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Roots and other residues from leys with or without red clover: Quality and effects on N2O emission factors in a partly frozen soil following autumn ploughing

Bleken, Marina Azzaroli; Rittl, Tatiana; Nadeem, Shahid and Hansen, Sissel (2022) Roots and other residues from leys with or without red clover: Quality and effects on N2O emission factors in a partly frozen soil following autumn ploughing. Science of The Total Environment, 828, p. 154582. [In Press]

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Revised IPCC guidelines assume that a constant share of N in decomposing crop residues is directly emitted as N2O (emission factor: EFN2O),and calculate the amount of nitrogen (N) in non-removable residues of temporary grasslands proportionally to the average annual herbage yield. However, EFN2O depends on the intrinsic quality of the residues and their interactions with environmental conditions. Only a few field studies on N2O emissions from grassland renewal are available, and none have simultaneously quantified the N amount and quality of non-removable residues (roots and stubble). To gain insight into the effect of non-removable residue quality on EFN2O, we studied the amount and quality of roots and stubble and their effect on EFN2O following the ploughing of three-year-old swards. The measured amount of N in non-removable residues was approximately 20, 25, and 31 kg N per 1 Mg average annual dry matter yield in grass, red clover-grass, and red clover, and 70–83% of it was below ground. However, the EFN2O of non-removable residues measured over 252 days was lower (0.24%, SE = 14% for grass and red clover-grass) than the IPCC default value (0.6%, CV: 50%) for wet regions, although within the uncertainty margin, and was significantly lower than the EFN2O of incorporated herbage, which was related to differences in EFCO2. We advocate for more specific studies that separate the effects of belowground and aboveground residues (ABG), considering the possibility of simplifying the accounting of N2O emissions from belowground residues while improving that of non-removable AGR from temporary grasslands and other green crops. We observed the accumulation of N2O in the frozen soil under snow, which was released during diurnal percolation of meltwater. N2O emissions from frozen soil accounted for 30% or more of the total emissions.

EPrint Type:Journal paper
Keywords:Grassland; Freeze-thaw; Plant litter; CO2; Denitrification; GHG inventory
Agrovoc keywords:
crop residues
nitrous oxide
Subjects: Crop husbandry > Crop combinations and interactions
Environmental aspects > Air and water emissions
Research affiliation: Norway > NMBU - Norwegian University of Life Sciences
Norway > NORSØK - Norwegian Centre for Organic Agriculture
H2020 or FP7 Grant Agreement Number:696356
Deposited By: F Rittl, Tatiana
ID Code:43981
Deposited On:06 May 2022 06:18
Last Modified:06 May 2022 06:18
Document Language:English
Status:In Press
Refereed:Peer-reviewed and accepted

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