Pastures cover nearly 50 million hectares in the Cerrado region. The Oxisols, which cover approximately half this area, are highly weathered soils composed mainly of kaolinite, iron and aluminum oxides. Iron and aluminum oxides have a great influence on the retention of phosphorus (P) in these soils. The aim of this study was to quantify the total phosphorus levels, as well as P availability and retention in Oxisols under pasture in the Cerrado region and to relate the data with soil mineralogical, textural and chemical characteristics. The relations between the studied parameters were analyzed by principal component analysis and linear correlation analysis. The ion-exchange resin extractable P was negatively correlated with mineralogical and texture soil characteristics, and positively with soil organic matter contents. Both the total free and the poorly crystalline oxides were negatively correlated with equilibrium P (Prem). Gibbsite, goethite as well as the total free and poorly crystalline oxides were negatively correlated with Prem, indicating their effects on P adsorption to Cerrado Oxisols. Conversely, kaolinite was not significantly correlated with Prem. The negative correlation between Prem and total carbon (C total) was due to the linear increase of soil carbon with the clay and silt contents. The iron and aluminum oxides were the characteristics that most influenced Prem of Cerrado Oxisols.
Oxisols; P availability; P sorption; remaining phosphorus; Fe and Al oxides
