Plastic films, extensively used in agriculture, have emerged as significant contributors to microplastic pollution in soil. These remnants can disrupt soil structure, affect water permeability, and potentially enter the food chain through plant absorption, posing risks to soil health and food security. In response, oxo-degradable plastics (ODPs) have been introduced as a “more sustainable alternative” to traditional plastics. These materials are designed to degrade under light and heat, eventually breaking down into carbon dioxide and water through microbial activity. However, questions remain about their actual degradation efficiency and potential impact on soil and crop quality.
In a recent study led by Professor Davey L. Jones from Bangor University, the effects of oxo-degradable plastics of varying sizes and concentrations on soil and corn growth were systematically examined. Published in the journal Frontiers of Agricultural Science and Engineering, this research provides critical insights into these concerns (DOI: 10.15302/J-FASE-2025623).
Understanding the Impact of Oxo-degradable Plastics
Unlike previous research that predominantly focused on traditional plastics or single-size plastics, this study is distinguished by its “dual-dimensional comparison.” It evaluates the differences between microplastics and macroplastics across a spectrum from typical field concentrations to extreme levels. Using corn as a model crop, the researchers monitored soil pH, electrical conductivity, and nitrate content over a six-week period. They also assessed plant growth, chlorophyll content, and nutrient absorption, employing infrared spectroscopy to track the plastics’ degradation process.
The findings were revealing. At low concentrations typical of actual fields, oxo-degradable plastics showed minimal impact on soil quality and corn growth. However, concentrations exceeding 1% led to notable changes in soil properties. In the microplastic treatment group, soil pH increased by nearly one unit, electrical conductivity doubled, and nitrate content significantly rose, whereas the impact of macroplastics was considerably weaker. This could be attributed to the larger surface area of microplastics, which allows for more extensive soil contact, thereby altering the soil’s structure and chemical environment more readily.
Effects on Plant Growth and Soil Quality
The study also highlighted the more pronounced effects of microplastics on plants. High concentrations of both microplastics and macroplastics resulted in decreased corn height and chlorophyll content, with microplastics having a more significant inhibitory effect. Despite this, corn biomass only slightly decreased at the highest concentration, indicating some level of plant tolerance. Interestingly, corn root biomass in the microplastic treatment group was higher at low concentrations, potentially due to increased soil nitrate levels promoting root growth.
Furthermore, the research uncovered the “degradation limitations” of oxo-degradable plastics. Infrared spectroscopy indicated that after six weeks of soil burial, only mild chain scission of the plastics occurred, with no significant production of oxidation products like ketones or aldehydes. This suggests that in the absence of light, the degradation process of oxo-degradable plastics is very slow, potentially leading to long-term persistence and accumulation in the soil. The study also analyzed the additive components in the plastics, finding primarily antioxidants and lubricants with very low heavy metal content, thus ruling out significant direct toxicity from the additives.
Implications for Policy and Future Research
This study not only fills a critical research gap regarding the “size-concentration-impact” relationship of oxo-degradable plastics in soil but also provides scientific support for policy-making through its multidimensional data. As the paper notes,
“A cautious approach is needed regarding the use of oxo-degradable plastics”—until truly efficient and environmentally friendly alternative materials are found, reducing the excessive use of plastic films may still be the most direct choice for protecting soil health.
The findings underscore the need for further research and development of alternative materials that can effectively degrade in natural environments without compromising soil and crop quality. As the agricultural industry continues to seek sustainable solutions, this study serves as a crucial reminder of the complexities involved in replacing conventional plastics with seemingly greener options.
