Abstract
Organic amendments (animal manure and biochar) to agricultural soils may enhance soil organic carbon (SOC) contents, improve soil fertility and crop productivity but also contribute to global warming through nitrous oxide (N2O) emission. However, the effects of organic amendments on N2O emissions from agricultural soils seem variable among numerous research studies and remains uncertain. Here, eighty-five publications (peer-reviewed) were selected to perform a meta-analysis study. The results of this meta-analysis study show that the application of animal manure enhanced N2O emissions by 17.7%, whereas, biochar amendment significantly mitigated N2O emissions by 19.7%. Moreover, coarse textured soils increased [lnRR‾ = 182.6%, 95% confidence interval (CI) = 151.4%, 217.7%] N2O emission after animal manure, in contrast, N2O emission mitigated by 7.0% from coarse textured soils after biochar amendment. In addition, this study found that 121–320 kg N ha−1 and ⩽ 30 T ha−1 application rates of animal manure and biochar mitigated N2O emissions by 72.3% and 22.5%, respectively. Soil pH also played a vital role in regulating the N2O emissions after organic amendments. Furthermore, > 10 soil C: N ratios increased N2O emissions by 121.4% and 27.6% after animal and biochar amendments, respectively. Overall, animal manure C: N ratios significantly enhanced N2O emissions, while, biochar C: N ratio had not shown any effect on N2O emissions. Overall, average N2O emission factors (EFs) for animal manure and biochar amendments were 0.46% and −0.08%, respectively. Thus, the results of this meta-analysis study provide scientific evidence about how organic amendments such as animal manure and biochar regulating the N2O emission from agricultural soils.
Highlights
Climate change mitigation and improving food security are consid ered to be the major challenges worldwide (Zhang et al, 2018)
Though the potential role of soil organic carbon (SOC) contents for N2O mitigation dependent on the physicochemical properties of soil and both organic amendments as well as application rates. This meta-analysis study showed that animal manure increased N2O emissions by 17.7%, whereas, 19.7% of N2O emissions mitigated after the biochar amend ment
Soil attributes had a strong effect on N2O emission after both organic amendments
Summary
Climate change mitigation and improving food security are consid ered to be the major challenges worldwide (Zhang et al, 2018). The new global synthesis of N2O budget (Tian et al, 2020) is considered a major greenhouse gas with over 114 years life span in the atmosphere (Zhang et al, 2016a,b), and it has 298 times more GWP (global warming potential) than carbon dioxide (CO2) over a 100-year period (Ren et al, 2019; Shakoor et al, 2018). Almost 60% of the total anthropogenic N2O emission is emitted from agriculture due to excessive use of N fertilizers (Syakila and Kroeze, 2011). Organic amendments such as animal manure and biochar have been widely adopted to increase soil organic matter (SOM) stocks and to mitigate the greenhouse gases (GHGs) emissions (Clough et al, 2010; Lal, 2004). The effect of animal manure and biochar on the mitigation of N2O emission remains inconsistent and suggests further scientific investigation
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