One feature of harvesting seed onions is that the impurities of the onion-soil pile coming from the digging executive devices to the separating executive devices contain soil lumps that are similar in size with the seed onion bulbs and hard to separate at the slotted (bar elevators, screens) executive devices (M. Tauseef Asghar, 2014). This problem is most urgent when collecting seed onions from the rolls, because together with the bulbs the separating executive devices receive the soil layer loosened by the digging executive devices during the first phase of harvesting seed onions, the fractional composition core of which is soil lumps similar to bulbs and hardly separable on slotted executive devices. This circumstance is explained by the fact that after the soil layer is undercut together with the saleable produce, a significant amount of soil lumps, hardly separable on the separating executive devices and causing damage to root crops and bulbs during their interaction, arrives to the separating executive device. In addition, separation of soil lumps on slotted executive devices (bar conveyors and screens) occurs according to dimensional properties and this does not solve the existing problem – separation of soil lumps comparable in size with seed onion bulbs. Consequently, to ensure qualitative indicators of harvesting seed onions, namely, the separation completeness of the bulbs from soil impurities, it is necessary to ensure a reduction or complete elimination of the flow of soil lumps to the separating executive devices at the second harvesting phase.