We analyzed the change in total soil organic carbon (SOC) in a long-term fertilization experiment (1980-2008) in a wheat-oat-barley-hay-hay rotation system at the University of Alberta Breton Classical plots. Soil samples were taken in 1980, 1990, 1998, 2003 and 2008 from plots that were fertilized with NPKS and NPK. The objective was to compare the relative effect of S fertilization on the SOC stocks in a S-deficient soil. Long-term S fertilization resulted in an increasing trend in soil organic carbon concentrations over 28 yr when N, P and K supply were adequate. The change in SOC with time was significantly different ( P<0.05) between the two treatments. Annual application of NPK in combination with S resulted in an increased accumulation of SOC at a rate of 0.11 Mg C ha -1 yr -1 in the 0- to 15-cm depth over NPK alone. Our results suggest that long-term S fertilization in an S-deficient soil helped to sequester C in the soil.
