The aim of this study was to verify whether the use of source-separated municipal waste compost could improve the physical quality of urban soils and create better conditions for their management when planted with herbaceous species. A sandy soil in traffic islands was tilled to a depth of 10？cm, and half of the surface was treated with compost (3？kg/m2). A mixture of 25 herbaceous annuals was then sown in the entire area. Organic carbon content and physical characteristics were determined at different times in the soil treated and not treated with compost. The vegetation was monitored in terms of its growth and flowering. The compost-treated soil showed an increase in organic carbon content. Total porosity increased with time in the compost-treated soil, due to a higher volume of transmission pores, which play a role in water movement. Soil aggregate stability also improved in the compost-treated soil. The duration of flowering of the individual species and the overall quantity of flowers were greater in the compost-treated soil. 1. Introduction Soil is one of the limiting factors for the successful cultivation of plants in towns and cities [1]. The poor quality of soils in urban areas is due to their chemical and biological properties but more often it is due to physical properties. Often urban soils are lacking in structure and humus, leading to asphyctic conditions, compaction, and erosion. These poor physical properties reduce the water available for plants and the penetrability of soils by the roots. Moreover, urban soils can be contaminated by several anthropogenic materials (bricks, concrete, and plastic), which can greatly reduce the volume available for plant roots. The use of source-separated municipal solid waste compost could provide a good solution for increasing the organic matter content in urban soils and for improving their physical properties. In Italy, the production of such compost is rapidly increasing due to the efforts of municipalities to achieve a better selection of organic solid waste and to improve composting processes. So using this compost in vast and heterogeneous sets of urban soils could also help to create a high-value market for locally produced compost, as pointed out by Cogger [2]. While compost effects on agricultural soils have been widely studied, less information is available on urban soils, though interest and research are increasing [3]. In particular one possible effective use of quality compost is in urban derelict soils. These kind of soils, found in roadsides, roundabouts, and filling soils, are generally
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