Simple use of the backwards Lagrangian stochastic dispersion technique for measuring ammonia emission from small field-plots

This study evaluates some simple procedures for measuring ammonia (NH3) emission from wind speed, NH3 concentration and an estimate of atmospheric stability using the backward Lagrangian stochastic (bLS) dispersion technique. The bLS technique, which requires measurements from only one height may prove useful when carrying out experiments simultaneously in a small field with several small plots. Commercial software exists that facilitates easy use of the bLS technique. Our study shows the bLS to be reliable using average wind speed at one height and average NH3 concentration derived from horizontal flux measurements of NH3 using passive flux samplers. The bLS technique underestimated the emission by 16-24% when applied at a measurement height of 0.5-1.55 m, but the inclination of bLS estimates versus integrated horizontal flux estimates was not different from 1 (P < 0.01). The emission of NH3 from urea applied to dry prairie soil was 29% of the nitrogen applied, emphasising the need of developing techniques for reducing NH3 emission from zero tillage arable soils.