Soil organic amendment affects biotic and abiotic processes that control the fate of pesticides, but the treatment history of the soil is also relevant. These processes were assessed in a multidisciplinary study with the aim of optimizing pesticide mitigation in soils. Soil microcosms pre-treated (E2) or not with diuron (E1) were amended with either winery (W) or olive waste (0) vermicomposts. Herbicide dissipation followed a double first-order model in El microcosms, but a single first-order model in E2. Also, diuron persistence was longer in El than in E2 (E1-DT50 > 200 day(-1), E2-DT50 < 16 day(-1)). The genetic structure of the bacterial community was modified by both diuron exposure and amendment. O-vermicompost increased enzymatic activities in both experiments, but diuron-degrading genetic potential (puhB) was quantified only in E2 microcosms in accordance with reduced diuron persistence. Therefore, O-vermicompost addition favoured the proliferation of diuron degraders, increasing the soil diuron-depuration capability. (C) 2015 Elsevier B.V. All rights reserved.