ASHS 2025 Conference

With freshwater supplies dwindling and sea levels rising, irrigation water for crops can become salinized. Therefore, salt-tolerant genotypes of food crops are needed. Here, we tested genotypes of Brassica juncea (brown mustard), a widely grown and consumed leafy green that has mineral and nutrient rich leaves and is also an important oil-seed crop, for their salt tolerance. Experiments were conducted to evaluate the performance of three mustard genotypes (var. ‘Florida Broadleaf’, ‘Carolina Broadleaf’, and ‘Southern Giant Curl’) grown in nutrient film-technique (NFT) hydroponic systems under varying salinity treatments. Five synthetic seawater dilutions (15, 22.5, 30, 37.5, and 45% Instant Ocean at approximately 10, 13.5, 17, 21, 24.5 dS/m conductivity, respectively) with added fertilizer (Masterblend 20-20-20 at approx. 1.5 dS/m) were compared to a control (fertilizer only at approx. 1.5 dS/m) to identify the optimal salinity range for vegetative production over 6 weeks after seeding. Two different production systems were used to evaluate the genotypes: production-scale NFT systems in a greenhouse in Citra, FL, and lab-scale tabletop NFT systems in an environmentally controlled room. In the greenhouse setting, plants were destructively harvested at 7 day intervals to gather growth over time, while in the lab setting, plants were harvested once at the end of the experiment to calculate the biomass and growth along with water and nutrient use efficiencies per genotype. Preliminary findings suggest that yields and water use efficiencies were improved at a 15% seawater dilution (approx. 10 dS/m) and showed a drop in biomass at higher seawater dilutions. The genotype ‘Florida Broadleaf’ demonstrated higher fresh biomass than either of the other genotypes with ‘Southern Giant Curl’ showing the most sensitivity to salt treatments in both the greenhouse and desktop systems. Data collected in these experiments will be used to construct a dynamic crop growth model for mustards that incorporates salinity to predict crop biomass. Crop models such as this could help inform plant breeders studying salt-tolerance and provide insights into yields and crop growth rates to agricultural producers farming in salt-afflicted soils or for use in saltwater hydroponics.

Kale (Brassica oleracea var. acephala), a member of the cruciferous (Brassicaceae) family, has gained significant popularity as a nutritionally dense leafy vegetable in recent years, attributed to its rich nutraceutical properties, including phytochemicals, antioxidants, and antiproliferative compounds. These properties play a critical role in addressing global nutritional deficiencies through cost-effective dietary sources, leading to kale’s designation as a superfood by the research community. Its popularity has steadily increased, particularly in the United States. To meet the growing demand for kale, optimizing production systems is essential. In this study, we evaluated leaf physiology, yield parameters, and nutrient content across kale cultivars grown under both organic and conventional farming systems. We observed substantial variation in leaf photosynthesis and other physiological traits, reflecting the different responses of cultivars to cultivation methods. Additionally, significant differences in mineral content and total soluble proteins were noted, with organic farming practices notably enhancing soluble proteins, leaf nitrogen content, nitrate nitrogen (NO3-N), and several key minerals compared to conventional practices. These findings suggest that organic farming practices may enhance the nutraceutical quality of kale, potentially offering superior nutritional benefits compared to conventional methods systems.

Saline water irrigation, higher summer temperatures, limited soil leaching and agricultural intensification with heavy reliance on chemical fertilizers are the main causes for high salt accumulations in high-tunnel soils. These salinity issues have led to soil degradation as well as decline in crop production. In order to improve soil health and bolster the crop yield, use of organic amendments like compost, crop residues and animal manure has been widely practiced. Studies have shown that biochar and vermicompost can improve soil homeostasis by adsorbing excess sodium and chloride ions and holding excess water in root zone. Furthermore, researchers have found that these soil amendments complement each other when used in combination, leading to high crop yield and enriched plant nutrient contents. However, research gaps exists in using emerging soil amendments like biochar, and vermicompost. Hence, the objective of our current study was to assess the growth and yield attributes of tomato under salinity stress and evaluating the role of these soil amendments alone and in combination to mitigate salt stress. Two potted experimental trials were conducted in late spring and early fall in high tunnel at Oklahoma State University. The treatments were arranged in a complete randomized design. Treatments included three levels of salinity (1.5, 4, 8 mS/cm) and different treatment combinations (0, 5, 10% v/v) of biochar and vermicompost in soilless media. Data collection was done on different yield parameters, phytochemicals, stress indicators along with soil media tests. Results show that soil amendments treatments helped reduce salinity stress to some extent and aid in overall crop performance. To sum up, our salinity stress study provides insights on minimizing the salt toxicity by appropriate use of emerging soil additives, providing practices for producers to improve crop production in high-tunnels.

