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N2O emission from grass-clover swards is largely unaffected by recently fixed N2

Thyme, M. and Ambus, P. (2004) N2O emission from grass-clover swards is largely unaffected by recently fixed N2. DARCOFenews (1).

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Online at: http://www.darcof.dk/enews/april04/index.html

Summary

The contribution of biologically fixed dinitrogen (N2) to the nitrous oxide (N2O) production in grasslands is unknown. To assess the contribution of recently fixed N2 as a source of N2O and the transfer of fixed N from clover to companion grass, mixtures of white clover and perennial ryegrass were incubated for 14 days in a 15N2-enriched atmosphere (0.4 atom% excess). Immediately after labelling, half of the grass-clover pots were sampled for N2 fixation determination, whereas the remaining half were examined for emission of 15N labelled N2O for another eight days using a static chamber method. Biological N2 fixation measured in grass-clover shoots and roots as well as in soil constituted 342, 38 and 67 mg N m-2 d-1 at 16, 26 and 36 weeks after emergence, respectively. The drop in N2 fixation was most likely due to a severe aphid attack on the clover component. Transfer of recently fixed N from clover to companion grass was detected at 26 and 36 weeks after emergence and amounted to 0.7 ± 0.1 mg N m-2 d-1, which represented 1.7 ± 0.3 % of the N accumulated in grass shoots during the labelling period. Total N2O emission was 91, 416 and 259 μg N2O-N m-2 d-1 at 16, 26 and 36 weeks after emergence, respectively. Only 3.2 ± 0.5 ppm of the recently fixed N2 was emitted as N2O on a daily basis, thus recently fixed N released via easily degradable clover residues appears to be a minor source of N2O.


EPrint Type:Journal paper
Keywords:emission factor, nitrogen fixation, nitrogen transfer, nitrous oxide, 15N2, white clover
Subjects: Soil > Nutrient turnover
Crop husbandry > Production systems > Pasture and forage crops
Environmental aspects > Air and water emissions
Research affiliation: Denmark > KU-LIFE - Faculty of Life Sciences
Denmark > DARCOF II (2000-2005) > I.13 (DINOG) Dinitrogen fixation and nitrous oxide losses in grass-clover pastures
Denmark > SOAR - Research School for Organic Agriculture and Food Systems
Deposited By: Carter, Mette Sustmann
ID Code:4148
Deposited On:07 Jan 2005
Last Modified:12 Apr 2010 07:30
Document Language:English
Status:Published
Refereed:Not peer-reviewed

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