Plastic mulch used in farming can break down into tiny microplastics, which end up in the soil. While biodegradable mulches are often promoted as a greener option, there’s still limited research on how they affect plant health compared to conventional plastics.
This study compared the effects of microplastics from two types of mulch: traditional polyethylene (PE) and a biodegradable blend made of starch and PBAT. Researchers tested these plastics on four food crops—barley, wheat, carrot, and lettuce—looking at both short-term (germination) and long-term (growth and leaf health) effects at three realistic concentrations.
Seed germination wasn’t impacted by either plastic type. However, early root growth in lettuce and wheat was reduced. Carrots showed stunted shoot growth and lower bud weight at the highest plastic levels. In longer-term exposure, barley and lettuce had lower shoot biomass, though lettuce also showed an increase in leaf count and chlorophyll content.
Overall, the negative effects were more noticeable in dicot plants (carrot and lettuce) than in monocots (barley and wheat). Surprisingly, the biodegradable plastic blend caused more consistent harm to plant growth than the conventional plastic, a trend also supported by other similar studies.
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