The Soil Wealth and Integrated Crop Protection (ICP) project works with growers nationally to put soil management and plant health research into practice. This column provides an update on a successful trial on mixed species cover crops in Tasmania. Soil Wealth ICP Phase 2 (VG16078) is a strategic levy investment under the Hort Innovation Vegetable Fund.

Since May 2019, Yuri Wolfert and his family have hosted a cover crop demonstration site in Kindred, north-west Tasmania, supported by Soil First Tasmania, Landcare Tasmania and followed by the team from Soil Wealth and Integrated Crop Protection. The trial aimed to demonstrate the effectiveness of using mixed species cover crops in cropping rotations and find out if they could improve growing conditions and the profitability for potato crops in particular, and potentially other vegetable crops.

The Kindred trial was unique as it consisted of one field with seven large plots for different cover crop mixes. These included:

• Plot 1: Lupins and grass.
• Plot 2: Lupins and oats.
• Plot 3: Lupins, grass and phacelia.
• Plot 4: Lupins, grass, phacelia, barely and tic beans.
• Plot 5: Lupins, grass and tic beans.
• Plot 6: Lupins, grass and barley.
• Plot 7: Lupins and barley.

After seeing other cover crop trials in the local area, Yuri decided to host this trial to fast-track his initial thoughts for using cover crops on-farm.

“We wanted to improve harvestability and the general soil health for all of our crops, because there are flow-on effects if you treat the paddock right,” he explained.

“Soil First Tasmania got the ball rolling and it meant we could do the trial in one field instead of many years of trials. It was set out fairly well with most plots being one hectare, which allowed for any variation in the field to be evened out and better comparisons within each plot.”

The cover crops were sown in May 2019, while laboratory soil testing and a field day was undertaken in August. The cover crops were incorporated (mostly mulched) in October before the potatoes were planted.

Yuri Wolfert.

Key findings

The cover crops with the most diverse mixture of species were the best performing plots in the trial. In particular, plot 3 (lupin, grass and phacelia) and plot 4 (lupin, grass, phacelia, barley and tic beans) produced the best soil that Yuri has seen on his property.

“The holding water in the terminated biomass improved, and at the same time the workability of the ground improved. We spent less money on fertiliser, and a lot less time in the paddock for ground preparation – that was an added benefit,” Yuri said.

“Our observations from early on, before groundwork, was that the mixed crop underneath the ground was drier than our previous mixes, which meant that we could get onto our soil earlier. The soil was drier, which may have been our dry spring, but it was also better at holding water, which was a win-win.”

It wasn’t all smooth sailing however, particularly when the mulcher broke due to the amount of biomass in the field.

Despite this minor setback, Yuri was happy with the performance of the trial and has since applied the learnings from this trial and others to help tailor different cover crop mixes to each crop on the farm.

“I’ve used more species in my next cover crop mix to try to achieve a more balanced nutrient base. I will be working in a more challenging paddock from a soil structure perspective, which has made me put other deeper rooting plants in the mix,” he said.

“I’m also going to do a small trial before planting Brussels sprouts in a poorer patch of paddock and use a very low amount of nitrogen fixing plants and a lot of deep and fibrous rooting plants, but no brassicas.”

Yuri is happy to host future trials, and has some advice for other growers who may be interested in starting their own cover crop trial.

“Find out what you want to achieve in terms of nutrient base and soil structure and work back from that to decide what cover crop species are going to achieve those goals for you,” he said.

“If you can find a way to improve your lifestyle and your bottom line as well, that’s a bonus.”

Mixed cover crop trial in Kindred, north-west Tasmania.

Find out more

To find out more on this trial, click here or the Soil First Tasmania Facebook page.

For more information, please contact project leaders Dr Gordon Rogers on 02 8627 1040 or gordon@ahr.com.au or Dr Anne-Maree Boland on 03 9882 2670 or anne-mareeb@rmcg.com.au.

This project has been funded by Hort Innovation using the vegetable research and development levy and contributions from the Australian Government. This cover crop trial was partly funded by Landcare Tasmania and the Tasmanian Landcare Fund.

Project Number: VG16078

This article first appeared in the winter 2020 edition of  Vegetables Australia. Click here to read the full publication.