How does microplastic pollution affect plant-soil system under different soil moisture contents?

Human activities have brought about Microplastic (MP) pollution and climate change into the environment, posing potential threat to plant-soil system. Therefore, we studied the effects of these factors on soil properties and plant growth, as well as compared differences under two soil moisture levels. We conducted a two-month greenhouse pot experiment with 16 treatments. Maize (Zea mays L.) was grown under two soil moisture levels (16.7% and 10.0% w/w) with and without MPs (0.2 % w/w, PLA+PBAT based). The role of soil biota was also considered, for instance, with and without earthworms (Lumbricus terrestris) was included. Generally, we found MP presence impeded plant growth. The presence of MP lowered soil pH under high soil moisture level and raised it under low moisture cases. The measurements of OM content were observed to increase with MP presence. Moreover, the effects of earthworm were found the largest on the plant-soil system. Specifically, dry biomass increased by 130%, fresh biomass and stem width increased by 110%, height increased by 20%, leaf number increased by 10%, while shoot C/N ratio decreased by 20% and pH decreased by 3%. Such effects were independent of the presence of plastic or other factors (e.g., moisture). In conclusion, this study showed the intricate effects associated with plastic pollution in the plant-soil system and they were not always consistent under different soil moisture levels.