A comparison of Earthworm densities in Grassland Set-A-Sides versus Cultivated Potato fields in Delta, British Columbia

Project Lead: Brittany Armstrong
Project Type: Undergraduate Thesis
Supervisor: Dr. Sean Smukler

This project is now complete. Download the report here

Earthworms are commonly recognized as the most important soil fauna, enhancing soil fertility and structure through a number of pathways.  As ecosystem engineers and as indicators of soil health, earthworms encourage water filtration and increase rooting depth through the formation of bio pores (Lagerlöf, Pålsson, & Arvidsson, 2011). Earthworms also aid in the mineralization of nutrients and induce stable aggregate formation through the excretion of nutrient enriched casts, where cast formation is highly dependent on soil moisture content as well as soil temperature (Coleman, Croccley, & Hendrix, 2004).  Turnover of soil organic matter by earthworms provides plant available nutrients and represents a mechanism for enhancing soil fertility.

Little is known about the density of earthworms in the soils of Delta, British Columbia or if there is a difference in the presence of earthworms between grassland set-a-sides and cultivated fields in the area. Earthworm population densities are believed to be heavily influenced by intensive soil cultivation, however following years of  perennial crop rotation, earthworm densities are believed to increase due to their species dependent life cycles of 42-72 weeks (Lagerlöf et al., 2011).

The main objective of this research is to understand whether a significant difference in earthworm presence exists between one year old grassland set-a-sides and fields which have undergone recent cultivation. Earthworm presence was quantified through the method of hand sorting and wet biomass measurements were completed. Investigation into other soil indicators including organic matter content, aggregate stability, pH and soil moisture content were gathered as secondary information to help provide a description of the physical and chemical conditions in which these earthworms live.

References Cited:

  • Coleman, D., Croccley, D.A, & Hendrix, P. Fundamentals of Soil Ecology. 2. Athens: Elsevier Academic Press, 2004. <http://site.ebrary.com/lib/ubc/docDetail.action?docID=10169762>.
  • Lagerlöf, J., Pålsson, O., & Arvidsson, J. (2011). Acta Agriculturae Scandinavica , Section B – Soil & Plant Science Earthworms influenced by reduced tillage , conventional tillage and energy forest in Swedish agricultural field experiments. Acta Agriculture Scandinavica, Section B- Soil & Plant Science62(3), 235–244.