Knowledge of phosphorus(P)behavior in long-term fertilized soils is essential for programming fertilization practices and for sustaining environmental quality.The long-term(1984-1997)effects of various fertilization treatments on P changes and sorption isotherms as well as the relationship of soil properties to P sorption and P forms were evaluated in an Ustic Isohumisol,a calcareous soil,on the Loess Plateau,China.Compared to 1984,after 13 years of crop production,total soil P in the no-P treatments(control and N treatment)decreased by 5%-7%,but in the phosphorus fertilizer alone(P), nitrogen and phosphorus fertilizers in combination(NP),manure alone(M),and nitrogen and phosphorus fertilizers and manure in combination(NPM)treatments,it increased by 22%,19%,28%,and 58%,respectively.Residual fertilizer P was found mainly in NH_4Ac-soluble P(Ca_8-P),followed by NaHCO_3-soluble P(NaHCO_3-P),and NH_4F-soluble P (A1-P).Phosphorus sorption in the soils with different fertilization practices fit the Langmuir equations.Phosphorus sorption capacity in the no-P treatments increased,whereas it decreased in the P-included treatments(P,NP,and NPM treatments).Phosphorus sorption maximum(Q_m)was significantly and negatively correlated to inorganic P including NaHCO_3-P,Ca_8-P,NaOH-Na_2CO_3-soluble P(Fe-P),and Al-P(P≤0.01).Moreover,long-term fertilization increased soil organic carbon in the NP,M,and NPM treatments and decreased pH in the NP and NPM treatments.Thus,the ability of the soil to release sorbed P to the environment increased under long-term P fertilization. Knowledge of phosphorus (P) behavior in long-term fertilized soils is essential for programming fertilization practices and for sustaining environmental quality. The long-term (1984-1997) effects of various fertilization treatments on P changes and sorption isotherms as well as the relationship of soil properties to P sorption and P forms were evaluated in an Ustic Isohumisol, a calcareous soil, on the Loess Plateau, China. Compared to 1984, after 13 years of crop production, total soil P in the no-P treatments (control and N treatment reduced by 5% -7% but in the phosphorus fertilizer alone (P), nitrogen and phosphorus fertilizers in combination (NP), manure alone (M), and nitrogen and phosphorus fertilizers and manure in combination (NPM) treatments , which increased by 22%, 19%, 28%, and 58%, respectively. Residual fertilizer P was found primarily in NH4Ac-soluble P (Ca8- P), followed by NaHCO3- soluble P (NaHCO3- P), and NH4F -soluble P (A1-P). Phosphorus sorption in the soils with different fertilization practices fit the Langmuir equations. Phosphorus sorption capacity in the no-P treatments increased, past it decreased in the P-included treatments (P, NP, and NPM treatments). Phosphorus sorption maximum (Q_m) was significantly and negatively correlated to inorganic P including NaHCO 3 -P, Ca_8-P, NaOH-Na_2CO_3-soluble P (Fe-P), and Al-P (P≤0.01) .Moreover, long-term fertilization increased soil organic carbon in the NP, M, and NPM treatments and decreasing pH in the NP and NPM treatments.Thus, the ability of the soil to release sorbed P to the environment increased under long-term P fertilization.