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Tasmanian Institute of Agriculture

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Published: 4 Oct 2018

Bernard Walker

One of the world’s longest running cover crop research trials will be open for inspection at the Tasmanian Institute of Agriculture’s (TIA) Forthside Vegetable Research Facility Open Day on Wednesday 10 October.

“The long-term cover crop research trial, known as Paddock 14, provides a unique time capsule of cropping history over 14 years,” TIA soil scientist Dr Richard Doyle said.  

“The site gives us an incredibly valuable tool to look at long-term soil health under different cover crops.  It is one of only a few in the world operating over such a time span and allows us to measure true indicators of sustainability that you just don’t see in the short term.”

Dr Doyle said ‘Paddock 14’ consists of 12 plots that are sown each autumn with either annual ryegrass, the bio-fumigant Caliente mustard, or left as fallow.  In spring and summer, a commercial crop is planted across the whole site  which has previously included potatoes, peas, poppies, barley, onions, broccoli and carrots.

“Tasmania’s processing potato industry and retired TIA scientist Dr Leigh Sparrow showed great foresight in establishing this site in 2006. Their vision was to better manage crop rotation times, measure changes in soil health under cover crops and reduce soil pathogens that cause powdery scab,” Dr Doyle said.

“There is good evidence that cover crops can be hugely beneficial to soil structure, fertility and preventing erosion, however their role in suppressing plant disease and nurturing healthy soil microbial populations is less well understood.”

TIA PhD candidate Bernard Walker is capitalising on the long history of this site to delve into a microbial world that he describes as ‘somewhat woolly’.  

“Soil contains some of the greatest biodiversity on the planet. A key part of my study is tracking how the soil microbial community responds to cover crops, particularly focusing on the time after incorporation,” Mr Walker said.

“What makes a ‘good’ soil microbe population and how to measure it is a relatively new and imperfect science. The fact that some microbes like to share their DNA across species can make it particularly tricky to classify and measure them.

“I will be drilling down to the detail of what makes a soil microbial community tick and taking a step back to look at the big picture of the whole system and crop productivity.”

Mr Walker said that whilst Paddock 14 represents a great model for North-West Tasmania’s Red Ferrosol soils even greater benefits may be realised on other soil types.  

“Typically Red Ferrosols are pretty resilient and that is why we see most of our vegetable production on these soils.  It is the trickier soil types, particularly erosion and compaction prone soils, where cover crops may really come into their own,” he said.

Another question being posed by Mr Walker’s study is ‘do biofumigants perform well under Tasmania’s relatively cool field conditions?’.  Mr Walker said currently there is limited hard science specific to Tasmania’s environment and soils.  

Paddock 14 will be open for inspection at the upcoming Forthside Vegetable Research Facility Open Day, including a demonstration of biofumigant incorporation.  TIA’s potato soil health team will be on hand to take you on the 14-year journey through the history of this site and the benefits now being realised from understanding the long-term effects on soil borne pathogens and soil sustainability.

The Open Day will be held on Wednesday 10 October from 10am to 6pm at 124 Forthside Road, Forth, and will conclude with a spit roast dinner.  For more information and to RSVP, please contact Leonie White on

This article appeared in the Advocate and Examiner newspapers on 4 October 2018.