Biochar reduces the efficiency of nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) mitigating N2O emissions

Authors: FUERTES-MENDIZABAL, TERESA - University Of Basque Country; HUERFANO, X - University Of Basque Country; VEGA-MAS, I - University Of Basque Country; TORRALBO, F - University Of Basque Country; MENEDEZ, S - University Of Basque Country; IPPOLITO, JAMES - University Of Colorado; KAMMANN, CLAUDIA - Hochschule Geisenheim University; WRAGE-MONNIG, NICOLE - Ruhr-University Bochum; CAYUELA, MARIA - Centro De Edafologia Y Biologia Aplicada Del Segura (CEBAS); Spokas, Kurt; BORCHARD, NILS - Ruhr-University Bochum; Novak, Jeffrey; GONZALEZ-MORO, MARIOA - University Of Basque Country; ESTAVILLO, JAMES - University Of Basque Country

Submitted to: Nature Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/7/2019
Publication Date: 2/20/2019
Citation: Fuertes-Mendizabal, T., Huerfano, X., Vega-Mas, I., Torralbo, F., Menendez, S., Ippolito, J.A., Kammann, C., Wrage-Monnig, N., Cayuela, M., Borchard, N., Spokas, K.A., Novak, J.M., Gonzalez-Moro, M., Gonzalez-Murua, C., Estavillo, J. 2019. Biochar reduces the efficiency of nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) mitigating N2O emissions. Nature Scientific Reports. 9(2346):1-16. https://doi.org/10.1038/s41598-019-38697-2.
DOI: https://doi.org/10.1038/s41598-019-38697-2

Interpretive Summary: Biochar is a hopeful soil amendment that has linked to several soil quality improvements, particularly greenhouse gas reduction following application. In this work, we analyzed the potential co-application of biochar with a nitrification inhibitor [DMPP; (3,4-dimethylpyrazole phosphate)], to further reduce N2O emissions following fertilization. We established 12 different treatments [2 biochar rates (0 and 2%) x 3 fertilizer management rates (unfertilized, fertilized, and fertilizer+inhibitor) x 2 water contents] and was conducted as a 160-day laboratory incubation. As expected, the nitrification inhibitor reduced net N2O production following application compared to the fertilized treatment. Unexpectedly, the biochar + inhibitor treatments did not function as well as the inhibitor only applications, since the production of N2O from the inhibitor + biochar treatment was higher than solely the inhibitor treatment. This study showed that this particular biochar reduced the efficiency of the nitrification inhibitor at both low and high soil water contents. These results are significant to farmers and policy makers and will assist scientists and engineers in understanding the potential pathways for mechanisms for biochar to improve carbon sequestration and reduce agricultural N2O emissions.

Technical Abstract: Nitrous oxide (N2O) is the strongest greenhouse gas emitted from agricultural soils. Among strategies suggested to decrease agricultural soil N2O losses, The use of nitrification inhibitors such as DMPP (3,4-dimethylpyrazole phosphate) has been proposed. This compound inhibits nitrification, thus reducing N2O emissions. However, the efficiency of DMPP might be affected by soil amendments, such as biochar, which has been shown to reduce N2O emissions. This study evaluated the synergic effect of a woody biochar applied in combination with DMPP on soil N2O emissions. A laboratory incubation study was conducted with a silt loam grassland soil and a biochar obtained from Pinus taeda at 500ºC. Two biochar rates (0 and 2% (w/w)) and three ammonium sulphate fertilization levels (unfertilized, fertilized and fertilized+DMPP) were assayed under two contrasting soil water content levels (40% and 80% of water filled pore space (WFPS)). Soil N2O emissions were monitored over a 163 day incubation period. Results showed that DMPP reduced N2O emissions to levels comparable to the unfertilized soils by reducing ammonia-oxidizing bacteria (AOB) populations and promoting the last step of denitrification (measured by the ratio nosZI+nosZII / nirS+nirK genes). Biochar showed ability to mitigate N2O emissions only at the low soil water content (40% WFPS) due to a reduction in ammonia-oxidizing bacteria (AOB) population. However, when DMPP was applied to the biochar amended soil, a counteracting effect was observed, since the N2O mitigation induced by DMPP was lower than without biochar. This study demonstrates that this particular biochar diminishes the efficiency of the nitrification inhibitor DMPP both at low and high soil water contents.