Soils Field Day March 2019

This article originally appeared in the Olive Grower & Processor, our thanks to that magazine for permission to reproduce it here.

Also thanks to Marie and Jim for hosting our group at Olives from Broke.

The Hunter Olives Association (HOA) field day held in March saw growers learning about grove management quite literally from the ground up. The day was hosted by member Marie Kearns at her Olives from Broke property and focussed on how to “read” and care for soil.

HOA president Patrice Newell said the event was member-driven and well supported.

“Over the years many growers have suggested we do more work on the specifics of soil, appreciating that the health of a tree is founded in the soil in which it grows. I don’t think you can ever have too many conversations about soil, so we invited the Hunter Local Land Services (HLLS) to come and speak to us,” she said.

“Nearly 30 members, from original to very new, attended and all gained valuable skills in understanding and assessing the biology of soil.”

The workshop was run by HLLS sustainable agriculture extension officer Col Freeman, who described it as “the story of how soil works and the elements you need to make it work well”. “It’s about understanding the factors of soil health and how mostly they’re inter-related: whether you start with structure or nutrient availability or moisture retention, you end up having the same conversation,” he said.

“I used a tool called the Northern Rivers Soil Health Card for Perennial Horticulture. It uses very simple assessments using bits of stuff that people have in their shed to look at the most fundamental properties of soil health.

“It’s physical, biological and chemical, and looks at the biological processes that are going on in soil. It’s that biological activity that provides your soil with good structure, infiltration and moisture-holding capacity, and increased levels of nutrient exchange and availability. The benefits of these is that they then maximise the uptake of fertiliser amendments.”

The practical, hands-on session saw Freeman demonstrate simple tools to assess current soil health – like a storm water pipe infiltrometer – and provide information about ways to improve it.

“Most of it just came out in conversation; people raising issues they were having in their groves and then discussing possible solutions,” he said.

“For example, we dug a hole and had a look at it, and the discussion went from there. Hard compacted soil: what could you do? Rip? Would it go back to being compacted? Or could you use roots of inter-row grasses to open it up?
“Another thing that came up which is specific to growing olives was about the inter-row section and mulching under the trees. We looked at soil health in the rows and inter-rows, and in the inter-rows it was quite poor. Grasses had been mown regularly and low, so had small root systems, which meant that all the benefits of rainfall and organic matter and nutrient cycling were contained to that top level, and water was running off rather than soaking in.
“So I applied some pasture grazing theory to that, the central idea being that because there’s more biomass below than above the ground in a grass plant, the way to improve the soil is to allow the grass to grow tall, then to mow it off and let it grow it again.

“It’s also part of the weed solution: if you focus on growing more grass, you won’t have as much weed.
“That then led to a conversation about mulching under the trees. The landowner was purchasing mulch to spread, which is cost and work, so if you were growing your mulch and slashing it to the side, that would reduce your cost.”
Newell described the day as “casual and inspiring”, providing attendees with a number of key messages.
“Feedback was that Col was helping us understand the bigger importance of soil – in its carbon sequestration and its water holding capacity, other than producing an olive,” she said.

“We learned that biology and the health of soil lives on regardless of elemental inputs or the existence of certain elements, and that you can have a lot of elements and still have poor soil function.

“The massive heatwave we’ve just gone through here as shown us that you’ve got to get a grip on the changing circumstances, and that we need to help the core things like soil as much as we can. So everybody, as we were discussing soil and water infiltration, how many bugs were in the soil, was thinking about their own circumstances and will now use those tests to see how they can care better for their soil.

“Hopefully the key outcome will be having improved productivity in their grove. We obviously can’t answer that yet but a happy olive grower is an improved olive grower, and we all walked away pretty happy.”