Seasonal Root-Zone Microbial Restructuring and Methane-Related Taxonomic Patterns Under GroMore® Crop-Protection Programs in Flooded Rice

Abstract

Crop-protection programs in flooded rice may influence root-zone microbial communities and their seasonal dynamics. This study evaluated microbial responses to untreated, conventional, and GroMore® crop-protection programs in a farmer-managed paddy field in Korea using 16S rRNA amplicon sequencing and soil pesticide residue analysis. Methanogen- and aerobic methanotroph-associated taxa were evaluated as taxonomic proxies and examined in relation to grain yield, seasonal CH4 emission, and greenhouse gas intensity (GHGI). GroMore did not consistently increase alpha diversity; however, treatment effects were significant for Shannon diversity (p = 0.025) and Chao1 richness (p = 0.024) in July, and treatment-associated differences in overall microbial community composition were evident from July through September (p = 0.001 for each month). During August, methane-related taxonomic proxies differed among treatments, but the methanogen-to-methanotroph taxonomic abundance ratio was not significantly associated with seasonal CH4 emission (r = 0.44, p = 0.377). Selected GroMore treatments showed 26.5–32.4% lower GHGI than the conventional treatment, primarily because of higher grain yield rather than reduced seasonal CH4 emission. Overall, GroMore programs were associated with seasonally structured root-zone microbial community differences, while methane-related taxa were interpreted as ecological proxies rather than direct indicators of methane-cycling function.