Researchers sketch out a manifesto for tackling farm plastic

DAILY SCIENCE

Researchers sketch out a manifesto for tackling farm plastic

12 million tonnes of plastic go into agriculture each year, some straight into the soil. Can we loosen plastic’s grip on farming?
September 29, 2023

Most of us are now aware of the ubiquity of plastic in our lives. It envelops our food, it’s in our furniture, it’s even used to make our clothes. But did you know that one of its biggest applications is in agriculture—where plastic is literally tilled into the soil, and is even infecting the crops that sprout from it? 

These and other revelations are the focus of a new academic review that highlights plastic’s grip on farming: around 12 millions tons is used in agricultural production each year. At the heart of the review is the question: can we get out of this harmful plastic bind?

One thing is for sure: it won’t be easy, given how embedded plastic is on farms. It’s present in reams of plastic sheeting and netting that protects crops against pests and the elements, also preserving soil moisture and heat. Field irrigation relies on miles of PVC piping. Plastic is used to stake and tether growing plants; it’s even used as a proactive coating for seeds, and for nitrogen fertilizer nodules to enable slow-release. 

These innovations have boosted food production and farmer income—and also bring environmental benefits that cannot be overlooked, the researchers say. Just take China for instance, where farmers would require an additional 4 million hectares of land to grow food, without the yield-enhancing benefits of plastic sheeting that shields crops. 

The new paper highlights a clear Catch-22: we need plastic, even as it heaps debilitating levels of pollution on our food systems—especially as some applications involve putting plastic directly into the soil. A growing body of evidence shows that plastic breaks down into micro- and nanoparticles that infiltrate the soil, some small enough to be taken up by microbes, and even by plants themselves. This microscopic plastic invasion has been linked to declining microbial communities and with them, reduced soil fertility, which has knock-on consequences for crop yields. Meanwhile, fragments of plastic in soil threaten its water-holding capacity and fertility too. Thus, using plastic on farms actually unravels much of its agricultural benefit, not to mention the environmental and potential human health impacts. 

 

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And it’s not just the polymers themselves, but their astounding variety of chemical additives that give them flexibility and durability: many of these we now know are toxic, like bisphenols and phthalates. An emerging focus in research is how these may be harming human health as they seep into growing vegetables and fruits.

The problem seems intractable: do we accept plastic’s harms for the benefits it brings? In fact, the researchers have some good news on this front: there are solutions to this seeming bind, and many of them are already at our fingertips.

They outline a manifesto for tackling the problem—starting with the fact that in general, agricultural plastic is reusable or recyclable, they say, like plastic sheeting which makes up 50% of all agricultural plastic. But they caution that even where reuse and recycling is possible, plastic needs to be redesigned to streamline the thousands of chemicals it contains, and to make these non-toxic for when they do inevitably leach into the soil.

For plastics where the risk of degrading and polluting the soil is high, biodegradable alternatives should be developed to replace conventional polymers that can persist for centuries in soil. One obvious low-hanging fruit is switching plastic coatings on seeds and fertilizers to biodegradable, non-toxic materials: the European Union has already proposed a ban on plastic-encased fertilizers. A caveat of biodegradables is finding replicas for the huge array of plastic that are still functional, but can also degrade in the soil. So far, much of the research into these alternatives has been confined to lab conditions, and it’s less clear how quickly these products would actually melt away in the soil. 

“While we can start, not all solutions are in place,” says Thilo Hofmann, professor of environmental geosciences at the University of Vienna, and lead author on the new paper. But in fact, the main obstacle isn’t more solutions, which will evolve in time: the bigger challenge is that solving it will require coordinated action across farms worldwide, due to the scale and interconnectedness of the plastic pollution problem. As with other types of plastic pollution, many now believe the global action that’s needed will only happen with regulation to drive it. 

On that front, there’s hope, says Hofmann: nations are currently negotiating an international, legally-binding Plastics Treaty to end plastic pollution. As he and his co-authors see it, it’s a golden opportunity to bring in mandates to make agricultural plastic cleaner, biodegradable, and to enforce their collection, recycling, and reuse.

With the right mix of approaches, we might one day free our food systems from plastic’s grip: “It’s possible,” Hofmann says. “I would not say you can reach zero impact, but we can minimise the impact very much so the benefits dominate.”

Hofmann et. al. “Plastics can be used more sustainably in agriculture.” Nature Communications: Earth & Environment. 2023. 

Image based on: The Veteran in a New Field (1865) by Winslow Homer. Original from The MET museum. Digitally enhanced by rawpixel.

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