We all depend upon a consistent supply of clean water; but increasing demand is draining traditional sources of that vital, natural resource.

Between 1972 and 1991 the volume of water used in Canada increased by more than 50 per cent, although the population grew by only five per cent. Recently, low rainfall and high temperatures in the spring and summer have further strained water supplies. In 2001, many municipalities were forced to implement mandatory water use restrictions.

A reliable supply of water is essential to Canada’s ornamental nursery industry, one of the country’s fastest growing agricultural sectors. As demand for ornamental plants continues to rise, water has become a major concern for growers. Most ornamental landscape plants are produced in nursery containers, a system that requires significant amounts of water.

Now more than ever before, research is needed to investigate opportunities for Ontario’s ornamental nursery industry to use recycled water rather than fresh water. Reusing nutrients that come from organic waste recycling processes also has important implications for the environment.

Funded by the Canada-Ontario Research & Development (C-ORD) Program, University of Guelph researchers focused on wastewater from composting operations. Compost wastewater contains high levels of nutrients that would be ‘lost resources’ if they were not recycled.

In the past, wastewater from commercial composting operations has been successfully used to grow ornamental trees and grasses. Marigold and tomato seedlings have been grown hydroponically in wastewater from mushroom compost. Whether container-grown nursery stock would thrive in compost wastewater was unknown.

Graduate student Rob Michitsch and University of Guelph professors, Dr. Calvin Chong and Dr. Paul Voroney got together with Dr. Bruce Holbein and Dr. Hua-Wu Liu from the Eastern Power / Super Blue Box Recycling Corporation (SUBBOR) to make recycled wastewater tea.

They made tea from spent mushroom compost, from City of Guelph municipal compost, and using diluted wastewater from anaerobically composted municipal solid waste.

The three types of tea were hydroponically fed to the woody plants Forsythia and Weigela, and to the turfgrass species Creeping Bentgrass and Kentucky Bluegrass. Separate groups of the plants were grown, with additional nitrogen, potassium and phosphorous, and without any supplemental nutrients.

The research indicated that compost teas have great potential. “With proper adjustments of pH and electrical conductivity and amendments of nitrogen, phosphorous, potassium and other nutrients, compost tea can be a good supplemental nutrient source for growing nursery stock and turfgrass,” said Michitsch.

“It is important to evaluate alternative irrigation and fertilizer sources both to conserve high quality water for human uses and to protect the environment,” said Ontario Agricultural Commodity Council Secretary, Graeme Hedley.

Along with the C-ORD Program, the research project was supported by the Canadian Mushroom Growers Association (CMGA), the Natural Sciences and Engineering Research Council of Canada (NSERC) and SUBBOR.

Another project funded by the C-ORD Program and the CMGA took a close look at whether it is a safe practice for mushroom growers to recycle wastewater.

Commercial mushroom production is an important horticultural industry. In 2001, Canadian growers produced 86 million kilograms of mushrooms at a farm gate value of $274 million.

Water that is used to wash down mushroom growing rooms is recycled to prepare composted growing media for subsequent crops. The wastewater contains valuable nutrients, but it also contains pesticides. “We needed to determine if pesticides in the wastewater are degraded by the composting process and if residues can accumulate in mushroom tissues,” said Dr. Danny Lee Rinker, Department of Plant Agriculture, University of Guelph.

Researchers at the University of Guelph conducted experiments to investigate the effects of the composting process by studying the influence of pH and temperature on the chemical and biological degradation of the pesticides.

“The composting process significantly degrades most pesticides from the recycled water and no pesticide residues accumulated in mushroom tissues,” said University of Guelph researcher Jianhui Yang.

“The research project concluded that wastewater from mushroom operations is safe to use in the production of compost that is used as a growing medium,” said Rinker.

“These are very worthwhile C-ORD Project projects that investigate opportunities to recycle water and nutrients in agriculture,” said Bob Bedggood, Chair of the Agricultural Adaptation Council. “The two projects address food safety, our dwindling water supply and nutrient and wastewater management.”

Now completed, the C-ORD Program was initiated in 1996 to improve the competitiveness of Ontario’s agri-food sector and increase its diversity and self-reliance through applied research and development. The C-ORD Program is funded by Agriculture and Agri-Food Canada and the Ontario Ministry of Agriculture and Food through an Agricultural Safety Net provision for research.

The Agricultural Adaptation Council is a non-profit coalition of 58 Ontario agricultural, agri-food and rural organizations that administers the C-ORD Program on behalf of the Ontario Agricultural Commodity Council.


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For more information contact:

Nadine Buitenhuis
Communications Coordinator
Agricultural Adaptation Council
Phone: 519-822-7554
Fax: 519-822-6248
Nadine's e-mail