Effects of Phosphorus-Containing Compounds on the Remediation and Soil Microbiota in Rice Contaminated by Lead, Zinc, and Cadmium

In the present study, a wetland root box experiment was conducted to investigate the impact of exogenous phosphorus (calcium dihydrogen phosphate) on heavy metal distribution and soil microbial population of rice using Bureau Community of Reference (BCR) sequential extraction and Phospholipid Fatty Acid (PLFA) analysis. The experimental results demonstrate that adding calcium dihydrogen phosphate could reduce levels of acid-soluble, reduced, and oxidized heavy metals while minimizing their toxicity to rice. However, an exception was observed with cadmium, which showed an adverse effect at the maturity stage of rice. Furthermore, the addition of calcium dihydrogen phosphate significantly enhanced soil microbial biomass by 133% during the jointing stage and by 154% at the maturity stage. An increase in the fungi-to-bacteria (F/B) ratio was also observed, alongside improvements in the microbial community structure, contributing to greater soil ecosystem sustainability. Notably, the most favorable outcomes were achieved with a P : Pb molar ratio of 2 : 1, leading to effective reduction in heavy metal activity, promotion of microbial growth, and mitigation of heavy metal accumulation in plants.