Soil amendment project a win-win

About 700 acres of willows have been densely planted in sandy soil prepared with biosolids from the City of Calgary’s waste water treatment system.
Willow chips are the final stage after the trees are harvested. They can be used for composting, livestock bedding or biofuel. 
Shawn Northwood of the bio-remediation company shows a willow sapling that will be planted directly into the fertilized soil. It will root within a few days.
|  Barbara Duckworth photo

Calgary project takes marginal land and treats it with biosolids, providing biomass for trees and crops to thrive

A 10-year project to rebuild sandy soil at the Mountainview Colony east of Calgary has turned out better than expected.

The colony agreed to use bio-solids from the City of Calgary to fertilize some marginal land.

The prepared material went on with a manure spreader and was incorporated into the top layer of soil, and 2.5 million willow saplings were then planted on 700 acres.

A hailstorm wiped out a field last year, so canola was planted with surprisingly good results, said farm manager Jack Tschetter.

“We could never grow a canola crop on that field,” he said during a farm tour.

The willow roots probably opened up the soil and the biosolids added fertility that could last several years.

“This year we have the agriculture productivity equivalent to a traditionally fertilized field or even better after the first or second year of application,” he said.

The project started in 2013 when the colony agreed to work with Calgary and Sylvis, a company that manages biosolids from waste water, pulp and paper residuals, ash, effluent and other byproducts.

The resulting product is then used to reclaim gravel pits and forestry cut blocks or is turned into fertilizer for agricultural and forestry purposes.

Calgary runs three waste water plants, and since 1983 it has had a partnership with the province, city and local farmers who spread biosolids on land to grow cereals, oilseeds, pulses, forages, sod and trees. The program is known as Calgro.

The Mountainview project planted the willows on land that received a treatment of biosolids the previous year. It is the largest single willow plantation of its kind in North America, said Shawn Northwood of Sylvis.

It has been done in Europe, so they are still learning how to make the concept work here.

The willows were derived from a hybrid program in New York. Twenty hybrids are on trial at the site to see which works best. They should be productive for 20 to 25 years.

Each tree goes into the ground as short sticks and take root within a few days. Within a year there is a dense forest of trees. The willows can be cut and composted, turned into livestock bedding or burned for energy.

“They grow, they add biomass above and below the ground and we harvest them,” said Northwood.

The groves are relatively maintenance free after the second year following establishment and appear to be drought tolerant once they are growing.

The trees can out compete weeds because they are so densely planted, but herbicides are used in the early phase.

The first commercial cutting this fall will use a specialized harvester to cut the trees to a height of about eight centimetres. They are then chipped for livestock bedding and fuel for energy. The highest value would be processing the chips into a biochar as a coal substitute, said Northwood.

Existing roots will regrow, and in three years the trees will be cut again. The plan is to eventually have staggered plantings so that there is a harvest every fall.

Added carbon in the soil could provide other environmental benefits.

Those involved in the program are also looking at the effect on microbes in the soil associated with this kind of amendment.

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