Conquering Soil Acidification: The Synergistic Effects of Basalt Powder, Lime, and PAM

Abstract. Soil acidification poses a substantial threat to agricultural productivity by releasing salt ions, diminishing soil fertility, and increasing susceptibility to aluminum toxicity. The aim of the study was to investigate the potential improvement of acid yellow soil through the combined application of basalt powder, lime, and polyacrylamide (PAM). Herein, 0.1 g mixed basalt powder and CaO with various proportion were added to 10 g acidic yellow soil with an initial pH of 4.16 to explore the efficient of mixed soil amendments. X-ray fluorescence (XRF) analysis of basalt powder revealed its effectiveness in supplementing soil mineral nutrients. The optimal results of reduced acidification and ion leaching of soil were obtained when the addition proportion of basalt powder to lime was 8/2 and addition ratio of PAM was 0.0002 %. The addition of mixed amendments markedly increased the pH (by up to >2.0 units) and acid-damage capacity (20.3 mmol/kg) of soil, meanwhile decreased the leaching of K⁺(58.1 %), Na⁺(42.9 %), Mg²⁺(26.3 %), and Al³⁺ (below the detectable limit) as shown by the optimal tests. The basalt powder undergoes decomposition in the soil solution, resulting in the formation of some weak acids (i.e., H₂SiO₄), the release of OH^-, and an increase in soil pH. The study reveals the underlying mechanisms of soil remediation with mixed amendment, which has potential guidance for the application of mixed soil amendment and the environment risks prediction of contaminated soil.