Complete removal of biomass from oilseed radish as a cover crop decreased nitrous oxide emissions

Abstract: One of the many benefits of utilizing cover crops in crop rotations is their carbon sequestrating effect. However, frost-sensitive cover crops could emit high levels of the potent greenhouse gas nitrous oxide. To avoid a system where the effect of carbon sequestration is simultaneously mitigated through nitrous oxide emissions, it is important to identify which methods that are able to decrease nitrous oxide emissions. A field trial was performed with 4 treatments of the frost sensitive cover crop oilseed radish; (1) untreated, (2) cut and removed, (3) uprooted and removed and (4) addition of a high C: N ratio material for immobilisation of nitrogen. The hypothesis was that all treatments 2-4 would decrease nitrouse oxide emissions from oilseed radish, but that treatment 3 would have the largest effect. The mean cumulative emissions over the whole measuring period of 78 days were 774.3, 459.2, 271.2 and 651.7 g N2O-N ha-1, for treatments 1, 2, 3 and 4, respectively. Only treatment 3 was significantly different from the other treatments and proved to have potential in decreasing N2O emissions from oilseed radish. However, the results need to be confirmed through further studies, as well as the treatments economic and practical feasability. The results for treatments 2 and 4 were not as expected, but raised questions and impulses for further research.