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 H2 O-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. © 2021 Society of Chemical Industry.
Keywords: P forms; P sorption-desorption; acidic red soil; dolomite; magnesium.
© 2021 Society of Chemical Industry.