What are nitrification inhibitors?

Nitrification inhibitors (NI) such as dicyandiamide (DCD), nitropyrin, and 3,4 dimethyl pyrazole phosphate (DMPP) slow the activity of Nitrosomonas, the genus of nitrifying bacteria responsible for the oxidation of NH₄⁺ to NO₂⁻ and this helps to retains N in the NH₄⁺ form longer in soil providing more chance plant to uptake NH₄⁺ (e.g., Abbasi and Adams, 2000; Di et al., 2007). Thereby NI can inhibit nitrification and further denitirification producing N₂O and it was found that NI reduce N₂O emissions 30 to 80% (e.g., Abbasi and Adams, 2000; Di et al., 2007; Zaman et al., 2009; Saggar et al., 2009; Akiyama et al., 2010). Nitrous oxide contributes to greenhouse effect (Wang et al., 1976) and the global warming potential of N₂O is 298 times that of carbon dioxide (CO₂) and 25 times that of methane (CH₄) in a 100-year time horizon (Forster et al., 2007). Of the entire anthropogenic N₂O emission (5.7 Tg N₂O–N yr⁻¹), agricultural soils provide 3.5 Tg N₂O–N yr⁻¹ (IPCC, 2006). Therefore, it has been suggested that NI use can be potent mitigation option for GHG emissions in agricultural lands (e.g., Bolan et al., 2004; Klein and Ledgard, 2005; Akiyama et al., 2010).