ASHS 2025 Conference

Bacteria associate with plants across diverse ecosystems, including agroecosystems, where they often benefit plant growth by increasing nutrient availability and mitigating stress, leading to improved productivity. Cranberries are clonally propagated perennials grown in highly acidic soils, where beneficial bacteria could help reduce the need for synthetic fertilizer and enhance nutrient availability, supporting plant health in the long term. We isolated 102 putative phosphorus-solubilizing bacteria in Pikovskaya’s Agar, and 112 putative plant hormone-synthesizing bacteria in Czapek Dox Agar, and assessed their metabolic function using specific assays: malachite green assay for phosphorus solubilization and a tryptophan-IAA assay for plant hormone synthesis. We found that of our 102 isolated phosphorus bacteria, 29 could solubilize more than 100 μM of phosphorus bound to iron within three days. Of the 112 hormone-synthesizing bacteria, 38 produced more than 20 μg/mL of the plant hormone indole-3-acetic acid (IAA) within three days. Next, we will assess these bacteria in soils associated with plants by inoculating cranberry plants under sterile and non-sterile environments and monitoring plant growth responses. This approach aims to reduce fertilizer costs and environmental impact by enhancing water quality and bolstering cranberry crop health.

Bamboo is a perennial crop cultivated for different purposes such as production of edible shoots, timber and energy, and an effective medium for carbon sequestration. Bamboo production in the United States has gained significant interest over the past two decades due to its many benefits. Despite this progress, there is still a knowledge gap regarding nutrient and irrigation management recommendations for bamboo production for the unique Florida agroecological conditions. Fertilizer and irrigation are important crop management strategies for supplying plants with adequate nutrients and water for plant growth and productivity. Understanding the nexus between plants, water-use efficiency, and nutrient uptake is critical for sustainable bamboo production. A 4 x 4 factorial completely randomized design consisting of four irrigation rates (50% evapotranspiration (ET), 75% ET, 100% ET, and 125% ET) and four potassium application rates (0, 100, 200 and 300 lbs K/acre), replicated 5 times was established under greenhouse conditions. The results showed that different K levels did not have any significant effect on culm height and stomatal conductance. The 125% ET showed the highest culm height in the first month but in the following month, the 75% ET and 100% ET resulted in the greatest heights suggesting that reasonable culm height can still be achieved while conserving water. The 100% ET and 75% ET resulted in higher stomatal conductance compared to 125% ET and 50% ET. This implies that excessive irrigation and low irrigation rates may limit stomatal regulations and overall water use.

Understanding how organic amendments influence nitrogen (N) mineralization and carbon (C) respiration is essential for improving soil health and nutrient management in agroecosystems. This study, conducted by the Spring 2025 PSC 5560 Soil Analytical Techniques class at Utah State University, investigated the effects of various organic materials on soil N mineralization and CO₂ respiration through a controlled laboratory incubation. Six treatments were applied to a homogenized loamy soil collected from 0–30 cm depth: Miller compost, softwood compost, hardwood compost, wheat straw, feather meal, and an unamended control. Each treatment was mixed with soil and incubated in sealed mason jars under moist conditions for 35 days. CO₂ evolution was monitored via headspace gas sampling and analyzed with gas chromatography. Inorganic N (NH₄⁺ and NO₃⁻) was quantified on days 0, 7, 14, 21, and 35 through KCl extraction and spectrophotometric analysis. Results showed that respiration rates and mineral N release varied by treatment, reflecting differences in organic matter quality. Feather meal, with the lowest C:N ratio (3.8), released the highest levels of mineral N early in the incubation, although it did not fit the first-order kinetic model. Wheat straw, with a high C:N ratio (80.0), showed high cumulative CO₂ evolution, suggesting substantial microbial activity despite limited N mineralization. Compost treatments exhibited intermediate responses. Rate constants (k) for both C and N mineralization differed significantly among treatments, with feather meal and wheat straw showing the fastest rates for N and C, respectively. First-order kinetic modeling provided estimates for potentially mineralizable N (No) and C (Co), highlighting the variability in amendment quality. While No did not differ significantly across treatments due to high variability, k values indicated differing mineralization dynamics. These findings underscore the importance of selecting organic amendments based on crop nutrient demands and decomposition behavior. This work demonstrates the utility of laboratory incubation assays for evaluating compost quality and forecasting nutrient release. Future directions include field-scale validation and microbial community profiling to better understand the mechanisms behind observed differences in decomposition and nutrient cycling.

