Increased N2O emissions from soils by adding plant extract released by freezing and thawing..
(S03-moerkved210218-poster)
Authors:
P.T. Moerkved* - Inst. of Energy Tech.
L.R. Bakken - Agric. univ. of Norway P. Doersch - Agric. univ. of Norway
Abstract:
Freeze-thaw events often result in a substantial release of N2O from soils. Release of easily degradable org. C and N to enhance denitrification or nitrification has been proposed as one factor of importance.
Despite that, little attention has been paid to the role of plant biomass as a source of freeze-thaw induced organic material release. In a series of incubation experiments, partly using 15N labelling, we measured microbial respiration, nitrification, denitrification and net N2O emission as invoked by freeze-thawing and/or frost-released material from clover leaves at different O2 levels. When adding plant extract to soil, a reduction of O2 content to 7% and less gave a large increase in N2O produced.
There was no further effect of freeze-thaw of the soil after addition of plant extract. A freeze-thaw treatment of pure soil gave little increase in N2O-production above 0% O2. At anaerobic condition the N2O production rate was still about half of that of the plant extract amended soil. Addition of glutamic acid to the soil gave significantly lower N2O production rates as compared to plant extract. The results suggest that frost released material from catch crops may be of great importance for the emissions of N2O from soils during late winter/early spring. Not only because the amounts are large, but also because it appears to invoke particular microbial phenomena which result in high N2O losses either from nitrification, denitrification or both.
Speaker Information: Paal Tore Moerkved, Inst. of Energy Tech., Pål Tore MørkvedPb 40, 2027 Kjeller,
; Phone: +47 63806158; E-mail: [email protected]
Session Information: Monday, November 3, 2003, 4:00 PM-6:00 PM Presentation Start: 4:00 PM (Poster Board Number: 1404)
Keywords: N2O-emissions from soils; Low temperature; Stable isotopes; Freeze-thaw