*Article* **Comparative Effectiveness of Four Nitrification Inhibitors for Mitigating Carbon Dioxide and Nitrous Oxide Emissions from Three Different Textured Soils**

**Yafei Guo, Asif Naeem and Karl H. Mühling \***

Institute of Plant Nutrition and Soil Science, Kiel University, Hermann-Rodewald-Strasse 2, 24118 Kiel, Germany; yguo@plantnutrition.uni-kiel.de (Y.G.); anaeem@plantnutrition.uni-kiel.de (A.N.) **\*** Correspondence: khmuehling@plantnutrition.uni-kiel.de; Tel.: +49-(431)-880-3189

**Abstract:** Nitrification inhibitors (NIs) can be used to reduce both NO3 −-N leaching and N2O-N emissions. However, the comparative efficacies of NIs can be strongly affected by soil type. Therefore, the efficacies of four nitrification inhibitors (dicyandiamide (DCD), 3, 4-dimethylpyrazole phosphate (DMPP), nitrogenous mineral fertilizers containing the DMPP ammonium stabilizer (ENTEC) and active ingredients: 3.00–3.25% 1, 2, 4-triazole and 1.50–1.65% 3-methylpyrazole (PIADIN)) were investigated in three different textured N-fertilized (0.5 g NH4 +-N kg−<sup>1</sup> soil) soils of Schleswig-Holstein, namely, Marsch (clayey), Östliches Hügelland (loamy) and Geest (sandy) under a controlled environment. Total CO2-C and N2O-N emissions were significantly higher from Marsch than Östliches Hügelland and Geest. In Marsch, DMPP showed the highest inhibitory effect on CO2-C emission (50%), followed by PIADIN (32%) and ENTEC (16%). In Östliches Hügelland, DCD and PIADIN showed the highest and equal inhibitory effect on CO2-C emission (73%), followed by DMPP (64%) and ENTEC (36%). In Marsch and Östliches Hügelland, DCD showed the stronger inhibitory effect on N2O-N emission (86% and 47%) than DMPP (56% and 30%) and PIADIN (54% and 16%). In Geest, DMPP was more effective in reducing N2O-N emission (88%) than PIADIN (70%) and DCD (33%). Thus, it can be concluded that DCD is a better NI for clay and loamy soils, while DMPP and PIADIN are better for sandy soils to inhibit soil nitrification and gaseous emissions.

**Keywords:** nitrification inhibitors; soil type; CO2 and N2O emissions; soil nitrogen dynamic
