Soil-Biodegradable Plastic Mulches Undergo Minimal in-Soil Degradation in a Perennial Raspberry System after 18 Months

Abstract

Soil-biodegradable plastic mulches (BDMs) are made from biodegradable materials that can be bio-based, synthetic, or a blend of these two types of polymers, which are designed to degrade in soil through microbial activities. The purpose of BDMs is to reduce agricultural plastic waste by replacing polyethylene (PE) mulch, which is not biodegradable. Most studies have evaluated the breakdown of BDMs within annual production systems, but knowledge of BDM breakdown in perennial systems is limited. The objective of this study was to evaluate the deterioration and degradation of BDMs in a commercial red raspberry (Rubus ideaus L.) production system. Deterioration was low (≤11% percent soil exposure; PSE) for all mulches until October 2017 (five months after transplanting, MAT). By March 2018 (10 MAT), deterioration reached 91% for BDMs but remained low for PE mulch (4%). Mechanical strength also was lower for BDMs than PE mulch. In a soil burial test in the raspberry field, 91% of the BDM area remained after 18 months. In-soil BDM degradation was minimal, although the PSE was high. Since mulch is only applied once in a perennial crop production system, and the lifespan of the planting may be three or more years, it is worth exploring the long-term degradation of BDMs in perennial cropping systems across diverse environments.

Keywords

• polyethylene mulch
• degradation
• deterioration
• mechanical property
• mesh bag study