Plastic cultivation refers to the use of plastic in agricultural activities. This may include soil fumigation, irrigation, packaging of produce, and protection of harvests from rainfall. Plastics also appear as coverings or greenhouse coverings.

Although plastic cultivation is touted as a way for farmers to effectively grow crops with less water and less fertilizers and pesticides, it has also been questioned due to environmental unsustainability. The problems mentioned include soil, water and food pollution; air pollution; and large amounts of plastic waste.  

Here, we delve into the pros and cons of this hot topic and reveal the sustainability of plastic culture.

The history of plastic culture begins with the mass production of plastics that began in the 1930s. Researchers have discovered that a type of plastic, polyethylene, is very suitable for agricultural use due to its durability, flexibility and chemical resistance. It was first used as a greenhouse building material in the 1940s as a substitute for glass. Plastics soon became widely used as artificial coverings.

Plastic mulch became commercially available in the 1960s. It uses plastic sheets to cover the soil with holes in it to allow plants to grow. Since then, it has become the most widely used form of plastic cultivation.

Plastic mulch can increase crop yield in the following ways:

Another application of plastic cultivation today is as a sealing covering for silage or other animal feed grains. Soft plastic sheets can be tightly wrapped around harvested grains and straw bales; this keeps them dry and fresh for months or more at a time. 

Polyvinyl chloride or PVC and polyethylene are commonly used for pipes in irrigation and hydroponic systems. These relatively light plastic pipe materials also have corrosion resistance, making them attractive alternatives to metal pipes. Petroleum-based nursery pots, crates, and other containers made of durable but lightweight plastic represent another important plastic culture category.

Perhaps the most visually prominent form of plastic cultivation is that it is used to construct greenhouses and high tunnel structures (hoop houses), allowing many crops to grow in a protective indoor environment.

These structures absorb heat and light from the sun, while regulating growth temperature and protecting plants from natural disasters. They are usually made of polycarbonate sheets that provide strength and durability. Then use a film made of ethylene-vinyl acetate copolymer or EVA to cover the tunnel.

Plastic greenhouses and tunnels can promote greater soil carbon sequestration and lock the warming carbon in the ground instead of being emitted into the atmosphere. They are also associated with lower water consumption and help protect against crop pests, which are especially useful in organic agriculture. 

Alas, the potential environmental benefits of plastic culture are often offset by adverse environmental impacts, such as greenhouse gas emissions, pollution of soil, water, air, and food, and the generation of large amounts of plastic waste. 

Perhaps there is no better explanation of the benefits and consequences of plastic cultivation than the vast greenhouses of Almeria in southern Spain (one of the driest places in Europe).

These intensive agricultural operations protect crops from wind, and highly controlled irrigation systems help save water and prevent evaporation. Here, plastic cultivation has significantly increased crop yields and changed the local economy. The huge plastic greenhouse covers the arid land and produces a lot of fruits and vegetables.

Although Spain may be the country with the highest concentration of plastic greenhouses, it still lags far behind China in terms of quantity. Since the introduction of plastic greenhouses in the 1970s, the number of plastic greenhouses in China has increased sharply, and China now owns about 90% of the world's plastic greenhouses. The agricultural plastic film used for mulching has significantly increased the output of Chinese crops, but its growing pollution footprint has begun to reverse productivity.  

Unrecycled agricultural plastics constitute a large amount of waste, and when they are buried, incinerated or dumped in landfills, they can cause further harm to the environment. This is particularly worrying in developing countries that lack adequate waste management infrastructure, but it is also a huge dilemma for developed countries.

In the United States, millions of tons of plastic film are used for mulch, row mulch, greenhouse mulch each year-this does not include plastic used for irrigation pipes, pipes, packaging and storage.  

A study of plastic greenhouses in China found that they are related to greater climate-changing greenhouse gas emissions, such as carbon dioxide and nitrous oxide, which are also the main culprits of air pollution because it produces particulate matter and ozone. 

Traditional plastics are petroleum-based products made from fossil fuels. In addition to releasing climate-changing greenhouse gases into the atmosphere, the plastic manufacturing process also causes air and water pollution, which affects workers and nearby communities.

Another emerging issue concerns how much plastic culture may affect the presence of microplastics in soil and water.

Especially the mulch film is very thin, it is easy to deteriorate into small pieces of plastic, which will affect the quality of the soil, affect the microorganisms and other organisms living in the soil. Plastic particles are washed into surface water by rainwater and irrigation, and finally into the ocean. They can also be absorbed by plants and finally enter the food system. 

Some recent studies have detected microplastics in rivers and oceans, fish, shellfish, and human excreta. The latter indicate that people are ingesting large amounts of microplastics. It is an emerging field of research to sort out the contribution of plastic culture to this problem. 

In addition, the burning of plastics emits persistent environmental pollutants, namely dioxins, while burying or sending plastics to landfills can cause leaching.

Although crops grown in plastic greenhouses may require less pesticides, the fact that greenhouses can extend the growing season and allow for additional harvests means that they are often places where overall fertilizer and pesticide usage is greater. These pesticides and fertilizers can seep into the soil, acidify the soil and contaminate groundwater. 

In addition, chemical additives in plastics can accumulate in the soil, and their impact on our food and water supply is still unknown. A 2019 study found that plastic mulch significantly increased the accumulation of phthalates (plasticizers) in wheat grains and their soil.

Although some heavy plastics used in greenhouse construction can be recycled or reused, a large part is not. The lighter plastic used for covering is less recycled because it is very thin and often contaminated with pesticides, dirt, and fertilizers, which makes reuse or recycling labor-intensive and costly. 

In the United States, most of the agricultural plastics that have been recycled in recent years have been shipped to Vietnam, China, and Malaysia, but these countries have now banned such transportation. This means that more agricultural plastics are now sent to landfills or incinerated. 

Scientists began to develop biodegradable alternatives to traditional plastic mulch films. Biodegradable substances can be converted into carbon dioxide, water and other natural substances by soil microorganisms. It does not need to be removed like the traditional polyethylene counterparts, these can be replanted back into the soil.

However, although they are biodegradable, there are still questions about the long-term effects of biodegradable plastics on soil ecosystems. In addition, biodegradable plastics are still made from petroleum products and may contain additives that have an adverse effect on the environment.

For these reasons, Australia has recently completely banned biodegradable plastics. The European Union has established standards for biodegradable mulch films, requiring them to limit harmful ingredients to avoid damage to the ecosystem.

A surprising source of plastic cultivation is organic agriculture, because plastic mulch and greenhouses can help organic growers protect crops from weeds and pests. Straw and paper mulches provide promising alternatives, but they are still too expensive and labor-intensive for many growers. 

Flower pots represent another opportunity to fight plastic waste. Plantable containers made of natural materials such as peat, cow dung, rice, wood pulp, coconut or paper can be used to grow plants underground.

Another option is plant containers made of natural materials that will not be grown but can be composted. Finally, there are recycled bio-based plastic containers, sometimes mixed with natural fibers, and gradually biodegraded. 

Although the use of more biodegradable plastics and non-plastic alternatives cannot completely solve the environmental problems associated with plastic cultivation, they can help to have a significant impact in combating the adverse effects of plastics in agriculture.

The more growers, consumers, and governments support sustainable alternatives to agricultural plastics—while expanding practices such as water conservation and reducing the use of fertilizers and pesticides—the healthier our communities, food systems, and the planet will be. 

Kasirajan, S., Ngouajio, M. Polyethylene and biodegradable coverings for agricultural applications: a review. Agron. maintain. Development. 32, 501–529 (2012). https://doi.org/10.1007/s13593-011-0068-3

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