Do earthworms (D. veneta) influence plant-available water in technogenic soil-like substrate from bricks and compost?

Abstract

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.

Management of soil carbon sequestration in urban areas

“…In order to optimise the properties of Technosols, the presence of worms and plants is required (Deeb et al, 2017). It has been shown that the earthworm species Dendrobaena veneta was able to improve properties such as plant available water content in Technosols (Ulrich et al, 2021). Earthworm activity can also promote SOC stabilisation (Le Mer et al, 2020).…”

Predicting Water Retention Curves for Binary Mixtures – Concept and Application for Constructed Technosols

“…Tams et al (2022) showed in a life cycle analysis, that the use of recycled brick particles instead of expanded clay reduces the CO2 footprint of the substrate layer by 50 % in an extensive green roof. The composition of waste materials and the processing (Ulrich et al, 2021) are the most important design levers to manipulate the properties according to their targeted application (Rokia et al, 2014;Fields et al, 2018;Willaredt and Nehls, 2021). Most UGI addresses the re-establishment of soil function related to the regulation of the water cycle (Grabowski et al, 2022).…”