Biodegradable microplastics reduce the effectiveness of biofertilizers by altering rhizospheric microecological functions

• Published in: Journal of environmental management 2024-02, Vol.352, p.120071-120071, Article 120071
• Main Authors: Li, Xinyang, Wu, Jialing, Cheng, Xueyu, Cai, Zhonghua, Wang, Zongkang, Zhou, Jin
• Format: Article
• Language: English
• Subjects: Biodegradable microplastics; Crop growth; Ecological risks; Enzyme activity; Root-associated microbiome
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2024.120071

The effectiveness of biofertilizers as a cost-effective crop yield enhancer can be compromised by residual soil pollutants. However, the impact of accumulated polyadipate/butylene terephthalate microplastics (PBAT-MPs) from biodegradable mulch films on biofertilizer application and the consequent growth of crop plants remains unclear. Here, the effects of different levels of PBAT-MPs in soil treated with Bacillus amyloliquefaciens biofertilizer were assessed in a four-week potted experiment. PBAT-MPs significantly decreased the growth-promoting effect of the biofertilizer on Brassica chinensis L., resulting in a notable reduction in both above- and belowground biomass (up to 52.91% and 57.53%, respectively), as well as nitrate and crude fiber contents (up to 12.18% and 13.64%, respectively). In the rhizosphere microenvironment, PBAT-MPs increased soil organic carbon by 2.63-fold and organic matter by 2.68-fold, while enhancing sucrase (from 67.55% to 108.89%) and cellulase (from 31.26% to 49.10%) activities. PBAT-MPs also altered the rhizospheric bacterial community composition/diversity, resulting in more complex microbial networks. With regard to microbial function, PBAT-MPs impacted carbon metabolic function by inhibiting the 3-hydroxypropionate/4-hydroxybutyrate fixation pathway and influencing chitin and lignin degradation processes. Overall, the rhizospheric microbial profiles (composition, function, and network interactions) were the main contributors to plant growth inhibition. This study provides a practical case and theoretical basis for rational use of biodegradable mulch films and indicates that the residue of biodegradable films needs pay attention. [Display omitted] •PBAT-MPs attenuated the crop growth promotion effect of biofertilizers more then 50%.•PBAT-MPs changed the structure, function and network complexity of rhizospheric microbes.•PBAT-MPs inhibited carbon fixation/degradation efficience of soil microorganisms.•Scientific basis is necessary for the safe and rational use of biodegradable film mulch.