# Duality of Biochar and Organic Manure Co-Compositing on Soil Heavy Metals and Enzymes Activity
## 3 Results and Discussion
### Soil Enzyme Activity
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline
**Soil** & **Sewage** & **Chicken** & **Horse** & **Vemi-** & **Naive** & **Biochar** & **Inorganic** & **Organic** \\
**Properties** & **Sludge** & **Manure** & **Manure** & **Compost** & **Soil** & **Seil** & **Fetillizer** & **Fertillizer** \\ \hline Urease 1 & 956.3 \(\pm\) 165 b & 993 \(\pm\) 192 b & 805.8 \(\pm\) 130 c & 1105.9 \(\pm\) 141a & 911.8 \(\pm\) 109 b & - & - & - \\ invertase 2 & 3696.9 \(\pm\) 312 a & 3736.1 \(\pm\) 339 a & 3610 \(\pm\) 282 a & 3970.3 \(\pm\) 27 a & 3234 \(\pm\) 265 b & - & - & - \\ Acid & 1435.4 \(\pm\) 107a & 1158.3 \(\pm\) 42 b & 1197.3 \(\pm\) 35 b & 1413.6 \(\pm\) 51 a & 1354.9 \(\pm\) 79 a & - & - & - \\ Phosphate 3 & 389.3 \(\pm\) 50 c & 524.43 \(\pm\) 80 a & 400.7 \(\pm\) 46 b & 309.38 \(\pm\) 45 c & 427.6 \(\pm\) 60 b & - & - & - \\ \hline \end{tabular}  
* Urease activity expressed in ug NH\({}_{4}\)+ ions per g\({}^{-1}\) dry soil. 2 Inverse activity expressed in ug glucose per g\({}^{-1}\) dry soil. 34 Soil acid and alkaline phosphatase activity expressed as ug p-nitro phenol released per g\({}^{-1}\) dry soil. ND indicates not detectable. Statistical analysis was carried out among soil treatments using analysis of variance (ANOVA). Values accompanied by different letter(s) in each row are significantly different (p \(\leq\) 0.05), as determined using [PERSON]’s multiple test for mean comparisons.  
\end{table} 
Table 1: _Cont._between biochar added to soil and soil not amended with biochar. Accordingly, there is no evidence of urease and invertase inhibition in response to heavy metals stress. However, the results indicate a reduction in alkaline phosphatase activity compared to acid phosphatase (Figure 4B). Alkaline phosphatase has three active sites for binding metals; two of them are occupied with Zn+2 ions, and the third Cd site is occupied with Mg+2 ions [46]. Accordingly, these active sites can be occupied by mineral ions in biochar and/or animal manure, causing enzyme inhibition. [PERSON] et al. [47] reported that enzyme inhibition can also be accomplished by Cd ions that reduce the enzyme's affinity to its substrate. Figure 6A,B represent the impacts of biochar added to soil on the activity of alkaline- and acid phosphatase, expressed as ug p-nitrophenol released per g\({}^{-1}\) soil. Overall, acid phosphatase activity before and after biochar addition tends to be similar, whereas the activity of alkaline phosphatase was slightly reduced due to the addition of biochar, as indicated by the trend line. This might be due to the impacts of Cd [42], Al3+, Fe2+, and Ca2+ ions [43] on alkaline phosphatase activity. Figure 4: Overall soil urease and invertase activity (**A**) and acid and alkaline phosphatase activity (**B**) at different sampling dates during the green pepper growing season, regardless of soil amendments. Statistical analysis was carried out among the dates of sampling for each enzyme using analysis of variance (ANOVA). Values accompanied by different letter(s) are significantly different (\(p\leq 0.05\)) using [PERSON]’s multiple test for mean comparisons. The dotted lines indicate trend lines. Figure 7A reveals that biochar added to vermicompost, horse manure, and the control treatments did not impact soil urease activity. Biochar added to inorganic mineral fertilizer, sewage sludge, and chicken manure reduced the activity of urease. Biochar added to the organic mineral fertilizer significantly increased urease activity. Figure 7B also reveals that biochar added to horse manure, sewage sludge, chicken manure, and the control treatments did not impact invertase activity, whereas biochar added to inorganic mineral and organic elemental fertilizers reduced invertase activity. On the contrary, vermicompost amended with biochar showed significantly increased invertase activity. These results are consistent with those of [PERSON] et al.