, which provides rotation to a spinning disc provided with a number of calibrated orifices through which the seeds housed in the disc orifices fall on a given point of the agricultural equipment. The metering and mixing system of solid particulates includes a solid particulate feeder that is positioned between the seed feeder and the rotary seed dispenser.