Cover crops more beneficial than herbicides, reveals Australian research
Australian vineyards could soon look very different if the findings of a recent study are embraced by the wine industry.
A four year study spearheaded by University of Adelaide agronomist Chris Penfold has revealed how beneficial cover crops below the vines are, supporting the soil and suppressing weed growth, rather than as is the current way of doing things, killing the weeds with herbicide and leaving the remaining ground bare.
Four sites in four different Australian regions were studied, and it was found that pasture legume and grass cover crops generated yields and gross margins equivalent to or greater than the herbicide controls, while also helping to repair damaged soil.
In the Barossa, for example, the herbicide control treatment generated a lower gross margin than straw mulch, or mixed with safeguard ryegreass, the latter generating increases in gross margins of $1600 to $1700 per hectare annually above the $5000 per hectare cost of the herbicide control treatment.
Penfold cautioned that such increases would not necessarily be experienced across all soil types, but he regards it as a good outcome, “provding an option for growers to consider where their soil is likely to be similary responsive.”
Similarly impressive results were yielded at the Eden Valley and Langhorne Creek sites, but Riverland was a different matter.
“You drive into the Riverland and you don’t see weeds growing up into the canopy because they have very good control mechanisms to stop that happening," said Penfold. "When you take that away like we did you do find yourself shocked at just how aggressive weeds can be given the warmth and the water supply and the nutrition being pumped in through the drippers. It’s a perfect storm.”
However, there is growing acceptance that this is an avenue that should be pursued, as growers are starting to see the impact of decades of using herbicides and drip irrigation that puts large amounts of water into the same spots with the Riverland starting to have issues with poor infiltration even with their light sandy soils.
‘While there is still research to be done, and in fact we are still completing the detailed soil biology analysis for two sites from this project, growers and regions can start acting now,” said Penfold.
The key is to get the right mix of plants, he explained, and making an active decision on adding a species that is going to be of benefit to the vines. The wrong species could result in an adverse outcome, with loss of productivity, and Penfold advised winemakers to seek the advice of a local agronomist as to which species are best suited to local conditions.
This year Penfold is starting to see the practices adopted, with some growers dipping their toe in the water with small trials, while others are embracing the concept with many hectares being planted.