Soil nitrous oxide emissions following crop residue addition: a meta‐analysis
TL;DR: A meta-analysis suggests that crop residues played roles beyond N supply for N(2)O production, by stimulating microbial respiration, crop residues enhanced oxygen depletion and therefore promoted anaerobic conditions for denitrification and N( 2)Oproduction.
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.
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TL;DR: Cumulatively, the findings support an approach where producers monitor their own impacts, flexibly meet environmental targets by choosing from multiple practices, and communicate their impacts to consumers.
Abstract: Food’s environmental impacts are created by millions of diverse producers. To identify solutions that are effective under this heterogeneity, we consolidated data covering five environmental indicators; 38,700 farms; and 1600 processors, packaging types, and retailers. Impact can vary 50-fold among producers of the same product, creating substantial mitigation opportunities. However, mitigation is complicated by trade-offs, multiple ways for producers to achieve low impacts, and interactions throughout the supply chain. Producers have limits on how far they can reduce impacts. Most strikingly, impacts of the lowest-impact animal products typically exceed those of vegetable substitutes, providing new evidence for the importance of dietary change. Cumulatively, our findings support an approach where producers monitor their own impacts, flexibly meet environmental targets by choosing from multiple practices, and communicate their impacts to consumers.
2,353 citations
TL;DR: Although plastic mulching can significantly increase crop yield and WUE, especially in dryland agriculture, it should also improve the technology for recovering residual plastic film to protect the environment.
305 citations
TL;DR: A global meta-analysis using 363 publications to assess the overall effects of straw return on soil Nr losses, C sequestration and crop productivity in agroecosystems shows that at a global scale, straw return increased net NR losses from both rice and upland fields due to a greater stimulation of NH3 emissions than the reduction in N leaching and runoff.
Abstract: It is widely recommended that crop straw be returned to croplands to maintain or increase soil carbon (C) storage in arable soils. However, because C and nitrogen (N) biogeochemical cycles are closely coupled, straw return may also affect soil reactive N (Nr) losses, but these effects remain uncertain, especially in terms of the interactions between soil C sequestration and Nr losses under straw addition. Here, we conducted a global meta-analysis using 363 publications to assess the overall effects of straw return on soil Nr losses, C sequestration and crop productivity in agroecosystems. Our results show that on average, compared to mineral N fertilization, straw return with same amount of mineral N fertilizer significantly increased soil organic C (SOC) content (14.9%), crop yield (5.1%), and crop N uptake (10.9%). Moreover, Nr losses in the form of nitrous oxide (N2 O) emissions from rice paddies (17.3%), N leaching (8.7%), and runoff (25.6%) were significantly reduced, mainly due to enhanced microbial N immobilization. However, N2 O emissions from upland fields (21.5%) and ammonia (NH3 ) emissions (17.0%) significantly increased following straw return, mainly due to the stimulation of nitrification/denitrification and soil urease activity. The increase in NH3 and N2 O emissions was significantly and negatively correlated with straw C/N ratio and soil clay content. Regarding the interactions between C sequestration and Nr losses, the increase in SOC content following straw return was significantly and positively correlated with the decrease in N leaching and runoff. However, at a global scale, straw return increased net Nr losses from both rice and upland fields due to a greater stimulation of NH3 emissions than the reduction in N leaching and runoff. The trade-offs between increased net Nr losses and soil C sequestration highlight the importance of reasonably managing straw return to soils to limit NH3 emissions without decreasing associated C sequestration potential.
219 citations
Cites background or result from "Soil nitrous oxide emissions follow..."
...For example, soil texture and clay content determine pore size distribution, and thus soil aeration and oxygen availability for straw decomposition, which in turn controls the intensities of different soil N transformations and associated Nr losses (Chen et al., 2013; Skiba & Ball, 2002)....
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...Studies that have examined the effects of straw return on environmental Nr losses often focused on N2O emissions (Chen et al., 2013; Miller et al., 2008; Shan & Yan, 2013) and not other Nr losses (e....
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...upland soils, faster straw degradation provides additional N substrate for autotrophic nitrification and heterotrophic denitrification, which stimulate N2O emissions (Chen et al., 2013; Davidson et al., 2000)....
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...The environmental Nr losses are closely linked to crop NUE (or crop N uptake), as shown in Cui, Yue, Wang, Zhang, and Chen (2013) and Groenigen, Velthof, Oenema, Groenigen, and Kessel (2010)....
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...As for straw quality, the increase in N2O emissions was significantly and negatively correlated with straw C/N ratio (Figure 4), a result that was also reported by previous studies (Chen et al., 2013; Huang, Zou, Zheng, Wang, & Xu, 2004)....
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TL;DR: It was concluded that straw could be positively effective on the improvement of the soil quality and the grain production, but it appeared that the straw return had several neglect negative effects, implying that further research and assessment on the returned straw are required before its large-scale promotion in China.
