ASHS 2024 Conference

Cover Crop Windbreaks for Slowing Biodegradable Mulch Deterioration and Improving Bell Pepper Productivity. - Caleb Wehrbein
Influence of Plastic Mulch Color on Yield and Quality of Day-neutral Strawberries - Tricia Jenkins
Exploring sustainable mulch solutions: a comparative study in strawberry production systems in northwestern Washington - Nayab Gull
Shade level effects on fruit yield of habanero chili (Capsicum chinense Jacq.) - Juan Carlos Diaz Perez
Quantum Dot Concentration in Photoconversion Covers Affects Growth Rates of Four Microgreens Species - Jeffrey Bates

Polyethylene mulch films have become a dominant production practice to increase the yield potential of high value crops, but they are a significant source of environmental contamination. Alternatively, biodegradable mulches are a potentially sustainable alternative , but are less popular among growers as they vary in durability and performance in the field environment. Cover crops when sufficiently tall may be able to improve biodegradable mulch durability by reducing wind intensity within a mulched bed. To quantify the utility of a cover crop windbreak, we tested the effect of a fall-planted, 6ft wide strip of cereal rye planted parallel to the southern side of mulched bell pepper beds. Whole plot treatments included presence or absence of rye and split plot treatments included a comparison of polyethylene mulch, biodegradable mulch, and a bare ground control. Day windspeeds were reduced in peppers protected by a south-facing cereal rye strip by 60% relative to unprotected peppers. Large hole occurrences in biodegradable mulch were reduced by 50% and small holes by 15% in peppers protected by a cereal rye strip relative to unprotected peppers. Peppers grown behind the cover of cereal rye had a 42% reduction in leaning plants compared to peppers without cereal rye. Stomatal conductance was increased by 27% in peppers protected by cereal rye relative to unprotected peppers as a result of reduced windspeeds, though there were no differences in fruit yields. Results suggest cover crops can extend the useful life of biodegradable mulch films, which may help address a common barrier to adoption. Ongoing research aims to better understand the effects of the cover crop on crop health, yield, and quality.

High tunnel production of day-neutral strawberries is a promising production system in the central U.S. The use of different colored plastic mulches in a high tunnel production system can vary the microclimate around plants and alter yield and fruit quality. This study was conducted to identify the most appropriate color plastic mulch in a high tunnel production system as it relates to yield and fruit quality. The experiment was conducted at the Kansas State University, Olathe Horticulture Research and Extension Center in 2020 and 2021 using a split-plot, randomized complete block design. We evaluated six plastic mulches (black, white, striped silver, silver, red, and green) and two day-neutral cultivars, ‘Albion’ and ‘Portola’. Soil temperature and UV light reflected from the mulch were measured to monitor microclimate modifications. Fruit quality was assessed by overall visual quality, color, soluble solids content, titratable acidity, sugar/acid ratio, total phenolics, and anthocyanin content of strawberries. 'Portola’ produced greater yields than ‘Albion’, but ‘Albion’ had better fruit quality. The plastic mulches altered the reflected UV light and soil temperatures. During the mid and late season, the silver mulch had higher fruit yields than the red and green mulches, likely due to its ability to limit solar warming during warm production months. The mulches had inconsistent impacts on fruit quality. Overall, the silver mulch maintained the best microclimate for day-neutral strawberry production in high tunnels.

