According to a new study, plastic sheets used for mulching – a practice of covering the soil to retain temperature and moisture to facilitate higher agricultural production lead to microplastic pollution of agricultural soils.
Microplastics are tiny plastic materials less than 5mm in diameter and are considered a major source of plastic pollution in the environment.
The NGO Toxics Link tested soil samples in the agricultural belts of Karnataka and Maharashtra as part of the study titled Plastic Mulching: Microplastics in Agricultural Soils and found tiny plastic particles at different depths, indicating contamination soil due to the widespread use of plastic mulch sheets.
A total of 30 samples were taken from mulched and unmulched fields and dumps – areas used by farmers to dump used plastic sheeting, other plastic waste and waste – at different depths in the selected regions.
The soil samples were tested at the Manipal Academy of Higher Education and microplastics were detected in all of them.
The abundance of microplastics in the mulched soil samples was much higher than in the unmulched soil samples. This clearly indicates possible soil contamination from the use of plastic mulch sheets, the report reads.
The highest microplastic contamination – 87.57 pieces per kg of soil – was found in a landfill in Maharashtra. This was almost double the abundance in the mulched soil, indicating that plastic mulch sheets dumped around the agricultural area are causing pollution, the researchers said.
In the case of all mulched soil samples, the highest concentration of microplastics 40.46 pieces per kg of soil was found at a depth of 15 cm at Badgaon in Maharashtra, while the lowest concentration of 8 .45 pieces per kg of soil was found at a depth of 30 cm at Khanapur in Karnataka.
Among all unmulched sites, Aurnol in Maharashtra recorded the highest concentration (20.54 pieces per kg) of microplastics at a depth of 15 cm, while Hukkeri in Karnataka had the lowest concentration (2. 83 pieces per kg) at the same depth.
The use of plastic in modern agriculture jeopardizes the overall sustainability of our ecosystem. The plastic used for mulching is relatively thin, and the removal and recycling of these plastic films from the agricultural field is labor-intensive, expensive, and difficult.
Therefore, it remains in the field or is dumped nearby and eventually disintegrates into microparticles (microplastics), accumulating in the soil. Microplastic contamination in soil can also lead to their uptake by plants or crops, affecting the environment and human health, said Priti Banthia Mahesh, Senior Program Coordinator, Toxics Link.
Mulching has been used around the world for centuries, using dry leaves, straw, trash, etc. for water conservation. The use of plastic film in mulching is a recent development all over the world, and in India it has only been around for a few decades. The idea of using polyethylene film as mulch in crop production originated in the mid-1950s and plastic mulch was first noticed for its ability to increase soil temperature.
A recent study detected microplastics in human blood for the first time, with scientists finding the tiny particles in nearly 80% of those tested.
A study conducted by Toxics Link in 2020 detected microplastics in the Ganges in Haridwar, Varanasi and Kanpur. Another study conducted by Toxics Link had found microplastics in tap water samples taken from different parts of Goa.