In north central Florida, the Santa Fe River Watershed is a mainly rural watershed whose water quality has been decreasing during the last decade. As part of a larger study that measured nitrate levels in the soil profile, we also looked at the mineralizability of the two most significant inorganic nutrients with surface water pollutant potential. Our objectives were to (1) contrast the main land uses in the watershed as to their distribution of extractable N and P in soil particle size fractions (2mm to 250 microns, 250 microns to 150 microns, 150 microns to 53 microns and less than 53 microns) in the surface 10 cm of soil and (2) contrast the mineralizability, both absolute and specific, of N and P in the particle size fractions by land use and particle size fraction. The surface 10 cm of mineral soil from 64 locations in the watershed, representing the range of land uses, were sampled, air-dried and sieved to recover particle size fractions. Nitrogen (N) and phosphorus (P) were extracted both before and subsequent to 2 weeks of aerobic mineralization. When nutrient release was measured, there were no interactions between land use and particle size class allowing us to look at each main effect independently. The most significant result is that, in these very sandy, low clay soils, both nutrients were found in significant extractable and mineralizable levels in all particle size classes, with the silt+clay fraction having the least absolute amounts. In general, the forest land use had lower amounts of extractable+mineralized N and P which were available for leaching than improved pasture and rangeland. These data combined with complementary measurement of soil NO3, total N, P and organic C indicate the advantage of having a watershed dominated by forest land use.