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Title: TRANSFORMATION & TRANSPORT OF NITROGEN FORMS IN A SANDY ENTISOL FOLLOWING A HEAVY LOADING OF AMMONIUM NITRATE SOLUTION: FIELD MEASUREMENTS AND MODEL SIMULATIONS

Author
item PARAMASIVAM, S - UNIV OF FLORIDA
item Alva, Ashok
item FARES, A - UNIV OF FLORIDA

Submitted to: Journal of Soil Contamination
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/1999
Publication Date: N/A
Citation: PARAMASIVAM, S., ALVA, A.K., FARES, A. TRANSFORMATION & TRANSPORT OF NITROGEN FORMS IN A SANDY ENTISOL FOLLOWING A HEAVY LOADING OF AMMONIUM NITRATE SOLUTION: FIELD MEASUREMENTS AND MODEL SIMULATIONS. JOURNAL OF SOIL CONTAMINATION, 9:65-86. 2000.

Interpretive Summary: Soluble nutrients present in the soil in excess of crop requirements tend to leach with the water as it percolates down the soil profile. In an uncultivated sandy soil with no confining layers within the top 2.7 cm, the heavy loading of ammonium and nitrate forms of nitrogen (as ammonium nitrate solution), leached rapidly and accumulated at the top of clay layer rat 2.7 m depth. On soil samples taken 180 days after the N loading, the ammonium and nitrate concentrations decreased to their background levels. The concentration of ammonium and nitrate forms of nitrogen measured in 2M KCL extraction from the soil samples at various depths compared favorably with the concentrations predicted by a computer model (Leaching Estimates and Christy Model - LEACHM.) This model also predicts the leaching of water. The amount of water predicted as being leached at 2.7 m depth represented 90% of total rainfall during that duration.

Technical Abstract: Understanding the factors influencing water nutrient transport though soil profile is important for the efficient management of nutrient and irrigation 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 transported quite rapidly (within 3 d) and accumulated above the clay layer at about depth of 2.7 m. The concentrations of NH4-N and NO3-N approached background levels throughout the soil profile by 184 d. More than 50% of ammonium and nitrate contained in the spilled solution leached from the entire depth of soil profile sampled during the first 95 d. The cumulative amount of rainfall 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 a few places with high concentrations. The cumulative amount of leachate at the bottom of the soil profile predicted by LEACHM represented 90% of total rainfall that occurred during the study period. This demonstrated a substantial potential for leaching of soluble nutrients through the sandy soil profile.