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Responses of Rhizosphere Soil Physicochemical Properties and Enzyme Activities to Polyethylene Microplastic Stress in Maize–Soybean Intercropping

Agriculture 2026
Debin Sun, Zhangyong Li, Yuanlan Lei, Yan Qiu, Jingxiu Xiao, Yi Zheng

Summary

Microplastic pollution from farm plastics is building up in soil and can throw off soil chemistry and nutrients, potentially affecting crop health and the food we eat. This study found that growing maize and soybeans together (rather than maize alone) helped protect soil from these negative effects, keeping soil chemistry more stable and preserving the natural enzymes plants need to access nutrients. This suggests a simple farming practice, intercropping, could be a low-cost way to help protect soil health as microplastic pollution increases, though more real-world farm testing is still needed.

Polymers

Agricultural microplastics threaten soil health, yet rhizosphere microecological responses to microplastic stress in intercropping systems remain unclear. We conducted a pot experiment using two cropping systems (maize monocropping and maize–soybean intercropping) and four polyethylene microplastic (PE-MP) levels (0%, 0.1%, 0.5%, 1.0%) to investigate rhizosphere physicochemical properties and enzyme activities. Results showed a significant interaction between PE-MPs and cropping systems (p < 0.05). In MM, 0.1% PE-MPs exacerbated soil acidification (pH −4.32%) and ionic fluctuations (electrical conductivity +11.12%). At ≥0.5%, PE-MPs significantly decreased total nitrogen (TN) and total phosphorus, induced abnormal available phosphorus accumulation (up to +98.4%), and dose-dependently inhibited β-glucosidase, urease, and catalase activities. Conversely, the IM system exhibited buffering capacity, maintaining pH, electrical conductivity, and TN stability, mitigating nutrient imbalances, and preserving key enzyme functions. PLS-SEM revealed enzyme-specific associations, suggesting that cropping systems and PE-MPs drive enzyme activities primarily by regulating TN and dissolved organic carbon (DOC). Conclusively, maize–soybean intercropping can buffer microplastic-induced physicochemical degradations, indicating its potential as an agronomic measure to mitigate microplastic pollution, though field-scale validations remain necessary.

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