[Effects of Different Microplastics on Cucumber Seedling Growth and Soil Chemical Properties]

Microplastics (MPs), as contaminants in the soil environment, have been widely detected in agricultural soils, yet their impacts on plant and soil health remain unclear. This study investigated the impact of six different microplastic types (PE, PPC, PBS, PLA, PHA, and PCL) with three addition amounts (1%, 1.5%, and 2%) on cucumber seedling growth, soil chemical properties, and soil available nutrients. Our results indicated that the inhibitory effect on fresh and dry weight of cucumber seedlings treated with 2% PCL was the strongest, which was 84.52% and 85.40% lower than that of the control, respectively (P<0.05). The PCL significantly (P<0.05) reduced the length, total surface area, volume, and diameter of the roots in cucumber seedlings as compared with the control at almost all addition amounts. The 2% PCL treatment exhibited the strongest inhibitory effect on chlorophyll content, reducing chlorophyll a and total chlorophyll content by 86.61% and 82.64%, respectively. The soil pH showed an increase with PPC, PBS, and PCL, and the soil EC was significantly (P<0.05) lowered at 2% addition compared with that in the control. Moreover, the 2% PCL caused significant reduction in soil NH₄⁺-N, NO₃^--N, and available potassium by 44.81%, 60.23%, and 52.17%, respectively, while the 1% and 1.5% microplastic treatments resulted in elevated phosphorous content (P<0.05). In conclusion, biodegradable MPs could reduce cucumber seedling growth by affecting the soil and nutrient status, and the negative impact of 2% PCL MPs on cucumber seedling growth and soil nutrients was most significant. The findings of this study lay the groundwork for the prevention and control of microplastic pollution and impacts on plant health.