# Carbon Storage Potential and Carbon Dioxide Emissions from Mineral-Fertilized and Manured Soil
## 4 Discussion
### Co\({}_{2}\)-C Soil Emission
In this study, the cumulative soil CO\({}_{2}\)-C emissions for the Ca + M treatment were much higher than for the CaNPK treatment (Table 1). High soil CO\({}_{2}\)-C emissions after the manure application were also recorded by [PERSON] et al. [24]. The amount of CO\({}_{2}\)-C released from the manured soil was more than two times higher than that from the non-treated soil. The data from this study showed that the difference in the CO\({}_{2}\)-C soil emissions between the soils that received manure and those that received mineral fertilizers was higher in the year characterized by above-average precipitation. Long-term fertilization with manure significantly increased the content of the SOC (Table 1) and was generally associated with improved physical soil properties [52]. Such improvements in the structure probably resulted in a higher aeration of the manured soil compared to the soils fertilized with mineral nutrients, which was particularly important during the periods of water excess in the soil. A higher soil aeration and porosity increased CO\({}_{2}\)-C soil emissions [53]. This was a likely explanation for the finding that the cumulative CO\({}_{2}\)-C soil emissions in the Ca + M treatment were similar during the observation years, whereas the cumulative CO\({}_{2}\)-C soil emissions in the CaNPK treatment in the first year was 32.2% higher than in the second year (wet year). [PERSON] et al. [21] showed that CO\({}_{2}\)-C emissions depend on the soil water content. The optimal soil moisture for CO\({}_{2}\)-C soil emissions was 60-70% of the water-filled pore space (WFPS). A soil moisture level below 50% WFPS did not affect the CO\({}_{2}\)-C soil emissions [24, 54]. When the water filled more than 70% of the pore space, CO\({}_{2}\) soil emissions were reduced to a minimum level. Therefore, in the study by [PERSON] et al. [48], [PERSON] et al. [46], and most likely in this study, a decrease in CO\({}_{2}\)-C soil emissions at a high soil water level could be observed. The amount of CO\({}_{2}\)-C released from the soil was related to the crop biomass production and changes in the SOC content. According to [PERSON] et al. [55], the soil carbon storage was the key factor driving CO\({}_{2}\)-C soil emissions. In the scientific literature, the SOC content was considered one of the most important drivers, along with the soil/air temperature, soil moisture, type of soil tillage, soil texture, crop residue management, and fertilization [11, 56]. A very strong correlation between the CO\({}_{2}\)-C soil emissions and the content of the SOC was described by [PERSON] and [PERSON] [17]. In this study, the cumulative CO\({}_{2}\)-C soil emissions were strongly and positively correlated with the content of the SOC in the soil profile up to a depth of 60 cm (Table 4). In the first year of the study, however, the cumulative CO\({}_{2}\)-C soil emissions were correlated more strongly with the soil carbon content in the E soil horizon than with its content in the Ap horizon. This might be explained by the multi-factor influence of the atmospheric and soil conditions in this year of the study. According to [PERSON] et al. [41], the content of the SOC in the topsoil was not a good predictor of CO\({}_{2}\)-C soil emissions in drier seasons. Corresponding to this, in the year with higher precipitation (second year), the cumulative CO\({}_{2}\)-C soil emissions were more strongly correlated with the SOC content in the topsoil than in the deeper soil horizons. Most of the CO\({}_{2}\)-C released from the soil came from decomposing short-lived organic matter [57]. According to [PERSON] et al. [41], a higher DOC content in the soil improved the biological activity, and thus affected the soil CO\({}_{2}\)-C emissions. A lower CO\({}_{2}\)-C release from the CaNPK-treated soil was associated with a lower availability of the readily biodegradable carbon compound content in the soil [58].