Nitrogen (N) is the most important element that influences both vegetative growth and fruiting in cranberry production. While many factors such as cultivar, age and vigor of vines are important, soil fertility is one of the most important factors impacting yield and fruit quality. The high fertilizer N used to support increased yield potential of new cranberry second generation hybrids can result in increased vegetative growth, thus creating a dense canopy resulting in a microclimate with high relative humidity (RH). Humid conditions during the warm summer months encourage the expression of cranberry fruit rot (CFR). The goal of this study was to determine the effect of N application rate on CFR occurrence in ‘Stevens’ and ‘Mullica Queen’ at the UMass Cranberry Station in East Wareham, Massachusetts. To measure biophysical data, we deployed micro climatic sensors in each treatment to measure ambient temperature and RH. Four N rates were used ranging from 46 kg N ha-1 to 112 kg N ha-1 in a replicated RCBD experiment. Fruit samples were collected at harvest from each treatment and used to measure total anthocyanin content (TAcy) by extraction with 0.2 N HCL. Cranberry biomass in both cultivars increased with increase in N rate and so did fruit rot. Fruit yield increased with N rate up to a point then it started to decline as rate increased. High N rate of 112 kg N ha-1 was associated with a low canopy temperature, and high RH compared to 46 kg N ha-1 in both cultivars. Total anthocyanins in the fruit decreased with N rate in both cultivars. Our results seem to suggest that high N rate encourage fruit rot expression.

Hidden hunger (micronutrient deficiency) is a global problem, with iron, zinc and selenium being the highly contributing members. Among these, iron deficiency is the most concerning. Deficiency of iron during pregnancy or in earlier childhood impairs the cognitive and behavioural development of children. Since the loss of iron from human body is minimal, iron deficiency occurs mainly because of insufficient intake. Therefore, increasing the iron content of vegetables (biofortification) is necessary, in order to meet the daily nutritional needs of humans. We conducted a field study in Fall 2024, comparing different iron fertilizers (FESO4, Fe-EDTA

Phosphorus (P) is a macronutrient essential for plant growth and development, involved in root formation, photosynthesis, and metabolic processes such as energy transfer, cell division and others. Phosphorus leaching is a crucial concern due to nutrient loss and eutrophication of water bodies. This study aimed to evaluate growth performance, yield, and phosphorus uptake efficiency of Snap Bean (Phaseolus vulgaris) across three different growth mediums: (1) Quartz Sand, (2) 50% Quartz 50% Soil, and (3) Soil. Additionally, bioavailable orthophosphate content in leachates and the impact of different phosphorus application rates on crop productivity were assessed. Two phosphorus application treatments: (1) a single application of 120 lbs/acre and (2) a split application of 20 lbs/acre applied weekly over a period of six weeks. Leachate samples were collected and analyzed weekly to determine phosphorus availability trends. Growth parameters such as plant height, leaf chlorophyll content, and yield parameters including the number of pods per plant and pod weight were recorded to evaluate crop performance. Phosphorus uptake efficiency was assessed to determine how different growth media and fertilization strategies influence nutrient utilization. Results showed that Quartz retained the least phosphorus, leading to higher orthophosphate concentrations in leachates. The mixed medium of 50% Quartz 50% Soil exhibited intermediate retention, while Soil treatments retained the most phosphorus, resulting in the lowest leachate orthophosphate levels. Overtime, the split application of 20 lbs/acre provided more stable phosphorus availability compared to the single high-dose application, which led to an initial peak followed by a significant decline. Plants under mixed media and split application present the higher crop performance and yield. These findings highlight the role of growth medium composition and fertilization strategy in phosphorus retention and availability. The study suggests that combining appropriate growth media and phosphorus application rates can maximize Snap Bean productivity while minimizing environmental impacts. Further research should explore the interactions of these factors under diverse environmental conditions to develop best practices for phosphorus management and sustainable agriculture.

