Effects of Long-term Fertilization History and Current N and S Fertilizer Applications on Nitrous Oxide Production from S-deficient Soils in a Laboratory Incubation

Nitrous oxide (N2O) production in four soils with unique fertilization management histories — collected from long-term fertility treatments receiving no fertilizer, NPKS, PKS, and NPK in a 5 yr cereal–forage rotation — in response to three sources of added N [100 kg N ha-1 urea, NH4Cl, Ca(NO3)2] with and without co-addition of elemental S (20 kg S ha-1) plus a 0-N and 0-S control was investigated in a 7 wk laboratory incubation in a loamtextured soil at 40% water-filled pore space. In all soils, cumulative N2O emissions and apparent, cumulative, net nitrification were significantly higher following addition of urea compared with other N fertilizers with and without co-addition of elemental S. Lower N2O emissions were observed in soils without a history of long-term N fertilization following addition of urea compared with soils that had historically received urea. Because the preincubation soil total N levels were similar in soils with a history of urea application (NPKS) and without urea (PKS), the results of this investigation suggest that the higher N2O production in the NPKS soil may be the result of a priming effect and (or) changes in microbial community composition induced by long-term urea applications rather than differences in the long-term soil N balance.