With the right approach, organic greenhouse production can be a success
By Luke Edwards
The challenge Freeman Herbs received in the early 2000s was, in essence, to do something new by doing something old.
American grocer and retailer Kroger put out the challenge for organically grown greenhouse produce.
“Organic is the traditional way of farming,” said Marco de Leonardis, research and development manager at Freeman Herbs. He was one of three speakers at a morning session on organic greenhouse at last month’s Canadian Greenhouse Conference.
For thousands of years farmers relied on what were essentially organic practices to grow their crops, de Leonardis said. That didn’t change until more recently as new chemicals and methods were developed over the past century.
The return to organic, in a greenhouse setting, presents challenges but is doable, de Leonardis and other speakers said. But it takes some planning to ensure the greenhouse crops are productive and healthy, and don’t fall prey to the diseases that can wreak havoc on a greenhouse.
“To have success with biological control, it’s important to be proactive, not reactive,” de Leonardis said.
Over the years, Freeman Herbs has had to contend with various disease pressures, including blights and aphids. While disease resistant varieties were available, de Leonardis said they didn’t live up to the quality standards Freeman Herbs set.
He did find success in the use of hydrogen peroxide, which stopped the spread of a blight that got into the greenhouse in 2013. The application had other benefits, too, keeping mould at bay and improving rooting.
It’s now part of the regular regime, where they mix in a small amount with the water system, applying a bit of peroxide every time they water.
Laval’s Martine Dorais shared some of her research on organic methods to improve growing media and fertilization in greenhouses. A growing media that introduces the right mixture of water and oxygen to promote a healthy microbiome is key to ensuring proper nitrogen cycling.
Some options for fertilizer include anaerobic digestion of tomato leaves and frass from black soldier fly larvae. Both can help replace existing fertilizers, and frass may also reduce disease pressure, her research has found.
Consultant Norm Hansen also spoke at the session, sharing some information on recent updates to the Canadian Organic Standards. One of the changes important for greenhouse growers, he said, is a clarification on soluble light usage, with a 20 per cent limit.
While thousands of hours of work go into the standards and reviews that are done every five years, Hansen said growers should think of it as just a baseline.
“The standard is just the minimum we do to be organic,” he said.
He compared the soil to a rainforest, where “we grow a jungle of creatures.” And if growers are doing it right, disease pressure should be kept to a minimum.
“We can make the change and switch to organics,” he said, adding yields can be strong with the right practices.
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