ASHS 2024 Conference

The use of polyethylene tarps is becoming popular for urban and small-scale vegetable farmers to manage weeds through occultation. Similar tarps can also be used as plastic mulch in high tunnels during the growing season. However, little is known about how this will affect crop productivity and soil moisture retention. Trials were conducted in 2022 and 2023 to determine the effect of white silage tarp, black silage tarp, paper mulch and black landscape fabric as compared to bare soil for lettuce and tomato grown in high tunnels. Two lettuce varieties (red and green) were planted in a split-plot randomized complete block design in the fall and tomatoes were grown during the summer. Soil samples were used in combination with soil moisture meter readings to determine gravimetric and volumetric soil moisture content throughout the season. Tomato trials were conducted in six high tunnels and six open-field plots. For both crops, harvesting occurred to monitor total, marketable, and non-marketable yield. According to a one-way ANOVA test, there was not a significant treatment effect in the 2022 lettuce trial. However, the 2023 lettuce trial revealed that white and fabric treatments were the most effective at conserving soil moisture. On average, there was 2.6% higher soil moisture in plots with white silage tarp and black landscape fabric as compared to the bare ground plots. In the high tunnel tomato trial, the bare plots had significantly lower volumetric and gravimetric soil moisture levels (P

Plastic pollution is a global concern due to its adverse effects on ecological systems. Plastic disposal and degradation release small fragments known as microplastics (MP) that can accumulate, infiltrate, and travel through soil, air, water, plants, and the environment. Studies indicate the omnipresence of MPs in soils and show their potential to influence seed germination, plant growth, and development. To investigate the effects of microplastics on seed germination, two replicated germination experiments were conducted under controlled conditions in germination chambers, SciBrite TM LED lighting at their optimum germination temperature of alternating 22/35°C day/night for a 14-hour photoperiod for 30 days at Florida Gulf Coast University. Seeds of Lettuce (Lactuca sativa), a widely cultivated horticultural crop were sown in petri plates (100 x 15 mm) containing four different soil amendments with microplastics PET (polyethylene terephthalate) fiber-filled microplastics (v/v) at 0.5%, 1%, 1.5%, and 2% concentrations and sizes < 125 µm, 126-250 µm, 251-375 µm, and 376-500 µm. Seeds were considered germinated with the protrusion of the radicle from the embryo. Germinated seeds were tossed away and calculated for Germination % (GP) and Mean Germination Time (MGT). Our preliminary results showed microplastics at lower concentrations of 0.5% and 1.0% decreased GP and increased MGT compared to higher concentrations of MPs. Small MP sizes showed negligible impact on the GP and MGTs. Future research will involve conducting pot experiments in a hoop house at the Southwest Florida Research and Extension Center (SWFREC), UF/IFAS, Immokalee to assess the impact of microplastics on plant growth, development, plant physiology and regulation. Data collection will include measurements of plant height, leaf chlorophyll content, photosynthetic gas exchange, leaf area Index (LAI), fresh and dry plant biomass (g), visual rating, and spectral signatures of healthy versus stressed plants at various intervals of crop growth stages. Keywords: PET microplastics, germination %, mean germination time, physiology, spectral signatures

Lignocellulosic film is a new biobased, soil-biodegradable mulch option for horticultural cropping systems, created as an environmentally friendly substitute to polyethylene (PE) and non-biobased soil-biodegradable mulch. PE mulch is widely known as a large contributor to agricultural plastic waste since it is made from non-biodegradable polymers. To provide a more sustainable alternative to PE mulch, commercially available soil-biodegradable mulches are on the market, as they are designed to biodegrade in soils upon tillage. One of the main limitations of the currently available soil-biodegradable mulches is that they are not allowed in certified organic agriculture, because they are not made with 100% biobased feedstocks. Lignocellulosic film is made with fully biobased, renewable feedstocks, such as wood chips, giving it the potential to address this problem. Lignocellulose is plant biomass consisting of the components of plant cell walls, which include lignin, cellulose, and hemicellulose. Wood chips are ground up, and through a facile dissolution/dispersion and regeneration process, lignocellulosic film is created. When preparing black lignocellulosic films, biochar may be added as a colorant. Within a recyclable solvent, the ground wood and biochar mixture are dissolved and/or dispersed. Once the mixture is cast into a sheet, it undergoes a washing and drying procedure, which results in an entirely biobased film. Information regarding the material properties of lignocellulosic film relative to other agricultural mulches will be presented along with future directions of research to improve end-of-life outcomes of agricultural mulch film in horticultural systems.

Biodegradable plastic mulches (BDMs) have been introduced as an alternative to polyethylene (PE) mulches, which are costly to remove and dispose of. The objective of this study was to evaluate the performance and suitability of biodegradable plastic mulches for winter strawberry production in Florida. We conducted a field experiment using ‘Florida Brilliance’ short-day strawberry in the 2023-2024 winter season in West Central Florida. The experiment consisted of five mulch treatments: black PE mulch (control), black starch-based BDM (Mater-Bi®), black resin-based BDM (Ecovio®), white starch-based BDM (Mater-Bi®), and white resin-based BDM (Ecovio®). Although mulch deterioration was minimal on the bed top, it was more evident on the sides or at the base of the bed, especially for starch-based BDMs. Compared to black PE and BDMs, white BDMs increased light reflection and light interception by the canopy. Consequently, white BDMs recorded lower mulch surface, canopy, and fruit temperatures. White BDMs had 35% and 15% higher early season marketable yield (December–January) than black PE and BDMs, respectively, whereas total marketable yield did not show any significant difference. White BDMs showed significantly higher fruit soluble solids content than all black mulches. These results of suggest that the performance and suitability of biodegradable plastic mulches depend on their colors and compositions.

The rise in the use of agricultural plastic mulch films raises environmental concerns, necessitating sustainable alternatives. Despite acknowledged benefits, the widespread adoption of biodegradable mulch over traditional plastic mulch remains a topic of debate. This review employs a comparative life cycle assessment perspective to explore the interplay between environmental impact and economic considerations associated with the production, use, and end-of-life of plastic and biodegradable mulch films. It also postulates impact mitigation strategies for mulch use in agroecosystem. Overall, biodegradable mulch films demonstrate superior merits in energy use and greenhouse gas emissions, but often contribute more to eutrophication, acidification, and land-use occupation compared to plastic mulch films. Environmental burden was found to vary based on polymer type, life cycle stage, end-of-life strategy, fertilizer application, additive content, film thickness, and climate. The manufacturing stage for both mulch types significantly contributed to greenhouse gas emissions and energy use, while plastic mulch film post-use stage contributed to human toxicity, ecotoxicity, eutrophication, acidification, GHG emissions, and photochemical effects depending on the end-of-life choices and adsorbed waste content. Energy and material recovery options are major strategies to mitigate post-use impacts, with recycling being preferable, albeit with the need to address eutrophication and human toxicity. Both mulch types increase yield, but deposited plastic mulch film residue creates soil health problems. On all fronts, biodegradable mulch films, especially starch-derived films, are more environmentally justifiable replacement for plastic mulch films, but higher production costs hinder widespread adoption. From an alternative perspective, straw mulch is a promising replacement for plastic mulch films in dryland areas due to yield, cost, and GHG reduction advantages. However, prevention of open burning and minimizing N-fertilizer applications to reduce N2O releases must be considered. The choice between plastic and biodegradable mulch films, therefore, requires a holistic assessment considering specific contextual nuances. This review elucidates these intricacies from economic, agronomic, and environmental viewpoints, providing an unbiased decision-making tool for agronomists, farmers, mulch film manufacturers, recyclers, and policymakers.