Abstract: Understanding the changes in soil properties accompanying land use is a prerequisite for landscape-level management that minimizes pollution and maintains the delivery of soil ecosystem services, particularly in a state like Florida, where an increasing population rapidly drives land use changes. Land uses were compared in a northern Florida watershed characterized by sandy soils and low soil organic carbon (SOC). The objective of this study was to investigate the relationships between land use, SOC, total nitrogen (N), extractable phosphorus (P), and short-term anaerobically mineralizable P in the surface soil in a sand-dominated North Florida watershed. Soil samples were separated by dry sieving into four soil size fractions: 2,000 to 250 μm, 250 to 150 μm, 150 to 45 μm, and less than 45 μm. Land use was found to affect SOC in the largest size fraction, with reduced SOC in land uses under tillage. Nitrogen content was greater in Improved Pasture and Rangeland land uses. The C:N ratios were lower in all fractions in the agricultural land uses compared with those in forested land uses, reflecting larger inputs and potential leaching of N to groundwater. Forested land uses had low extractable P, whereas land uses with intensive management plans had high levels of extractable P. The high P immobilization potential in the less than 45-μm size fraction and the high extractable P in the 150- to 45-μm size fraction were unexpected. Potential P mineralization of Crop and Improved Pasture was small considering the high extractable P levels in these land uses. Monitoring large soil size fractions will provide information-related changes in C sequestration and help determine sites with the greatest risk of off-site P movement, especially intensively managed land uses.