Suppressive soils offer defence against grain diseases

Suppressive soils offer defence against grain diseases

Cropping
Associate Professor Pauline Mele is coordinating part of the GRDC Soil Biology Initiative II.

Associate Professor Pauline Mele is coordinating part of the GRDC Soil Biology Initiative II.

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HIGH rainfall zone (HRZ) grain growers stand to increase yields and save significant amounts of money on chemicals, if the secrets of suppressive soils can be unlocked.

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HIGH rainfall zone (HRZ) grain growers stand to increase yields and save significant amounts of money on chemicals, if the secrets of suppressive soils can be unlocked.

Soil biology is tipped to be the ‘next big thing’ in terms of productivity gains and a five-year research program is currently being funded by the Grains Research and Development Corporation (GRDC) to address some of the knowledge gaps.

Associate Professor Pauline Mele, LaTrobe University and principal research scientist, Department of Primary Industries Victoria (DPI), is co-ordinating an investment in soil biology that includes a team of some 90 researchers working on 15 different projects as part of the GRDC Soil Biology Initiative II.

She says understanding suppressive soils is one of the priorities, along with monitoring soil quality for better decision making and improving nutrient availability.

“There are soils right across the country where the incidence or severity of disease is suppressed, even in the presence of the pathogen that causes it, a host plant and a favourable environment,” A/Professor Mele said.

“In fact, we believe every soil has the potential to be suppressive – it’s just a matter of working out what management techniques will encourage it.

“We know the effect is due to the presence of a diverse range of ‘good’ micro-organisms, because upsetting the balance or sterilising the soil can cause the disease to strike with a vengeance.

“At this stage, though, we’re still trying to identify exactly what organisms, or combination of organisms, are doing the work.”

One of the keys is understanding the biological composition of soils and how they function and contribute to grain production.

“The arrival and rapid development of new technologies means we are finally in a position to delve deep into the soil biological communities and see not only who is there but what they are doing, not only as individual species but as highly interactive communities,” A/Professor Mele said.

“Soils are habitats and every habitat is different which usually means that each community is different, with potentially different types of soil biota in different areas. The million dollar question is whether these differences have any bearing on key functions related to plant performance.”

General knowledge about the benefits of living organisms in the soil is being refined to the point where, eventually, it will provide farmers with regionally specific information about the impact of different inputs and management techniques on the health of their land.

A/Professor Mele said there is enormous scope for new thinking about how we should treat and manage our soils and the practices we can put in place to drive productivity and profitability.

“The soil biological resource under our feet is seen as something of the ‘last frontier’ for the grains industry.

“We know it’s about competition for resources. If we create a habitat that favours one type of soil microbe, say through repeated use of the same management practice such as addition of fertiliser or sowing the same plant types, the community may end up with fewer types of biota present; thereby reducing the resilience of the system.

“The ultimate aim of this theme of the initiative is to establish the link between crop management and the development of disease suppressiveness, and the degree to which regional factors influence this. We know that communities of soil biota vary with soil type, climate and crop management regimes,” A/Professor Mele said.

Once the project has identified the beneficial micro-organisms present in disease suppressive paddocks, researchers will review farm management practices that may have fostered them by investigating the history of the paddocks, focussing on rotations, inputs and soil characteristics.”

The efforts to determine the traits and transferability of disease suppressive soils will focus on several questions and issues:

  • What are the physical, chemical and biological features of disease suppressive soils? Are these features common across regions or are they region specific? Is suppression a temporal phenomenon?
  • Is disease suppressiveness pathogen-specific or more generalised? Can we use the disease complex to identify the suppressiveness complex?
  • Can a disease suppressiveness index be developed based upon a genetic signature of the soil community?
  • How can the crop-soil ecosystem (physical and chemical environment) be managed to enhance disease suppressiveness?
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