Nitrification inhibitors — climate change mitigation tool recommended by the IPCC – may be less effective than previously thought

Nitrification inhibitors are thought to mitigate climate change by reducing emissions of nitrous oxide — a potent greenhouse gas — from land. However, they may not be as effective as once thought, a new study suggests. The researchers found that, while inhibitors decrease emissions of nitrous oxide, they can increase emissions of ammonia — which is later converted to nitrous oxide. They recommend these effects are considered when evaluating inhibitors as a mitigation technology.’

This is the start of an excellent summary by the EU’s Science for Environment Policy briefs on this paper published in Global Change Biology.

Abstract

Nitrification inhibitors show promise in decreasing nitrous oxide (N2O) emission from agricultural systems worldwide, but they may be much less effective than previously thought when both direct and indirect emissions are taken into account. Whilst nitrification inhibitors are effective at decreasing direct N2O emission and nitrate (NO3–) leaching, limited studies suggest that they may increase ammonia (NH3) volatilization and, subsequently, indirect N2O emission. These dual effects are typically not considered when evaluating the inhibitors as a climate change mitigation tool. Here, we collate results from the literature that simultaneously examined the effects of nitrification inhibitors on N2O and NH3 emissions. We found that nitrification inhibitors decreased direct N2O emission by 0.2–4.5 kg N2O-N ha−1 (8–57%), but generally increased NH3 emission by 0.2–18.7 kg NH3-N ha−1 (3–65%). Taking into account the estimated indirect N2O emission from deposited NH3, the overall impact of nitrification inhibitors ranged from −4.5 (reduction) to +0.5 (increase) kg N2O-N ha−1. Our results suggest that the beneficial effect of nitrification inhibitors in decreasing direct N2O emission can be undermined or even outweighed by an increase in NH3 volatilization.

Reference

Lam, S., Suter, H., Mosier, A. & Chen, D. (2016). Using nitrification inhibitors to mitigate agricultural N2O emission: a double-edged sword? Global Change Biology. DOI: 10.1111/gcb.13338

You can find the original article here (paywall). The EU’s Science for Environment Policy summary can be read here.