Nutrient biofortification in leafy vegetables can enhance dietary health benefits, improve crop nutritional quality, and promote sustainable agricultural practices. Deep water culture hydroponic production along with micronutrient exploration can lead to solutions to optimize nutrient uptake. 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) remains underexplored in controlled environment agriculture systems. This 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 water cress varieties cultivated in deep water hydroponics. The controlled environment environment system provides an ideal environment for plant growth, allowing precise manipulation of nutrient levels, pH, temperature, and light intensity. The selenium treatments are based on a randomized complete block design to ensure statistical accuracy. Various growth parameters, biomass accumulation, and biochemical analyses of carotenoid and glucosinolate levels were measured to determine the interactions between selenium uptake and metabolite biosynthesis. Carotenoid content was quantified using high-performance liquid chromatography (HPLC). Glucosinolate concentrations were determined through chromatographic and spectrophotometric methods to measure bioactive compound content. Research suggests that selenium supplementation may modulate plant physiological responses and enhance carotenoid and glucosinolate synthesis. It is essential to study ways to optimize hydroponic deep water culture production systems to improve the nutritional and functional quality of leafy greens like watercress. These findings can provide information to guide controlled environment and sustainable agricultural practices. Results from this research may also 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, Deep Water Hydroponic, Watercress, Agricultural sustainability, Controlled Environment Agriculture

Sweet peppers are a warm-season vegetable prized for their vibrant colors, rich flavor, and high nutritional value. Biostimulants are a new class of agricultural products consisting of microorganisms or bioactive substances, used as a sustainable approach to enhance plant growth and productivity. This experiment aimed to evaluate the effects of biostimulant applications on plant growth, yield, and quality of sweet pepper cultivars grown in a container production system. Three biostimulants were tested including a seaweed extract (Kelpak Maxx, 1% solution), a plant growth-promoting rhizobacteria (Continuum V2, at a rate of 2 ml per gallon), and stabilized monosilicic acid (Dune, at a rate of 2 ml per gallon). Six sweet pepper cultivars were selected for the study: Cornito Giallo, Escamillo, Green Machine, Carmen, SVPB8500, and Cornito Rosso, all purchased from Johnny’s Selected Seeds. Biostimulant treatments were applied biweekly through manual fertigation with 120 ml of solution. Plants in the control group were fertigated with 120 ml of water. Plant vegetative growth including plant height, widths, and leaf SPAD were measured three times during the growing season. Once fruit ripening began, pepper fruits were harvested every two weeks from July to September. At each harvest, marketable and unmarketable yield and fruit number were recorded. Fruit quality variables including fruit length, diameters, and color were also measured. Results showed that the sweet pepper cultivars varied in vegetative growth, fruit yield, and quality. The two cultivars Green Machine and SVPB8500 had higher leaf SPAD of 64.2 and 63.9, respectively, than Carmen, Escamillo, Cornito Giallo, or Cornito Ross. The cultivars Carmen, Cornito Giallo, Cornito Rosso, and Escamillo had similar plant heights ranging from 36.4 cm to 38.4 cm, higher than Green Machine or SVPB8500. Biostimulant treatment did not affect leaf SPAD or plant height early in the season.

Rising temperatures, erratic precipitation, and increased periods of drought present significant challenges to vegetable crop production by disrupting growth reducing yield and crop quality. To address these challenges, biostimulants have been used in crop production for their ability to enhance plant growth, improve nutrient uptake, and increase resilience against environmental stresses. However, there exists a research gap in the mode of applications and rates of different biostimulants in various vegetable crops grown in open-field conditions. Hence, the current study evaluated the effects of two distinct biostimulants (silicon and brassinosteroids) on arugula (Eruca sativa) production. Although silicon is not universally recognized as an essential nutrient for plant growth, it is considered beneficial and has been proven to exhibit biostimulant properties. Contrarily, brassinosteroids are a class of plant hormones crucial in regulating growth, development, and stress responses in crops. These biostimulants were applied independently through the soil and foliar application at two different rates to assess their effects on the growth, yield, and nutritional quality of arugula. Treatments were arranged in a randomized complete block design with three blocks in open-field conditions. Data was collected on various parameters, including the number of leaves per week, fresh and dry weight at harvest, and mineral and phytochemical content such as chlorophylls, carotenoids, sugars, phenols, and flavonoids content. Results show that silicon applied plants have improved yield. By assessing biostimulants impact on the yield and nutrient composition of arugula, the current research concludes the potential of biostimulants as a sustainable approach to improve growth of arugula under challenging environmental conditions

