Dynamics of soil CH 4 and CO 2 fluxes from cattle urine with and without a nitrification inhibitor, and dung deposited onto a UK grassland soil

Abstract

Food production systems associated with livestock management are significant sources of greenhouse gases (GHGs). Livestock excreta is one of the primary sources GHG emissions from grazing livestock. Against this context, a field experiment was established in a UK grassland to establish the extent of soil CH₄, CO_2, and N₂O fluxes upon the deposition of (i) cattle urine (U), (ii) urine + DCD (U + DCD), (iii) artificial urine (AU), and dung (D), and compared with a (iv) control, where neither urine nor dung was applied. Applications of excreta were made at three periods during the grazing season; early-, mid, and late-season. Soil N₂O emissions data have been published already; hence this paper summarizes the emissions of soil-borne CH₄ and CO₂ emissions, and explores in particular, the effects of the addition of DCD, a nitrification inhibitor used to reduce direct and indirect N₂O emissions from urine patches, on these C-GHGs. Soil moisture, soil temperature, and nitrate (NO₃⁻) and ammonium (NH₄⁺) availability and C addition were key controls of both soil CH₄ and CO₂ emissions. The dung treatment stimulated the production and subsequent emissions of soil CH₄ and CO₂, a significantly high net CH₄ and CO₂-based GWP. The findings of the current study lay a foundation for an in-depth understanding of the magnitude and dynamics of soil-borne soil CH₄ and CO₂ upon urine and dung deposition during three different seasons. This study implies that the use of DCD may have the potential to reduce C-GHGs from the urine and dung of grazing animals.