Conventional non-biodegradable plastic mulching film inhibits weed growth, reduces evaporation from the soil and decreases run-off due to rainfall. However, mulching film can leave large quantities of microplastic in the agricultural soil, according to a study by Toxics Links. Microplastics are tiny plastic materials less than 5 mm in diameter and are regarded as a major source of plastic pollution in the environment.
The researchers from NGO Toxics Link tested soil samples in agricultural belts in Karnataka and Maharashtra under the study titled “Plastic Mulching: Microplastics in Agricultural Soils” and found tiny plastic particles at various depths, indicating soil contamination due to the rampant use of plastic mulch sheets.
A total of 30 samples were collected from mulched and un-mulched fields and dumpsites -- areas being used by farmers to dump used plastic sheets, other plastic waste and waste material -- from varying depth 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 the un-mulched soil samples. This clearly points towards a possible contamination of soil due to the usage of plastic mulch sheets, the report read.
The highest microplastic contamination -- 87.57 pieces per kg of soil -- was found at a dumpsite in Maharashtra. This was almost double the abundance in mulched soil, indicating that plastic mulch sheets dumped around the agriculture area cause pollution, the researchers said.
In 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 in Badgaon in Maharashtra, whereas the lowest concentration of 8.45 pieces per kg of soil was found at a depth of 30 cm in Khanapur in Karnataka.
Among all un-mulched 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.“Use of plastic in modern agriculture is jeopardising 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 labour intensive, costly, and challenging.
“Consequently, it remains in the field or is dumped nearby and ultimately disintegrates into micro-particles (microplastics), accumulating in the soil.