# Effects of Manure Waste Biochars in Mining Soils
## Results
### CO\({}_{2}\) Emissions and qCO\({}_{2}\) Quotient in Amended Mining Soils
Nevertheless, the application of biochars prepared at 600 \({}^{\circ}\)C (BPL600 and BRM600) reduced the CO\({}_{2}\) emissions (30-32%) in soil Z3, sequestering C in the soil. In general, the soil CO\({}_{2}\) emissions after the application  
Figure 2: Cumulative CO\({}_{2}\) emissions of all treatments after 180 days: (**a**) Zarandas-Andalusia area. (**b**) Mijarojos-Cantabria area. (**c**) Portman-area. of biochar prepared at 450 \({}^{\circ}\)C were lower than after amendment of biochar prepared at 600 \({}^{\circ}\)C. In the case of the Mijarojos-Cantabria area, there was not a significant increment of CO\({}_{2}\) emissions in soil M2 after any biochar application. For soil M1, the CO\({}_{2}\) emissions only increased after the amendment of BPL450 biochar (+26%), while the CO\({}_{2}\) emissions of the soil M3 increased after the application of BPL600 and BRM450 (+15%) and BPL450 (+40%). Finally, for the Portman-Murcia area, the soil CO\({}_{2}\) emissions increased by more than 21% in soils P1, P2, and P3 after biochar addition, while the application of BPL600 and BPM600 reduced the CO\({}_{2}\) emissions in the soil P4 (-28% to -33%). Figure 3 shows the soil metabolic quotient (qCO\({}_{2}\)) values in the three areas after biochar application. Results were different depending on the studied area, although each biochar had a positive effect on qCO\({}_{2}\) in more than 60% of the soils. Indeed, BRM600 biochar had a positive effect in seven of 10 soils, improving the microorganism activity in the four soils of the Portman-Murcia area. In general, after the application of biochars, the lowest qCO\({}_{2}\) values were generally obtained in the treated soils of the Zarandas-Andalusia area (Figure 3a), while the highest values corresponded to both Mijarojos-Cantabria and Portman-Murcia areas (Figure 3b,c). Figure 3: qCO\({}_{2}\) of all treatments after 180 days: (**a**) Zarandas-Andalusia area. (**b**) Mijarojos-Cantabria area. (**c**) Portman-area. Figure 4 shows the GMea values for the control soils and soils amended with the four biochars of the studied areas at the end of the experiment. The variation of GMea in different treatments with respect to control soils adopted the following sequences in the different areas:  
* For the Zarandas-Andalusia area (Figure 4a): Soil Z1: Z1 + BRM450 (\(-\)27%) \(<\) Z1 + BPL450 (\(-\)35%) \(<\) Z1 + BPL600 (\(-\)50%) \(\approx\) Z1 + BRM600 \(<\) Z1 (0.29); Soil Z2: Z2 + BRM600 (\(-\)56%) \(\approx\) Z2 + BPL600 (\(-\)61%) \(<\) Z2 (0.23) \(\approx\) Z2 + BPL450 \(\approx\) Z2 + BRM450; Soil Z3: Z3 + BPL600 (\(-\)18%) \(<\) Z3 (0.17) \(\approx\) Z3 + BPL450 \(<\) Z3 + BRM450 (40%) \(\approx\) Z3 + BRM600. * For the Mijarojos-Cantabria area (Figure 4b): Soil M1: M1 + BRM600 (\(-\)35%) \(\approx\) M1+BRM450 \(\approx\) M1 + BPL600 \(<\) M1 (0.69) \(<\) M1 + BPL450 (23%); Soil M2: M2 + BPL600 (\(-\)37%) \(<\) M2 + BRM600 (\(-\)18%) \(\approx\) M2 + BPL450 \(\approx\) M3 + BRM450 \(<\) M2 (1.08); Soil M3: M + BRM600 (\(-\)35%) \(\approx\) M3 + BRM450 \(\approx\) M3 + BRM450 \(<\) M2 (1.08); Soil M3: M + BRM600 (\(-\)35%) \(\approx\) M3 + BRM450 \(\approx\) M3 + BRM450 \(<\) M2 (-\(\)5%) \(\approx\) M3 (0.69). * For the Portman-Murcia area (Figure 4c): Soil P1: P1 (0.03) \(\approx\) P1 + BRM600 \(\approx\) P1 + BPL600 \(<\) P1 + BRM450 (62%) \(<\) P1 + BPL450 (32%); Soil P2: P2 + BRM600 (\(-\)57%) \(<\) P2 + BPL600 (\(-\)42%) \(\leq\) P2 (0.07) \(<\) P2 + BRM450 (+11%) \(<\) P2 + BPL450 (+239%); Soil P3: P3 + BPL600 (\(-\)50%) \(\approx\) P3 + BRM600 \(<\) P3 (0.04) \(<\) P3 + BRM450 (60%) \(>\) P3 + BPL450 (264%); Soil P4: P4 + BRM450 (\(-\)92%) \(\approx\) P4 + BRM600 \(<\) P4 + BPL450 (\(-\)50%) \(<\) P4 + BPL600 \(<\) P4 (0.04). Figure 4: Geometric mean (GMea) of all samples after 180 days: (**a**) Zarandas-Andalusia area. (**b**) Mijarojos-Cantabria area. (**c**) Portman-area. These data showed that the GMea behavior was greatly variable depending on the soil characteristics and biochar added.