Abstract
of nitrate (NO3) from agricultural cropping systems have
considerable negative impacts on climate and the environment.
Although these environmental burdens are less per
unit area in organic than in non-organic production on average,
they are roughly similar per unit of product. If organic
farming is to maintain its goal of being environmentally
friendly, these loadings must be addressed. We discuss
the impact of possible drivers of N2O emissions and NO3
leaching within organic arable farming practice under European
climatic conditions, and potential strategies to reduce
these. Organic arable crop rotations are generally diverse
with the frequent use of legumes, intercropping and
organic fertilisers. The soil organic matter content and the
share of active organic matter, soil structure, microbial and
faunal activity are higher in such diverse rotations, and the
yields are lower, than in non-organic arable cropping systems
based on less diverse systems and inorganic fertilisers. Soil
mineral nitrogen (SMN), N2O emissions and NO3 leaching are low under growing crops, but there is the potential for
SMN accumulation and losses after crop termination, harvest
or senescence. The risk of high N2O fluxes increases when
large amounts of herbage or organic fertilisers with readily
available nitrogen (N) and degradable carbon are incorporated
into the soil or left on the surface. Freezing/thawing,
drying/rewetting, compacted and/or wet soil and mechanical
mixing of crop residues into the soil further enhance the
risk of high N2O fluxes. N derived from soil organic matter
(background emissions) does, however, seem to be the
most important driver for N2O emission from organic arable
crop rotations, and the correlation between yearly total Ninput
and N2O emissions is weak. Incorporation of N-rich
plant residues or mechanical weeding followed by bare fallow
conditions increases the risk of NO3 leaching. In contrast,
strategic use of deep-rooted crops with long growing
seasons or effective cover crops in the rotation reduces NO3
leaching risk. Enhanced recycling of herbage from green manures,
crop residues and cover crops through biogas or composting may increase N efficiency and reduce N2O emissions
and NO3 leaching. Mixtures of legumes (e.g. clover or vetch)
and non-legumes (e.g. grasses or Brassica species) are as efficient
cover crops for reducing NO3 leaching as monocultures
of non-legume species. Continued regular use of cover
crops has the potential to reduce NO3 leaching and enhance
soil organic matter but may enhance N2O emissions. There
is a need to optimise the use of crops and cover crops to enhance
the synchrony of mineralisation with crop N uptake to
enhance crop productivity, and this will concurrently reduce
the long-term risks of NO3 leaching and N2O emissions.
| Original language | English |
|---|---|
| Pages (from-to) | 2795-2819 |
| Number of pages | 25 |
| Journal | Biogeosciences |
| Volume | 16 |
| Issue number | 14 |
| Early online date | 17 Jul 2019 |
| DOIs | |
| Publication status | First published - 17 Jul 2019 |
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Reviews and syntheses: Review of causes and sources of N2O emissions and NO3 leaching from organic arable crop rotations. / Hansen, Sissel; Frøseth, Randi; Stenberg, Maria; Stalenga, Jaroslaw; Olesen, Jorgen E; Krauss, Maike; Radzikowski, Pawel; Doltra, Jordi; Nadeem, Shahid; Torp, Torfinn; Pappa, AV; Watson, CA.
