Nitrous Oxide Emissions from Clayey Soils Amended with Paper Sludges and Biosolids of Separated Pig Slurry

Wastes from animal production and from the paper industry are often used as amendments to agricultural soils. Although data exist on the impacts of raw animal wastes on N 2 O production, little is known regarding the effects of paper wastes and biosolids from treated animal waste. We measured N 2 O emissions for two consecutive snow‐free seasons (mid‐May through the end of October) from poorly drained clayey soils under corn ( Zea mays L.). Soils were amended with raw pig slurry (PS) or biosolids (four PS‐derived and two paper sludges) and compared with soils with mineral N fertilizer (CaNH 4 NO 3 ) or without N addition (Control). Area‐based N 2 O emissions from the mineral N fertilizer (average, 8.2 kg N 2 O–N ha −1 ; 4.2% of applied N) were higher ( P < 0.001) than emissions from the organic amendments, which ranged from 1.5 to 6.1 kg N 2 O–N ha −1 (−0.4 to 2.5% of applied N). The N 2 O emissions were positively correlated with mean soil NO 3 availability (calculated as “NO 3 exposure”), which was highest with mineral N fertilizer. In plots treated with organic amendments (i.e., biosolids and raw PS), NO 3 exposure was negatively correlated to the C:N ratio of the amendment. This resulted in lower N 2 O emissions from the higher C:N ratio biosolids, especially compared with the low C:N ratio PS. Application of paper sludge or PS‐derived biosolids to these fine‐textured soils, therefore, reduced N 2 O emissions compared with raw PS and/or mineral N fertilizers ( P < 0.01).