Greenhouse Gas Emissions Measured 24 Hours after Surface and Subsurface Application of Different Manure Types

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 is 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 h after application using a static chamber method. 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 injected treatments were 3.2 times greater 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 liquid manure applications were also greater than the CO2-e fluxes from solid manure applications, probably due to greater levels of ammonium available for nitrification and subsequent denitrification. Methane (CH4) fluxes were negligible for all manure types and application methods 24 h after application. For this particular study, 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 manure applied.