All earthworms survived by the end of the experiment exceptthose that were exposed to the highest Cd (1000 mg kg1). Themortalities of earthworms in soils spiked with 1000 mg kg1 of Cdwere 15.0 13.8% and 73.3 5.4% (mean SD, n ¼ 4), respectively,with and without maize plants, indicating that maize plants couldreduce the toxicity of Cd to earthworms survival. Similarly, thepresence of maize plants mitigated the toxicity of Cd to earthwormreproduction (F ¼ 187.461, p < 0.01). At lower range of Cd exposurelevels (<220 mg Cd kg1), earthworms cohabited with maize plantsproduced more cocoons than those that were exposed to the samecorresponding levels of Cd but tested with no maize plants (Fig.1a).When Cd concentrations added were larger than 460 mg kg1, nococoon was produced by earthworms regardless of the presence ornot of maize plants (Fig. 1a). The EC10, EC20, and EC50 for cocoonoutput were 80.7, 101.2, and 152.8 mg kg1, and 58.1, 76.9, and129.4 mg kg1, respectively, with and without maize plants(Table 1). The earthworm biomass change was expressed as thepercentage of the initial weight. A reduction of 30e50% of bodymass was observed after 28 d inoculation of earthworms in thefluvo-aquic soils (Fig. 1b). Generally, earthworms in soils withoutmaize plants had a sharper change in body mass reduction thanthose worms that inhabited in the corresponding Cd-contaminatedsoils with maize plants, indicating again that the presence of maizeplants could effectively reduce the toxicity of Cd to earthworms(F ¼ 15.616, p < 0.01). However, comparing to the earthwormreproduction endpoint (i.e., the cocoon output in the presentstudy), the biomass change of the earthworms seemed not to be asensitive endpoint to Cd and, therefore, the effective concentrationsfor earthworm body mass were not determined.
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