Nitrification inhibitor DMPP mitigated N2O emissions and decreased N2 losses in a low-nitrate vegetable soil after application of manure 

Abstract

<p>In China, amounts of organic manure as basal fertilizer application along with flooding irrigation usually resulted in large N<sub>2</sub>O emissions from intensively protected vegetable soils. However, little attention paid on the N<sub>2</sub>O emission bursts after application of manure, in a newly established vegetable soil with a low-nitrate content. The nitrification inhibitor, 3,4-dimethylpyrazole phosphate (DMPP), can be used to reduce N<sub>2</sub>O emissions from agricultural soils, little is known about how DMPP affect N<sub>2</sub> emissions and gaseous nitrogen (N<sub>2</sub>O+N<sub>2</sub>) losses. Here, we conducted a microcosm experiment in a robotized incubation system under an aerobic (O<sub>2</sub>/He) condition. Dried chicken manure was applied with and without DMPP to a protected vegetable soil. Two drying-rewetting events occurred during the 19 days monitoring period, and the relevant soil properties (e.g., NO<sub>2</sub><sup>-</sup>, WFPS, DOC, DON, SMBC) were analyzed. Our results showed DMPP addition strongly retarded soil nitrification process that kept a higher NH<sub>4</sub><sup>+</sup> concentration than that of only manure application. A significant decline of NO<sub>2</sub><sup>-</sup> and NO<sub>3</sub><sup>-</sup> concentration was found in a manure-treated soil with DMPP addition. Clearly, DMPP addition significantly reduced N<sub>2</sub>O emissions from the protected vegetable soil by 77.0% and remarkably decreased N<sub>2</sub> emissions and overall N<sub>2</sub>O+N<sub>2</sub> losses (compared with manure alone) by 51.9% and 54.0%, respectively. Pearson analysis showed that soil N<sub>2</sub>O fluxes were significantly related to soil WFPS, NH<sub>4</sub><sup>+</sup>, SMBC (P<0.01) and SMBN (P<0.05), whereas N<sub>2</sub> fluxes were significantly correlated with soil WFPS, SMBC (P<0.01), NO<sub>2</sub><sup>-</sup>, NH<sub>4</sub><sup>+</sup> and SMBN (P<0.05) during the whole incubation. The fluxes of N<sub>2</sub>O+N<sub>2</sub> were positively correlated with WFPS, NO<sub>2</sub><sup>-</sup>, SMBC and SMBN, whereas negatively correlated with NH<sub>4</sub><sup>+</sup> (P<0.05). Moreover, the ratio of N<sub>2</sub>O to N<sub>2</sub>O+N<sub>2</sub> (N<sub>2</sub>O/(N<sub>2</sub>O+N<sub>2</sub>)) was positively correlated with NO<sub>3</sub><sup>-</sup><sup> </sup>(P<0.05), and negatively correlated with DOC, DON and SMBC (P<0.01). An aggregated boosted tree (ABT) analysis further indicated that the relative influence of WFPS, SMBC and NH<sub>4</sub><sup>+</sup> on N<sub>2</sub>O fluxes were 19.4%, 14.9% and 12.8%, respectively. Moreover, the relative influence of WFPS on N<sub>2</sub> fluxes was the largest (47.4%), followed by SMBC and SMBN (14.3% and 9.66%, respectively). In addition, the relative influence of WFPS, SMBN and SMBC on N<sub>2</sub>O+N<sub>2</sub> losses were 32.6%, 17.0% and 12.6%, respectively, and the relative influence of SMBC, DOC and NO<sub>2</sub><sup>-</sup> on N<sub>2</sub>O/(N<sub>2</sub>O+N<sub>2</sub>) were 22.5%, 20.2% and 11.1%, respectively. In conclusion, our data show that DMPP combined with manure can significantly reduce N<sub>2</sub>O and N<sub>2</sub> emissions in a low-nitrate newly established vegetable soil, and their emissions were strongly affected by WFPS. </p>