Greenhouse gas emissions from land application of manure
Greenhouse gas (GHG) emissions from agricultural activities such as land application of livestock manure cannot be ignored when assessing overall emissions from anthropogenic sources. The magnitude of these emissions will be influenced by management practices such as manure placement during land application. The objective of this work was to compare GHG fluxes resulting from the surface and subsurface application of liquid and solid manure. For this comparison, all measurements were made 24 hours after application. The results showed that subsurface application significantly increased carbon dioxide equivalent (CO2-e) fluxes for both solid and liquid manure. The overall CO2-e fluxes from the injected treatments were 3.2 times higher than CO2-e fluxes from the surface applied plots, mainly due to a pronounced increase in N2O fluxes which was likely caused by increased denitrification rates. The CO2-e fluxes from the liquid manure applications were also higher than the CO2-e fluxes from the solid manure applications, probably due to higher levels of ammonium available for nitrification and subsequent denitrification. For this particular study, the measured specific fluxes (total flux per kg N applied) remained relatively constant with application rate, indicating that GHG emissions from manure applications were approximately proportional to the amount of land applied manure.
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