British Columbia Mine Reclamation Symposium

The impacts of municipal biosolids on some indicators of soil health Forge, Tom; Broersma, Klaas; Neilsen, Gerry; Yu, Shaobing; Roddan, Bruce


The abundance and diversity of soil organisms are considered to be prime indicators of soil health, which has been defined as the capacity of soil to sustain productivity. Municipal biosolids are good sources of N, P and micronutrients for short-term crop production. The long-term impacts of biosolids on indicators of soil health are, however, less well understood. As inputs of organic C, biosolids have potential to increase soil biodiversity and improve soil health. However, because they contain greater concentrations of some metals than receiving soil, there is also potential for biosolids to have regressive effects on soil biodiversity and soil health. We have been studying the impacts of biosolids on arbuscular-mycorrhizal fungi (AMF) and diversity of soil microfauna, as well as nutrient availability, at three sites in the southern interior of BC: (1) irrigated alfalfa, (2) crested wheatgrass, and (3) native range vegetation. We have found that high biosolids application rates (e.g. 60 Mg/ha) can cause slight reductions in diversity of microfauna and colonization of alfalfa roots by AMF, relative to untreated soil. The reduced colonization of alfalfa by AMF appears to be the result of enhanced availability of P. Since uptake of P, Cu and Zn is the primary benefit of AMF to crop plants, the implications of reduced AMF colonization (in response to enhanced P availability) are not yet clear. It is also still unclear if the reduced diversity of micro-fauna is the result of nutrient loading or metals. We hypothesize that the use of biosolids in reclamation projects, where the reference point is degraded soil, is more likely to enhance soil health.

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