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By 2050, we will need to feed almost 1.8 billion more people, when our .

We have less land available for agriculture due to urban sprawl (and other competing needs), but we also need to avoid clearing more forested land for farms, while boosting crop production at the same time.

But we can't afford the current of using large amounts of synthetic (nitrogen-based) fertilizers.

Environmental cost of food production

As well as contributing to , soil acidification and biodiversity loss, inefficient use of nitrogen-based fertilizers leaves excess nutrients that leach into waterways, leading to that suffocate aquatic lifeforms.

In the sugarcane-growing region of Far North Queensland, this poses a major threat to the already fragile .

Nitrogen pollution of air and water also causes multiple human health problems, including respiratory diseases and some cancers. Despite all these issues, reducing fertilizer application is not always .

The risk of not using fertilizers in a changing global environment is often not worth the loss in crop yields or prospective revenue for farmers.

Plastic coatings provide a solution (and pose another problem)

One solution is to coat fertilizers in a thin layer of plastic that slows release to better align with the needs and timing of plant growth, thereby reducing nitrogen waste and pollution.

However, these coatings degrade into that run off into our waterways or are absorbed by crops, entering our food chain and our bodies.

Recent research has shown that microplastics can even , and their accumulation in organs is implicated in a range of diseases.

There is no legislation in Australia that polices the use of plastic-coated fertilizers—which are readily available and sold at many garden and hardware stores.

The United Nations Environment Assembly is wisely seeking a . So, we urgently need alternative solutions to reduce nitrogen pollution while boosting crop production.

Since 2021, researchers in the multidisciplinary ARC Research Hub for Innovative Nitrogen Fertilizers and Inhibitors (Smart Fertilizers) have been developing for this purpose.

Native Australian soil microbes can safely break down some plastics

One focus we're exploring is the use of biodegradable plastic coatings (or bioplastics) to slow the release of fertilizer while minimizing the environmental impact of the coating.

In a study recently in Science of The Total Environment—a collaboration with industry partners, Incitec Pivot and Elders—researchers from the Faculty of Science and the Faculty of Engineering and Information Technology tested several bioplastic candidates in a natural agricultural soil.

We studied the bioplastics under typical growing conditions to learn whether soil microbes could break them down into safe substances.

Previous research in this area has focused on other ecosystems (e.g., marine) or used purified laboratory microbe cultures or elevated conditions, like high temperature or boosted ultraviolet light.

Encouragingly, four of the seven plastic coatings we tested were degraded and ultimately converted to carbon dioxide and water under typical growing conditions by bacteria and fungi native to Australian agricultural soils.

There also appeared to be no negative effects of this degradation on the microbe populations.

Additionally, we identified the microbe species involved in the degradation to inform our design of bioplastic-coated fertilizers.

Some of the plastic-eating microbes provide the extra benefit of producing key plant nutrients, like phosphorus.

Other microbe species we found could also help tackle our through the production of specific enzymes that can —which could then be used in landfills.

Food from a healthy planet, for healthy people

Our next step is to test whether the four biodegradable plastics we found will enable efficient fertilizer delivery in glasshouse and field trials and assess their commercial viability.

A key challenge is to keep the cost of bioplastic-coated fertilizers competitive with market alternatives, to .

Our research highlighted the importance of testing the ability of plastic degradation of the whole soil ecosystem, rather than focusing on individual microbe species.

The types and functions of microbes vary between different soils and can depend on each other or external factors like water availability.

So we need more research to determine how bioplastic fertilizer coatings degrade in diverse agricultural settings.

Another area for future research is the ability to tailor the thickness of the bioplastic coating to match the rate of fertilizer release to the growth pattern of key agricultural crops, which would optimize their effectiveness.

By meeting these challenges, we aim to increase sustainable food production and ensure the health of our soils, plants, people and planet well into the future.