Submission Date

5-4-2026

Document Type

Paper- Restricted to Campus Access

Department

Biology

Adviser

Denise Finney

Committee Member

Colleen Bove

Committee Member

Patrick Hurley

Department Chair

Denise Finney

Project Description

Plastic film mulching is widely used in agriculture to improve crop productivity, but it leads to the accumulation of microplastics (MP) in soils, with poorly understood consequences for carbon and nutrient cycling. This project examined how MP influence carbon (C) and nitrogen (N) mineralization of organic substrates of differing quality. In a controlled 30-day soil incubation at 22°C, soils were treated with polyester (PE) or polypropylene (PP) microplastic fibers (1000 – 5000 µm) and incubated with green tea (GT; high-quality residue) or rooibos tea (RT; low-quality residue). Plastic type significantly affected respiration 24 hours into incubation (p=0.001), with PP reducing rates in GT (p=0.003) and RT (p=0.037) compared to soils without MP or with PE. An interactive effect between plastic and substrate was found 4 days into incubation (p< 0.001) with PE and PP increasing respiration in only in GT (p< 0.001). Plastic type had no effect on respiration during late incubation (p=0.232). A significant interaction occurred in residue mass loss (p=0.012), where GT exhibited lower mass loss when treated with PE (p=0.004) and PP (p=0.006) compared to no MP. Post-incubation total soil C was significantly higher in plastic-amended soils (p=0.002), while net N mineralization was unaffected (p=0.053). These findings suggest that microplastics induce transient disruptions in microbial activity and slow the physical decomposition of high-quality residues. This may lead to a mismatch between nutrient release and crop demand, indicating that long-term residue management strategies may require adjustment in soils with a legacy of plastic mulching.

Download

Share

COinS