Competitive adsorption of phytotoxic exchangeable Al3+ and directed enrichment of microbial community introduced by base ion-enriched additive and industrial by-product enhance soil fertility and maize yield

Soil acidification seriously threatens sustainable agriculture by promoting phytotoxic exchangeable aluminum ions (Al3+) accumulation and impairing crop growth. However, conventional soil amendments, such as lime and biochar, have known limitations, making the introduction of more sustainable soil amendments crucial for mitigating soil acidification. Furthermore, the biological and chemical mechanisms by which amendments alleviate acidification and enhance soil fertility remain unclear. This impedes the search for more cost-effective soil amendments to rehabilitate infertile acidic soils. In this study, pot experiments, microbial sequencing, and molecular modeling calculations were employed to assess the response of soil fertility and maize yield to the combined application of sodium carboxymethylcellulose (CMC) and desulfurized phosphogypsum (DP) in strongly acidic soils, as well as the underlying biological and molecular dynamic mechanisms. The results indicated that CMC + DP significantly reduced soil exchangeable Al3+ by 78.68–79.60%, while enhancing the base ion concentration by 59.93–102.27% and acid buffering capacity by 46.47–49.55% compared to the control (CK) in strongly acidic soils. Additionally, CMC + DP-amended soil exhibited a 24.47–48.65% increase in photosynthetic rate and a 50.57–155.48% increase in the weight of 100 grains. CMC contributed to Al3+ immobilization and base ion release via competitive electrostatic attraction and complexation of Al3+ on the surface of –COOH and –OH functional groups. CMC + DP application promoted direct enrichment of microbial communities, increasing the abundance of functional microbial taxa, including Acidobacteriota, Gemmatimonadota, and Ascomycota, and soil enzymes related to organic matter decomposition and phosphorus metabolism. These findings suggest that CMC + DP could be used as a promising strategy to mitigate soil acidification, enhance soil fertility and crop yield, and highlight the synergistic potential of biodegradable polymers and industrial by-products for acidic soil remediation. They enhance our understanding of the synergistic biological and molecular dynamic mechanisms of amendments, mitigating soil acidification and enhancing soil fertility. These findings may help identify more effective soil amendments and application strategies to ensure cropland health and promote sustainable agriculture.