Rice researchers and farmers report that additional N needs to be added to fields, depending on soil type and N fertilizer. For example, in Arkansas an additional 45 kg N per ha added to clay soils as compared to silt loams can increase annual costs up to 2.2 million dollars. The objectives of this research are to determine 1) the degree in which flood water adds N (either 90 mg N as urea or as ammonium sulfate) into silt loam soil and 2) the distribution of N during the immediate time intervals following fertilizer additions. In this study N availability was measured in intact cores (7.62-cm dia., 10-cm depth) containing DeWitt silt loam that were leached with a constant flood for 0.5, 1, 2, 4, 8, or 12 hr. After removing the flood, cores were frozen, sectioned into 2-cm depths, extracted with 2M KCl, and analyzed for nitrate and ammonium concentrations. Nitrate was always less than 27 mg N kg^-1 at all depths in all cores. Ammonium in soil receiving ammonium sulfate decreased from 520 to 360 mg N kg^-1 within the surface 2 cm during the 12 hr flood. In contrast, concentrations at the 2-4 cm depth increased from 150 to 300 mg N kg^-1 over12 hr. Ammonium decreased with depth and ranged between 5 and 40 mg N kg^-1 below 6 cm, even after 12 hr of leaching. In soil receiving urea, ammonium ranged from 110 to 240 mg N kg^-1 at 0-2 cm and from 240-350 mg N kg^-1 at 2-4 cm. Additionally, below 4 cm, ammonium concentrations were higher than in soil receiving ammonium sulfate and did increase over time. These results have demonstrated immediate and deeper movement of ammonium into silt loam soil receiving urea as compared to ammonium sulfate.