Improving urban soil quality for city re-greening through learning-service actions

Abstract

A space for citizien action towards the improvement of environmental health, the so-called City Station, was set up as one of the elements of the exhibition “After the end of the world”, held by Centre de Cultura Contemporania de Barcelona, CCCB. Many activities were organized in order to bring environmental problems and their possible solutions closer to citizenship. One of the environmental issues treated was the low quality of urban soils that hampers vegetation growth. The use of compost and biochar as amendments can improve plant growth by diminishing soil compaction, and increasing soil water and nutrient retention. In this context, two different approaches were followed to assess these improvements: field and rhizotron experiments. Besides, learning-service actions were conducted. In both field and rhizotron experiments, we treated the soil with three doses of biochar, compost and compost mixed with biochar. Plant parameters as shoot hight, number of leaves, green area and plant biomass; and soil parameters as acid neutralization capacity, water holding capacity and humidity, were assessed. In general, the addition of amendments improved soil properties that leads, for example, on water savings. Increasing benefits are found at higher doses of amendment. Furthermore, the best option was the combination of biochar and compost since biochar allows keeping nutrients and water for longer while sequestrering carbon and reducing CO2 releases into the atmosphere. Regarding learning-service actions, we designed and performed different activities with citizens e.g. “Moviment Biochar” and workshops with students. “Moviment Biochar” was a set of workshops and informative talks about the benefits of adding biochar to urban soils, organized and made along with IDÀRIA SCCL and MontBio project. In the workshops students could confirm by themselves the increase of water holding capacity of a soil when biochar is added. Citizens appreciated the activities and were very interested and closer to the environmental issue and the proposed action based on biochar.