ASHS 2025 Conference

A forum for discussion of potential collaborations with regards to plant growth and culture – i.e. propagation, root growth, water management, weed control, PGRs, plant nutrition, etc.

Overview of Workshop: Horticultural crop production depends on plastic mulch film to suppress weeds, optimize the soil microclimate, and overall improve economic and efficient production of crops within both conventional and organic systems. Unfortunately, the benefits of plastic mulch are often overshadowed by its poor end-of life outcomes with growers frequently landfilling, stockpiling, burying, or burning mulch waste at the end of a production season. Some of this mulch waste can become pollutants of soil and water. The horticultural industry needs new technologies that reduce persistent plastic waste generation with the expansion of extended producer responsibility, circularity, and sustainability initiatives. This interactive workshop will educate participants on promising solutions that preserve the essential functions of plastic mulch while reducing waste generation with an emphasis on soil-biodegradable plastic mulch and new collection, retrieval, and recycling technologies for non-biodegradable plastic mulch.  
The workshop is divided into three interactive sessions that will provide participants with a balance of academic and private industry perspectives. The sessions include: 1) Identifying the problem and possible solutions; 2) Lessons learned and recommendations from industry; and 3) Socioeconomic considerations and future prospects. Each session will have a panel of experts that will provide a brief presentation on a targeted topic. Invited industry speakers will share lessons learned and experience-shaped strategies to reduce plastic mulch waste generation. At the end of each session, samples of materials (e.g., soil-biodegradable mulch, mulch made with recycled resin) will be circulated and questions will be asked from the audience. The moderator will also poll the audience to promote engagement and to gather information about shared experiences related to sustainable mulch management. This information will be leveraged to discuss and design participant-tailored recommendations for sustainable end-of-life mulch management within their regions and communities at the end of the workshop. 
Moderators: Lisa W. DeVetter and Carol Miles

Session 1: Identifying the Problem and Possible Solutions (40 minutes total)
Speakers:

• Lisa DeVetter / Washington State University / Associate Professor of Horticulture
• Carol Miles / Washington State University / Professor of Horticulture
• Gene Jones / Southern Waste Information eXchange/ CEO

Session 2: Lessons learned from Industry (40 min total)
Speakers:

• Shuresh Ghimire/ Vegetable Assistant Extension Educator / University of Connecticut
• Ben Andros / Andros Engineering Cooperation / President
• Hillary Thomas / Naturipe Berry Growers, Inc. / Research and Technical Director  

Session 3: Socioeconomic Considerations and Future Prospects (40 min total)
Speakers:

• Jessica Goldberger / Washington State University / Professor of Crop and Soil Sciences
• Sam Wortman / Associate Professor and Environmental Horticulturist / University of Nebraska-Lincoln
• Pierre Sarazin / Polyexpert / Vice President of R&D and Sustainability

Maintaining soil health for open field and high tunnel (HT) production of vegetables has become prioritized by growers in recent years. In particular, there have been growing concerns about the sustainability of HT systems. Their hot and dry conditions, compounded by intensive practices, lead to challenges with soil temperature and moisture management, compaction, salinity, and ecosystem health. This report investigates how established and novel mulch types can help growers manage soil temperature, moisture, and health conditions across growing systems and climatic conditions. Tomato and lettuce trials were conducted from 2022 to 2024 in HTs and open-field plots to determine the effect of various mulch treatments (bareground, black plastic film, black woven fabric, paper mulch, white silage tarp and black silage tarp) on soil temperature, moisture, and health. Gravimetric and volumetric soil moisture content were determined weekly and bi-weekly in the lettuce and tomato trials, respectively. Soil temperatures were recorded at 10.2 cm depth throughout the growing seasons for both crops. EC, bulk density, and respiration data were collected at termination of all trials to assess soil health. In tomato, the application of black plastic mulch, fabric mulch, and black silage tarp was associated with higher average soil temperatures (23.7°C-28.9°C), compared to (22.4°C-26.8°C) under white tarp and paper mulch. In the lettuce trials, all mulch types retained soil heat in the early season (0.7°C-2.2°C) compared to bareground. The use of silage tarp maintained up to 21% more soil moisture than the bareground treatment for tomato and all mulches were effective at managing moisture loss. Limited effects on soil health criteria were observed, though higher measurements of bulk density and EC may be associated with increases in soil moisture. Results indicdate that mulch color and material affect soil temperatures and soil moisture in the summer, whereas in fall all mulches may reduce heat loss in the early period of the growing season and soil moisture (5-7%) in the late season. As growers address soil health concerns, an integrated approach will need to be adopted that utilizes multiple practices. This study shows that mulch color and type/material can be selected to alter the microclimate of the soil environment across production systems. More research is needed to determine how these impacts affect long-term soil health. The development of regional growing practices that ensure soil health will be instrumental to support a growing population and using mulches for vegetable production can help achieve this goal.