Agricultural plastic mulch made from non-biodegradable polyethylene (i.e., “PE mulch”) provides many horticultural benefits. However, PE mulch requires annual removal and disposal, which generates large volumes of plastic waste that is rarely recycled and can become a pollutant. Incomplete removal of PE mulch also can leave behind plastic fragments that threaten soil and ecosystem health. To address these challenges, soil-biodegradable mulches (BDMs) have emerged as a potentially more eco-friendly alternative. BDMs are designed to provide the same advantages for specialty crop production as PE mulch and naturally biodegrade when incorporated into the soil. In addition, non-biodegradable reflective mulch has emerged as a promising mulch technology that may reduce key insect pests. The objective of this research was to evaluate the impacts of different mulch technologies, including soil-biodegradable and reflective mulches, on horticultural and pest dynamics in day-neutral strawberry (Fragaria×ananassa cv. Albion) in northwest Washington. Seven mulch treatments were established in a randomized complete block design with four replications in 2023. Treatments included green and black BDM made with ecovio and Mater-Bi feedstocks, non-biodegradable metalized mulch, and controls of black PE mulch and unmulched plots. Yield from all mulch treatments did not differ significantly from black PE control except for the green BDM made with ecovio feedstock. The green BDM made with ecovio resulted in significantly lower (32%) yield, similar to unmulched control. Lower yield may be attributed to the rapid deterioration of the green BDM treatments, which lacks carbon black and deteriorated more rapidly compared to other mulch treatments. However, black BDM made from MaterBi feedstock and metalized mulch were 37% and 11% less deteriorated than PE control respectively. Additionally, all mulch treatments suppressed weeds better than the unmulched control and were not different from black PE mulch. Aphid and thrips populations were highest in unmulched plots, whereas metalized mulch had fewer thrips (on sticky cards) and fewer aphids (on leaves) than all other treatments. Overall, the study highlighted that black BDM performs similarly to PE mulch with regards to potential weed suppression and maintenance of yield, whereas the rapid deterioration of green BDM could effect the soil microclimate and subsequent plant growth. Despite rapid mulch deterioration, the study did not observe compromised weed management. Metalized mulch may contribute to reducing pest populations but impacts on pollination and biological control remains unknown. Additional research on soil health effects is required given the fate of BDMs is in-soil incorporation.

Habanero chili fruit is shiny, orange, or red, about 5 cm long, and very pungent (200,000 to 300,000 Scoville heat units). It is popular in Mexico, Central America, and the Caribbean, although it is increasing in demand in the U.S. There is reduced information on chili production under shade nets. The objective was to determine the effects of shade level and cultivar on the fruit yield of habanero chili. The study was conducted in Tifton, Georgia, under field conditions in two seasons. Habanero plants were grown using raised beds, black plastic film mulch, and drip irrigation, following the University of Georgia extension recommendations for bell peppers. The experimental design was a randomized complete block with four replications and 10 treatments (5 shade levels x 2 cultivar combinations). Habanero chili ‘Kabal’ and ‘Kukulkan’ were grown at 0% (unshaded), 30%, 47%, 62%, and 80% shade levels. Marketable fruit number and yield decreased quadratically with shade level, although there were no statistical differences in marketable yield for plants in unshaded conditions and 30% and 47% shade levels. Mean marketable yields were 33.6 t/ha (unshaded) and 5.7 t/ha (80% shade level). Less than 2.5% of total fruit were affected by sunscald and blossom-end rot. Total and marketable fruit numbers and yields and individual fruit size were higher in ‘Kukulkan’ than in ‘Kabal.’ In conclusion, although shading increased fruit size, it did not improve marketable yield compared to unshaded conditions.

Compared to standard polyethylene agricultural covers, plants grown under quantum dot-infused covers (QD, QDCs) that redshift the light spectrum have exhibited greater yields. While whole-plant and -canopy morphological changes under photoconversion products have been documented, impacts on seedling growth rate (<3 weeks post-germination) are not known. In the current study, four microgreens (alfalfa [Medicago sativa], amaranth [Amaranthus tricolor], kohlrabi [Brassica oleracea var. gongylodes], and pea [Pisum sativum]) were grown in an ebb and flow hydroponic growth chamber under metal halide lamps coupled with QDCs (UV/blue to red/far-red) containing different QD concentrations. Growth measurements derived from image-based phenotyping and traditional, destructive methods were analyzed on a species-specific level. Plants exhibited increased leaf area, biomass accumulation, and growth rate on a species-specific basis. Commercially relevant, it was estimated that some species could be ready for sale days earlier than their control counterparts. Germination rate was not affected significantly.

Conserving Soil Moisture in High Tunnels to Maintain Soil Health - Claire Barnhart
Impact of Microplastic Amended Soils on Growth and Physiology of Lettuce Crop - Vanaja Kankarla
Introducing A New Biobased, Biodegradable Mulch: Lignocellulosic Film - Aidan Williams
Performance and suitability of biodegradable plastic mulches for winter strawberry production in Florida: Mulch deterioration, microenvironment modification, and growth and yield responses - Hadi Ghasemi
Plastic and Biodegradable Mulches in Agroecosystem: A Comparative Life Cycle Assessment Perspective to Environmental Impact and Economic Considerations - Oluwatunmise Dada

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.