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Nitrous Oxide Fluxes and Soil Oxygen Dynamics of Soil Treated with Cow Urine
Author(s) -
Owens Jen,
Clough Tim J.,
Laubach Johannes,
Hunt John E.,
Venterea Rodney T.
Publication year - 2017
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2016.09.0277
Subject(s) - loam , chemistry , lolium perenne , soil water , nitrous oxide , pasture , zoology , water content , nitrification , environmental chemistry , nitrogen , perennial plant , agronomy , soil science , environmental science , biology , geotechnical engineering , organic chemistry , engineering
Core Ideas Heavy irrigation, surface flooding, and urine decrease soil oxygen. When soil oxygen decreases, N 2 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 (N 2 O) are produced by aerobic and anaerobic microbial pathways. However, limited measurements of in situ soil oxygen (O 2 )–N 2 O relationships hinder the prediction of N 2 O emissions from urine‐affected soil. This study tested whether soil O 2 concentration or relative diffusivity of O 2 ( D p /D O ) could explain N 2 O emissions from urine patches. Using a randomized plot design, N 2 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 O 2 , 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 N 2 O flux, compared with 65, <60, and <20% for WFPS, O 2 and other measured variables, respectively. Soil pH, O 2 , 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 N 2 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 O 2 diffusion threshold for elevated N 2 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.