Adsorção e dessorção de fosfato em horizontes com diferentes quantidades de matéria orgânica em Latossolos do Cerrado no Triângulo Mineiro

Abstract

Oxisols comprise approximately 46% of the Cerrado biome in Brazil. The mineralogy of weathered soils has high phosphorus retention capacity. On the other hand, the organic matter can contribute to reduce this nutrient retention by soil minerals present in clay fraction, increasing its availability to plants. In this context, this work evaluated the phosphorus adsorption and desorption in soil samples collected from horizons with different organic matter concentrations of three profiles of Oxisols in Cerrado region in Triângulo Mineiro. Soil samples were collected from A and Bw horizons of three Oxisols and processed for following characterization: texture, organic matter, available and remaining phosphorus concentrations, pH, delta pH and zero charge point. Adsorption essay was carried out using 0,3 g of soil and 30 mL of 0.03 mol L-1 NaCl with phosphorus added to soil in the following concentrations: 0; 5; 15; 30; 45; 60; 75; 90; 105 and 120 mmolc kg-1 . After that, desorption was performed using 30 mL of 0.03 mol L-1 NaCl. Phosphorus quantification was analyzed by colorimetry. Adsorption concentrations were quantified and Langmuir and Freundlich models evaluated to describe the sorption behavior of phosphorus on soil. The behavior of desorption concentrations was described by polynomial regression. According to the results, the A horizon of the Oxisols presented lower phosphorus adsorption capacity compared with Bw horizon of three soils. Higher organic matter content contributed to reduce phosphorus sorption on soil samples, increasing its availability to plants.