Nitrate Movement and Denitrification Defined Relative to Bromide Tracer in Tile-Drained Land

摘要

A 3-year field experiment initiated in 1975 was designed to study the movement of nitrogen (N) as nitrate (NO3) and bromide (Br) through the soil profile and into tile lines, following application of N fertilizer and ammonium bromide. The study was carried out to assess the NO3 leaching rate from the soil surface to the tile drains, to test the use of Br ion as a tracer, and to use the data to estimate the relevance of N transformation (e.g., mineralization; denitrification (DN), in the fate pathways of N. Tile drain water concentrations of both NO3 and Br approached maximum nearly a year after fertilizer and bromide application; in this interval, about 325 mm water had flowed from the tile drains. Ratios of NO3/Br in tile drainage water decreased from 4.7-2.5 and from 2.5-0.26 for the two tiles used during a 14-month dry period. The decrease in NO3 levels and in NO3/Br ratios with time was interpreted as being due to DN.