The desorption of phosphate determines the transformation and translocation of phosphorus in soils,and affects the P nutrition of soils and the environmental effect of phosphorus.Accordingly,it is of great importance to study the desorption characteristics of phosphate.In she present study laterite (L),volcanic ash soil (V),kaolinite (K1) and synthetic amorphous aluminum silicate (A_Al-si),amorphous iron oxide (A_Fe)and gibbsite (G) were used to investigate the desorption characteristics of phosphate on the variable-charge surface in soils.The results showed that the phosphate desorbed by 0.01 mo1L^-1 NaF (pH 9.08) was determined by phosphate adsorbed previously,and the relationship between them could be well described by using linear and exponential equations.The average desorption percentages were shown as follows: Kl(66%)>A_Al-si;(60%)>L(55%);A_Fe(29%)>G(23%)>>V(9%).The variatton degree of desorption percentage was related to the constituents of samples.The phosphate desorption was determined by the pH of desorption solution which could affect the proton dissociation of phosphate and the surface charges of colloids.The phosphate desorption increased consistently with the initial pH(pHi) of desorbent except that for the kaolinite and gibbsite it decreased at first and then increased.The p1H of equilibrium desorption solution (pHe) firstly showed an to crease and then followed by a decrease.When the ΔpH,the difference of pHe and pHi,was equal to zero,the pH of desorption solution was affected by the surface characteristics of minerals.The critical pH for the samples was V(7.7)>A_Al-Si>(6.9)>L(6.8)>A_Fe(6.%)>Kl(6.1)>G(4.2).