Organic Greenhouse Tomatoes: Pick of the Crop

Organic Agriculture Centre of Canada

The Canadian greenhouse vegetable industry is a vital and growing facet of agriculture in this country, with a farm value worth 2.3 billion in 2007, the last year for which statistics are readily available. Canadians enjoy greenhouse-grown tomatoes, cucumbers, peppers, herbs, and other produce year-round from greenhouses operations located throughout the country.

Many of these crops are raised using conventional growing systems. However, some producers, seeing potential for lucrative niche marketing as well as ways to be even better environmental stewards, are turning to organic production of greenhouse crops, particularly tomatoes, the most commonly-grown greenhouse crop.

Researchers participating in Canada’s Organic Science Cluster (OSC) are working on developing a more environmentally friendly, energy- and cost-efficient organic greenhouse growing system for growing organic tomatoes.

The team of researchers includes scientists from Agriculture and Agri-Food Canada centres in Québec and British Columbia, professors and research scientists from Université Laval, McGill and Université de Montreal, as well as collaborating researchers in Israel and Sweden and a host of industry partners. 

Their ambitious three-year project has a number of objectives. As with any agricultural operation, greenhouse producers are always looking for ways to achieve more efficient use of irrigation and fertilization systems. They are keen to produce larger crop yields of tasty, nutritious tomatoes, while minimizing their environmental footprint by a reduction in nutrient effluent, or runoff, into surrounding soil and water.

The OSC researchers are studying methods of optimizing nutrient input, so that crops get the best benefit out of the fertilizers applied. They are comparing conventional and organic systems: growing conventional plants treated with nutrient solutions used in conventional greenhouse operations, and organic plants cultured in certified growing medium and fertilized under an organic regimen.

Many producers recycle their nutrient solutions, both to save on both water and fertilizer use, and to reduce the environmental footprint. To do this, they must disinfect the nutrient solution before reusing it. The research team will collect the nutrient solution used in their experiments and recirculate it through their tomato crops, either without treatment or by filtration through wetlands.

When crops are produced in greenhouses using soil-based growing systems, whether organic or conventional in nature, there can be problems with nutrient emission or runoff into surrounding groundwater. Greenhouse producers are concerned about such runoff, and look for various ways to reduce or eliminate the potential for problems. Using wild plants or biochar as part of a filtration system can be an environmentally friendly and approved method for coping with nutrient emission.

Some types of plants act as natural filtration systems, removing nutrients, various pathogens and other potentially harmful elements from groundwater and preventing runoff into waterways. Cattails (Typha latifolia), certain species of ferns, the common reed (Phragmites australis), and other plants have been successfully used in phytoremediation, a process that uses plants to help return an ecosystem to a more natural state.

The OSC researchers are using these species as well as the common blue flag iris (Iris versicolor) in controlled trials to assess their efficacy in removing nutrients from wetlands. These plants all spread by underground stems or rhizomes, meaning they can relatively quickly be introduced to an area needing protection or recovery from nutrient runoff.

Those who keep goldfish or tropical fish know the value of charcoal filters in reducing impurities in aquariums. Recent years has seen a growing interest in the use of biochar—charcoal made from burning biomass such as woodchips, tree bark, and even animal manure—as a soil amendment or as an environmental management tool. Some of the work being done by the OSC team includes using biochar in filtration tests to help reduce impurities and pathogens. They’re also evaluating the use of biochar as an amendment to organic soils to help improve fruit quality as well as disease and pest tolerance.

Producers considering making a switch from conventional to organic tomato production need to know the overhead costs, if any, for making a switch, and how that can affect their profit margin.  As part of their work, the scientists will compare their proposed organic growing system with a conventional growing system, in terms of efficiency as well as cost effectiveness. Ultimately, they hope to provide growers with solutions that will be both environmentally friendly and cost-effective in the quest to provide Canadians with organic, locally-grown produce.

This article was written by Jodi DeLong on behalf of the OACC with funding provided by Canada’s Organic Science Cluster (a part of the Canadian Agri-Science Clusters Initiative of Agriculture and Agri-Food Canada's Growing Forward Policy Framework).  The Organic Science Cluster is a collaborative effort led jointly by the OACC, the Organic Federation of Canada and industry partners. For more information: or 902-893-7256.

Posted June 2011