Publikasjoner
NIBIOs ansatte publiserer flere hundre vitenskapelige artikler og forskningsrapporter hvert år. Her finner du referanser og lenker til publikasjoner og andre forsknings- og formidlingsaktiviteter. Samlingen oppdateres løpende med både nytt og historisk materiale. For mer informasjon om NIBIOs publikasjoner, besøk NIBIOs bibliotek.
2019
Forfattere
Vibeke LindSammendrag
Det er ikke registrert sammendrag
Forfattere
Vibeke LindSammendrag
Det er ikke registrert sammendrag
Forfattere
Vibeke LindSammendrag
Det er ikke registrert sammendrag
Forfattere
Vibeke LindSammendrag
Det er ikke registrert sammendrag
Sammendrag
Det er ikke registrert sammendrag
Forfattere
Vibeke LindSammendrag
Det er ikke registrert sammendrag
Sammendrag
An annual sheep production system in Norway incorporates grazing natural pastures for five months. Yet no measurements of enteric methane emissions from grazing sheep have been performed under Norwegian conditions. A pilot study was conducted with 12 Norwegian White ewes to test the feasibility of using the sulphur hexafluoride (SF6) tracer technique under Norwegian conditions. The ewes were split onto one of two pastures, mixed grass (Bromus inermis dominated, Poa pratensis, Festuca pratensis) or white clover (Trifolium repens). After five days adaptation to pastures, breathe samples were collected into evacuated one L PVC canisters over three consecutive days where capillary tubes (0.38 to 0.42 mL/min initial flow) restricted flow. Gas samples were analysed by gas chromatography. Feed intakes were not recorded. Average live weights were 64 kg and 66 kg for ewes on grass and clover pastures, respectively. Methane emissions were 23.9 g/d from sheep on mixed grass and 28.2 g/d for sheep on white clover. Methane emissions were not correlated (p=0.33) to ewe live weight. One explanation for the 15% difference in methane emission could be differences in feed intake. The few days of sample collection could also explain some of the observed difference since the technique is recommended to be used over five days to reduce errors in observations. This pilot study shows that using the SF6-technique is a feasible method for future research. More experiments measuring enteric methane emission over a longer period from grazing sheep and cattle under Norwegian conditions are planned for the future.
Sammendrag
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Forfattere
Marit JørgensenSammendrag
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Sammendrag
Nitrous oxide (N2O) emissions from cultivated soils correlate positively with the amount of N-fertilizer applied, but a large proportion of the annual N2O emission occurs outside the cropping season, potentially blurring this correlation. We measured the effect of split-N application (total N addition varying from 0 to 220 kg N ha−1) on N2O emissions in a spring wheat plot trial in SE Norway from the time of split-N application until harvest, and during the following winter and spring thaw period. N2O emissions were largest in the two highest N-levels, whereas yield-scaled emission (N2O intensity) was highest in the 0 N treatment. Nitrogen yield increased by 23% when adding 80 kg N ha−1 compared to adding 40 kg N ha−1 as split application, while corresponding N2O emissions were reduced by 16%. No differences in measured emissions between the N-fertilization levels were observed during the winter period or during spring thaw. Measurements of soil air composition below the snow pack revealed that N2O production continued throughout winter as the concentration in the soil air increased from 0.37 to 30.0 µL L−1 N2O over the 3 months period with continuous snow cover. However, only 7–28% of the N2O emitted during spring thaw could be ascribed to accumulated N2O, indicating de novo production of N2O in the thawing soil. The direct effect of split-N fertilizer rate on N2O emissions in sub-boreal cereal cropping was limited to the first 15–21 days after N-addition.