Purpose Topsoil and peat are often taken from intact rural ecosystems to supply the urban demand for fertile soils and soil-like substrates. One way of reducing this exploitation is to recycle suitable urban wastes to produce Technosols and technogenic soil-like substrates. In this study, we investigate the role earthworms can play in impacting the hydraulic properties of such a soil-like substrate. Materials and methods In a 4-month microcosm experiment, the influence of the earthworm species D. veneta on the hydraulic properties of brick-compost mixture was examined. Of the ten boxes filled with ca. 11 dm3 of ground bricks (0.7 cm3 cm−3) and green waste compost (0.3 cm3 cm−3), five contained earthworms (W-boxes) and the remaining five were used as controls (C-boxes). The substrate was periodically irrigated and the weight of the boxes and of the drained water was monitored. At the same time, images were taken from the front of the boxes to quantify the activity of the earthworms by image analysis and soil aggregation was studied with micrographs. Before and after the experiment, water retention curves were determined from disturbed samples of the substrate using the simplified evaporation method. Results and discussion After 6 weeks, differences between the C- and the W-boxes were evident. Micrographs showed brick-compost aggregates only for the substrates processed by earthworms. The earthworm activity leads to reduced evaporation and an increased water content in the respective microcosms. The effect persists even after disturbing the substrate. The proportion of plant-available soil water is about 0.02 cm3 cm−3 higher for the substrate processed by earthworms (0.250 ± 0.009 cm3 cm−3) compared with the control (0.230 ± 0.008 cm3 cm−3). Conclusions This study shows that earthworms are capable of ingesting and processing crushed bricks together with compost. The earthworms produced aggregates which persisted after disturbance and had a positive influence on the water retention capacity of such a soil-like substrate constructed from waste.

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<p>Formation of mineral-associated organic matter (MAOM) supports accumulation and stabilization of carbon in soil, and thus, is a key factor in the global carbon cycle. Little is known about the interplay of mineral type, land use, and management intensity on the extent of MAOM formation. We addressed this research question by exposing mineral containers with pristine minerals (goethite, as a representative of oxide-type mineral phases, and illite, representing layered aluminosilicate minerals) for five years to ambient soil conditions at 5 cm depth in 150 grassland and 150 forest plots in three regions across Germany. After recovery, the content of organic carbon (OC) of the minerals was determined by dry combustion. Results show that irrespective of land use and management intensity, more OC accumulated on goethite than illite (on average 0.23 and 0.06 mg m<sup>-2</sup> mineral surface, respectively), demonstrating that mineral type was the most crucial factor for MAOM formation. Carbon accumulation was consistently greater in coniferous forests than in deciduous forests and grasslands. Structural equation models revealed that in grasslands, fertilization had contradictory effects on carbon accumulation, with the positive effect being mediated by enhanced plant productivity and the negative effect by reduced plant species richness. Overall, our results suggest that OC stabilization in soil is primarily driven by mineral type, in particular iron and other metal oxides. The mineral-driven MAOM formation is further modified by land use and management intensity.</p>

<p>Topsoil and peat are often taken from intact rural ecosystems to supply the urban demand for fertile soils and soil-like substrates. One way of reducing this exploitation is to recycle suitable urban wastes to produce Technosols and technogenic soil-like sub­strates. In this study we investigate the role earthworms can play in improving the hydraulic properties of such a soil-like substrate.</p><p>In a four-month microcosm experiment, the influence of the earthworm species D.veneta on the hy­draulic properties of brick-compost mixture was examined. Of the ten boxes filled with ca. 11 dm³ of ground bricks (0.7 cm³ cm-3) and green waste compost (0.3 cm³ cm-3), five contained earthworms (W-boxes) and the re­maining five were used as controls (C-boxes). The substrate was periodically irrigated and the weight of the boxes and of the drained water was monitored. At the same time, images were taken from the front of the boxes to quantify the activity of the earthworms by image analysis. Before and after the experiment, water retention curves were determined from disturbed samples of the substrate using the simplified evaporation method.</p><p>After six weeks, differences between the C- and the W-boxes were evident. Micrographs showed brick-compost aggregates only for the substrates processed by earthworms. The earthworm activity leads to reduced evaporation and an increased water content in the respec­tive microcosms. The effect persists even after disturbing the substrate. The propor­tion of plant-available soil water is about 0.02 cm³ cm-3 higher for the substrate processed by earthworms (0.250 ±0.009 cm³ cm-3) compared to the control (0.230 ±0.008 cm³ cm-3).</p><p>This study shows that earthworms are capable of ingesting and processing crushed bricks together with compost. The earthworms produced aggregates which persisted after disturbance and had a positive influence on the water retention capacity of such a soil-like substrate constructed from waste.</p>