Nitrous Oxide Emissions Respond Differently to Mineral and Organic Nitrogen Sources in Contrasting Soil Types

The use of various animal manures for nitrogen (N) fertilization is often viewed as a viable replacement for mineral N fertilizers. However, the impacts of amendment type on N 2 O production may vary. In this study, N 2 O emissions were measured for 2 yr on two soil types with contrasting texture and carbon (C) content under a cool, humid climate. Treatments consisted of a no‐N control, calcium ammonium nitrate, poultry manure, liquid cattle manure, or liquid swine manure. The N sources were surface applied and immediately incorporated at 90 kg N ha −1 before seeding of spring wheat ( Triticum aestivum L.). Cumulative N 2 O–N emissions from the silty clay ranged from 2.2 to 8.3 kg ha −1 yr −1 and were slightly lower in the control than in the fertilized plots ( P = 0.067). The 2‐yr mean N 2 O emission factors ranged from 2.0 to 4.4% of added N, with no difference among N sources. Emissions of N 2 O from the sandy loam soil ranged from 0.3 to 2.2 kg N 2 O–N ha −1 yr −1 , with higher emissions with organic than mineral N sources ( P = 0.015) and the greatest emissions with poultry manure ( P < 0.001). The N 2 O emission factor from plots amended with poultry manure was 1.8%, more than double that of the other treatments (0.3–0.9%), likely because of its high C content. On the silty clay, the yield‐based N 2 O emissions (g N 2 O–N kg −1 grain yield N) were similar between treatments, whereas on the sandy loam, they were greatest when amended with poultry manure. Our findings suggest that, compared with mineral N sources, manure application only increases soil N 2 O flux in soils with low C content.