Soil acidification and phosphorus enrichment enhanced silicon mobility in a Hydragric Anthrosol

Purpose Phosphorus (P) and silicon (Si) mobility and their interactions in soils are sensitive to soil pH. Although Si fertilizer application has been reported to efficiently increase P availability in soils, the responses of Si mobility and availability to soil P enrichment are not well understood. Materials and methods This study investigated the effects of P addition and artificial soil acidification on Si sorption and availability in a Hydragric Anthrosol using adsorption, soil incubation, and rice growth pot experiments. Results and discussion When Si and P were simultaneously added at equimolar concentrations between pH 3.5 and 6.5, the presence of P decreased Si adsorption by 22–88% at the corresponding pH, suggesting that P had a greater affinity to soil solids than did Si. Si sorption by the soil generally increased with pH increasing in the pH range of our study, and the reduction of Si sorption due to P addition was more significant under higher pH conditions (e.g., CK (soil without pH adjustment, pH = 6.4) and pH 5.5 treatments). Soil acidification and P addition that decreased Si sorption resulted in greater Si mobility and availability, as indicated by higher soil CaCl 2 -extractable Si content and greater Si uptake and Si content of rice plant. Conclusions Our results highlight the importance of Si mobility or loss due to P enrichment and soil acidification in weathered soils used for Si-accumulating plants such as rice.