Sustainable fresh vegetable crop production using lunar regolith as a growth media is critical for establishing large-scale space farming on the lunar surface. While lunar regolith contains essential mineral nutrients, it lacks organic carbon and nitrogen, which limits mineral bioavailability and nutrient-holding capacity. Tetradesmus deserticola is a terrestrial, photosynthetic algae that self-propagate in minimal media using light and carbon dioxide. It contributes organic matter to marginal soils through photosynthesis and has been used as biostimulant. The objective of this research was to evaluate the effects of T. deserticola inoculation on the growth, physiological, and morphological responses of lettuce (Lactuca sativa) plants at ammonium nitrate rates of 0, 1, and 2 mM, and 15N–3.9P–10K controlled-release fertilizer (CRF) at rates from 0 to 8.4 g·L-1 in a containerized silica sand media. Lettuce seeds were sown in the containerized media and inoculated with dried T. deserticola. After seed emergence, plants were irrigated with nitrogen-free Hoagland’s solution supplemented with ammonium nitrate or top-dressed with CRF at rates from 0 to 8.4 g·L-1. Electrical conductivity (EC), pH, and nitrate-nitrogen concentrations in leachate were recorded weekly. Gas exchange rates were measured, and plants were harvested 59 days after sowing to assess growth and morphological responses. Nitrate-nitrogen concentration and EC in leachate increased with increasing levels of ammonium nitrate in the Hoagland’s solution and CRF rates. In addition, the plant growth index and relative chlorophyll content of leaves was enhanced with the increase of ammonium nitrate levels and CRF application rate. Compared with non-inoculated plants, lettuce inoculated with T. deserticola showed higher plant growth index and relative leaf chlorophyll content when receiving nitrogen-free Hoagland’s solutions with 0, 1, and 2 mM of ammonium nitrate. However, the inoculation of T. deserticola did not increase plant growth index and relative chlorophyll content for plants treated with CRF. The T. deserticola inoculation enhanced growth and physiology of the Romaine lettuce at ammonium nitrate levels ranging from 0 to 2 mM. However, T. deserticola did not affect plant development when the plants were treated with CRF. Under the conditions of this study, the effects of T. deserticola inoculation on plant growth differed between fertilizer management.

Fertilizers are commonly applied to bamboo to enhance quality and productivity. Bamboo is widely used for consumption, construction, and fabrication. Bamboo production has expanded to 690 ha in Florida. However, there are no clear phosphorus (P) fertilization guidelines, despite P playing a crucial role in plant growth and production. This study evaluated the effects of varying P rates on Dendrocalamus asper under greenhouse conditions. Two trials were conducted on one-year-old bamboo plants at different P rates (0, 22.4, 44.8, and 89.6 kg P ha-1) for five months in 2023 and 2024. Growth, physiological parameters, and biomass accumulation were assessed. Data were analyzed using one-way analysis of variance with a linear mixed model for repeated measures. Results showed that P fertilization significantly influenced bamboo growth, culm biomass accumulation, culm production, and chlorophyll content across both years. The highest biomass in culms, total biomass, number of culms, and clump height occurred at 22.4 and 44.8 kg P ha-1 in 2023 and 2024, respectively. Higher P rates (44.8 and 89.6 kg P ha-1) increased below-ground biomass. The highest P rate (89.6 kg P ha-1) increased soil P by 74% in 2023 and 84% in 2024 from the initial concentration. Soil P positively correlated with Ca in 2023 and K in 2024. Although no clear optimal P rate was established, moderate P application (22.4-44.8 kg P ha-1) benefited young bamboo growth. These findings provide a foundation for developing P fertilization guidelines in Florida. Further field-scale studies are needed to determine the optimal application rate.

