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The P critical levels in plants depend from soil characteristics which reflect phosphate buffer power. In Pernambuco, soils mineralogical characteristics change at different regions where corn is cultivated. To evaluate P critical levels in corn plants in soil cultivated in different soils and contact periods of this element in the soil, aiming to study the relationships between these critical levels and P adsorption, it was realized an experiment using subsuperficial samples of a Vertissolo Ebanico ortico (VEo) (Mollisol), clay textured with predominance of 2: 1 clay mineral and a Nitossolo Vermelho distroferrico (NVdf) (Nitosol), high clay content, predominantly hematitic, colleted at the semi-arid and humid regions of Pernambuco State, Brazil, respectively. The P doses were defined in function of the levels 0; 0.2; 0.4; 0.8 and 1.0 from the P Maximum Capacity of Adsorption (CMAP) of each soil and were incubated by 90; 60; 30; 15; and 0.5 days. The experiment was realized into a greenhouse in a factorial scheme (5x5x2), five P levels, five incubation periods and two soils, in randomized blocks delineation with three replicates each. Corn plants were more efficient to utilize P in NVdf, the soil with higher CMAP. The corn shoot critical levels decreased in accordance to the period of incubation in VEo, the soil with lower CMAP.