Visual Assessments of Biodegradable Mulch Deterioration Are Not Indicative of Changes in Mechanical Properties

Abstract

<jats:p>The functionality of biodegradable mulch can be evaluated in agricultural field settings by visually assessing mulch intactness over time (a measure of deterioration), but it is unclear if mulch deterioration is indicative of mulch degradation as measured by mechanical properties (like breaking force and elongation). This 3-year study (2010–12) examined mulch percent visual deterioration (PVD) during the summer growing season in open-field and high tunnel production systems, and compared these to mulch mechanical properties at mulch installation (12–30 May), midseason (22 July–9 Aug.), and season end (6–25 Oct.), to determine if the field-based measures reliably predict degradation as revealed by changes in mulch mechanical properties. Four different types of biodegradable mulches [two plastic film mulches marketed as biodegradable (BioAgri and BioTelo); one fully biodegradable paper mulch (WeedGuardPlus); and, one experimental spunbonded plastic mulch designed to biodegrade (SBPLA)] were evaluated against a standard nonbiodegradable polyethylene (PE) mulch where tomato (<jats:italic>Solanum lycopersicum</jats:italic> L. cv. Celebrity) was planted as the model crop. Each year for the 3 years, PVD increased earlier for WeedGuardPlus than the other mulches in both the high tunnel and open field, and WeedGuardPlus had the greatest PVD in both high tunnels and the open field (6% and 48%, respectively). Mechanical strength of WeedGuardPlus also declined by the end of the season both in the high tunnel (up to 46% reduction) and in the open field (up to 81% reduction). PVD of BioAgri and BioTelo reached a maximum of 3% in the high tunnel and 28% in the open field by the end of the season. Mechanical strength of BioAgri and BioTelo did not change over the course of the season in either the open field or high tunnel, even though the ability of these mulches to elongate or stretch declined 89% in the open field and 82% in the high tunnel. SBPLA and PE mulches did not show a change in PVD or mechanical properties in either the high tunnel or the open field. Overall, PVD was three to six times greater by midseason in the open field than in the high tunnels. Although there were significant relationships between visual assessments and various mechanical properties for each mulch except SBPLA, the relationships differed for each mulch when evaluated separately and had coefficients of determination (<jats:italic>R</jats:italic><jats:sup>2</jats:sup>) below 30%. Furthermore, PVD overestimated mechanical deterioration of BioAgri and BioTelo. Results of this study indicate that mulch visual assessments may reflect general trends in changes in certain mechanical properties of the mulch; however, visual assessment and mechanical properties provide different information on deterioration. Each should be used as needed, but not as a substitute for each other.</jats:p>

Humic and Acetic Acids Have the Potential to Enhance Deterioration of Select Plastic Soil-Biodegradable Mulches in a Mediterranean Climate

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Plastic Mulches Improved Plant Growth and Suppressed Weeds in Late Summer-planted Floricane-fruiting Raspberry

“…The slightly lower breaking force and especially the smaller elongation (i.e., less elasticity) of BDMs indicate that these formulations and thicknesses were more susceptible to on-farm activities that can puncture the film and cause damage. Cowan et al (2016) and Thompson et al (2019) reported that bio-based plastic mulches have lower tensile strength and mechanical resistance compared with PE mulch. Dharmalingam et al (2015) and Mendes et al (2016) reported that tensile strength of plastic mulches is reduced when thermoplastic starch [e.g., polylactic acid (PLA)] is included.…”

Degradable Mulch as an Alternative to Polyethylene for Watermelon Production

“…During the deterioration evaluation, each experimental unit (replicate, 12 m long) for the four blocks was divided into 12 sub-blocks to reduce the assessment error; then, the total area covered by mulch was measured with a measuring tape to determine PVD. Mulch percent visual deterioration was estimated as the percent of soil exposed within the evaluated area such that 0% represented intact mulch and 100% represented completely deteriorated mulch (Cowan et al, 2016). At the harvest stage (120-130 DAP), marketable yield (pounds per acre) and fruit quality (TSS) were determined during each harvest for a total of three harvests.…”