Vitamin C is a vital antioxidant that plays a crucial role in plant photosynthesis, enzymatic reactions, and stress resistance, while also being a key micronutrient for human health. Evaluating the potential of enhancing vitamin C content in food crops like lettuce (Lactuca sativa L.) can contribute to better health outcomes and disease prevention. This study investigates the effect of ascorbic acid foliar application on biomass, phytochemicals, and mineral nutrient content in lettuce using a Nutrient Film Technique (NFT) hydroponic system. Lettuce was treated with different concentrations of ascorbic acid (0, 500, 750, and 1000 ppm) via foliar application. Chlorophyll and biomass were recorded, while vitamin C content was analyzed using high-performance liquid chromatography (HPLC). Other micronutrients were also analyzed and assessed based on treatments. Results from this study will contribute to understanding how micronutrient deficiency in humans can be addressed and potentially maximized through agronomic biofortification.

Food waste liquid anaerobic digestate (FWLAD) has strong potential as an organic fertilizer due to its nutrient-rich composition. However, organic nutrient solutions often have lower dissolved oxygen (DO) levels than inorganic ones, which may limit oxygen availability in the root zone, restricting nutrient uptake and plant growth. This study examines whether increasing perlite content in a soilless substrate and aerating the nutrient solution can enhance root-zone oxygen availability and improve lettuce (Lactuca sativa 'Muir') growth when cultivated with FWLAD. Lettuce seeds were sown in a 128-cell plug tray filled with a peat-based growing mix blended with perlite at 100%:0%, 70%:30%, and 40%:60% (v:v). Increasing perlite content from 0% to 60% increased substrate porosity from 47% to 56%, while air space remained between 30% and 33%. One week after sowing, seedlings were sub-irrigated with four nutrient solutions prepared from either crude or nitrified FWLAD at an electrical conductivity (EC) of 2 dS·m-1, each under aerated and non-aerated conditions. Control nutrient solutions were prepared using inorganic fertilizer at 2 dS/m EC. Lettuce seedlings were grown indoors for three weeks at the air temperature of 24°C with a photosynthetic photon flux density of 210 µmol·m-2·s-1 under an 18-hour photoperiod. Regardless of nutrient solution type, increasing perlite from 0% to 60% had little to no effects or decreased leaf number (by 7-13%), leaf area (by 13-26%), and shoot fresh mass (by 10-42%). DO levels remained below 1.5 ppm in non-aerated crude or nitrified FWLAD solutions, while aerated solutions and inorganic fertilizer treatments maintained DO above 6 ppm. Aerating the nutrient solution with crude FWLAD decreased total leaf number (by 4-17%), total leaf area (by 28-45%), and shoot fresh mass (by 37-44%) across all substrate conditions, whereas aeration with nitrified FWLAD increased these parameters by 22-35%, 174-343%, and 138-325%, respectively. At each substrate condition, lettuce seedlings grown with inorganic fertilizer had the highest leaf number, leaf area, and shoot fresh mass. These results suggest that increasing perlite content did not enhance lettuce growth under FWLAD. Aeration improved growth with nitrified FWLAD but reduced it with crude FWLAD. Across all conditions, inorganic fertilizer resulted in the highest growth, suggesting that factors beyond oxygen availability may limit the effectiveness of FWLAD as a nutrient source.

