Taxonomic and functional responses of soil microbial communities to slag-based fertilizer amendment in rice cropping systems

The effective utilization of slag-based Silicon fertilizer (silicate fertilizer) in agriculture to improve crop productivity and to mitigate environmental consequences turns it into a high value added product in sustainable agriculture. Despite the integral role of soil microbiome in agricultural production and virtually all ecosystem processes, our understanding of the microbial role in ecosystem functions and agricultural productivity in response to the silicate fertilizer amendment is, however, elusive. In this study, using 16S rRNA gene and ITS amplicon illumina sequencing and a functional gene microarray, i.e., GeoChip 5, we report for the first time the responses of soil microbes and their functions to the silicate fertilizer amendment in two different geographic races of Oryza sativa var. Japonica (Japonica rice) and var. Indica (Indica rice). The silicate fertilizer significantly increased soil pH, photosynthesis rate, nutrient (i.e., C, Si, Fe, P) availability and crop productivity, but decreased N availability and CH4 and N2O emissions. Moreover, the silicate fertilizer application significantly altered soil bacterial and fungal community composition and increased abundance of functional genes involved in labile C degradation, C and N fixation, phosphorus utilization, CH4 oxidation, and metal detoxification, whereas those involve in CH4 production and denitrification were decreased. The changes in the taxonomic and functional structure of microbial communities by the silicate fertilizer were mostly regulated by soil pH, plant photosynthesis, and nutrient availability. This study provides novel insights into our understanding of microbial functional processes in response to the silicate fertilizer amendment in rice cropping systems and has important implications for sustainable rice production.