Global Change Biology, October 2017, Vol.23(10), pp.4068-4083
Animal manure application as organic fertilizer does not only sustain agricultural productivity and increase soil organic carbon () stocks, but also affects soil nitrogen cycling and nitrous oxide (NO) emissions. However, given that the sign and magnitude of manure effects on soil NO emissions is uncertain, the net climatic impact of manure application in arable land is unknown. Here, we performed a global meta‐analysis using field experimental data published in peer‐reviewed journals prior to December 2015. In this meta‐analysis, we quantified the responses of NO emissions to manure application relative to synthetic N fertilizer application from individual studies and analyzed manure characteristics, experimental duration, climate, and soil properties as explanatory factors. Manure application significantly increased NO emissions by an average 32.7% (95% confidence interval: 5.1–58.2%) compared to application of synthetic N fertilizer alone. The significant stimulation of NO emissions occurred following cattle and poultry manure applications, subsurface manure application, and raw manure application. Furthermore, the significant stimulatory effects on NO emissions were also observed for warm temperate climate, acid soils ( 〈 6.5), and soil texture classes of sandy loam and clay loam. Average direct NO emission factors (s) of 1.87% and 0.24% were estimated for upland soils and rice paddy soils receiving manure application, respectively. Although manure application increased stocks, our study suggested that the benefit of increasing stocks as sinks could be largely offset by stimulation of soil NO emissions and aggravated by emissions if, particularly for rice paddy soils, the stimulation of emissions by manure application was taken into account. The uncertain manure effects on NO emissions constrain evaluation of the net climatic impact of manure application in arable lands. A global meta‐analysis was performed to quantify the overall responses of NO emissions to manure application relative to synthetic N fertilizer in agricultural soils. Manure application on average significantly increased NO emissions by 32.7% as compared to synthetic N fertilizer alone, and the sign and magnitude of NO emissions were dependent on manure characteristics, climate, and soil properties. The benefit of C sequestration could be largely offset by stimulation of soil NO emissions and aggravated by CH emissions if, particularly for rice paddy soils, the stimulation of CH emissions by manure application was taken into account.
Animal Manure ; Emission Factor ; Greenhouse Gas Balance ; Manure Characteristics ; Meta‐Analysis ; Nitrous Oxide ; Soil Ph ; Soil Texture