Thursday, November 30, 2023

More than hot air to ozone crop treatment

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A crop treatment with zero residue and a limitless raw material supply seems too good to be true, but a Bay of Plenty company is about to trial just that.
John Clements, left, and Allan Noble of HortO3 say that tech such as ozone treatment needs to be adopted sooner rather than later to keep ahead of impending changes in export markets’ spray residue rules.
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A Bay of Plenty company is hoping to win over more growers with a crop treatment technology its director says will help New Zealand adapt to market demands for significantly lower crop chemical residues.

John Clements of HortO3 says he is concerned NZ grower groups and industry face the pressure of having to meet tighter European Union Green Deal conditions by 2030, but are going to hit the end of this decade underprepared for the deal’s demands.

“What it includes is an expectation that by 2030 chemical residue levels will be reduced by 50%. In addition, many of the chemicals we currently used will not be permitted, and the approval process means we are risking having few options with only seven years to run.”
He and longtime Bay of Plenty market gardener Allan Noble established HortO3 after seeing overseas operators opt for ozone as a treatment alternative.

Their technology focuses on using ozone-treated water applied to crops and soils as a sanitising, disinfecting and treatment agent, replacing some conventional spray treatments.

The tech is based on a sprayer-mounted ozone generating unit that takes air from the atmosphere and concentrates the oxygen to 95% purity. Through electrical discharges it converts oxygen (O2) to ozone (O3). 

This is then injected into a water tank and sprayed on as a treatment.

Extensive research papers into ozone highlight the chemical’s ability to be an economic and sustainable replacement for synthetic crop chemicals, with zero residue and a limitless raw material supply in the form of the atmosphere.

Uses overseas include as a treatment agent for poultry drinking water, washing fruit post-harvest, and treating fungicides in seedling soil beds. Studies have shown it to be as effective as chlorine, a common treatment agent used for sanitising. 

As an agent chlorine will become problematic under the new EU rules due to the chlorate residuals it leaves on produce. The Green Deal requires these be significantly reduced.

Ozone gained a flurry of attention over a decade ago here as kiwifruit growers desperately searched for treatment options to reduce the impact of the Psa outbreak.

At present Clements is running a trial on the use of ozone in avocados. 

Athenree grower Russell Whiteman has split his 4ha orchard in half, to treat one half with ozone spray and the other with conventional sprays.

Whiteman says the treatment appeals because he is wanting to reduce his use of sprays, and he is aware of the success overseas in using it on the likes of olive crops.

“I am finding it is doing a good job controlling thrip, mite and leaf roller and seems to be helping with fungal levels also,” he says.

In April he intends to analyse the two halves of the orchard for differences in fruit and leaf composition.

Professor Nigel French of Massey University and director of the New Zealand Food Safety Science and Research Centre, says ozone is a proven water treatment agent and is used in greenhouse applications for removing pathogens.  

Outbreaks of E.coli-type diseases in leafy greens in Europe and United States have accelerated its uptake as an effective tool against pathogens, he said.

“It is regarded as being well trialled.”
Ozone has also proven to be an effective sanitiser in the dairy processing sector. 

The International Journal of Dairy Technology has reported it has also been used to successfully treat mastitis with an efficacy rate comparable to antibiotics.

A Plant and Animal Health NZ spokesperson says the organisation supports ozone as another tool in farmers’ toolbox, but notes it has limitations, including cost-benefit issues.

It comes at a higher capital cost and involves double handling, but is useful when being applied to treat mites. It cannot be used for biosecurity decontamination because it does not target every pest and disease. 

However, it does not require Environmental Protection Authority approval and is more environmentally friendly than the likes of methyl bromide.

Allan Noble, an ex-HortNZ board member, says he was drawn to try ozone in the wake of the profile it gained during the Psa outbreak and has been treating his plants with it for nine years.

“We get far healthier seedlings by spraying them with ozone-treated water, and yields are up. 

“Our broccoli grew that much more we had to raise the height on our harvesting tractor,” he says. 

He claims a 15% gain in his crop’s nutritional density from the application.

HortO3 is about to also embark on a trial in Nelson treating boysenberries with ozone to reduce botrytis fungal infection, something it is also used to treat Italian grapes for.

Clements is careful to qualify that ozone is not a silver bullet solution for NZ growers and farmers. 

However, he says he is concerned NZ is on the precipice of a global shift in produce production where not only are consumers demanding lower chemical residuals in their produce, but other countries are moving faster to meet those needs.

“Europe is adopting ozone at scale, and it is something we need to get on top of quickly. The year 2030 means growers have to start now on solutions, to give themselves time to invest and adopt the technology.”

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