# Changes in Soil Chemical Properties Due to Long-Term
###### Abstract  
Maintaining rice yield, soil function, and fertility are essential components of long-term compost fertilization. However, paddy fields are major sources of anthropogenic methane emissions. The aim of the study is to evaluate the changes in soil chemical properties and their concurrent impact on the abundance of methanogenesis (_mcrA_) and methane oxidation (_pmoA_) related genes among compost (Com), NPK+Compost (NPKCom), and unfertilized (NF) fallow paddy fields under long-term compost fertilization. Results showed that compost and NPK+Compost fertilization altered the soil chemical properties of paddy fields with a significant increase in the functional gene abundance potentially associated with Methanobacteriaceae for _mcrA_ (\(1.23\times 10^{6}\) to \(3.84\times 10^{6}\) copy number g\({}^{-1}\) dry soil) and methane oxidizing bacteria such as _Methylomonas_ and _Methylobacter_ for _pmoA_ (\(1.65\times 10^{6}\) to \(4.3\times 10^{6}\) copy number g\({}^{-1}\) dry soil). Ordination plots visualized these changes, where treatments clustered distinctly indicating that Com and NPKCom treatments were characterized by paddy soils with elevated OM, TN, K and P content and higher abundances of methanogenesis and methane oxidation related genes. The study showed that long-term compost fertilization resulted in paddy fields with high nutrient content and high gene abundance, attributed to methanogens and methane oxidizing bacteria that responded well with compost fertilization. These results indicated the potential of these fallow paddy fields for methane emission and methane oxidation and that they are 'primed', potentially influencing subsequent paddy field responses to long-term compost application. long-term compost fertilization; soil chemical properties; functional gene abundance; paddy soils; rice fallow period; methane emission; methanogenesis; methane oxidation; _mcrA_; _pmoA_ 4.0/. +
Footnote †: Copyright** © 2022 by the authors. and microbial components as critical indicators of sustainable agriculture to mitigate environmental issues [1; 2; 3]. In conjunction, methane as a greenhouse gas is a major factor in global warming [4]. The global methane emissions in 2017 reached a record with 600 Tg CH\({}_{4}\) yr\({}^{-1}\) of which 61% was anthropogenic primarily from agriculture-related sources [5]. Rice paddies are major sources of methane, generating approximately 11% of global anthropogenic methane emissions [6; 7]. Methane emission dynamically changes in different soil types under aerobic and anaerobic states dictated by the balance of methane production through methanogenesis and methane oxidation [8]. Long-term compost application, alone or in combination with inorganic fertilizers such as NPK, has been adapted to combat interrelated environmental problems such as soil degradation and unsustainable land use, leading to beneficial impacts such as improved soil carbon sequestration, biodiversity, biogeochemical cycles, fertility, and crop yield [9]. Although compost fertilization plays a positive role in climate change mitigation through soil carbon sequestration, its role in increased methane emission is well documented, particularly in paddy fields under submerged conditions [10; 11]. In addition, compost fertilization could affect the physicochemical and biological components of soil paddy fields, which ultimately reflects on the soil biogeochemical processes affecting methane emission [12]. We have greatly expanded our understanding of methanogenesis and methane oxidation and their links to processes and factors such as global warming and greenhouse gas emissions, soil functions, and edaphic components [4; 8]. We have also improved on precision agriculture, maximizing yield with optimal input. Extensive studies on these processes allow us to analyze and create an overview for larger or long-term scale scenarios and to incorporate potential environmental impact [6; 7], helping develop models to help understand and mitigate environmental issues [1].