The anticipated impacts of climate extremes on food production have led research into novel paths aimed at optimizing cultivation techniques and developing genotypes resilient to abiotic stresses. Research over the last 20 years led to a considerable amount of evidence that the regulation of polyamine metabolism (and in particular of thermospermine) through the overexpression or gene mutation of polyamine oxidases (PAOs) genes, could enhance plant resilience. However, there are still limited data on how the differential expression of PAOs genes affects physiological and morpho-anatomical traits that contribute to plant resilience. Therefore, in this study we explored the morpho-anatomical and functional-physiological variability of leaves of 8 tomato genotypes, one reference (cv. Moneymaker), and 7 with modified thermospermine metabolism, comprising 3 overexpressing genotypes and 4 loss-of-function mutants for two thermospermine-specific PAO genes, SlPAO3 and SlPAO4. The plants were cultivated under greenhouse conditions following standard commercial practices, and a total of 17 morpho-anatomical and functional traits were assessed for each genotype. Based on plasticity indices (IP), notable phenotypic variability among genotypes was observed, particularly in leaf morpho-anatomical traits, pigment concentrations, performance index (PItotal), plant height, and total leaf area. In contrast, the lowest IP values were recorded for traits related to gas exchange and Fv/Fm. Principal component analysis (PCA) identified two main axes accounting for 78% of the total variation, and a clear grouping of genotypes emerged according to the type of PAOs gene expression modification (overexpression or gene mutation). These findings reveal substantial differences in leaf structural traits among genotypes, depending on PAOs expression levels, aligning with previous studies highlighting the role of polyamines in organogenesis. Considering the critical importance of leaf structure–function interactions in determining both productivity and stress resistance, further investigation into the role of PAOs as a potential tool for enhancing plant resilience to abiotic stresses is warranted.

Nitrogen is a vital element for plant growth, playing a crucial role in photosynthesis and protein synthesis. The bio-stimulant "Utrisha N," which contains the bacteria Methylobacterium symbioticum, has the potential to enhance nitrogen availability by fixing atmospheric nitrogen, thereby promoting sustainable agricultural practices. While it has been evaluated in other row crops, its application in vegetable crops remains untested. This study examined the effects of the foliar application of "Utrisha N" on yield, nitrogen metabolism, and phytochemical profiles under various nitrogen conditions. The results indicated that the foliar application of "Utrisha N" during the developmental phase of spinach significantly increased both fresh and dry biomass and chlorophyll content. No significant changes in nitrogen mineral metabolism were observed regardless of nitrogen availability. We assessed nitrogen assimilation by calculating the percentage accumulation of amino acids in the vegetative tissues. The differential expression of genes related to nitrogen metabolism influenced by Methylobacterium symbioticum is currently being analyzed. This study's results will help clarify the potential benefits of Methylobacterium in improving nitrogen metabolism and boosting spinach productivity.

Temperature constraints on tomato production challenge local production in warm climates. In Oklahoma, there is a narrow optimum temperature window required for fruit set, which ultimately results in a decline during late July and August. Growers are motivated to select heat tolerant tomato genotypes for better results. Previous research shows that there is a range of physiological responses when considering heat tolerant and heat sensitive cultivars. To investigate further, a controlled environment trial will be designed to evaluate eight different tomato cultivars at two different temperature regimes, optimum (26°C / 20°C) and elevated (36°C/26°C). Morphological measurements will be collected daily and are to include days to first truss, days to first open flower, days to first fruit set, and flower-fruit set ratio. Non-destructive physiological measurements will be collected weekly, including net photosynthetic rate, stomatal conductance, leaf temperature, and chlorophyll fluorescence. Electrolyte leakage will be measured once upon the completion of the trial. Differences in net photosynthetic rate and stomatal conductance were found to be significant between the two temperature regimes (p > 0.001) at 28 days after transplanting. Net photosynthetic rate averages were 4.358 µmol m-2 s-1 for the elevated temperature and 7.815 µmol m-2 s-1 for the optimum temperature. Stomatal conductance averages were 0.081 mol m-2 s-1and 0.150 mol m-2 s-1 for elevated and optimum regimes respectively. A Euclidean Distance will be calculated between the responses to the two temperatures upon completion, creating a heat tolerant index. The results will assist with the development of a screening tool for heat tolerant cultivars.

Microgreens are young seedlings of various vegetable and herb species that are usually harvested 10 to 14 days after germination. They are a popular specialty crop because they are rich in mineral nutrients and health beneficial phytochemicals, grow quickly, need little space, and can be produced year-round in a protected environment. The choice of substrate is critical for successful microgreen production because it affects shoot growth, nutrient absorption, and total shoot yield. Compared with commonly used peat-based substrate, easy-to-use hydroponic mat products made from various fibers serve as sustainable alternative growing media. This study examines the effect of five substrates on the growth performance of four microgreen species including ‘Red Garnet’ amaranth (Amaranthus tricolour), ‘Red Gruner’ purslane (Portulaca oleracea), Rainbow Sprinkles Mix (with chard and beet, Beta vulgaris), and Shungiku (Glebionis carinata). The five substrates include bamboo mat, coco coir fiber mat, Ectone mat (made from recycled plastic bottle), jute mat, and a peat based soilless substrate. Results showed that fresh shoot weight was affected by the interaction between species and substrate type. Shungiku grown on peat and coco coir produced the highest fresh shoot weights of 74.7 and 70.2 g per growing tray, respectively, among all treatment combinations. Microgreens species varied in their preference of substrate for maximum shoot yield, with peat producing in higher fresh shoot weight than other substrate types in purslane and Rainbow Sprinkles Mix. Overall, peat and coco coir mat resulted in higher dry shoot weight than jute, bamboo, or Ectone mat across the four tested species. These results show the importance of choosing the right substrate for maximum yield and quality in microgreen production.