Nitrous Oxide Emissions From An Organic Potato Rotation in Eastern Canada as Influenced by Legume Green Manure and Organic Amendment.

The source of nitrogen (N) supplied to the crop can significantly affect nitrous oxide (N₂O) emissions from agricultural soils. In this study, N₂O emissions from potato crop (Solanum tuberosum L.) planted after either red clover (RCl) or oat/pea/vetch (OPV) mixture with or without composted paper mill biosolids (PMB) or mineral N fertilizer application were examined. Nitrous oxide flux measurements were taken over the entire year, with primary focus on the non-frozen period, using non-steady-state vented chambers. Nitrous oxide emissions in potatoes were also compared with red clover. The emissions from potatoes were about four times greater after RCl than after OPV (1.30 vs. 0.28 kg N₂O-N ha^-1). In the non-fertilized potatoes, N₂O emissions were 16% lower than the synthetically fertilized potatoes (0.82 vs. 0.96 kg N₂O-N ha^-1). The PMB application reduced N₂O emissions compared with control by about 30%. When comparing N₂O emissions in non-fertilized potatoes with RCl underseeded with oats; the emissions were two times greater in potatoes than in RCl.  Nitrous oxide emissions from organic potatoes can be mitigated by rotation crop and organic amendments. Lower N₂O emissions coefficients should be assigned to legume-derived N than fertilizer-derived N.