Iron (Fe) deficiency is one of the leading micronutrient deficiencies in the world, impacting almost two billion people globally. Contributing factors include non-diverse diets (cereal grain-centered diets, processed and junk foods) that are characterized by relatively low bioavailable Fe levels. Additionally, 30% of cultivated soils around the world report low Fe availability. Inadequate levels of dietary Fe can cause numerous physiological disorders and impaired cognitive functioning, with pregnant women and infants being particularly vulnerable. To help alleviate the harm of Fe malnutrition, a straightforward and sustainable solution to increase dietary Fe availability is through agronomic biofortification of crops. Unfortunately, Fe uptake by plants is problematic, especially in alkaline and oxidizing conditions. However, various studies have reported the role of ascorbic acid (AA) as an enhancer of Fe absorption. A suitable candidate crop for Fe biofortification are microgreens, as they are nutritional powerhouses that have low phytic acid levels, short growth cycles, and are typically consumed raw. Testing the use of AA for Fe biofortification in microgreens has received limited attention in literature. Therefore, in this study we investigate in a soilless system the effect of different Fe sources with and without organic acids (Ferric sulfate, Ferric sulfate 0.1% Ascorbic acid, Ferric citrate), applied via fertigation at different concentrations (0, 15, 30, 45 mg/L of Fe), on Fe content of sunflower microgreens. Treatments were arranged in a completely randomized factorial design using three replications. We discovered that Ferric sulfate 0.1% AA provided at 45 mg/L was the most effective source and rate in increasing Fe content, resulting in approximately 300% increase compared to the untreated control. Fertigating with Ferric sulfate 0.1% AA also showed a significant increase in total antioxidants and total phenol concentrations, but a decrease in chlorophyll and carotenoid levels. When using sodium hydroxide (NaOH) to adjust the nutrient solution pH, the same treatment was associated with relatively high Na content and resulted in an average reduction in fresh and dry biomass of 50% and 30%, respectively. Further assessment of Fe sources, concentrations, and bases for pH adjustment should be considered to not compromise yield and nutritional quality. However, these results indicate that through fertigation, the supplementation of AA with Fe fertilizers can significantly promote the enrichment of Fe as well as certain phytochemicals in sunflower microgreens. This strategy can produce Fe-biofortified functional foods that can potentially improve health outcomes of Fe-deficient individuals.

Circadian rhythm, a vital adaptive mechanism in green organisms, synchronizes plants' physiological processes with daily and seasonal environmental changes. Circadian clock oscillator genes significantly regulate transcriptional and post-transcriptional changes, emphasizing their role in mediating plant responses to environmental stresses. Understanding these regulatory mechanisms is essential for optimizing plant growth, enhancing productivity, and improving resilience to ecological changes, contributing to sustainable agriculture and food security. Nitrogen is an essential plant nutrient; both depleted and excessive nitrogen fertilization can negatively impact plant growth, development, and yield. Overapplication of nitrogen fertilizers can disrupt soil properties, limiting nutrient availability and altering soil composition (including soil acidification, salinization, and disruption of beneficial microbial communities). Additionally, excessive nitrogen usage contributes to harmful gas emissions from the soil into the atmosphere, which can affect human health, climate, and overall ecosystems. Effective nitrogen management is crucial for promoting healthy plant growth and minimizing environmental damage, making a balanced approach essential for sustainable agriculture. This study evaluated the daily regulation of transcriptional changes in nitrogen metabolism under nitrogen depletion (Low N: 50 ppm) and spinach leaf repletion (High N: 200 ppm) conditions. The RNA-Seq analysis reveals that high nitrogen (HN) conditions induce more significant transcriptomic changes than low nitrogen (LN), particularly in nitrogen assimilation, transport, and amino acid metabolism genes. Expression patterns of these genes vary across time points, with distinct regulation during light and dark cycles. Validation through qPCR and RNA-Seq confirms that nitrogen assimilation peaks at the end of the dark cycle. In contrast, nitrogen transport (NRT1) and amino acid synthesis are more pronounced during the light cycle under HN conditions. The circadian clock gene Late Elongated Hypocotyl (LHY) regulates the timing of nitrogen assimilation. LHY expression increases at the end of the dark cycle, correlating with higher expressions of nitrogen assimilation genes, including Nitrate Reductase (NIA) and Nitrite Reductase (NiR). These results underscore the significance of circadian rhythms, mainly through LHY, in optimizing nitrogen acquisition and utilization.

