Will cyanobacteria fertiliser save our soil?

As global soil health dwindles, Aussie researchers are investigating the production of a sustainable organic nitrogen fertiliser, using something that lives in ponds – cyanobacteria.

Cyanobacteria is also known as blue-green algae, and it is a type of water-dwelling bacteria that takes nitrogen out of the air and converts it into nitrates and ammonia. Nitrogen is critical to plant growth and converted forms are often in fertilisers.

Researchers in the US, Europe and Australia are investigating how the new biofertiliser, made from the freshwater cyanobacterium, Tolypothrix, could heal soil fertility. The fast-growing and inexpensive fertiliser could be an organic alternative to commercial fertilisers.

“Australian soils, in particular in the marginal wheat belt in Western Australia, are structurally degraded, which cannot be overcome by applications of synthetic fertilisers,” says Flinders University researcher Kirsten Heimann, who was part of the study.

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“To improve soil structure, organic carbon applications are required to return the soils’ capacity to sustain a healthy soil microbiome and to improve the soils’ cation exchange of nutrients and water-holding capacity.”

The team found that the non-toxic cyanobacteria could be produced in ponds on farming land, or even in slightly salty and industrial wastewater. The energy costs to produce the fertilisers could also be offset by producing a methane-rich biogas, that could fuel future production, they show in their paper, published in Chemosphere.

“Many soils are degraded and becoming less fertile. This challenges agriculture to produce sufficient high-quality food to feed the continuously growing population, which is further exacerbated by climatic instability threatening crop production,” says Heimann.

The United Nations estimates that the world population will be 8.5 billion by 2030, and 9.7 billion by 2050, so the researchers suggest that a cheap, renewable cyanobacteria fertiliser may be necessary for quality crops on such a large scale.

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