Measurement and mitigation of nitrous oxide emissions from a high nitrogen input vegetable system

The emission and mitigation of nitrous oxide (N(2)O) from high nitrogen (N) vegetable systems is not well understood. Nitrification inhibitors are widely used to decrease N(2)O emissions in many cropping systems. However, most N(2)O flux measurements and inhibitor impacts have been made with small chambers and have not been investigated at a paddock-scale using micrometeorological techniques. We quantified N(2)O fluxes over a four ha celery paddock using open-path Fourier Transform Infrared spectroscopy in conjunction with a backward Lagrangian stochastic model, in addition to using a closed chamber technique. The celery crop was grown on a sandy soil in southern Victoria, Australia. The emission of N(2)O was measured following the application of chicken manure and N fertilizer with and without the application of a nitrification inhibitor 3, 4-dimethyl pyrazole phosphate (DMPP). The two techniques consistently demonstrated that DMPP application reduced N(2)O emission by 37–44%, even though the N(2)O fluxes measured by a micrometeorological technique were more than 10 times higher than the small chamber measurements. The results suggest that nitrification inhibitors have the potential to mitigate N(2)O emission from intensive vegetable production systems, and that the national soil N(2)O emission inventory assessments and modelling predictions may vary with gas measurement techniques.