Soil nitrous oxide emissions following crop residue addition: a meta-analysis

Authors

  • Huaihai Chen,

    1. Department of Soil Science, North Carolina State University, Raleigh, NC, USA
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    • These authors contributed equally to this work.
  • Xuechao Li,

    1. Department of Soil Science, North Carolina State University, Raleigh, NC, USA
    2. Laboratory of Soil Ecology, College of Resources and Environmental Sciences, Nanjing Agricultural University, Jiangsu, China
    3. Wujiang Environmental Protection Bureau, Suzhou, Jiangsu, China
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    • These authors contributed equally to this work.
  • Feng Hu,

    1. Laboratory of Soil Ecology, College of Resources and Environmental Sciences, Nanjing Agricultural University, Jiangsu, China
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  • Wei Shi

    Corresponding author
    • Department of Soil Science, North Carolina State University, Raleigh, NC, USA
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Correspondence: Wei Shi, tel. + 919 513-4641, fax + 919 515-2167, e-mail: wei_shi@ncsu.edu

Abstract

Annual production of crop residues has reached nearly 4 billion metric tons globally. Retention of this large amount of residues on agricultural land can be beneficial to soil C sequestration. Such potential impacts, however, may be offset if residue retention substantially increases soil emissions of N2O, a potent greenhouse gas and ozone depletion substance. Residue effects on soil N2O emissions have gained considerable attention since early 1990s; yet, it is still a great challenge to predict the magnitude and direction of soil N2O emissions following residue amendment. Here, we used a meta-analysis to assess residue impacts on soil N2O emissions in relation to soil and residue attributes, i.e., soil pH, soil texture, soil water content, residue C and N input, and residue C : N ratio. Residue effects were negatively associated with C : N ratios, but generally residue amendment could not reduce soil N2O emissions, even for C : N ratios well above ca. 30, the threshold for net N immobilization. Residue effects were also comparable to, if not greater than, those of synthetic N fertilizers. In addition, residue effects on soil N2O emissions were positively related to the amounts of residue C input as well as residue effects on soil CO2 respiration. Furthermore, most significant and stimulatory effects occurred at 60–90% soil water-filled pore space and soil pH 7.1–7.8. Stimulatory effects were also present for all soil textures except sand or clay content ≤10%. However, inhibitory effects were found for soils with >90% water-filled pore space. Altogether, our meta-analysis suggests that crop residues played roles beyond N supply for N2O production. Perhaps, by stimulating microbial respiration, crop residues enhanced oxygen depletion and therefore promoted anaerobic conditions for denitrification and N2O production. Our meta-analysis highlights the necessity to connect the quantity and quality of crop residues with soil properties for predicting soil N2O emissions.

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