Australia
June 17, 2014
By GRDC Northern Region Panellist Will Martel
Soil biology, soil nutrition and soil structure are essential building blocks for the production of healthy and profitable crops.
In the past there has been significant research focussed on soil nutrition and structure, however the Grains Research and Development Corporation (GRDC) is recognising the fundamental importance of soil biology with investment in three key research areas – disease suppressive soils, nutrient management and soil quality monitoring.
As part of the disease suppressive soils work, over 130 soils from the northern region were surveyed for the presence of natural enemies to Root Lesion Nematodes (RLN).
Information is currently being compiled on the soil characteristics and crop management histories to understand which soils and management will better support these organisms.
Preliminary results have shown the addition of a fungal endophyte has significantly reduced RLN P. thornei multiplication however more work is needed to confirm this biocontrol.
Additionally, a new glasshouse based bioassay method to quantify the Disease Suppression Potential (DSP) has been standardised for soils from the northern region. This DSP bioassay has also been used successfully to identify disease suppression in South Australia and Western Australia.
It is finding that management practices which increase carbon inputs into the soil, such as stubble retention, will improve DSP. However they need to be combined with other management practices centred on crop rotation to successfully reduce pathogen inoculum levels and therefore soil borne disease impacts.
In the area of nutrient management, estimates of the nitrogen fixation capability of Free Living Nitrogen (FLN) fixing bacteria has been found to range from <0.2 to 2.9 kg N/ha/day.
Carbon availability is a critical factor in FLN fixation and the removal of stubble through burning or grazing has a negative impact on amount of N fixed. The findings suggested that agronomically significant amounts of FLN fixation are produced in Australian soils and they can be manipulated.
Strategic tillage used to manage weeds, disease and improve stubble handling may also provide additional benefits when done after a legume crop. These include increasing the number of soil microbes able to process N rich organic matter and reducing N loss by disrupting the microbial process associated with leaching and denitrification.
Other key findings within the nutrient management work include that minimising fertiliser application at sowing will enhance microbial processing of soil organic N and that molecular tools may be used to assess the mineralisation potential in a wide range of soils.
The final theme area of GRDC’s soil biology investment – soil quality monitoring – has characterised FLN populations and identified the key environmental and management influences (seasonal, rainfall, soil type, tillage and rotation).
DNA tests have been developed that can detect more than 80% of the FLN present in Australia. Once this has been regionally validated it will allow growers to monitor FLN as indicator of biological soil health.
The GRDC is working hard to ensure these soil biology research results are converted to management practices that farmers can adopt making them more profitable.
For more detailed information on the GRDC’s soil biology research initiative, please visit www.grdc.com.au/soilbiology.
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