Arbuscular mycorrhizal (AM) fungi and crops can work together for mutual gain, according to AHDB research. A new Ph.D. studentship report examines how these crop-friendly fungi can be nurtured by management.

Most land plants, including agricultural crops, form beneficial (symbiotic) relationships with AM fungi. When these fungi colonise root cells, they form branch-like structures (arbuscules) that can help transfer nutrients (largely phosphate and nitrogen) to crops.

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These fungi may benefit crops in other ways too. For example, some studies show a link between them and crop tolerance to pests, pathogens, and drought. However, some farming practices can reduce the abundance and diversity of AM fungal populations:

-Artificial fertilisers by reducing AM fungi supply of nutrients to crops

-Soil disturbance by damaging mycorrhizal networks

-Bare land by breaking down mycorrhizal networks

In 2018, AHDB and the AgriFood Charities Partnership funded a Ph.D. studentship project to develop a better understanding of how to tap into the power of these root-loving organisms. Working with NIAB and the University of Cambridge, PhD student George Crane has now submitted the project’s findings in a new report.

What did the study include?

The work set up bespoke trials in the field and glasshouse whilst also capitalised on established field-based projects. George inoculated crops with five AM fungal species which was applied individually or in a five-species commercial mix.

He studied four cash crops which were spring barley, maize, leek, and oats, and several cover crop species. Some trials also investigated the influence of nitrogen application rate and the use of anaerobic digestate.

Several measurements were taken to help gauge treatment impact, including assessment of percentage root length colonisation (RLC) by AM fungi, the abundance and diversity of AM fungi, and crop yields.

Crop impacts

In general, inoculation of crops did not increase the amount of root colonised by or the diversity of AM fungi. The applied species were also not found in high abundance. The exception was in a highly mycorrhizal leek crop, which displayed increased diversity and RLC compared to some other treatments. These increases were associated with higher yields in leek.

In general, increased AM fungi diversity and RLC had a mixed impact on crop growth and yield. In an oats field trial, higher yields correlated with increased RLC. However, no significant positive effect was detected in spring barley and maize field trials.

A glasshouse trial recorded a reduction in spring barley biomass with increased RLC. In this inoculated trial, there was a dominance of one AM fungi species.

George also found that multiple iterations of cover crops could positively influence the diversity and abundance of AM fungi as well as increase their plant-colonising ability.

Nitrogen application

As expected, nitrogen fertilisation had positive impacts on yield. However, when nitrogen was applied at half the recommended rate, there may have been nutrient supplementation by rhizobia associated with leguminous cover crops.

Although nitrogen application did not influence RLC in spring barley, it did influence AM fungal community composition, with the full recommended rate associated with a simplified AM fungi community compared with the 0% and 50% treatments.

A single application of anaerobic digestate resulted in variable impacts on AM fungal community composition and had no effect on cash crops. However, a lack of treatment replication made it a challenge to draw firm conclusions.


The relationships between AM fungi and plants are ancient and complex. Despite this, a growing body of evidence suggests that AM fungal populations need to be nurtured over time. Certainly, the impact of any amendment applied once is likely to be limited.