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Australia - Quick check-up on cropping soil health on the way


Australia
November 26, 2014

Through a GRDC-funded Soil Biology Initiative project, Dr Katherine Linsell of SARDI and her team of researchers have developed a suite of DNA tests that can detect and quantify free-living nematode groups in cropping soils. Photo SARDI

A new set of tests to measure soil health is being developed to enable grain growers to better plan and manage their cropping programs.

Research funded by the Grains Research and Development Corporation (GRDC) through its Soil Biology Initiative II is aiming to produce a testing system which uses free-living nematodes as an indicator of a soil’s health.

South Australian Research and Development Institute (SARDI) researchers have developed a suite of DNA tests that can detect and quantify the major free-living nematode groups in Australian cereal-growing soils.

These nematode DNA tests will ultimately become part of SARDI’s PreDicta B® DNA-based soil testing service for growers and agronomists.

The PreDicta B service currently offers tests to identify which soil-borne pathogens (both fungal and nematode) pose a significant risk to broadacre crops in southern Australia prior to seeding. Grain producers currently access PreDicta B via agronomists accredited by SARDI to interpret the results and provide advice on management options to reduce the risk of yield loss.

“PreDicta B measures the pathogen level DNA and uses that along with the environmental conditions, farming management practices and the susceptibility of the crop, to predict disease,” says SARDI senior research officer Katherine Linsell.

“We want to do the same thing with this new test. By measuring the free-living nematode community DNA levels and combining that information with environmental factors and farming management practices, we will be able to measure and monitor soil health.

“Nematodes can act as indicators of the soil microbial community to give us a snapshot of the degree of the soil’s structure and enrichment. Most growers know that nematodes are important pests of cereal crops, but are probably not aware that soils also contain non-parasitic nematodes.

“These are known as free-living nematodes and they provide a wealth of information on a soil’s biological status and are therefore useful indicators of soil health,” said Dr Linsell, who spoke about the new development at recent GRDC grains research Updates in the southern cropping region.

A ‘healthy soil’ that is enriched and well-structured will have an abundant and diverse range of free-living nematodes with a good balance between bacterial and fungal feeders and will also contain omnivorous and predatory nematodes, according to Dr Linsell.

“But the problem with using nematodes as soil health indicators is that microscopic characterisation of free-living nematodes is time consuming and requires specialised taxonomic expertise which only a handful of people have worldwide. That means only small numbers of samples can be assessed.

“In order to use free-living nematodes as soil health indicators on a large scale and routinely, we need to use technology that can detect and quantify free-living nematodes quickly and robustly. One way to do that is through DNA assays.”

Through the GRDC-funded project, Dr Linsell and her team of researchers have developed a suite of DNA tests that can detect and quantify free-living nematode groups in cropping soils.

To arrive at that point, an extensive soil sampling and analysis effort was undertaken, involving the collection of 450 soils from 22 sites across the southern, western and northern cropping regions.

Soils subject to different tillage and stubble management practices were sampled, soil nutrients were measured and different cropping plant rotations and organic matter additions were taken into consideration.

Nematode DNA was extracted from soil samples, and from a large and complex soil data set, researchers were able to analyse which free-living nematode groups were good indicators of soil health and how different management practices and environments affected free-living nematode communities and thus soil health.

It was found that nematode communities respond significantly to the addition of nitrogen, potassium, sulphur and phosphorous, as well as recent and annual rainfall. Soil types are a factor, and the inclusion of fallows and pulses in cropping rotations has an impact, as does the addition of organic matter and different tillage regimes.

Before implementing the new DNA tests as part of SARDI’s PreDicta B diagnostic service for monitoring soil health, further regional validation is required.

“We also need to look at the impact of other farming management practices like compaction and herbicide/pesticide applications on nematode communities,” Dr Linsell said.

“However, most importantly, we need to work on information delivery to growers. We need to find the best way to communicate the complex results in a way that is simple but informative.

“We need to develop a soil health rating based on a traffic light or index system with associated recommendations for improving biological soil health.”

More information about GRDC’s Soil Biology Initiative II is available via www.grdc.com.au/soilbiology.



More solutions from: GRDC (Grains Research & Development Corporation)


Website: http://www.grdc.com.au

Published: November 26, 2014


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