23/08/2021

Rethink your orchard and vineyard floor

Published on Stuff.co.nz by Gerhard Uys

Orchards traditionally have zones beneath the trees that are commonly kept free from weeds and other unwanted growth through herbicide application or by mechanical means.

This is seen as necessary as weeds can host pests and diseases, and compete with trees for soil nutrition and moisture.

Such an orchard floor also gives growers a solid platform to work on. Most orchard floors have a weed-free zone directly beneath trees, with a grass section (called sward) between tree rows.

Orchard
Orchard
Orchard
Orchard

John van der Linden, technology specialist at Corteva, said these kinds of orchard floors needed continual management.

The current approaches could also be costly and not friendly to the environment.

“Most growers look at the orchard floor as an afterthought and never ask themselves what it could do for them. If the entire orchard floor becomes a living sward, then it can create a hands-off system with less chemical and mechanical intervention,” van der Linden said.

“It will also encourage predator presence and as a result help control pests like brown apple moth. It will create deep, more resilient root systems, help manage tree vigour and sequester carbon.

John van der linden
John van der Linden technology specialist at Corteva, supports the creation of "hands-off" orchard floors.
John van der linden
John van der Linden technology specialist at Corteva, supports the creation of "hands-off" orchard floors.

“My vision is a completely hands-off approach that doesn't need to be mowed or controlled with herbicides.”

Van der Linden said growers were not addressing the real issues with current methods of management.

“We tend to be too focussed on killing things or using interventions when we really need to think about how we can eliminate the problem,” he said.

“To control weeds, we tend to use herbicides. If you don't want to use herbicides, then you use mechanical methods. But mechanical methods are half the speed of herbicides, burn fossil fuels and need four or five [tractor] runs to have the same effect as herbicides.

“Mechanical methods can also cause root damage and ironically help create a nice seedbed for weed germination,” he said.

Traditionally, orchard floors are sprayed to keep weeds at bay, and may have sections of open soil.
Traditionally, orchard floors are sprayed to keep weeds at bay, and may have sections of open soil.

At a recent pip-fruit workshop, van der Linden contrasted his idea of a hands-off approach for the orchard floor with current methods used in a vineyard.

He said most floor-management methods required seven to nine tractor passes for mowing or mulching, and two to five passes for weed control.

“Instead of traditional orchard-floor management methods, why not choose to plant the floor with biological plant mixes that eliminate the need for weed control, do not compete as aggressively for resources, host beneficial insects and improve the soil to increase production and quality.

“There’s no rule book, but we have chosen to have a dead zone under trees, then an inter-row strip of grass and then another dead zone. And it all needs to be maintained,” van der Linden said.

He added that saving on intensive manual labour could also be a motivator to rethink orchard floor and other orchard management methods.

“For example, grapevines need disbudding two to three times per year. I solved the problem in my own vineyard by simply wrapping trunks with rubb“One could repurpose a waste steam or use a biodegradable rubber for wrapping purposes, but instead we currently continue to use labour to carry out costly tasks like disbudding.

“Given that there is a skilled labour shortage, why not eliminate the problem rather than creating a mechanical method or a spray that does this task?”

He said growers often highlighted legitimate reasons for not trying new approaches like living orchard floors, but he said they were often good at looking at what couldn’t happen, instead of what could.

He said growers anticipated the potential problems with a living orchard floor, but they could be largely overcome with wise plant selection.

Choosing biological plant mixes could be tricky as not many seed companies currently had commercially available options. However, he said grasses like Poa imbecilla (currently the subject of a trial by PGG Wrightson) and plants like Leptinella squalida (available through NoMow) were commercially available and good options to start with as ground cover.

At first glance Leptinella squalida can look like a patch of dead soil, but in this floor it covers an entire strip.
At first glance Leptinella squalida can look like a patch of dead soil, but in this floor it covers an entire strip.

Leander Archer, horticultural consultant at AgFirst, said Kiwi growers were world leaders in horticulture and should continually analyse their methods and consider means of improvement.

The pip-fruit industry recently hosted a workshop on managing the orchard floor without the use of glyphosate, and Archer said more markets were demanding growers use less chemicals and some markets were banning chemicals like glyphosate outright.

“I hope if such a ban is placed in New Zealand it is backed by science, and that the industry won’t respond by simply using another herbicide that may be a step backwards for soil health,” she said.

Archer agreed with van der Linden that “killing weeds” should not be the only consideration when managing orchard floors or herbicide strips below trees in an orchard.

But where van der Linden preferred creating a living floor, Archer proposed the use of mulch as an improvement over bare soil.

Leander Archer, horticultural consultant at AgFirst.
Leander Archer, horticultural consultant at AgFirst.

“The key is that mulch should be a by-product of another industry. This works financially, but also contributes to circular use of resources,” Archer said.

“Woodchips as forestry by-products and cardboard from recycling are methods that have been tested overseas. Mulch options from by-products will likely be region-specific because of this, and because regionally orchards require different things from the orchard floor.”

The use of mulch and living floors could suit different stages of orchard growth, Archer said.

“Small trials need to be done in different regions to see how options compete with tree or vine growth.

“The challenge with a lot of research on living orchard floors is that trials are often funded for short periods and cover only the first years of tree growth.

“Young trees have undeveloped, shallow root systems and are often susceptible to competition at this stage. “One could use mulch in the first four years of growth and then progress to a living floor cover when trees have established themselves and are less susceptible to competition, or at which point you might want some competition for tree vigour control.

Mulch can help protect the roots of young plants.
Mulch can help protect the roots of young plants.

A living floor can be home to beneficial predatory insects. It can aid moisture conservation, protect soil structure, add organic matter and improve soil fertility. It can potentially be used to increase or decrease vigour as another tool in the grower toolbox.

“It could be an improvement for practical management, as well as make sure growers are ahead of market requests to use as little chemicals as needed.”

Archer said growers often cited the need for a clean work area under trees for health and safety purposes, or open spaces under trees to see if fruit fell during picking.

She said growers needed to see a demonstration of a new system in a commercial orchard that used new ways of thinking practically, so they could be convinced of its effectiveness.

“Growers have a lot on their plate and are expected to be experts in everything. It is becoming hard for owner-operator growers to know all aspects of the business, and they look for a visible, practical alternative.

“So to support positive change, we need to demonstrate that living floors and mulches can be practical for their businesses,” Archer said.

“Better soil structure and organic matter will improve soils and orchards over the long term, but to convince growers to buy into new ways of thinking they need to be shown some good local numbers on this, and also that this works for the shorter-term practicality too.

“The industry needs innovative growers that are willing to try new things on their orchards, or host trials.”