Mitigation of methane emission in a rice paddy field amended with biochar-based slow-release fertilizer

Despite improving soil quality and reducing nitrogen (N) loss in paddy soil, replacing chemical fertilizer with organic fertilizer would significantly accelerate greenhouse gas emission in terms of methane (CH₄). The application of slow-release fertilizer has been proposed an effective approach to control CH₄ emissions, in addition to reducing N loss. Yet, the understanding of CH₄ emissions from paddy fields with the additions of different fertilizers is still less known. Therefore, the effects of different fertilizer treatments, including chemical fertilizer treatment (CF), mixed chemical and organic fertilizer treatment (OF), biochar-based slow-release fertilizer treatment (SF), and no fertilizer control treatment (CK) on CH₄ emissions and methanogenic community structure in paddy soils were investigated through a field experiment. Results showed that slow-release fertilizer addition significantly decreased CH₄ emissions by 33.4%, during the whole rice growing season compared to those in OF. The cumulative CH₄ emissions were in a significantly positive relation to soil NH₄⁺-N. Slow-release fertilizer amendment decreased the relative abundances of Methanosarcina and Methanoregula and increased the relative abundances of hydrogenotrophic Methanocella and Rice Cluster I. Reduced CH₄ emissions with slow-release fertilizer amendment might be mainly attributed to the different forms of N in the fertilizer and available potassium (K) in the paddy soil. Our findings produce novel insights into the application of slow-release fertilizer in controlling CH₄ emissions from rice fields.