Distribution of C and inorganic phosphorus fractions in different aggregate sizes under forestry, agroforestry system and pasture

Abstract: The objective of this study was to evaluate the organic carbon (OC) distribution and inorganic phosphorus (P) fractions on different soil aggregates classes under forestry fragment of Atlantic Forest, pasture and agroforestry managed for a long period. Soil samples were collected at depths of 0.00-0.10, 0.10-0.20 and 0.20-0.60 m, and the aggregate stability analysis was performed at each depth. The OC and the inorganic P fractions (Pbic readily available, NaHCO3 0.5 mol L-1; PNa1 moderately available, NaOH 0.1 mol L-1; and PNa2 restricted availability, NaOH 0.5 mol L-1) were determined in the respective classes of soil aggregates 4-2, 2-1, 1-0.5, 0.5-0.25 mm. Soil under forestry fragment showed higher OC contents and regardless the land use, highest values of inorganic P were found in the aggregates > 1 mm. Forestry showed highest levels of Pbic, while agroforestry showed the highest levels of PNa1, and pasture had highest values of PNa2.