Affiliation:
1. Swift Current Research and Development Centre, Agriculture and Agri-Food Canada, Swift Current, SK S9H 3X2, Canada
2. Viresco Solutions, Edmonton, AB T6J 6T4, Canada
3. Department of Soil Science, University of Saskatchewan, Saskatoon, SK S7N 5A8, Canada
Abstract
Conservation agriculture (CA) is increasingly promoted to build soil organic matter (SOM) based on findings from predominantly small-plot long-term agroecosystem experiments (LTAEs), with minimal on-farm data. Using commercial producer fields ( n = 20) in the Brown Chernozemic soil zones of Saskatchewan, Canada, which were sampled before (1996) and after (2018) adopting direct-seeding and continuous cropping (1997), we examined changes in soil organic carbon (SOC) and soil total nitrogen (STN) stocks, along with C and N stocks in particulate (POM) and mineral-associated organic matter (MAOM), and compared them to an LTAE in the same soil zone. After 21 years, SOC and STN stocks (0–30 cm depth) increased by 13% and 21%, respectively, in commercial producer fields, and were more pronounced in finer- than coarser-textured soils. Conversely, there were no significant changes (0–30 cm depth) after 18 years (1998–2016) with CA (continuous wheat and pulse-wheat under no-tillage (PW-NT)) in the LTAE, except that STN stock for PW-NT decreased by 7.7%. The estimated rate of change to 30 cm depth was similar between the commercial fields and LTAE for SOC (0.28 and 0.16 Mg C ha−1 year−1, respectively), but not STN (0.04 and −0.03 Mg N ha−1 year−1, respectively). Changes were more evident in the MAOM than POM fraction in both cases. Although the impact of CA may be similar, as observed for SOC, actual on-farm changes will depend on site-specific factors, and specific CA practice. Therefore, on-farm monitoring studies are needed for more accurate assessments of SOM changes and C sequestration potentials.
Funder
Saskatchewan Wheat Development Commission
Saskatchewan Barely Development Commission
Saskatchewan Canola Development Commission
Saskatchewan Pulse Growers
Saskatchewan Soil Conservation Association
Agriculture and Agri-Food Canada
Saskatchewan Flax Development Commission
Government of Saskatchewan through the Agricultural Development Fund
Saskatchewan Oat Development Commission
Publisher
Canadian Science Publishing