Dual effects of nitrification inhibitors on agricultural N2O emission

Shu Kee Lam1, Helen Suter1, Rohan Davies2, Mei Bai1, Jianlei Sun1, Arvin R. Mosier1 and Deli Chen1*

1 Crop and Soil Science Section, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, VIC 3010, Australia, Email: [email protected]

2 BASF Australia Ltd., Level 12, 28 Freshwater Place, Southbank VIC 3006, Australia

Abstract

Nitrification inhibitors are effective in decreasing nitrous oxide (N2O) emission from agricultural systems worldwide, but can increase ammonia (NH3) volatilization and subsequently, indirect N2O emission. This is often neglected when evaluating the inhibitors as a climate change mitigation tool.  In our recent literature review, we found that when the indirect N2O emission from deposited NH3 was considered, the overall impact of nitrification inhibitors ranged from –4.5 to +0.5 kg N2O-N ha–1. We noted that no such experiment was reported in the literature for vegetable production systems, which have high risk of NH3 and N2O loss from high N input (as manures and synthetic fertilizers) and high water input. We therefore conducted a case study field experiment to simultaneously quantify the effect a nitrification inhibitor, 3,4-dimethylpyrazole phosphate (DMPP) on NH3 and N2O emissions from surface applied chicken manure and synthetic fertilizers in a vegetable production system using a micrometeorological approach. The cumulative NH3 emissions over the measurement period were 19.7 and 27.0 kg N ha–1 for the control and DMPP treatment (an increase of 7.3 kg N ha–1, or 37% with DMPP). The corresponding values for the cumulative direct N2O emission over the measurement period were 6.0 and 3.8 kg N ha–1 (a decrease of 2.3 kg N ha–1, or 38% with DMPP). This suggests that the beneficial effect of nitrification inhibitors in decreasing direct N2O emission may be undermined by the concomitant increase in NH3 volatilization.