Evaluation of Soil Biodegradable Mulches used in Plasticulture System Under Different Climatic Regions of North Carolina With Tomato as A Model Crop E. Atley, G. Yang, and T. McGee, Department of Natural Resources and Environmental Design, North Carolina A

The widespread use of plastics in agriculture (plasticulture), including greenhouse films, plastic mulches, plastic pots, seedling trays, pesticide containers and drip irrigation systems, although contributing to short-term productivity, has long-term detrimental consequences for the ecosystem and human health. The accumulation of plastics in soil, chemical leaching from plastics and their degradation into microplastics (particles smaller than 5 mm) is one of the most serious environmental challenges, affecting soil fertility, plant health, and the human food chain. Micro- and nanoplastics and the additives used to enhance the performance and appearance of these plastics can potentially damage tissues and cellular systems by activating various chains of tissue function. Thus, various types of micro- and nanoplastics lead to inflammation, cytotoxicity, genotoxicity and immunotoxicity in cells and tissues. Reproduction is particularly affected by these pollutants, as many of these pollutants can cause endocrine disruption. Efforts to mitigate the negative impacts of plastics include recycling plastic waste, developing biodegradable alternatives, and improving waste management practices. In this regard, Behzist Danesh Narvan Company has used modern technology to produce biodegradable pots (Lignum Vitae) made from completely natural materials such as plant fibers and bio-based adhesive. These flower pots have many advantages as being breathable, 100% biodegradable and ecofriendly, rapid decomposition, having high percentage of organic matter, compatibility with different climates and reducing plastic pollution. These pots can act as a natural fertilizer and enhances plant growth after decomposition.

Open to all

High tunnels (HT) are utilized by vegetable growers to extend the growing season and improve the yield and quality of crops. However, concerns about the sustainability of HT soil health can have direct effects on yield and profitability. Recently, growers and researchers have expressed concerns related to soil moisture in high tunnels and potential negative consequences to soil health. The use of non-permeable polyethylene tarps has become popular for urban and small-scale vegetable farmers to manage weeds through occultation. Similar tarps could also be used as mulch, but little is known about how this will affect crop productivity compared to other mulch types. The goal of this study was to examine silage tarps and other mulch types in HTs and the open field to determine how this practice may affect yield and quality of tomato and lettuce. Tomato and lettuce trials were conducted from 2022 to 2024 in HTs and open-field plots to determine the effect of various mulch treatments (bareground, black plastic film, black woven fabric, paper mulch, white silage tarp and black silage tarp) on tomato and lettuce yield and quality. For tomato, harvesting occurred weekly to monitor total, marketable, and non-marketable yield. Texture and organoleptic quality were assessed from 3 harvests across the two years. In 2023, lettuce were harvested and yield data were collected. Leaf color and water content were also assessed. In the HT tomato trials, mulch had the greatest effects on yield during the early season and the application of white silage tarp and plastic film mulch increased early marketable fruit yield by 58% compared to the bareground treatment. Mulch type had no significant effect on tomato or lettuce on the postharvest qualities that were assessed. Our data indicate that silage tarps may be an effective mulch, particularly for HT growers that are looking to conserve soil moisture and ultimately improve soil health. Yield and quality of tomato and lettuce were not penalized when tarps were utilized, and in some cases, yield was improved. As growers continue to adopt practices that help sustain or improve soil health, it is likely that silage tarps and other mulch types can be effective at maintaining crop productivity

