N2O emission from organic barley cultivation as affected by green manure management

[摘要] Legumes are an important source of nitrogen in stockless organic cerealproduction. However, substantial amounts of N can be lost from legume-grassleys prior to or after incorporation as green manure (GM). Here we reportN₂O emissions from a field experiment in SE Norway exploring differentgreen manure management strategies: mulching versus removal of grass-cloverherbage during a whole growing season and return as biogas residue to asubsequent barley crop. Grass-clover ley had small but significantly higherN₂O emissions as compared with a non-fertilised cereal reference duringthe year of green manure (GM) production in 2009. Mulching of herbage inducedsignificantly more N₂O emission (+0.37 kg N₂O-N ha⁻¹)throughout the growing season than removing herbage. In spring 2010, all plotswere ploughed (with and without GM) and sown with barley, resulting ingenerally higher N₂O emissions than during the previous year.Application of biogas residue(60 kg NH₄⁺-N + 50 kg organic N ha⁻¹) before sowing didnot increase emissions neither when applied to previous ley plots nor whenapplied to previously unfertilised cereal plots. Ley management (mulchingvs. removing biomass in 2009) had no effect on N₂O emissions duringbarley production in 2010. In general, GM ley (mulched or harvested)increased N₂O emissions relative to a cereal reference with low mineralN fertilisation (80 kg N ha⁻¹). Based on measurements covering thegrowing season 2010, organic cereal production emitted95 g N₂O-N kg⁻¹ N yield in barley grain, which wassubstantially higher than in the cereal reference treatment with 80 kgmineral N fertilisation (47 g N₂O-N kg⁻¹ N yield in barleygrain).

[学科分类] 地球化学与岩石