Investigation of differential levels of phosphorus fixation in dolomite and calcium carbonate amended red soil

BACKGROUND The pH adjustment of acidic red soils with lime materials is beneficial for the reduction of phosphorus (P) fixation. However, the reasons for varying levels of P activation after adding different lime materials have not been fully investigated. Therefore, this study examined changes in soil labile P and P forms after phosphate application to calcium carbonate (CaCO3) and dolomite amended red soil during a 120-day incubation period. Also change of P sorption properties in the amended soil samples from day 120 were examined through a sorption-desorption experiment. RESULTS The increase of soil H2O-P and NaHCO3-P in the CaCO3 and dolomite amended soil treatments was mainly ascribed to the decline of the NaOH-P. However, when compared with the control treatment after 120 days, soil Olsen-P significantly increased by 34% and 66% in the CaCO3 and dolomite treatments. The Hedley P fractionation results demonstrated that the CaCO3 application caused a notable increase of HCl-P (stable Ca-P), which was 88.4% higher than that in the dolomite treatment. However, the formation of stable P was strongly suppressed in the dolomite treatment due to the presence of magnesium (Mg), which was identified by the negative relationship between M3-Mg and HCl-P. In line with these findings, P sorption-desorption work showed weaker P binding energy in the dolomite treatment relative to the CaCO3 treatment. CONCLUSION In terms of increasing P availability in red soil, this study suggests that dolomite should be used to substitute CaCO3 in order to reduce the soil P fixation. (c) 2021 Society of Chemical Industry.

Automated summary

The study found that using dolomite to amend red soil can significantly increase the availability of phosphorus in soil, thereby reducing phosphorus fixation. Dolomite treatment led to a significant increase in HCl-P (stable Ca-P), while the presence of magnesium (Mg) in dolomite suppressed the formation of stable P.