June 16, 2021

Plasticulture: A double-edged sword

Written by Sam Cusworth:

Plasticulture; the use of plastics in agriculture, is a worldwide practice and has been ever-expanding since the 1950s. Replacing the traditional materials of straw, manure, paper and crop mulch, plastics have transformed global agriculture into a more productive and efficient system. From boosting crop productivity to maintaining a competitive advantage in global fresh produce markets, plastics have provided a long-awaited solution.

Plastic is embedded in each of our lives, we interact with it everyday. From the bristles of the toothbrush we use in the morning to the plastic cables we charge our phones with overnight. However, our reliance on this material is not without its consequences. The majority of plastics are derived from fossil-fuel feedstocks and our use of the material is not sustainable. Within agriculture, once plastic has served its purpose, it is often mismanaged. Agricultural plastics are frequently sent to landfill, buried, burned or ploughed into the soil. Within the soil these residues degrade into smaller particles – microplastics and nanoplastics. Both have become well acquainted with the weekly news: “Microplastics found in the brain tissue of a…”, “Nanoplastics found in the Arctic circle, researchers couldn’t believe what they saw next…”, “Scientists discover the effect of microplastics on…”. 

Therefore, we find ourselves in a juxtaposition, where plastics and the associated pollution pathways are recognised as one of, if not, the most pressing environmental problem we face. Yet, they are debatably the most important material on Earth due to their versatility. Do we simply abandon this material with the risk of an agricultural crisis?

That is certainly the opinion of Le Moine and Ferry, two researchers who published a paper in 2018 suggesting that a complete abandonment of plastic could compromise up to 60% of global animal and crop production [1]. This supports my current research, in which I have conducted a meta-analysis to compare two scenarios; one where plastic is used for crop production within the UK, and a scenario where plastic is not used. Whilst this research is not yet published, preliminary findings suggest that crop yields averaged over the year would be significantly lower within the UK, across the growing season. As a result of this, the UK would have to subsidise this loss with imports. The effects of this are potentially more environmentally, socially and economically damaging than using plastics; increased food miles, modern slavery, exploitation, environmental negligence, trade disruption, import taxes etc.

On the flip side, the expansion of UK plasticulture could increase food security, alleviate the environmental strain from imports and buffer the future impacts of climate change. Considering this, could plasticulture be the saviour for the UK food system?

Expanding plastic use in agriculture would undoubtedly lead to more pollution. The volume of plastic waste to landfill would increase, where it may remain for an excess of 100 years. Over this period, it would pose ecotoxicological risks, not only in the immediate vicinity, but wherever it may leach; the atmosphere, soils, oceans, fauna and flora. Whilst the effects of plastics, specifically micro- and nanoplastics are relatively unknown, studies describe their distribution to be ubiquitous. Keeping a focus on agriculture, increasing plastic use for crop production would increase the load of plastic residues into agricultural soils. One of my other experiments focusses on this matter, testing agricultural soils for microplastic concentrations across the UK. This makes comparisons between carrot and potato fields that utilise a plastic crop cover, against fields that are devoid of plastic. So far, there is a significant difference between the two. Fields without plastic have been found to contain ~2000 counts of microplastics per kg of dry soil, compared to ~5000 counts in fields that utilise a plastic crop cover. Two alarming points spring to mind, amongst others. Why are the concentrations so high for fields where there should be very little plastic contamination? What are the sources behind these microplastics?

The consequences of microplastic pollution are relatively unexplored. However, some studies have found that the accumulation of plastic residues may reduce yield, due to negative effects on shoot and root development [2], whilst others have theorised that presence of plastic residues favour the release of greenhouse gases. The impact of plastic residues upon soil structure and dynamics is overwhelmingly negative, progressively degrading the soils, year on year. As Steinmetz et al (2016) summarises, are we simply trading short-term agronomic benefits for long-term soil degradation? [3]

Too often we fail to consider the long-term consequences of our actions, in light of the short-term benefits they provide. Due to the environmental persistence and worldwide distribution of plastic residues, the consequential environmental effects shall be a lasting legacy of plastic use.

However, it’s not all doom and gloom. The development of sustainable, bio-based, biodegradable plastics and alternatives are of great focus. With the prospect of an environmentally friendly plastic on the horizon, there is a bright future for plasticulture. But for now, the existence of this practice hangs in balance.

[1] Le Moine, B. and Ferry, X., 2018, May. Plasticulture: economy of resources. In XXI International Congress on Plastics in Agriculture: Agriculture, Plastics and Environment 1252 (pp. 121-130).

[2] Steinmetz, Z., Wollmann, C., Schaefer, M., Buchmann, C., David, J., Tröger, J., Muñoz, K., Frör, O. and Schaumann, G.E., 2016. Plastic mulching in agriculture. Trading short-term agronomic benefits for long-term soil degradation?. Science of the total environment550, pp.690-705.