## 3 Results
### CH\({}_{4}\) Fluxes  
All plots became a sink of CH\({}_{4}\) on 29 July (Figures 6 and 7). The lowest absolute fluxes occurred during the months of September and October. Total cumulative CH\({}_{4}\) fluxes over the period of the study at site A were \(-\)24.2 \(\mu\)g CH\({}_{4}\) m\({}^{-2}\) in digestate, \(-\)13.7 \(\mu\)g CH\({}_{4}\) m\({}^{-2}\) in control, \(-\)20.1 \(\mu\)g CH\({}_{4}\) m\({}^{-2}\) in urea, and \(-\)19.9 \(\mu\)g CH\({}_{4}\) m\({}^{-2}\) in hydrochar treated plots. The total cumulative CH\({}_{4}\) flux over the  
Figure 4: Cumulative CO\({}_{2}\) fluxes in mg m\({}^{-2}\) from subplots in sites A and B treated with digestate, hydrochar, urea (nitrogen), and control treatments from June–October 2018. Values are a mean of two replicated plots with error bars representing the standard error.  
Cumulative CH\({}_{4}\) fluxes were not affected by fertilizer treatment (Figure 8) or site. There was no significant interaction between treatment and site. In site B, however, the CH\({}_{4}\) flux in digestate treatment plots was significantly greater than CH\({}_{4}\) fluxes in the hydrochart treatment (\(p<0.05\); Figure 8).  
In repeated measures comparisons, test results suggest there was a statistically significant effect of sampling date on CH\({}_{4}\) fluxes in the four treatments (\(p<0.001\)). A Bonferroni multiple comparison test showed that CH\({}_{4}\) fluxes in week 3 of sampling were significantly higher than CH\({}_{4}\) fluxes in weeks 6, 10, 14, 15 and 17 (\(p<0.05\)). Furthermore, CH\({}_{4}\) fluxes in week 7 of sampling were significantly lower than CH\({}_{4}\) fluxes in all other weeks (\(p<0.001\)).  
Figure 8: Cumulative CH\({}_{4}\) fluxes in \(\mu\)g m\({}^{-2}\) from subplots in sites A and B treated with digestate, hydrochar, urea (nitrogen), and the control treatment from June–October 2018. Values show a mean across two replicated plots with error bars representing the standard error.  
Figure 7: Time series CH\({}_{4}\) fluxes measured from June to October 2018 at site B in \(\mu\)g CH\({}_{4}\) m\({}^{-2}\) h\({}^{-1}\) by treatment: (**a**) control, (**b**) digestate, (**c**) hydrochar, and (**d**) urea. Values show a mean across two replicated plots with error bars representing the standard error.  
Mean instantaneous fluxes ranged from \(-0.0085\)\(\mathrm{\SIUnitSymbolMicro\mathrm{g}}\) CH\({}_{4}\) m\({}^{-2}\) h\({}^{-1}\) in the digestate treatment plots at site A to 0.0091 \(\mathrm{\SIUnitSymbolMicro\mathrm{g}}\) CH\({}_{4}\) m\({}^{-2}\) h\({}^{-1}\) in digestate treatment plots at site B. The average cumulative CH\({}_{4}\) fluxes across all four blocks in each treatment were: control (\(-7.91\)\(\mathrm{\SIUnitSymbolMicro\mathrm{g}}\) m\({}^{-2}\)), digestate (0.85 \(\mathrm{\SIUnitSymbolMicro\mathrm{g}}\) m\({}^{-2}\)), hydrochar (\(-14.53\)\(\mathrm{\SIUnitSymbolMicro\mathrm{g}}\) m\({}^{-2}\)), and urea (\(-14.32\)\(\mathrm{\SIUnitSymbolMicro\mathrm{g}}\) m\({}^{-2}\)). CH\({}_{4}\) fluxes in control plots were positively related to soil moisture (r = 0.25, \(p<0.05\)), although the positive trend is driven by the CH\({}_{4}\) fluxes measured for timepoints with soil moisture contents between 10 and 23% and there is wide variation (Figure 9). CH\({}_{4}\) fluxes were also positively related to soil moisture in digestate plots (r = 0.31, \(p<0.01\)) (Figure 9).