Polyethylene (PE) mulch is a valuable tool that suppresses weeds, optimizes the soil and canopy microclimate, and enhances efficient production of quality fruits and vegetables. However, PE mulch is not biodegradable and limited cost-effective waste management options lead to large amounts of used PE mulch being annually landfilled, stockpiled on farms, burned, and sometimes buried in soil. The objective of this presentation is to review the status of alternative mulch technologies that have the potential to reduce plastic waste generation in strawberry (Fragaria × ananassa) cultivation with an emphasis on soil-biodegradable plastic mulch (BDM), hydromulch, and cellulose-based film. Several commercial BDM products have been available in the market since the 1990s and are made using a blend of fossil-fuel derived and biobased ingredients. Trials conducted in Washington State show strawberry yield and fruit quality are comparable when plants are grown with black PE mulch or BDM. Green BDM deteriorates rapidly depending on environmental conditions. Rapid deterioration may lead to increased weed pressure and reduced production similar to bare ground cultivation. Hydromulch is a sprayable mulch alternative that can be formulated with ingredients that meet the requirements for certified organic production in North America, whereas commercially available BDMs do not meet these requirements. Trials carried out in Washington State and North Dakota demonstrated hydromulch maintains strawberry yield and fruit quality. Hydromulch formulations with guar gum demonstrate superior mechanical properties relative to formulations without or with other tackifiers. Reduced weed suppression, the logistics of sourcing hydromulch feedstock, lack of specialized application equipment, and high material and application costs are current barriers to this emerging technology. Cellulose-based film, such as lignocellulose film, is another fully biodegradable and emerging alternative to PE mulch and can be made with ingredients suitable for certified organic production. Field trials with cellulose-based film are limited, but current findings show high levels of biodegradability and maintenance of crop growth. Growers, crop consultants, and marketers should consider biodegradable mulch alternatives to reduce plastic waste generation and persistent plastic pollution in agricultural and environmental settings, particularly if recycling is not available or a cost-effective option.

An estimated two million tons of plastic mulch films (PMFs) are used in horticultural production worldwide due to the benefits these films provide that may lead to yield increases. Despite the high usage rates of PMFs, there are many environmental drawbacks to the implementation of plastic mulches. To investigate potential mitigation strategies, two plastic and two biodegradable plastic films were used for multiple consecutive growing seasons. Soil conditions, plant yield and mulch durability were used to evaluate the soundness of reusing mulch films for multiple growing seasons. There were no significant differences between mulch types for the first season, with the highest yield being 307.23 pounds of tomatoes and the lowest yield being 235.62 pounds of tomatoes per 50 row feet. There were significant yield differences between mulch types for the second season, where each cabbage head produced on plastic mulches weighed an average of 3.68 pounds while each cabbage head produced on biodegradable mulches weighed between 1.22 and 1.84 pounds. The yield differences observed in season two may be in part due to increased soil penetration resistance under the biodegradable mulches, which had to be replaced at the end of the first season. The biodegradable mulches had to be replaced at the end of the first season due to their extreme degradation, but they were replaced at unfavorably high soil moisture conditions which led to considerable compaction, and higher penetration resistance, in those plots. Biodegradable mulched plots exhibited more than 50% bare ground at the end of the first growing season while plastic mulched plots both exhibited less than 10% bare ground. In addition to their in-field degradation, biodegradable films are also significantly weaker materials than PMFs, with average tensile strengths of 2.02 N and 2.91 N at the end of season one, compared to the average tensile strength of 4.56 N of conventional polyethylene. These results suggest that biodegradable PMFs may not be a good option for use over multiple seasons. Further research is needed to determine the optimum management practices for increased profitability PMFs in vegetable production systems while also improving environmental friendliness.

