Study of earthworm biofertilization for the recovery of marginal lands

Lisa Ciadamidaroa, M.O. Fotsing Pekaa, V. Etievanta, S. Breuila, A. Trouvea, C. Pelosia, I. Lamya

a ECOSYS UMR 1402-INRA, Versailles-Grignon, France

lisa.ciadamidaro@inra.fr

It is well known the existence of ~1,350,000 hectares of land in Europe deemed less favourable for conventional agriculture. This land has been either abandoned because of its productivity, or it is used as grassland. Nowadays, these soils are identified as “marginal lands”. Contaminated and degraded soils, such as trace element (TE) contaminated sites, are also included in the classification of marginal lands. Faced with this situation, biofertilization seems to be one of the ways to overcome the problem. It consists in improving the soil properties by inoculation of biological species (earthworms, termites, fungus, and microorganism) in soils, in order to promote the recycling of nutrients, and to quantify the positive and negative externalities induced by this practice on the development of non-food biomass crops. The aim of the present study was to assess the effects of exposition of earthworms to a TE contaminated site. In a microcosm experiment, under controlled conditions, two species of earthworms, Eisenia Fetida (as required for the ISO regulation) and Aporrectodea caliginosa (an ubiquitously species), were exposed to a Cd, Zn, Cu contaminated soil (Chanteloup les Vignes, France) during 14 days. For each species, 5 replicates were established and 5 earthworms per cosm were inoculated. Three different treatments were established depending on the water holding capacity (WHC) of the soil: 30, 50 and 70% WHC. Environmental trace element availability was quantified by measuring TE concentration in soil while environmental bioavailability was assessed by measuring TE concentrations in depurated whole earthworm bodies. Finally, toxicological bioavailability was investigated by measuring earthworm survival rate (at 7 and 14 days) and body weight changes (at 14 days). According to the microcosm experiment the results showed that i) although, the studied soil is not favourable for the E. fetida growth (loss of body weight ≈ 3.97%), it seems beneficial for A. caliginosa growth (increase of body weight ≈ 44.11%); ii) soil pH, considered as an indicator of worm activity, decreased significantly in time (from 7.9 at initial time to 7.4 at final time). Finally, this study revealed that A. caliginosa showed a better adaptation to stressful condition, such as reduced WHC and TE contamination, and it could be considered for in situ biofertilization trials of marginal lands.

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