This present paper, focused on root crop communities of light soils, is a part of the wide range characteristics of segetal communities of the Podlaski Przełom Bugu (Podlasie Bug River Gorge) mesoregion. On the basis of 160 phytosociological relevés made according to the Braun-Blanquet method, phytocenoses representing the <i>Panico-Setarion</i> alliance were distinguished. Most often, patches of the association <i>Echinochloo-Setarietum</i> were recorded in the study area. Heterogeneous habitat conditions affect its floristic diversity. Two subassociations of the phytocenosis, divided according to the species composition into 9 lower syntaxa, were identified on light soils. The following subassociations were distinguished: <i>Echinochloo-Setarietum setarietosum glaucae</i> in a typical variant and a variant with <i>Juncus bufonius</i>, both with subvariants with <i>Digitaria ischaemum</i>, as well as a typical variant of <i>Echinochloo-Setarietum typicum</i>, a variant with <i>Juncus bufonius</i> and a subvariant with <i>Oxalis stricta</i> in the typical and wet variant. Another association found in root crops on light soils of the Podlaski Przełom Bugu mesoregion is <i>Digitarietum ischaemi</i>. Its patches were observed in cultivations on light, acidic, poor soils. The characteristic feature of this community is the occurrence of numerous acidophilous species. In habitat conditions typical for the Podlaski Przełom Bugu mesoregion, <i>Digitarietum ischaemi</i> is differentiated into the typical and wet variant. Quite frequent patches of the <i>Setaria pumila-Setaria viridis</i> community were noted in intermediate habitat conditions, between those characteristic for <i>Digitarietum ischaemi</i> and <i>Echinochloo-Setarietum</i>.