Did you know that the same plastic used to boost crop yields is leaving harmful traces in our soil and even making its way into our food? Microplastics are now found in human blood, raising questions about their hidden impact on health and the environment.
Plastic mulching is acknowledged as an innovative agricultural method that enhances crop yields, particularly in arid and cold climates. This technique entails applying thin plastic films over the soil to retain moisture, regulate soil temperature, and inhibit weed proliferation. The advantages encompass improved water utilization efficiency, expedited planting and harvesting, and superior pest management.
Plastic mulching (Image: Epic Gardening).
However, the disadvantages are becoming progressively apparent. The deterioration of plastic mulches results in the presence of microplastics (MPs) in the soil, defined as fragments smaller than 5 mm. Over time, these MPs aggregate, modifying the physical, chemical, and biological characteristics of the soil. They not only degrade soil health but also diminish crop productivity and provide a significant hazard to the agroecosystem. MPs serve as vectors for many environmental pollutants, including as heavy metals and pesticides, hence enhancing their toxicity. Consequently, microplastics have surfaced as a concealed contaminant in agricultural soils, jeopardizing the long-term viability of farming methods.
How microplastics disrupt soil fertility and plant growth
Microplastics (MPs) adversely affect soil fertility by interfering with enzyme activities essential for nutrient cycling, including urease and catalase, hence compromising overall soil health. MPs can modify soil carbon and nitrogen dynamics, thereby diminishing the availability of vital nutrients such as nitrogen (N) and phosphorus (P) for plant development. They also influence soil aggregation and porosity, altering microbial community structures and diminishing biodiversity, which can impair the soil's resilience. Moreover, MPs disrupt root development and nutrient uptake, occasionally obstructing cellular pathways and diminishing seed germination and biomass yield. The cumulative effect of MPs on soil structure, fertility, and microbial diversity presents a significant risk to plant growth and sustained soil productivity.
A threat to human Health?
Microplastics (MPs) and nanoplastics (NPs) may present considerable health hazards as they can infiltrate the human body via air, water, and food sources, including fruits and vegetables. A study by Ballesteros et al. (2020) reveals that these particles can penetrate deep into human organs, including the colon and placenta, and have been associated with DNA damage in immune cells. The elevated relative surface area of nanoparticles amplifies their capacity to transport and disseminate hazardous substances, potentially augmenting their toxicity. Research has indicated the presence of MPs in human blood, prompting significant worries regarding their long-term effects on human health.
The Spread of microplastics in the food chain: A One Health Perspective. Figure reproduced from Aardema et al. (2024).
Eco-friendly alternatives to plastic mulching
Biodegradable plastic mulches provide an environmentally sustainable substitute for conventional polythene (PE) mulch, decomposing in soil without necessitating removal at the end of the season; nevertheless, their use is constrained by expense and variable degradation rates. Biodegradable paper mulch, prevalent in Japan, exhibits comparable efficacy to polyethylene in moisture retention and weed suppression, simultaneously enhancing soil with organic matter. Organic mulches, like straw and compost, improve soil quality and moisture retention; nevertheless, their application is labor-intensive and expensive. Innovative solutions such as sprayable biodegradable mulches, which stick to soil surfaces, demonstrate potential in weed suppression and moisture retention.
Conclusions
Although polythene mulch is economical and beneficial for crop development, its disposal challenges and role in microplastic pollution, provide significant environmental hazards. Biodegradable plastic, paper, and organic mulches have environmentally sustainable advantages without disposal costs; however, these are constrained by durability issues and increased expenses. Despite these challenges, biodegradable mulches have a clear advantage in reducing CO2 emissions and environmental impact. Ongoing research aims to develop more durable and affordable biodegradable plastics to further enhance sustainability in agriculture.
References:
Salama, K., & Geyer, M. (2023). Plastic mulch films in agriculture: Their use, environmental problems, recycling and alternatives. Environments, 10(10), 179.
Khalid, N., Aqeel, M., Noman, A., & Rizvi, Z. F. (2023). Impact of plastic mulching as a major source of microplastics in agroecosystems. Journal of hazardous materials, 445, 130455.
Author:
Ph.D. Student
Department of Marine & Environmental Sciences
University of Algarve, Portugal
Informative and well written