Mulch films play a crucial role in enhancing crop yields and suppressing weeds; however, conventional plastic mulch films (PEMs) contribute significantly to environmental burdens, particularly at the end-of-life (EOL) stage. In response, soil-biodegradable mulch films (BDMs) have emerged as an alternative, offering potential benefits in reducing waste and emissions. This study conducts a cradle-to-grave life cycle assessment (LCA) of BDMs (PBAT/PLA, 30/70 PBAT/TPS, 70/30 PBAT/TPS blends) compared to PEMs (LDPE) across ten environmental impact categories in the production of 1 kg of strawberries per hectare in California, USA. Multiple EOL scenarios were evaluated, including soil-biodegradation, anaerobic digestion, and composting for BDMs, and landfill (with and without energy recovery) for PEMs. Results indicated that during the manufacturing stage, BDMs exhibited the lowest fossil fuel depletion, with the 30/70 PBAT/PLA achieving a 72% reduction; however, all BDMs had higher global warming potential (GWP). The highest environmental burdens in manufacturing were associated with BDM-PBAT/PLA due to its high energy requirements. During the mulch use stage, all BDMs consistently outperformed PEMs slightly in key impact categories such as GWP (reducing emissions by approximately 4.7%), acidification, and smog formation. No significant differences were observed among BDMs in this stage, suggesting that primary environmental distinctions arise from manufacturing and EOL scenarios rather than field application. The EOL stage significantly influenced the overall sustainability of mulch films. In terms of fossil fuel consumption, carbon emissions, and human toxicity potential, the most favorable scenarios were BDM-soil-biodegradation (-2.65 kg CO2-eq) and BDM-anaerobic digestion (-20.9 kg CO2-eq), both of which also reduced ecotoxicity (approximately -51 CTUe) and carcinogenic effects while minimizing fossil fuel depletion (approximately -1.72 MJ). In contrast, BDM-composting resulted in higher acidification (up to 0.344 kg SO2 eq) and smog formation, making it a less favorable option. PEMs, even under energy recovery scenarios, exhibited higher impacts and lacked the benefits of biodegradability, emphasizing the sustainability advantages of BDMs. When considering the full cradle-to-grave life cycle, BDMs demonstrated superior environmental performance under optimal EOL strategies. Although PEMs had a lower manufacturing footprint, their EOL challenges negated these benefits. Among BDMs, PBAT/TPS blends, particularly the 30/70 PBAT/TPS, exhibited the most balanced performance, offering reduced manufacturing burdens alongside excellent EOL outcomes. This study provides a detailed analysis of the environmental benefits and trade-offs of BDMs. The findings, along with nuanced recommendations, support the transition toward more sustainable mulch film applications.

Lignocellulosic film is a biodegradable alternative to traditional, non-biodegradable polyethylene (PE) mulch, and is made with fully biobased feedstocks. The biobased composition of lignocellulose film renders it suitable for certified organic production in the United States and Canada, whereas soil-biodegradable plastic mulches are not permitted given they are not made with fully biobased feedstocks. However, information regarding the horticultural performance of lignocellulose film as a mulch is lacking. The objective of this study was to address this knowledge gap by comparing the functionality of lignocellulosic film to other mulch treatments using raspberry grown in a greenhouse. ‘Cascade Premier’ tissue culture transplants were planted in 12.7 x 12.7 cm (1.89 L) pots and grown for 112 days. Mulch treatments were placed over the surface of the media and around the base of the plants before being arranged in a randomized complete block design with eight replicates. Treatments included PE, soil-biodegradable mulch (starch-based, PBAT copolyester), paper mulch, lignocellulosic film, lignocellulosic film with biochar, cellulose film, and no mulch. Mulch treatment did not significantly impact overall plant growth throughout the trial, although variations in soil temperature were observed with lignocellulosic film having the highest reported temperature overall. Following the greenhouse experiment, new mulch samples were subjected to a soil biodegradation assay whereby samples were buried in two contrasting climates in Washington (i.e., warm-summer Mediterranean and cold semi-arid climates) with four replicates per location. Lignocellulosic film made with a hot press and lignocellulosic film with biochar and a hot press were added as additional treatments. Mesh bags containing the mulch samples were collected and analyzed for visual breakdown. Differences in breakdown were observed across mulch treatments with cellulose film being the most degraded, PE mulch being the least degraded, and lignocellulose being intermediate. After 3 months, lignocellulose had degraded by approximately 50% in both locations. Results to date indicate films made with lignocellulose maintain plant growth relative to PE mulch and biodegrade rapidly once incorporated into the soil. Future work should focus on scaling up lignocellulose material generation so they may be evaluated in open-field settings.

