The concept of soil construction based on local waste materials has emerged in the last two decades. The strength of this concept lies in creating customized soils that provide predefined ecosystem services. The purpose of this article was to review current knowledge and address gaps in the development of soil construction practices that would enhance their carbon sequestration in urban green spaces. More precisely, the objectives were to document the initial composition and contents of organic carbon (OC) and inorganic carbon (IC) used to construct soils, and their impacts on soil carbon dynamics (storage, inputs, outputs) through an analytical framework. To answer this, we undertook a scoping review of literature that assembled 1035 references, from which we selected 37 experiments of constructed soils, as well as 20 soil specification guidelines. Since few studies reported data on OC and IC stocks, and OC inputs, we used OC and IC content, and plant growth respectively as indicators of these variables. Our results highlighted the large heterogeneity among constructed soils in terms of contexts, materials, and carbon content. Initially, constructed soils presented OC content ranging from 0.03 to 304.8 gOC.kg −1 (mean of 65 gOC.kg −1 ), in accordance with city soil specifications for organic matter (mean of 45 gOC.kg −1 ), and IC content from 0 to 127 gIC.kg −1 (mean of 32 gIC.kg −1 ). Increasing the initial proportion of organic materials was one approach to densify soil OC, as this relative increase persisted across studies of varying duration (up to five years), and could be sustained through the associated gains in plant productivity. However, it also enhanced carbon losses through mineralization and leaching. Future research should focus on stabilization and carbonation mechanisms, analyzing the effects of the nature of mineral and organic materials, texture, and depth. Finally, despite its strong development potential, experiments with constructed soils are limited in duration and depth. Long-term studies are needed to better assess capacity of constructed soils to improve carbon sequestration in soils.
Strukelj et al. (Sat,) studied this question.