Improving organic C and N in a sulphur-deficient soil with S fertilization
A field experiment was conducted over nine years (1999 to 2007 growing seasons) in northeastern Saskatchewan on a S-deficient Gray Luvisol (Typic Haplocryalf) soil to determine the relative effectiveness of N alone versus combined annual application of N (120 kg N ha-1) and S (15 kg S ha-1) fertilizers to wheat-canola rotation on storage of total organic C [TOC and N (TON), and light fraction organic C (LFOC) and N (LFON)] in soil. Compared to N alone, annual applications of S fertilizer in spring in a combination with N resulted in an increase of TOC (by 2.18 Mg C ha-1), TON (by 0.138 Mg N ha-1), LFOC (by 1018 kg C ha-1) and LFON (by 42 kg N ha-1) mass in soil. The relative increases in organic C or N due to S fertilizer application were much higher for light organic fractions (36.9% for LFOC and 27.5% for LFON) than for total organic fractions (9.2% for TOC and 7.3% for TON). The findings suggest the importance of balanced/combined application of N and S fertilizers to crops in storing more organic C and N in S-deficient soil, but further research is needed on a number of S-deficient sites.
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