N&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O emission from organic barley cultivation as affected by green manure management

S Nadeem,S Hansen,M Azzaroli Bleken,P Dörsch

doi:10.5194/bg-9-2747-2012

N&lt;sub&gt;2&lt;/sub&gt;O emission from organic barley cultivation as affected by green manure management

S Nadeem, S Hansen + Show 2 more

Open Access

https://doi.org/10.5194/bg-9-2747-2012

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Abstract

Abstract. Legumes are an important source of nitrogen in stockless organic cereal production. However, substantial amounts of N can be lost from legume-grass leys prior to or after incorporation as green manure (GM). Here we report N2O emissions from a field experiment in SE Norway exploring different green manure management strategies: mulching versus removal of grass-clover herbage during a whole growing season and return as biogas residue to a subsequent barley crop. Grass-clover ley had small but significantly higher N2O emissions as compared with a non-fertilised cereal reference during the year of green manure (GM) production in 2009. Mulching of herbage induced significantly more N2O emission (+0.37 kg N2O-N ha−1) throughout the growing season than removing herbage. In spring 2010, all plots were ploughed (with and without GM) and sown with barley, resulting in generally higher N2O emissions than during the previous year. Application of biogas residue (60 kg NH4+-N + 50 kg organic N ha−1) before sowing did not increase emissions neither when applied to previous ley plots nor when applied to previously unfertilised cereal plots. Ley management (mulching vs. removing biomass in 2009) had no effect on N2O emissions during barley production in 2010. In general, GM ley (mulched or harvested) increased N2O emissions relative to a cereal reference with low mineral N fertilisation (80 kg N ha−1). Based on measurements covering the growing season 2010, organic cereal production emitted 95 g N2O-N kg−1 N yield in barley grain, which was substantially higher than in the cereal reference treatment with 80 kg mineral N fertilisation (47 g N2O-N kg−1 N yield in barley grain).

Highlights

Nitrous oxide (N2O) is a potent greenhouse gas involved in ozone depletion and global warming (Ravishankara et al, 2009)
There is a broad consensus that cultivation history, crop rotation and local soil conditions modify fertiliser induced N2O emissions and that management strategies have to be studied in a local context if regionalised emission factors are to be defined (Petersen et al, 2006)
We evaluated the effect of grass-clover GM itself relative to a moderately fertilised (80 kg N ha−1) reference treatment without green manure

Summary

Introduction

Nitrous oxide (N2O) is a potent greenhouse gas involved in ozone depletion and global warming (Ravishankara et al, 2009). Agriculture is estimated to be responsible for 38 % of the N2O emitted to the atmosphere (IPCC, 2007). Direct N2O emissions from cultivated soils are often estimated as a constant fraction of applied N (Tier 1, IPCC, 2007) reflecting the importance of fertiliser induced emissions for annual N2O budgets. There is a broad consensus that cultivation history, crop rotation and local soil conditions modify fertiliser induced N2O emissions and that management strategies have to be studied in a local context if regionalised emission factors are to be defined (Petersen et al, 2006). There is no conclusive evidence so far linking specific cultivation systems to specific emission factors, . Agronomic systems cannot be studied independently of local environmental and economical settings and, cultivation-specific N2O emission potentials must be determined locally

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