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Our study focuses on the phosphorus (P) balance in two long-term fertilization experiments which were carried out in characteristic soils of Hungary with four fertilization treatments and four main crops. The objectives of this study are: (1) to quantify the P accumulation rate in the upper soil layers and (2) to calibrate and validate the P-balance module of the 4M crop model. The concentration of ammonium-lactate soluble P (AL-P) increased with time in both soils. The mean AL-P accumulation rates in the 0-20, 20-40 and 40-60 cm soil layers were 3.7, 0.7, 0.1 and 3.7, 4.3, 0.6 mg/kg/year in the chernozem and the sandy soil, respectively. The P accumulation rates in the top layers (0-20 cm) changed significantly in time as these gradually decreased from around 6.5 mg/kg/year to zero in about 26 years in both soils. The model results of the phosphorus content in different soil layers, as well as the plant phosphorus uptake were in good agreement with the observed values.