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Down and dirty with soil health in WA

Research & Extension

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Managing and protecting soil health has been recognised as fundamentally important to Western Australia’s $11 billion-a-year agrifood industry in the recently released Western Australian Soil Health Strategy 2021-2031.  This will guide policy, R&D and on ground management to improve or sustain soil health into the future. 

Read the full strategy here. 

WA orchardists already have their eyes clearly focused on soil health. The recent Soil Your Undies challenge gave them the chance to test their soils in a fun and unusual way and share some results at the recent WA Future Orchards Orchard Walk. The challenge has been a part of the PIPS3 Program’s Improved Australian apple and pear orchard soil health and plant nutrition project (AP19006), led by the Tasmanian Institute of Agriculture. The Future Orchard Walk was conducted at the project’s regional demonstration site located at Manjimup and coordinated by Pomewest’s Susie Murphy-White.  

Here’s what growers discovered when they aired their ‘soiled laundry’ in the name of soil health.  

Jason Jarvis, Donnybrook

YTD Rainfall (10 November): 1039mm (Sept/Oct above average) 

Average temp Sep-Nov 2021: 1.5-26.9 degrees Celsius  

Soil temp at time of unearthing undies: 15.6-26.8 degrees Celsius  

“I think it was a good way to get people thinking about the soil and what’s happening in their orchard. Hopefully it provokes some thought and conversation.  

For us, it was just a confirmation that we are getting the microbial activity that we’re aiming for – all the undies buried in areas where we undertook our standard practice showed good results. We had one area that was under much more compost for the purpose of the experiment, and we found that had slightly less breakdown of the undies. We attribute that to the fact that the microbes had more carbon in the soil to break down, and that reduced the breakdown of the undies as a result. But that wasn’t our usual rate of compost.  

One thing the experiment doesn’t show is the ratio of fungi, bacteria and macropods that are breaking down the undies. High fungi to bacteria ratios are the preference for tree crops, but we can follow this up with other tests to determine that.”  

Mark & James Scott, Nannup

YTD Rainfall (10 November): 961.6mm (Sept/Oct close to average) 

Average temp Sep-Nov 2021: 1.6-27.6 degrees Celsius  

Under tree row bare herbicide strip vs. an inter-row grassed strip

“It was a really interesting result, but it gave us more questions. For example, the most eaten undies in our test were from the bare herbicide strip, which was the opposite of what we would expect. You wouldn’t think there’d be a lot of microbial activity, and as I understand it cotton is relatively hard organic matter to break down. A lot of something is definitely happening in there.   

We’d be really interested to know what the primary indicators for ‘good soil’ are so we can test and find out whether what’s happening under there is a sign of healthy soil.” 

Bec Whittaker, Ladycroft, Manjimup

Rainfall YTD (10 November): 1170.2mm (Sept/Oct close to average) 

Average temp Sep-Nov 2021: 2.4-26.1 degrees Celsius  

Soil temp at time of unearthing undies: 16.3-25 degrees Celsius  

“I thought we would have had more microbial action under the young trees, but there were plenty of worms and other insects, so things are definitely happening the way they should be. It’s possibly because we didn’t have the heat in the soil this season that would encourage more microbial activity. We’re adding bacillus strain QST713 to the soils in the new plantings, so hopefully that gets something sparking. 

The herbicide strip under the established 26-year-old trees showed more activity. Those trees look super healthy, and we are careful with our herbicide use, so it’s not a big surprise. Next year we’ll test the soil health under the young trees and inter-row with the cotton undies and see what results we get then.”  

John Hearman, Donnybrook

YTD Rainfall (10 November): 1039mm (Sept/Oct above average) 

Average temp Sep-Nov 2021: 1.5-26.9 degrees Celsius  

Soil temp at time of unearthing undies: 26.8-15.6 degrees Celsius  

“It was interesting. We buried two pairs, one under some young trees where we had done manure mulching before planting and put down straw afterwards, and another under some ten-year-old apples where we hadn’t done as much, just mow and throw and the odd crop of rye grass. 

Where I’d gone to more effort with the soil under the young trees, there was basically nothing left of the undies. But I was really surprised by how eaten away the undies were under the older trees where I hadn’t really done anything, so overall the soil isn’t too bad.  

There are a lot of variables, but I’ll probably incorporate mulch whenever I’m planting a new orchard or replanting, as it seems that this does help.”  

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