Biodegradable microplastics decreased plant-derived and increased microbial-derived carbon formation in soil: a two-year field trial

Summary

This two-year field experiment examined how conventional and biodegradable microplastics alter soil organic carbon (SOC) stabilization pathways. Biodegradable polylactic acid (PLA) microplastics reduced plant lignin contribution to SOC by 32% whilst simultaneously increasing microbial necromass contributions by 35%, driven by enhanced fungal diversity and macroaggregate formation. The findings suggest that biodegradable microplastics restructure SOC composition without changing total C stocks, with necromass accrual emerging as an overlooked carbon stabilization pathway, though N limitation triggered preferential bacterial necromass depletion.

Regional applicability

The study was conducted as a field trial but the specific geographic location is not stated in the abstract. The findings on microplastic impacts on soil carbon dynamics would be relevant to United Kingdom agricultural policy and soil management given growing microplastic contamination concerns, though site-specific soil conditions, climate and management practices would influence transferability.

Key measures

Lignin phenol content (% reduction); microbial necromass contribution to SOC (% change); plant-derived carbon contribution; microbial diversity (% increase); network complexity (% increase); fungal and bacterial necromass proportions; K-strategist abundance; oxidase and N-acquiring enzyme activity

Outcomes reported

The study measured soil organic carbon (SOC) composition, plant lignin phenol content, microbial necromass contributions, microbial diversity, and network complexity in soils amended with conventional (PP) and biodegradable (PLA) microplastics over two years. Neither plastic type altered total SOC, but PLA reduced plant-derived carbon and increased microbial-derived carbon formation in soil.

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