## 4 Discussion
In the biochar-amended treatments, there was no significant weight loss in the earthworms (Figure 2). In addition, EC values could not be determined in all the biochar-amended soils because of insufficient weight loss (Table 2). The results indicate that biochar amendment helps preserve earthworm biomass. [PERSON] et al. [20] recently reported similar findings after exposing _E. fetida_ to imidalcoprid in 10% biochar-amended soils for 28 days. Despite evidence suggesting that biochar helps to alleviate the effects of chemical toxicity on earthworm biomass, there are recurring literature findings indicating that biochar amendment on its own (in the absence of a chemical toxicant) is capable of causing weight loss in earthworms. This usually seems to happen in a high amendment rate. [PERSON], [PERSON] et al. [24] reported significant weigh loss in _E. fetida_ after exposure to 10 and 20% apple wood sawdust biochar-amended soil for 28 days. [PERSON] et al. [23] reported significant weight loss in _Eisenia fetida_ exposed to soil amended with 68 and 90 Mg/ha biochar from poultry litter. According to [PERSON] et al. [24], 90 t of biochar/ha at a tillage depth of 10 cm corresponds to 10% amendment. This means that 68 and 90 Mg biochar/ha by [PERSON] et al. [19] represents 7.55 and 10% amendment. Interestingly, together with the poultry litter biochar, [PERSON] et al. [23] also tested a biochar prepared from pine chips and found no adverse effects on earthworm biomass at the same amendment rates. These findings suggest that the adverse effects of biochar on earthworms depend not only on the rate of amendment but also on the feed used to make the biochar. After a 96-h exposure of _E. fetida_ to GLY in the absence of biochar, we found no differences in the AChE level, regardless of the GLY concentrations (Figure 3). This implies that, within the concentration range assessed, GLY alone did not cause any neurological stress to the earthworms. These results are in conformity with those of [PERSON] et al. [40] who found that AChE activity remained unchanged after a 48-h exposure of _E. fetida_ to GLY concentration as high as 2000 mg/L. [PERSON] et al. [41] also observed no significant differences in AChE activity in three earthworm species (_Alma millisecondi, Eudrilus eugeniae_, and _Lybyodrilus violaccus_) contained in pots planted with weeds (_Tridax procumbense, Ludwig pasturis_, and _Pannicum maximum_) and sprayed with 83.2 g of GLY/m\({}^{2}\). Contrary, at day 7 of a 28-day experiment, [PERSON] et al. [42] found a significant increase in relative AChE activity in the earthworm _Dendrohaen veneta_ exposed to GLY at concentrations overlapping those used in our study (i.e., \(\leq\)2160 \(\upmu\)g/kg). By day 28, however, this initial increase in activity vanished. [PERSON] et al. [18] also observed significant increases at day 3, 7, and 14 in the AChE activity of _E. fetida_ exposed to GLY concentrations (\(\leq\)450 mg/kg) but by day 21, no significant differences in AChE activity were observed. With regard to the effects of biochar on AChE, our results reveal that dramatic increases in AChE levels were only observed in the biochar-amended treatments. In the 15% biochar amendment, a significant increase occurred in the control (in the absence of GLY) and the lowest GLY concentrations (Figure 3). However, no significant differences in AChE were observed in the 5 and 10% biochar amendment. These results show that high biochar amendment (especially 15%) caused a spike in AChE activity even in the negative control. As in our study, [PERSON] et al. [20] documented a pattern of low inhibition of AChE (i.e., high AChE activity) in biochar-amended soil contaminated with imidalcoprid. As in our case, this lack of inhibition (this high activity), although observed predominantly in the amended treatments, was statistically significant only in the lowest concentration of the toxicant. [PERSON] et al.