Phosphorus (P) is one of the most important elements used in fertilizing soils in tropical regions due to the low efficiency of phosphate fertilization.This work aimed to fractionate inorganic P (Pi) in tropical soils of different mineralogical compositions and to relate these fractions with their respective phosphate buffer eyeliner capacity (PBC) indicators.The soils were characterized physically, chemically and mineralogically.Additionally, we evaluated the P concentration that remained in solution of soil after equilibrium was met; this was termed P remaining (P-rem).In general, the Pi fractions of soils did not correlate with the PBC indicators.
The P-H2O fraction showed a negative correlation with the P-Al fraction.Ferric minerals did not influence P fixation.P-rem showed a strong correlation with the maximum P adsorption capacity, adsorption energy, and the amorphous and crystalline forms of Fe.The Zodiac DC33 Parts minerals of aluminum contributed the most to P fixation.P-rem was the best estimator of PBC.
The soils with high, moderate and low rates of P fixation showed high amounts of the fractions P-Al, P-Ca, and P-Fe, respectively.The results showed that P fixation was influenced by the fractions of P in the soil, suggesting that the efficiency of phosphate fertilizers in tropical soils depends on the mineralogy of the clay fraction within those soils.