While agricultural plastic mulch significantly enhances crop yields, its widespread use generates substantial plastic waste, raising serious environmental concerns. Traditional disposal methods such as landfilling and incineration not only contribute to greenhouse gas emissions but also result in valuable resource losses. To address these challenges, this study performs a systematic life cycle assessment (LCA) comparing five end-of-life (EOL) strategies for polyethylene (PE) mulch films in strawberry cultivation: conventional landfilling, incineration, pyrolysis-based conversion, wood-plastic composite (WPC) production, and asphalt modification. A gate-to-gate LCA framework was adopted, with system boundaries spanning from on-farm mulch collection to final material or energy recovery. Environmental impacts were evaluated using the TRACI 2.1 methodology, encompassing global warming potential (GWP), cumulative energy demand, air/water pollution, land occupation, resource recovery efficiency, microplastic leakage risks, and human health impacts. Results reveal distinct trade-offs among the EOL pathways. Pyrolysis emerges as the optimal energy recovery strategy, reducing fossil fuel dependence by converting 85% of plastic waste into syngas while mitigating microplastic release. WPC production demonstrates superior material circularity, repurposing 92% of waste into durable construction materials with a 40-year service life. Asphalt modification offers the lowest GWP (1.2 kg CO₂-eq/kg plastic) and reduces virgin polymer demand by 30%, though its long-term microplastic leaching requires further investigation. In contrast, landfilling and incineration exhibit 60-75% higher life cycle emissions and fail to recover material value. This study provides the first comprehensive comparison of agricultural plastic waste management strategies that integrates both energy recovery and material upcycling paradigms. By extending traditional LCA boundaries to include microplastic pollution risks and long-term degradation effects, the findings offer actionable insights for policymakers to prioritize scalable, resource-efficient solutions that align with circular economy principles in agri-plastic management.

Biodegradable plastic mulches (BDMs) have been introduced as a sustainable alternative to polyethylene (PE) mulches, which can contribute to plastic contamination and incur high removal and disposal costs. The objective of this study was to evaluate the performance and suitability of BDMs for winter strawberry production in Florida. We conducted field experiments using ‘Florida Brilliance’ short-day strawberry during the 2023–2024 (Season 1) and 2024–2025 (Season 2) winter seasons in West Central Florida. Five mulch treatments were evaluated: black PE mulch, black Mater-Bi® BDM (black MB–BDM), black Ecovio® BDM (black EV–BDM), white Mater-Bi® BDM (white MB–BDM), and white Ecovio® BDM (white EV–BDM ). Mater-Bi® is primarily starch-based but also contains polyester resins such as polybutylene adipate terephthalate (PBAT) and polycaprolactone. By contrast, Ecovio® is predominantly resin-based, comprising PBAT, polylactic acid, and other biodegradable polymers. The film thickness was 27.9 μm for the black PE and 22.9 μm for all BDMs. Season-dependent trends were observed in some results. In Season 1, all BDMs exhibited minimal deterioration with only minor tearing, and there was no significant difference in marketable yield compared to the black PE. In Season 2, all BDMs developed splits or tears within a month after transplanting, with the black EV–BDM and both white BDMs showing higher deterioration rates than the black PE. Orthogonal contrast analysis was used to assess BDM performance based on color and composition. Compared to the black PE, marketable yield was reduced by 28% for the black BDMs (34.0 vs. 26.5 t·ha–1) and by 8% for the white BDMs (34.0 vs. 31.3 t·ha–1). The white BDMs produced 18% higher yield than the black BDMs (31.3 vs. 26.5 t·ha–1), whereas no significant difference was found between the MB–BDMs and the EV–BDMs (28.8 vs. 29.1 t·ha–1). Soluble solid content remained unaffected by mulch treatment across both seasons and all growth stages. These results suggest that the performance of BDMs depends on seasonal weather conditions, mulch color, and composition, presenting challenges for commercial adoption. Enhancing the reliability and adoption of BDMs may require optimization of color, material composition, and film thickness.