Unveiling the impact of soil depth on degradation of durable nanocomposite mulch-derived residue migration dynamics in plant ecosystems

Abstract

The increasing use of biodegradable mulches, such as polylactic acid (PLA), offers a promising approach to tackling plastic waste. However, if PLA is improperly disposed of and degraded uncontrollably, it can negatively impact soil health and plant growth, compromising environmental benefits. This study demonstrates an interaction between hydrophobically modified nanocellulose (CA-CNC(MgSt)), which serves as a plasticizer within a PLA matrix, to create a self-degradable mulch film (PC). Specifically, PC exhibits an impressive toughness of 3.55 MJ·m⁻³. The use of PC mulch increased soil moisture content, stem length, and leaf area by 31.6 % and 63.2 %, respectively, while maintaining high biosafety. The degradation behavior of PC mulch varied with soil depth (-2, −7, and −14 cm), enhancing soil porosity and lowering pH, which accelerated its degradation and promoted root growth. Additionally, PC degraded faster than pure PLA (k_p < k_pc), attributed to the preferential hydrolysis of ester bonds. Biodegradable microplastics (BMPs) generated from mulch degradation, including P-BMPs and PC-BMPs, were studied using cherry radish growth models to explore plant-soil-microplastic interactions. This study demonstrates the potential of PC mulch to reduce plastic pollution through effective biodegradation while enhancing the stability of the soil-plant ecosystem. However, comprehensive ecological risk assessments are essential before their large-scale application.