Inorganic amendments improve acidic paddy soils: Effects on soil properties, Al fractions, and microbial communities.

Alkaline soil inorganic amendments (SIAs) have been extensively used to improve acidic soils. In this study, we arranged 9 treatments of low, medium, and high application dosages of silicon calcium magnesium potassium fertilizer, calcium magnesium phosphate fertilizer, and lime in the field to study the mechanism of SIAs in improving acidic soils. The Al sequential extraction experiment showed that the application of SIAs tended to transform from active to stable fractions of Al. By amplicon sequencing, it was observed that the application of SIAs significantly affected microbial community compositions in rhizosphere soils. With the decrease in soil acidity, the microbial function was also enhanced, especially the activity of dehydrogenase. In this study, the acidity-related indicators in soils (pH, exchangeable acid, and exchangeable base cations) were first integrated into an index-AIV (acidity improvement value), which was used to assess the relationship with other soil properties. The redundancy analysis and correlation network between soil chemical and biological indexes indicated that SIAs did not greatly affect the fungi community structure, while greatly increased or decreased the abundance of bacteria, especially Acidobacteria, Nitrospirae, and Crenarchaeota. Our data revealed the SIAs optimized soil environment for rice growth jointly by decreasing Al mobility, improving soil microbial function, and increasing soil fertility.