Linkage between N2O emission and functional gene abundance in an intensively managed calcareous fluvo-aquic soil

Liuqing Yang,Xiaotang Ju,Xiaojun Zhang

doi:10.1038/srep43283

Liuqing Yang, Xiaotang Ju + Show 1 more

Open Access

https://doi.org/10.1038/srep43283

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Abstract

The linkage between N2O emissions and the abundance of nitrifier and denitrifier genes is unclear in the intensively managed calcareous fluvo-aquic soils of the North China Plain. We investigated the abundance of bacterial amoA for nitrification and narG, nirS, nirK, and nosZ for denitrification by in situ soil sampling to determine how the abundance of these genes changes instantly during N fertilization events and is related to high N2O emission peaks. We also investigated how long-term incorporated straw and/or manure affect(s) the abundance of these genes based on a seven-year field experiment. The overall results demonstrate that the long-term application of urea-based fertilizer and/or manure significantly enhanced the number of bacterial amoA gene copies leading to high N2O emission peaks after N fertilizer applications. These peaks contributed greatly to the annual N2O emissions in the crop rotation. A significant correlation between annual N2O emissions and narG, nirS, and nirK gene numbers indicates that the abundance of these genes is related to N2O emission under conditions for denitrification, thus partly contributing to the annual N2O emissions. These findings will help to draw up appropriate measures for mitigation of N2O emissions in this ‘hotspot’ region.

Highlights

The linkage between N2O emissions and the abundance of nitrifier and denitrifier genes is unclear in the intensively managed calcareous fluvo-aquic soils of the North China Plain
The soil organic carbon (SOC) in Nopt, CNopt and CM increased by 15.8, 18.5, and 67.1%, and the total nitrogen (TN) correspondingly increased by 10.1, 15.2 and 52.5%, respectively, compared with the N0 treatment. This indicates that all N fertilization treatments tended to increase SOC and TN compared to the N0 control but the effect was only statistically significant for the manure treatment (Table 1)
These results show that the long-term application of urea-based fertilizer and/or manure induced and enhanced bacterial amoA gene copies, which was related to a strong nitrification process, and consumed O2 in the soil matrix triggered denitrification as shown by our previous study[24]

Summary

Introduction

The linkage between N2O emissions and the abundance of nitrifier and denitrifier genes is unclear in the intensively managed calcareous fluvo-aquic soils of the North China Plain. The overall results demonstrate that the long-term application of urea-based fertilizer and/or manure significantly enhanced the number of bacterial amoA gene copies leading to high N2O emission peaks after N fertilizer applications. These peaks contributed greatly to the annual N2O emissions in the crop rotation. Nitrous oxide is emitted from both natural and anthropogenic sources, and agricultural soils amended with chemical nitrogen (N) fertilizers and/or manure are mainly anthropogenic sources, which contribute up to 66% of the current global anthropogenic N2O emissions[3] and approximately 75% of anthropogenic emission in China[4].

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