215 citations
TL;DR: In this article, a meta-analysis of N2O emissions from agricultural soils receiving organic amendments was conducted, which yielded a global EF for all organic sources, EForg, equal to 0.30%, which is lower than the IPCC default EF of 1 for synthetic fertilizers.
204 citations
References
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Book Chapter•
01 Oct 2007
5,004 citations
27 May 2008
3,383 citations
"Soil nitrous oxide emissions follow..." refers background in this paper
...The effect size was considered to be significantly positive or negative at a = 0.05 level when 95% CIs did not overlap zero (Hedges & Olkin, 1985)....
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TL;DR: In this paper, the ozone depletion potential-weighted anthropogenic emissions of N2O with those of other ozone-depleting substances were compared, and it was shown that N 2O emission currently is the single most important ozone-destroying emission and is expected to remain the largest throughout the 21st century.
Abstract: By comparing the ozone depletion potential-weighted anthropogenic emissions of N2O with those of other ozone-depleting substances, we show that N2O emission currently is the single most important ozone-depleting emission and is expected to remain the largest throughout the 21st century. N2O is unregulated by the Montreal Protocol. Limiting future N2O emissions would enhance the recovery of the ozone layer from its depleted state and would also reduce the anthropogenic forcing of the climate system, representing a win-win for both ozone and climate.
3,363 citations
Journal Article•
TL;DR: Nitrous oxide emission currently is the single most important ozone-depleting emission and is expected to remain the largest throughout the 21st century, and N2O is unregulated by the Montreal Protocol, which would enhance the recovery of the ozone layer from its depleted state and reduce the anthropogenic forcing of the climate system.
3,069 citations
"Soil nitrous oxide emissions follow..." refers background in this paper
...This potential of soil C sequestration, however, can be offset if crop residue amendment substantially increases soil emissions of N2O, a potent greenhouse gas and ozone depleting substance (IPCC Climate Change TPSB, 2007; Ravishankara et al., 2009)....
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TL;DR: In this article, the authors presented a methodology to calculate annual country level N2O emissions from agricultural soils, including direct emissions from agriculture, indirect emissions from animal production, and indirect emissions indirectly induced by agricultural activities.
Abstract: In 1995 a working group was assembled at the request of OECD/IPCC/IEA to revise the methodology for N2O from agriculture for the National Greenhouse Gas Inventories Methodology. The basics of the methodology developed to calculate annual country level nitrous oxide (N2O) emissions from agricultural soils is presented herein. Three sources of N2O are distinguished in the new methodology: (i) direct emissions from agricultural soils, (ii) emissions from animal production, and (iii) N2O emissions indirectly induced by agricultural activities. The methodology is a simple approach which requires only input data that are available from FAO databases. The methodology attempts to relate N2O emissions to the agricultural nitrogen (N) cycle and to systems into which N is transported once it leaves agricultural systems. These estimates are made with the realization that increased utilization of crop nutrients, including N, will be required to meet rapidly growing needs for food and fiber production in our immediate future. Anthropogenic N input into agricultural systems include N from synthetic fertilizer, animal wastes, increased biological N-fixation, cultivation of mineral and organic soils through enhanced organic matter mineralization, and mineralization of crop residue returned to the field. Nitrous oxide may be emitted directly to the atmosphere in agricultural fields, animal confinements or pastoral systems or be transported from agricultural systems into ground and surface waters through surface runoff. Nitrate leaching and runoff and food consumption by humans and introduction into sewage systems transport the N ultimately into surface water (rivers and oceans) where additional N2O is produced. Ammonia and oxides of N (NOx) are also emitted from agricultural systems and may be transported off-site and serve to fertilize other systems which leads to enhanced production of N2O. Eventually, all N that moves through the soil system will be either terminally sequestered in buried sediments or denitrified in aquatic systems. We estimated global N2O–N emissions for the year 1989, using midpoint emission factors from our methodology and the FAO data for 1989. Direct emissions from agricultural soils totaled 2.1 Tg N, direct emissions from animal production totaled 2.1 Tg N and indirect emissions resulting from agricultural N input into the atmosphere and aquatic systems totaled 2.1 Tg N2O–N for an annual total of 6.3 Tg N2O–N. The N2O input to the atmosphere from agricultural production as a whole has apparently been previously underestimated. These new estimates suggest that the missing N2O sources discussed in earlier IPCC reports is likely a biogenic (agricultural) one.
1,230 citations
"Soil nitrous oxide emissions follow..." refers background in this paper
...Based on an emission factor derived from synthetic N fertilizers (Bouwman, 1996) that 1.25% of N input can be emitted in the form of N2O within a year, Mosier et al. (1998) estimated that 0.4 million metric tons of N2O–...
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