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Review of key causes and sources for N2O emmisions and NO3-leaching from organic arable crop rotations

Hansen, Sissel; Frøseth, Randi Berland; Stenberg, Maria; Stalenga, Jarosław; Olesen, Jørgen E.; Krauss, Maike; Radzikowski, Pawel; Doltra, Jordi; Nadeem, Shahid; Torp, Torfinn; Pappa, Valentini and Watson, Christine (2018) Review of key causes and sources for N2O emmisions and NO3-leaching from organic arable crop rotations. https://doi.org/10.5194/bg-2018-455, x, x-xx. [In Press]

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Online at: https://doi.org/10.5194/bg-2018-455

Summary

Abstract. The emissions of nitrous oxide (N2O) and leaching of nitrate (NO3) have considerable negative impacts on climate and the environment. Although these environmental burdens are on average less per unit area in organic than in non-organic production, they are not smaller per unit of product. If organic farming is to maintain its goal of being an environmentally friendly production system, these emissions should be mitigated. We discuss the impact of possible triggers within organic arable farming practice for the risk of N2O emissions and NO3 leaching under European climatic conditions, and possible strategies to reduce these. Organic arable crop rotations can be characterised as diverse with frequent use of legumes, intercropping and organic fertilizers. The soil organic matter content and share of active organic matter, microbial and faunal activity are higher, soil structure better and yields lower, than in non-organic, arable crop rotations. Soil mineral nitrogen (SMN), N2O emissions and NO3 leaching are low under growing crops, but there is high potential for SMN accumulation and losses after crop termination or crop harvest. The risk for high N2O fluxes is increased when large amounts of herbage or organic fertilizers with readily available nitrogen (N) and carbon are incorporated into the soil or left on the surface. Freezing/thawing, drying/rewetting, compacted and/or wet soil and mixing with rotary harrow further enhance the risk for high N2O fluxes. These complex soil N dynamics mask the correlation between total N-input and N2O emissions from organic arable crop rotations. Incorporation of N rich plant residues or mechanical weeding followed by bare fallow increases the risk of nitrate leaching. In contrast, strategic use of deep-rooted crops with long growing seasons in the rotation reduces nitrate leaching risk. Reduced tillage can reduce N leaching if yields are maintained. Targeted treatment and use of herbage from green manures, crop residues and catch crops will increase N efficiency and reduce N2O emissions and NO3 leaching. Continued regular use of catch crops has the potential to reduce NO3 leaching but may enhance N2O emissions. A mixture of legumes and non-legumes (for instance grasses or cereals) are as efficient a catch crop as monocultures of non-legume species.


EPrint Type:Journal paper
Keywords:organic arable crop rotations; Nitrous oxide; leaching;GHG Mitigation;soil mineral nitrogen;FertilCrop
Agrovoc keywords:
LanguageValueURI
EnglishBNF -> biological nitrogen fixationhttp://aims.fao.org/aos/agrovoc/c_27742
Englishnitrous oxidehttp://aims.fao.org/aos/agrovoc/c_12838
Englishleachinghttp://aims.fao.org/aos/agrovoc/c_15591
EnglishFertilCropUNSPECIFIED
Subjects:"Organics" in general
Crop husbandry
Environmental aspects > Air and water emissions
Soil
Environmental aspects
Research affiliation: Switzerland > FiBL - Research Institute of Organic Agriculture Switzerland > Soil Sciences
Denmark > AU - Aarhus University > AU, DJF - Faculty of Agricultural Sciences
Spain
Norway > NIBIO – Norwegian Institute of Bioeconomy Research
Norway > NORSØK - Norwegian Centre for Organic Agriculture
Poland
Sweden > Swedish University of Agricultural Sciences (SLU)
UK > Scottish Rural Colleges (SRUC - previously SAC)
USA
H2020 or FP7 Grant Agreement Number:618107
DOI:https://doi.org/10.5194/bg-2018-455
Related Links:https://www.fertilcrop.net/fc-home-news.html
Deposited By: Pommeresche, Reidun
ID Code:34138
Deposited On:23 Feb 2019 12:27
Last Modified:23 Feb 2019 12:27
Document Language:English
Status:In Press
Refereed:Not peer-reviewed

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