In the soil, forms and content of water-soluble carbon (WSC) are influenced by factors such as organic matter quality and content, soil acidity, nutrient availability, mineralogy, and aspects related to the microbial community. This study aimed to evaluate forms and quantities of carbon (C) in leachates from Latosols (Oxisols) with different Fe contents, amended with lime and/or phosphorus. Samples of mesoferric Red Latosol (LV1) and hypoferric Red Latosol (LV2) were collected in the Rio das Mortes wathershed, state of Minas Gerais, Brazil, and treated as follow: 1- control, 2- phosphorus (50 % of maximum phosphorus adsorption capacity), 3- liming (V= 85 %), 4- liming+phosphorus (doses equivalent to treatments 2 and 3). The experimental design was completely randomized, with three replications. Quantities of WSC and molar mass distribution were measured in ten consecutive leachate samples. Contents and types of low molar mass organic acids, associated with WSC, were also measured. In both soils, the quantities of water-soluble carbon increased in the following order: control < liming < phosphorus < liming + phosphorus. Water-soluble carbon in the LV2 was higher than in the LV1. Liming + phosphorus increased the average molecular mass of the WSC fractions in the leachates over time. The highest masses were found when the LV2 was amended with phosphorus or liming + phosphorus. More C in the organic acid form was leached from the LV1 than from the LV2.
organic acid; fulvic acid; molar mass; water-soluble carbon; tropical soils; iron oxides
