Transformation and transport of nitrogen forms in a sandy entisol following a heavy loading of ammonium nitrate solution: Field measurements and model simulations

Understanding the factors influencing water and nutrient transport through soil profile is important for the efficient management of nutrient and irri gation to minimize nutrient leaching below the rootzone. Transport of NO3-N and NH4-N was studied in a Candler fine sand following a heavy loading of a liquid fertilizer containing ammonium nitrate. Both NO3-N and NH4-N trans ported quite rapidly (within 3 d) and accumulated above the clay layer at a bout depth of 27 m. The concentrations of NH4-N and NO3-N approached backgr ound levels throughout the soil profile by 184 d. More than 50% of ammonium and nitrate contained in the spilled solution leached from the entire dept h of soil profile sampled during the first 95 d. The cumulative amount of r ainfall during this period was 329 mm, which accounted for 65% of the total rainfall for the entire study period. The concentrations of NH4-N and NO3- N at various depths within the entire soil profile reasonably predicted by the Leaching Estimation and Chemistry Model (LEACHM) and compared favorably with the measured concentrations however, there are few places with high c oncentrations. The cumulative amount of leachate,sf the bottom of the soil profile predicted by,LEACHM represented 90% of fetal rainfall that occurred during the study period. This demonstrated a substantial potential for lea ching of soluble nutrients through the sandy soil profile.