In: Biogeosciences, Vol. 16, No. 14, 17.07.2019, p. 2795-2819.Research output: Contribution to journal › Review article
TY - JOUR
T1 - Reviews and syntheses: Review of causes and sources of N2O emissions and NO3 leaching from organic arable crop rotations
AU - Hansen, Sissel
AU - Frøseth, Randi
AU - Stenberg, Maria
AU - Stalenga, Jaroslaw
AU - Olesen, Jorgen E
AU - Krauss, Maike
AU - Radzikowski, Pawel
AU - Doltra, Jordi
AU - Nadeem, Shahid
AU - Torp, Torfinn
AU - Pappa, AV
AU - Watson, CA
PY - 2019/7/17
Y1 - 2019/7/17
N2 - The emissions of nitrous oxide (N2O) and leachingof nitrate (NO3) from agricultural cropping systems haveconsiderable negative impacts on climate and the environment.Although these environmental burdens are less perunit area in organic than in non-organic production on average,they are roughly similar per unit of product. If organicfarming is to maintain its goal of being environmentallyfriendly, these loadings must be addressed. We discussthe impact of possible drivers of N2O emissions and NO3leaching within organic arable farming practice under Europeanclimatic conditions, and potential strategies to reducethese. Organic arable crop rotations are generally diversewith the frequent use of legumes, intercropping andorganic fertilisers. The soil organic matter content and theshare of active organic matter, soil structure, microbial andfaunal activity are higher in such diverse rotations, and theyields are lower, than in non-organic arable cropping systemsbased on less diverse systems and inorganic fertilisers. Soilmineral nitrogen (SMN), N2O emissions and NO3 leaching are low under growing crops, but there is the potential forSMN accumulation and losses after crop termination, harvestor senescence. The risk of high N2O fluxes increases whenlarge amounts of herbage or organic fertilisers with readilyavailable nitrogen (N) and degradable carbon are incorporatedinto the soil or left on the surface. Freezing/thawing,drying/rewetting, compacted and/or wet soil and mechanicalmixing of crop residues into the soil further enhance therisk of high N2O fluxes. N derived from soil organic matter(background emissions) does, however, seem to be themost important driver for N2O emission from organic arablecrop rotations, and the correlation between yearly total Ninputand N2O emissions is weak. Incorporation of N-richplant residues or mechanical weeding followed by bare fallowconditions increases the risk of NO3 leaching. In contrast,strategic use of deep-rooted crops with long growingseasons or effective cover crops in the rotation reduces NO3leaching risk. Enhanced recycling of herbage from green manures,crop residues and cover crops through biogas or composting may increase N efficiency and reduce N2O emissionsand NO3 leaching. Mixtures of legumes (e.g. clover or vetch)and non-legumes (e.g. grasses or Brassica species) are as efficientcover crops for reducing NO3 leaching as monoculturesof non-legume species. Continued regular use of covercrops has the potential to reduce NO3 leaching and enhancesoil organic matter but may enhance N2O emissions. Thereis a need to optimise the use of crops and cover crops to enhancethe synchrony of mineralisation with crop N uptake toenhance crop productivity, and this will concurrently reducethe long-term risks of NO3 leaching and N2O emissions.
AB - The emissions of nitrous oxide (N2O) and leachingof nitrate (NO3) from agricultural cropping systems haveconsiderable negative impacts on climate and the environment.Although these environmental burdens are less perunit area in organic than in non-organic production on average,they are roughly similar per unit of product. If organicfarming is to maintain its goal of being environmentallyfriendly, these loadings must be addressed. We discussthe impact of possible drivers of N2O emissions and NO3leaching within organic arable farming practice under Europeanclimatic conditions, and potential strategies to reducethese. Organic arable crop rotations are generally diversewith the frequent use of legumes, intercropping andorganic fertilisers. The soil organic matter content and theshare of active organic matter, soil structure, microbial andfaunal activity are higher in such diverse rotations, and theyields are lower, than in non-organic arable cropping systemsbased on less diverse systems and inorganic fertilisers. Soilmineral nitrogen (SMN), N2O emissions and NO3 leaching are low under growing crops, but there is the potential forSMN accumulation and losses after crop termination, harvestor senescence. The risk of high N2O fluxes increases whenlarge amounts of herbage or organic fertilisers with readilyavailable nitrogen (N) and degradable carbon are incorporatedinto the soil or left on the surface. Freezing/thawing,drying/rewetting, compacted and/or wet soil and mechanicalmixing of crop residues into the soil further enhance therisk of high N2O fluxes. N derived from soil organic matter(background emissions) does, however, seem to be themost important driver for N2O emission from organic arablecrop rotations, and the correlation between yearly total Ninputand N2O emissions is weak. Incorporation of N-richplant residues or mechanical weeding followed by bare fallowconditions increases the risk of NO3 leaching. In contrast,strategic use of deep-rooted crops with long growingseasons or effective cover crops in the rotation reduces NO3leaching risk. Enhanced recycling of herbage from green manures,crop residues and cover crops through biogas or composting may increase N efficiency and reduce N2O emissionsand NO3 leaching. Mixtures of legumes (e.g. clover or vetch)and non-legumes (e.g. grasses or Brassica species) are as efficientcover crops for reducing NO3 leaching as monoculturesof non-legume species. Continued regular use of covercrops has the potential to reduce NO3 leaching and enhancesoil organic matter but may enhance N2O emissions. Thereis a need to optimise the use of crops and cover crops to enhancethe synchrony of mineralisation with crop N uptake toenhance crop productivity, and this will concurrently reducethe long-term risks of NO3 leaching and N2O emissions.
U2 - 10.5194/bg-16-2795-2019
DO - 10.5194/bg-16-2795-2019
M3 - Review article
VL - 16
SP - 2795
EP - 2819
JO - Biogeosciences
JF - Biogeosciences
SN - 1726-4170
IS - 14
ER -