Soil fungi link to healthy grain

Zinc is an important nutrient for human health; deficiencies can lead to a range of medical problems.

While most developed countries get their dietary zinc from red meat, developing nations dependent on cereal-based diets can be at risk if zinc concentrations in grain are low.

A two year Canberra-based CSIRO study that was led by Dr Megan Ryan, who is now at the University of Western Australia, investigated how crop management can affect the levels of zinc in cereal grain by examining the effects of crop sequence, fertiliser regime and soil fungi on mineral content.

Arbuscular mycorrhizal fungi (AMF) are beneficial soil micro-organisms that colonise plant roots, assisting the uptake of some mineral nutrients, including zinc. Crops colonised by AMF were shown to be higher in zinc.

Phosphorus (P) fertiliser can increase yields by 50 per cent or more, but also reduces colonisation by AMF. The study showed that grain zinc concentrations were reduced in fertilised crops by 33-39 per cent.

Crop sequence also reduced zinc concentrations. While break crops like canola reduce root disease they can also reduce colonisation by AMF. Wheat following canola and fallow also had lower zinc concentrations.

For most farmers, P fertiliser and break crops are important tools for good yields and healthy crops. Improving grain zinc concentrations may require the use of fertilisers that include zinc, or industrial fortification of cereal products during processing.

The study highlights the importance of nutritional content as a wheat quality component, especially for wheat exports.

This work contributes to CSIRO’s goal of improving crop agronomy and wheat quality and is supported by the Grains Research and Development Corporation.

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