Coordinated nitrogen and sulfur management in S-deficient soils

Long-term soil experiments have shown management practices such as rotation, tillage and fertilization affect soil nutrient cycling and crop response to fertilizer. The majority of soil fertility research has quantified the benefit of fertilizers in the growing season they are applied, but there is a need for research quantifying the effects of long-term fertilizer applications on soil quality, nutrient use efficiency and nitrous oxide fluxes. Further, there is a need for research focusing on N and S interactions because many prairie soils are potentially S deficient, and S deficiency may be increasing because of increased crop removal by high yielding, S-demanding crop species (i.e. canola), increased cropping intensity, and decreased industrial S emissions into the atmosphere. The objective of this research is to quantify and compare nitrous oxide emissions in treatments with different long-term N and S fertilization regimes at the University of Alberta - Breton Plots long-term research site, near Breton, AB.

In the 2014 growing season, weekly nitrous oxide fluxes were measured on the wheat phase of the control, NPKS, NPK, PKS, and manure treatments of the wheat-oats-barley-hay-hay rotations and wheat-fallow rotations. Growing season precipitation was 286 mm, about 100 mm below normal (393 mm), but growing degree days (1,269) were slightly greater than normal (1,230). Based on the calculated cumulative evapotranspiration of 497 mm, a significant water deficit was experienced. The nitrous oxide flux and grain yield data from the 2014 growing season is still being processed so no further interpretation can be made at this time. Data processing and analysis is expected to be completed in the spring of 2015.