Wetland soil affects phosphorus lability

Wetlands act as filters, retaining phosphorus (P). The objective of this study was to evaluate the degree of P lability of hydromorphic (Histosol) and non-hydromorphic (Cambisol) soils under natural condition (no P addition) and with mineral P addition. The mineral P added was equivalent to 100% of the maximum phosphorus adsorption capacity, incubated during 0 and 120 days, at depths of 0-10 and 40-60 cm. The sequential P extraction was: labile, moderately labile, low lability, and residual. Under the natural condition, the moderate and low lability fractions were predominant in the Histosol, indicating lower P lability compared to the Cambisol. Total phosphorus (Pt) and organic phosphorus (Po) were higher in the Histosol compared to the Cambisol. After 120 days incubation with mineral P, the labile fraction decreased and the moderately labile fraction increased in the Histosol, demonstrating the effect of time on P stability. The addition of mineral P increased inorganic P (Pi) and also Po in both soils, indicating a strong interaction of mineral P with soil organic matter. The Po extracted with NaOH 0.1 mol L^-1 (moderately labile) was predominant in both soils and it was higher in the Histosol when compared to the Cambisol. In general, under both conditions (natural and mineral P addition), the Histosol stored P in more stable forms, reinforcing the need for permanent preservation of wetlands.