Electrochemistry and organic matter concentrations in the surface horizons of Oxisols are closely related. This study evaluated the electrochemical properties in the surface horizon of seven Brazilian Oxisols after the removal of humic substances by alkaline extraction. Based on their mineralogy the soils were grouped as kaolinitic or oxidic. Less than 3 % of the total organic matter were soluble humic substances extractable by NaOH 0.1 mol L-1, indicating their strong specific adsorption to the inorganic mineral sites. The removal […]

The ion exchange resin method used in some laboratories in Brazil requires soil grinding for the determination of available P. As a consequence of grinding, the extraction of internal labile P in aggregates is expected, increasing the concentration of available-P. On the other hand, finer grinding increases the exposure of soil particle surface, which creates additional sites for further P adsorption. The aim of this study was to evaluate extraction efficiency available-P by Mehlich-1, and anion exchange resin in beads […]

The use of the pH SMP to estimate the potential acidity has advantages in relation to the 0.5 mol L-1, pH 7, calcium acetate method, but it requires previous edaphic regionalization to estimate the H + Al values with safety. In the northwestern region of the State of Paraná there are soils originally developed from sandy sedimentary rock of the Caiuá Formation, called Caiuá Sandstone, of the Cretaceous period. These soils are characterized by low contents of clay and organic matter, and a low buffer capacity, […]

Samples of 30 soils were taken with the objective of characterizing the Capacity Factor of Phosphorus (CFP) and its relation with several properties of soils of Entre Ríos, Argentina. Isotherms of adsorption and a quick test of P adsorption were estimated. Langmuir and Freundlich equations described the adsorption phenomenon satisfactorily. The maximum adsorption capacity varied between 46 and 716 mg kg-1 of P in the soil, considering that the soils analyzed have from medium to low CFP. The adsorption capacity […]