Cut-and-come-again, or repeat harvesting, is a practice in which a single planting of greens is harvested on multiple occasions. This is a common practice among small-scale, urban, and home producers in which the outermost leaves are removed, leaving the growing center of the plant intact enabling multiple harvests without compromising plant health. As this practice is not common among large-scale and commercial producers, there are currently no research-based fertilizer recommendations for cut-and-come-again greens. General guidance simply suggests continued, nitrogen-heavy fertilizer applications to ensure repeated harvests. This type of guidance is not easy to follow and could lead to overapplications and nutrient leaching. An experiment was designed to examine eight different fertilizer application strategies to determine which provided better growth and nutritional quality in later collard harvests while limiting nutrient leaching. Fertilizer applications for the cut-and-come-again treatments (CC) ranged from an initial fertilizer application matching local nutrient recommendations, to repeated applications either the initial complete application or a nitrogen side dressing at every third, every other, or at each harvest. A single harvest control grown to maturity (ODM) was also monitored for nutrient leaching. Leachate from collards was collected weekly and the volume measured. Leachate was then tested for pH, conductivity, color, and turbidity using bench top instruments. A portion of the leachate was also filtered and tested for nitrate-nitrogen, ammonia-nitrogen, and phosphate using microplate spectroscopy. Another filtered portion was acidified and tested for mineral nutrient content using ICP-OES. Nutrient management treatment had no effect on leachate volume, which was affected by sample collection time, season, and year, likely due to weather variation and plant growth factors. Nutrient management treatment did have an effect on water quality metrics; however, no metric displayed a dose response. Differences between nutrient management treatments were seen during the spring of 2024 more often than any other growing season. Most metrics were higher in the spring than in the fall, which could be due to poor growth and fewer harvests in the fall, and therefore lower nutrient additions. While the two fall growing seasons were very similar to each other, there were some differences between the spring of 2023 and the spring of 2024, although which had higher nutrient content depending on the nutrient measured. Leachate pH, color, and increased with the number of days after planting in most cases. Leachate conductivity, turbidity, potassium, magnesium, total phosphorus, and sodium decreased with number of days after planting.

Nutrient biofortification in leafy vegetables is a promising strategy to enhance dietary health benefits, improve crop nutritional quality, and promote sustainable agricultural practices. Advanced plant cultivation techniques, such as hydroponic production and targeted micronutrient fertilization, provide a controlled environment for optimizing nutrient uptake and secondary metabolite synthesis. Selenium (Se), an essential micronutrient, has been shown to influence plant metabolism, particularly the synthesis of bioactive compounds such as carotenoids and glucosinolates. However, its role in modulating these phytochemicals in hydroponically grown Nasturtium officinale (watercress) and Barbarea verna (upland cress) remains underexplored. This ongoing study investigates the effects of selenium fertilization at varying concentrations (0, 1.0, 2.0, and 4.0 mg Se·L⁻¹) on carotenoid and glucosinolate accumulation in two cress varieties cultivated under controlled hydroponic conditions. The hydroponic system provides a consistent environment for plant growth, allowing precise manipulation of nutrient levels, pH, temperature, and light intensity. Selenium treatments follow a randomized complete block design to ensure replication and statistical rigor. Growth parameters, biomass accumulation, and biochemical analyses of carotenoid and glucosinolate levels are being monitored to determine the interactions between selenium uptake and secondary metabolite biosynthesis. Carotenoid content in plant tissues will be quantified using high-performance liquid chromatography (HPLC), while glucosinolate concentrations will be determined through chromatographic and spectrophotometric methods, ensuring precise assessment of bioactive compound accumulation. Preliminary observations suggest that selenium supplementation may modulate plant physiological responses, potentially enhancing carotenoid and glucosinolate synthesis. Differences in metabolite accumulation between the two cress varieties indicate potential genotype-specific responses to selenium fertilization. Understanding these interactions will contribute to optimizing hydroponic production systems, improving the nutritional and functional quality of leafy greens, and informing sustainable agricultural practices. Findings from this study could advance nutrient-fortification strategies, enhance functional food development, and address micronutrient deficiencies, thereby supporting both horticultural innovation and public health. Keywords: Selenium fertilization, Beta-carotene, Hydroponic, Watercress varieties, Agricultural sustainability, Crop yields, Environmental impact, Spectrophotometric analysis,