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Summary - Part 6

Following this stop, the group headed over to a biosolids test site. Joiner is currently experimenting with biosolids applications on his deeded grasslands in order increase yields, boost protein and extend the growing season. Biosolids are produced from five wastewater treatment plants in the Greater Vancouver Regional District. Once produced, the material is shipped to several ranches in B.C.’s interior grasslands, one of which is Joiner’s OK Ranch.

In addition to the biosolids test site, workshop participants visited a biosolids research site – one of four sites on OK Ranch that will be monitored over the next five years by Ministry of Forests and Agriculture Canada to address the question of possible plant species shifts associated with one-time biosolids applications.

Here is a brief summary of the

Biosolids research site

The Ministry of Forests and Agriculture Canada are collaborating on a joint research project designed to address the question of possible plant species shifts associated with a one-time biosolids application at 20 dry tonnes/ha. Vascular plant species, litter, exposed soil, and microbiotic crust will be monitored over the next 5 years (Reg Newman; BCMOF). Soil chemistry (Klaas Broersma; AGCAN) and soil micro-faunal communities (Tom Forge; AGCAN) and meso-faunal communities (Jeff Battigelli; Earthworks) will also be monitored. Four exclosures were established at the OK Ranch and one half of the area was treated with biosolids in the fall. This design was repeated at two other ranches (Nicola and Ashcroft).

Some possible negative plant species shifts

• We may see reduced diversity of plant species as dominant nitrogen loving species outcompete lower-growing species. For example, it's possible that Kentucky bluegrass will competitively exclude other species when fertilized with N in a mixed stand.
• We may see increases of weeds. Weeds in general are adapted for rapid colonization, and for early and rapid growth. So there is a potential that weeds will get the first chance at the additional nutrients supplied by biosolids.
• A shift toward earlier seral plant species has been reported by some authors using chemical N on native rangelands.

Some possible positive plant species shifts:

• We may see suppression of weeds as they are outcompeted by desirable N-loving grasses. Simply increasing plant cover and thereby reducing the amount of bare ground will reduce the potential habitat for many weeds.
• A shift toward later seral plant species and desirable plants has been reported by some authors. Rogler and Lorenz (1973) changed the condition from poor to excellent in 3 years with annual fall application of 45 kg N/ha in a mixed prairie association. They declared this practice to be better than complete rest from grazing.

Ecosystem restoration

There is a great potential to use biosolids as a tool to restore ecological integrity by accelerating the successional process. We know that recovery of late seral species on degraded grasslands can take decades even with the complete exclusion of grazing. Boisolids have the potential to kick start the recovery process with an injection of N; thereby boosting above and below-ground biomass, leading to improved water use efficiency, soil organic matter inputs, and increased litter. The resulting improvement in plant vigour and reproductive capacity may lead to increases in desirable species.

Results

The first post-treatment data is only just being analyzed. Preliminary analysis and anecdotal observations indicate that the plant community will likely shift towards later-seral characteristics.

Photos from top:
Paul Sanborn
Mike Duffy-research site

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