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SOIL BIOLOGY & BIOCHEMISTRY

Fungal and Bacterial Abundance in Long-Term No-Till and Intensive-Till Soils of the Northern Great Plains

^a Saskatoon Research Centre, Agriculture and Agri-Food Canada, 107 Science Pl., Saskatoon, SK, Canada S7N 0X2
^b Dep. of Soil Science, 51 Campus Dr., Univ. of Saskatchewan, Saskatoon, SK, Canada S7N 5A8

^* Corresponding author: (helgasonb{at}agr.gc.ca).

Abundance of fungi and bacteria in long-term no-till (NT) and intensively tilled (IT) soils in the Northern Great Plains were measured using phospholipid fatty acid analysis (PLFA) to determine if a shift in the relative abundance of fungi and bacteria occurs as the result of conversion to NT. Four tillage trials located in four different soil zones were sampled in spring of 2005 and 2006 before the crop was seeded to evaluate the long-term effect of tillage on the microbial community. With the exception of one site-year, total, bacterial, and fungal PLFA were greater in NT than IT soils at the soil surface (0- to 5-cm depth) (p < 0.05). Increases ranged from 8 to 202% for total biomass, 26 to 58% for bacterial biomass, and 0 to 120% for fungal biomass. At one site (Ellerslie) all biomass measurements were greater in IT than NT in 2005 and bacterial biomass was also greater under IT in 2006. The influence of tillage on microbial biomass was less pronounced with depth. Fungal dominance is commonly assumed under NT; however, our results demonstrate that although biomass of both fungi and bacteria increase in NT, the abundance of fungi vs. bacteria was not consistently greater under NT in the soils studied. Further research is needed to determine if fungi may be able to exert a more functionally dominant role in NT soils without an increase in relative abundance.

Abbreviations: IT, intensive-tillage • NT, no-tillage • PLFA, phospholipid fatty acid analysis • SOM, soil organic matter