GRDC Research Updates unveil tomorrow's tools and technologies – Goondiwindi
GroundCover™ Issue: 122 | 02 May 2016
GRDC Research Updates are a hothouse of new projects, debate, knowledge-sharing, ready-to-go innovations and a sneak peek at what is on the horizon for our cropping industry. For this issue of Ground Cover crossed the country to cover Updates in Adelaide, Wagga Wagga, Goondiwindi, Auburn, Perth and Yuna.
Self-defence soils a disease-control option
Dr Nikki Seymour from the Queensland Department of Agriculture and Fisheries (DAF) discussed the potential for soils to biologically suppress root lesion nematodes (RLN) at the Grains Research Update in Goondiwindi, Queensland.
Disease suppression is defined as a soil’s ability to reduce the incidence or severity of crop disease. Driving this disease suppression is a diversity of soil microorganisms, the activity of which is influenced by on-farm practices, such as the addition of organic matter to soil.
Dr Seymour said GRDC-funded trials found that biological suppression occurred in most of the 130 soils tested at 24 sites in northern New South Wales and southern Queensland.
“Biological suppression occurs in most soils we tested from the northern grain-growing region, showing that populations of the RLN Pratylenchus thornei are being reduced by parasites and predators in the soil,” Dr Seymour said.
The catch is that these naturally occurring biological controls appear to be low in number, so research is needed to find ways to increase their presence or effectiveness.
Dr Seymour said the trials, over four years, have identified a variety of beneficial soil organisms. These include predatory nematodes, which were found in 77 per cent of soils, nematode-trapping fungi observed in 42 per cent of soils and a bacterial parasite found in 25 per cent of soils.
She said the discovery of the bacterial parasite from the Pasteuria genus is significant because this organism had not previously been observed on P. thornei in Australian soils.“This bacterium has the potential to infest and kill RLN, but populations appear too low to be having any great impact.”
RLN were infected with Pasteuria in just six per cent of soils where both the pathogen and parasite were detected.
“More study is required to better understand the life cycle and ecology of this highly specialised parasite,” she said.
Of the four species of nematode-trapping fungi found in 26 soils, researchers have developed a method for extracting DNA from the soil to distinguish between these different species and their influence on disease suppression.
She said a fungal endophyte (Fusarium nygamai) collected from wheat roots on a property near North Star, NSW, also showed biocontrol potential, but further research is required. In a glasshouse experiment examining soil in pots, this endophytic fungus reduced P. thornei multiplication by 40 per cent.
“Overseas work has shown that the presence of endophytic strains of Fusarium in roots enhance a plant’s capacity to defend itself from nematode attack,” she said.
Dr Seymour said the research highlighted two on-farm management practices that can help lift a soil’s capacity to biologically suppress RLN.
Specifically, zero-tillage and stubble retention were found to enhance disease suppression, she said.
“Without these practices, we estimate that RLN multiplication would be significantly greater, especially in topsoils, resulting in much greater losses in the productivity of susceptible crops.”
As a measure of the importance of these on-farm control options, RLN (P. thornei and P. neglectus) are estimated to cost Australian grain growers more than $250 million per year.
Dr Seymour said zero-tillage and stubble retention helped reduce RLN pressure because these management practices affect the top 10 centimetres of the soil profile, where biological suppression is most active.
The research looking at disease suppression at different depths showed it was most effective from 0 to 15cm, compared with the 30 to 45cm soil layer.
The research further found that RLN suppression is influenced by the addition of soil organic matter, such as stubble, and continuous cropping.
In the first year of the trials, incorporating stubble in the topsoil at a high rate (20 tonnes per hectare) reduced RLN pressure and lifted beneficial nematode populations, Dr Seymour said.
However, these effects subsided in subsequent years of the trials.
Continuous cropping was found to improve overall soil biology, lifting RLN suppression, particularly in topsoil, compared with soils on fallow country.
More information:Nikki Seymour,
07 4639 8837,
GRDC Research Updates:
GRDC Project Code DAQ00164
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