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

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 N(2)O, a potent greenhouse gas and ozone depletion substance. Residue effects on soil N(2)O emissions have gained considerable attention since early 1990s; yet, it is still a great challenge to predict the magnitude and direction of soil N(2)O emissions following residue amendment. Here, we used a meta-analysis to assess residue impacts on soil N(2)O 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 N(2)O 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 N(2)O emissions were positively related to the amounts of residue C input as well as residue effects on soil CO(2) 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 N(2)O production. Perhaps, by stimulating microbial respiration, crop residues enhanced oxygen depletion and therefore promoted anaerobic conditions for denitrification and N(2)O production. Our meta-analysis highlights the necessity to connect the quantity and quality of crop residues with soil properties for predicting soil N(2)O emissions.

Crop residues exacerbate the negative effects of extreme flooding on soil quality

“…Our results therefore suggest that shorter periods of soil inundation (<4 weeks) with no history of flooding should result in very low CH 4 emissions, possibly due to the lack of a large methanogen community (Hansen et al 2014). CH 4 consumption can form an important part of the CH 4 budget in some soils increased N 2 O emissions, presumably due to complete denitrification (to N 2 ) or immobilization within the microbial biomass (Baggs et al 2000;Chen et al 2013;. This is consistent with the lack of O 2 , the high C:N ratio of our crop residues (Gentile et al 2008) and the low NH 4 + concentrations in our soil solution (Rice and Tiedje 1989).…”

“…In some situations, this may have positive benefits as it may reduce NO 3 − leaching; however, this effect is not always observed (Doring et al 2005;Hansen et al 2015). The effect of cereal residues on greenhouse gas emissions (GHG), particularly N 2 O fluxes, is also controversial (Chen et al 2013). Specifically, they may increase nitrification under aerobic conditions (Frimpong and Baggs 2010), and provide energy for denitrifiers facilitating denitrification under anaerobic conditions, both of which can produce N 2 O (Davidson 1991).…”

Conservation Agriculture practices reduce the global warming potential of rainfed low N input semi-arid agriculture

“…By contrast, the N 2 0 emissions during campaign 2 were higher in wheat in monoculture than in rotational wheat. This effect could be a result of better environmental conditions for the mineralization of crop residues from the previous year (Chen et al, 2013). In monoculture wheat, a combination of residue inputs with a high C:N ratio (mean C:N ratio of 160.3) and mineral N fertilizer, both at seeding and dressing, may have stimulated denitrification losses from mineral N added to soil (Li et al, 2016), as residues provide an energy supply for denitrifying microorganisms (Sarkodie-Addo et al, 2003;Sanz-Cobena et al, 2014).…”

Responses of soil nitrous oxide production and abundances and composition of associated microbial communities to nitrogen and water amendment

“…Soil texture regulates soil N 2 O emissions through influencing O 2 availability (Corre et al 1999), because soil texture can affect the size and distribution of soil pores and therefore influence soil aeration and water content (Singurindy et al 2006;Chen et al 2013a). Soil pH has been identified as another key regulator of soil N 2 O emissions (Butterbach-Bahl et al 2013), and product ratios of N 2 O/(N 2 + N 2 O) have a significantly negative relationship with soil pH within the normal range from pH 5 to 8 in agricultural soils (Chapuis-lardy et al 2007).…”