Mechanism analysis of soil amelioration and phosphorus recovery by using a mineral soil conditioner in southern China

This study aims to identify the processes and mechanisms affecting physicochemical properties of soil following application of mineral soil conditioner and to investigate the behavior of PO4 sorption among 1:1 and 2:1 clay minerals and Fe/Al oxides in a ferralsol. Three replicates of five treatments, i.e., (1) a control without any application of inorganic P (CK), (2) inorganic P fertilization (CKP), and (3) combinations of inorganic P fertilization with mineral soil conditioner applied at 750 (M1), 975 (M2), and 1200 (M3) kg ha(-1), were used to explore the influence of phosphate (PO4) sorption capacity and dynamic changes in clay mineralogy in the ferralsol, as examined using geochemical modeling (Factsage 6.1) and physical measurements (zeta potential, XPS, FTIR, and XRD analysis). We have found that the new formation of illite (a 2:1 phyllosilicate) was generated from the kaolinite (a 1:1 phyllosilicate) in the ferralsol after mineral soil conditioner (MSC) application. The iron in the ferralsol as well as the K+, Mg2+, and Si4+ in the MSC, played important roles in the clay mineral transformation. Meanwhile, the observed trends of phosphorus sorption competition suggested that the PO4 sorption capacity of the 2:1 clay minerals may be close to or even higher than that of the 1:1 clay minerals and Al oxides. The effects of Fe oxides on PO4 sorption could be ignored when Al oxides were present in the ferralsol. In comparison to the control and P-fertilized treatments, the PO4-binding capacity of the clay minerals in the MSC treatments could exceed that of the Al oxides because of the new formation of 2:1 clay minerals (illite). We demonstrate that the combination of zeta potential, XRD, FTIR, and XPS analysis is a promising strategy for distinguishing relationships between clay minerals and Al oxides in terms of phosphorus sorption. The MSC application was highly effective for soil amelioration and phosphorus sorption.