The Responses of Soil N2O Emissions to Residue Returning Systems: A Meta-Analysis

Naijuan Hu,Qian Chen,Liqun Zhu

doi:10.3390/su11030748

Abstract

Background: Much attention has been focused on the influences of residue returning on N2O emissions. However, comprehensive quantification of the effect size on N2O emission following crop residue returning in subtropical, tropical and warm temperate conditions remains untested. Methods: To identify site-specific factors that influence N2O emission (kg N2O-N ha−1) in residue returning systems, we performed a meta-analysis involving 260 comparisons from 72 studies. Results: The data indicated that significant promoting effects were observed under residue returning by rotary tillage, no-tillage and mulch, whereas N2O release was significantly inhibited by 8% under residue returning by plough. For other contributors, the stimulatory and significant effects occurred in upland fields, under short- and medium-term residue returning durations, acidic/neutral soils, medium organic C and clay content. Nitrogen fertilizer application significantly stimulated N2O emission, even though application rate at 100–150 kg N ha−1 was inhibitory. Although a negative correlation between residue C/N ratio and N2O emission has been shown, residue returning could not reduce N2O emission with a higher C/N ratio and amount. Conclusions: Some options, such as converting residue returning methods, decreasing N fertilizer application rate, and regulating soil C/N ratio could be adopted to mitigate soil N2O emission following residue returning.

Highlights

Anthropogenic greenhouse gas emission (e.g., CO2, CH4, and N2O) is a major contributor to global warming [1], and agricultural activities account for 10–12% of total anthropogenic greenhouse gas emission [2]
Note: PT represents residue returning with conventional tillage/plowing/plough/20 cm depth/25 cm dep6th; RT represents residue returning with rotary tillage/shallow-rotary tillage/10 cm depth/12 cm depth; NT represents residue returning with no-tillage/reduced tillage/zero tillage; MC represents residue mulch on the fields
Further studies will be helpful for understanding the effect of residue returning on N2O emission from a global perspective regarding soil temperature and water-filled pore space. In this meta-analysis, we found that residue returning increased N2O emissions, and the effects were positively related to residue amount and N input, but negatively associated with residue C/N ratio

Summary

Introduction

Anthropogenic greenhouse gas emission (e.g., CO2, CH4, and N2O) is a major contributor to global warming [1], and agricultural activities account for 10–12% of total anthropogenic greenhouse gas emission [2]. N2O is mainly derived from nitrification process, in which autotrophic nitrifiers convert NH4+ to NO3−. Under anaerobic soil conditions, denitrification is the main pathway for N2O production. During this process, heterotrophic denitrifiers transform NO3− to N2O and N2 [8]. Comprehensive quantification of the effect size on N2O emission following crop residue returning in subtropical, tropical and warm temperate conditions remains untested. Methods: To identify site-specific factors that influence N2O emission (kg N2O-N ha−1) in residue returning systems, we performed a meta-analysis involving 260 comparisons from 72 studies. Conclusions: Some options, such as converting residue returning methods, decreasing N fertilizer application rate, and regulating soil C/N ratio could be adopted to mitigate soil N2O emission following residue returning

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Conclusion