Nitrous Oxide Fluxes and Soil Oxygen Dynamics of Soil Treated with Cow Urine. Issue 2 (20th April 2017)

• Record Type: Journal Article
• Authors: Owens, Jen; Clough, Tim J.; Laubach, Johannes; Hunt, John E.; Venterea, Rodney T.
• Is Part Of: Soil Science Society of America Journal. Volume 81:Issue 2(2017)
• Page Start: 289
• Page End: 298
• Publication Date: 2017-04-20
• Subjects: Soils -- United States -- Periodicals; Soil science -- Periodicals; Periodicals; 631.4973
• DOI: 10.2136/sssaj2016.09.0277
• Languages: English
• ISSNs: 0361-5995

Abstract

Abstract : Core Ideas: Heavy irrigation, surface flooding, and urine decrease soil oxygen. When soil oxygen decreases, N2 O fluxes rapidly increase when nitrogen is available. Nitrous oxide fluxes are explained well using relative soil gas diffusivity. Ruminant urine deposition onto pasture creates hot‐spots where emissions of nitrous oxide (N2 O) are produced by aerobic and anaerobic microbial pathways. However, limited measurements of in situ soil oxygen (O2 )–N2 O relationships hinder the prediction of N2 O emissions from urine‐affected soil. This study tested whether soil O2 concentration or relative diffusivity of O2 ( D p /D O ) could explain N2 O emissions from urine patches. Using a randomized plot design, N2 O emissions were measured daily from a perennial ryegrass ( Lolium perenne L.) pasture for 56 d following bovine ( Bos taurus ) urine deposition to an imperfectly drained silty loam soil. Soil O2, volumetric water content, pH, conductivity, and extractable N and C were measured in urine‐amended and non‐amended soil. Values of water‐filled pore space (WFPS) and D P / D O were modeled. When data from treatments were pooled together, daily mean D P / D O explained 73% of the total variance in mean daily N2 O flux, compared with 65, <60, and <20% for WFPS, O2 and other measured variables, respectively. Soil pH, O2, volumetric water content, WFPS and D P / D O all explained more of the variance in the urine‐amended compared with the non‐amended soil. Daily N2 O fluxes increased substantially at D P / D O values around 0.006, which was consistent with past laboratory studies. These results demonstrate for the first time an O2 diffusion threshold for elevated N2 O fluxes in the field, expressed as D P / D O ≈ 0.006. Further studies should examine the consistency of this threshold under varying N and C substrates and a range of soil pH.