## 3 Results
### Soil CH\({}_{4}\) Fluxes  
Although soil CH\({}_{4}\) fluxes were highest in digestate-treated plots, this flux was only significantly greater than the hydrochar treatment (\(p<\) 0.05). With no other significant differences in soil CH\({}_{4}\) fluxes, our hypothesis that urea would produce the highest CH\({}_{4}\) fluxes was not supported. As expected, CH\({}_{4}\) fluxes were generally very low compared to fluxes of CO\({}_{2}\) throughout the season, except in late July to early August when most soil microorganisms were likely very active due to high temperatures coupled with high soil moisture. CH\({}_{4}\) emissions in hydrochar treatments were similar and not significantly different from control treatments. Both the control and hydrochar treatment acted as sinks for CH\({}_{4}\) fluxes. This finding is similar to [PERSON] et al. (2019) where hydrochar additions to soil were effective at lowering CH\({}_{4}\) emissions, but the GHG emissions produced were similar to control treatments and were neither affected by hydrochar type or application. [PERSON] et al. (2019) also observed lower CH\({}_{4}\) fluxes at lower application rates of the hydrochar (0.5%) and advised that the amount of hydrochar used should be carefully considered before applying to soil. A few occasional positive CH\({}_{4}\) fluxes were observed in the digestate treatment plots on 3 July (0.15 mg m\({}^{-2}\) h\({}^{-1}\)) and 9 August (0.09 mg m\({}^{-2}\) h\({}^{-1}\)), both at site B. All treatments were CH\({}_{4}\) sinks at site A. Site B digestate treatment plots were a net source of CH\({}_{4}\) fluxes, while all other treatment plots were a net CH\({}_{4}\) sink. The trend of most treatment plots acting as CH\({}_{4}\) sinks at site A could be explained by the differences in soil properties at site A and B. Firstly, site B had higher average soil moisture (28% VWC) than site A (15% VWC), and CH\({}_{4}\) production requires anaerobic conditions that are more prevalent in high-moisture soils. Secondly, soils usually act as sinks under aerobic conditions ([PERSON] et al., 2016), explaining why all treatments at site A with a lower moisture level acted as CH\({}_{4}\) sinks. Finally, baselinesoil C analysis indicates site B had a soil C content of 3.18% while site A had 2.66% C. The larger soil C content at site B may explain why more C in site B was converted into CH\({}_{4}\) resulting in a CH\({}_{4}\) source. According to [PERSON] and [PERSON] [55], soil exchange of CH\({}_{4}\) with the atmosphere is regulated by two groups of microorganisms: methanogens, which are very active in anaerobic conditions, and methanotrophic bacteria, which are active in aerobic conditions. Methanogens mainly produce CH\({}_{4}\) as a byproduct of metabolism and are the main biological source of CH\({}_{4}\) across systems, while methanotrophic bacteria metabolism is based on the oxidation of CH\({}_{4}\)[55]. The moisture content of the soil, which is generally correlated with precipitation level for most of the growing season, was low at both sites throughout our study period. Both sites A and B are non-wetland soils, suggesting that methanotrophic bacteria could be responsible for the higher uptake of CH\({}_{4}\). This trend cannot, however, be assumed for the digestate-treated plots, which had relatively high soil moisture (0.46 m\({}^{3}\) m\({}^{-3}\)). [PERSON] and [PERSON] [56] reviewed the literature on the effects of N enrichment on CH\({}_{4}\), CO\({}_{2}\), and N\({}_{2}\)O fluxes, and the results suggested that N additions caused a general stimulation of CH\({}_{4}\) emissions and a suppression of CH\({}_{4}\) uptake across multiple types of ecosystems. Results from our study contradict this pattern that would have predicted that the methanotrophic population would oxidize less CH\({}_{4}\) into the atmosphere after a soil N addition.