# Changes in Soil Chemical Properties Due to Long-Term
## 6 Conclusions  
This study showed that long-term compost fertilization containing cattle manure and rice straw or a combination of NPK and compost fertilization increased the OM, TN, P\({}_{2}\)O\({}_{5}\) and K content in the paddy fields. Compost fertilization provided a more readily available DOC, while the addition of inorganic chemical fertilizer, NPK, in combination with compost resulted in paddy soils with higher Ca, Mg and pH. The changes in soil chemical properties of compost-fertilized paddy fields concurrently resulted in the increased abundance of methanogenesis and methane-oxidation-related genes as well as the overall soil variabilities among unfertilized, compost, and NPK+Compost-fertilized fields. Paddy fields under long-term compost fertilization are characterized by soils with increased nutrient content and an increased abundance of methanogenesis and methane-oxidation-related genes. These soil conditions are present even during the fallow period, indicating their potential impact on methane emission and methane oxidation during the fallow season or when rice paddies are recurrently amended with compost and NPK+Compost. The study clearly indicates that the soil and biological conditions in long-term compost-fertilized paddy fields are distinctly different from those of unfertilized paddy fields and these are the conditions that initially or continuously respond to different treatments and agricultural management practices in relation to methane emission and methane oxidation.  
The following are available online at [[https://www.mdpi.com/article/10.3390/app12052652/s1](https://www.mdpi.com/article/10.3390/app12052652/s1)]([https://www.mdpi.com/article/10.3390/app12052652/s1](https://www.mdpi.com/article/10.3390/app12052652/s1)), Table S1: characteristics of qPCR primer pair and programs [59; 61; 62; 63]; Figure S1: k-means clustering and heatmap of the different treatments based on the soil chemical properties under long-term compost fertilization. EC--electrical conductivity; OM--organic matter; TN--total nitrogen; DOC--dissolved organic carbon. Table S2: Pearson correlation coefficient between the abundance of methanogenesis (\(mcrA\)) and methane oxidation (\(pmoA\)) functional genes and soil chemical properties of paddy fields under long-term compost fertilization.  
**Author Contributions:** Conceptualization, T.S. and A.R.C.; methodology, T.S. and S.L.; software, C.K. and A.R.C.; validation, T.-Y.H. and T.S.; formal analysis, D.I.W., C.K. and T.-Y.H.; investigation, D.I.W., C.K., S.L., H.C. and K.P.; resources, T.S., C.K. and S.L.; data curation, D.I.W., C.K., S.L., H.C. and K.P.; writing--original draft preparation, D.I.W. and C.K.; writing--review and editing, D.I.W., A.R.C., C.K. and T.S.; visualization, C.K.; supervision, T.S., Y.L. and S.L.; project administration, T.S., Y.L. and S.L. All authors have read and agreed to the published version of the manuscript.  
This study was carried out with the support of PJ015584042021, Rural Development Administration, Republic of Korea.  
Not applicable.  
The sequences of the clones were submitted in the BankIt portal in NCBI and the accession numbers were mentioned in the Methods section.  
We would like to acknowledge the technical advice of [PERSON] and [PERSON] on the conduct and analysis of qPCR.  
The authors declare no conflict of interest.