ASHS 2025 Conference

Plasma activated water (PAW) is produced when plasma generated by high-voltage discharge is delivered to an atmospheric gas and interacts with water to create a new solution containing reactive species. The resulting water contains nitrate nitrogen (ca. 20-176 ppm N), small amounts of nitrite and ammonium, as well as reactive oxygen species. The benefits of PAW use for agricultural crops can include improved germination, increased seedling vigor and health, resistance to pests and disease, an alternative nitrogen source, and an overall improved plant health and yield. However, further research is needed to understand the characteristics of PAW, PAW shelf-life stability, crop specific PAW application and timing, and its overall effects in plant production. Our overall objective is to determine if PAW can enhance plant quality/yield in organic greenhouse tomato production. Studies were conducted to evaluate tomato germination and seedling growth in response to PAW application. A study was conducted to evaluate if germination of tomato seeds and subsequent growth in seedling trays with container media is affected when soaked prior to seeding with plasma water or tap water for three, six, or 12 hours. The study was replicated four times over time, with each replicate lasting for 15 days. Data was collected on daily germination, weekly heights and widths, and fresh mass, dry mass, and leaf area at harvest. Most seed treatments for 6 or 12 hours, regardless of water treatment, enhanced germination on day 5 and day 6 compared to control. However, by final harvest at day 15 there were no significant differences between treatments and control. Our second phase of research evaluated PAW application during organic tomato seedling production stage. Seedlings were treated with a drench of 4 mL per cell of different PAW sources generated for 5, 10, 30, or 60 minutes for a total of three applications every three days. On day 7, 30-minute PAW had significantly greater germination counts compared to the control. At final harvest on day 22 60-minute PAW had significantly greater fresh mass, dry mass, and leaf area compared to the control. In conclusion, a pre-seed soaking treatment for 12 hours is recommended for earlier germination and a drench application of PAW generated at a duration of 60 minutes is recommended for greater seedling growth. Further research includes PAW application timing and frequency and its carry-over effects in tomato crops grown to fruiting.

Light of different wavelengths influences the crop yield and quality by modulating metabolic pathways, resulting in variations in phytochemical abundances. Therefore, optimized light conditions could enhance the plant-protecting and health-promoting attributes of tomato fruit. However, the effects of supplemental blue (B) and ultraviolet-B (UV-B) light on amino acids (AAs) and phenolics, particularly hydroxycinnamic acids (HCAs), as well as fruit firmness and yield characteristics in tomatoes, are not well understood. Therefore, the current study examined the effects of supplemental light on yield, firmness, and levels of amino acids (AAs) and hydroxycinnamic acids (HCAs) in red-ripe, greenhouse-grown tomato fruits. This study was conducted with two tomato varieties (Plum Regal and TAM Hot-Ty) exposed to supplemental blue light (238 µmol m-2 s-1 at 40 cm from the plants for 8 hours), UV-B light (5 µmol m-2 s-1 at 46 cm from the plants for 4 hours), a combination of blue and UV-B light (B UV-B), and a control group with no supplemental lighting. Our findings revealed that blue light alone significantly enhanced yield and firmness in both varieties. Similarly, UV-B light alone resulted in increased yield and higher HCA levels. The combined B UV-B treatment produced firmer fruits with high HCAs without compromising yield. Important amino acids like γ-amino butyric acid (GABA) and glutamine were also significantly enhanced by B UV-B. Therefore, supplemental blue and UV-B light could be used to improve nutritional value by increasing the abundance of bioactive compounds in tomato fruits grown under controlled environmental conditions. This work was partially supported by USDA-NIFA-2024-51181-43464, USDA-NIFA-AFRI 2023-67013-39616 through the Vegetable and Fruit Improvement Center and Institute for Advancing Health Through Agriculture of the Texas A

Consumers want year-round supply of high quality fresh produce. However, the low sunlight has limited greenhouse vegetable during the winter months in high-latitude region. In order to boost yields and meet market demand, supplemental lighting is required. However, utilizing electric lighting, even high-efficient LED fixtures results in high electricity costs. Photoperiod extension (up to 24h) is a promising strategy which can be implemented in many countries as the utility companies incentivize the use of low cost, off-peak electricity use during the night. In this way, extending the photoperiod from the conventional 16h up to 24h can result in reduced electricity cost when the daily light integral (DLI) remains the same. In this study, we look at the impact of two different 24h lighting strategies in two cherry tomato cultivars and their impact on photoperiod injury compared to a 16h control. One 24h treatment involved a change from white light during the day to blue light at night at a reduced photosynthetic photon flux density (PPFD; i.e., dynamic) while the other kept a static spectrum and PPFD for 24h. In addition, each treatment also had a low blue (10%) and high blue (30%) variation. The experiment took place in a glass greenhouse at the Harrow Research and Development Centre in Harrow, Ontario, Canada. It was determined that the 24h dynamic lighting strategy has similar maximum quantum yield of photosystem II (Fv/Fm) values as the 16h controls while the 24h static treatments values were drastically reduced. What’s more, the Fv/Fm value from the 24h static treatment with high blue content was lowest among all treatments indicating that elevated levels of blue light may be detrimental during a 24h photoperiod. In addition, the overall yield from the 24h dynamic treatments were similar to the 16h controls while the 24h static treatments were statistically lower. Taken together, these results indicated that a 24h dynamic light treatment is essential to mitigate photoperiodic injury in cherry tomato. This data suggests that the use of such a lighting strategy could also reduce electricity costs for greenhouse cherry tomato producers.

The thermotolerance responses of tomato plants have been assessed using various physicochemical parameters. However, even within the same genotype, thermotolerance strategies can vary among plant organs. This study aimed to investigate heat stress responses in tomato genotypes across vegetative and reproductive stages, focusing on a comprehensive analysis of thermotolerance mechanisms. Ten tomato varieties, including seven commercial cultivars and three Texas A

Small-scale greenhouse growers commonly use perlite as substrate in the Dutch bucket hydroponic production of vine crops such as tomatoes. However, perlite is prone to an excessive nutrient solution leaching primarily due to its free-draining and low water holding capacity properties. Alternative organic substrate to perlite is needed for a sustainable hydroponic production of these fruiting vegetables in the Dutch bucket system. This study thus evaluated the growth and yield performance of two tomato cultivars (BHN 589 and Geronimo) in five substrates (clay pebbles, loose rockwool, perlite, coco coir, and Lensli) in a randomized complete block design with three replications inside a polyethylene film greenhouse from February to July 2024. Results showed no significant effects of the interaction of substrates and cultivars on all the measured growth and yield traits. Averaged over the two cultivars, the substrates tested significantly influenced the total yield ranging from 338 to 464 Mg/ha and marketable yield ranging from 328 to 445 Mg/ha. More specifically, Lensli increased marketable yields by 15, 31, and 36% than those of coco coir, perlite, and clay pebbles, respectively. These increases are primarily due to a significant increase in the number of marketable fruit per plant (19%) and average marketable fruit weight (10%). Lensli also increased leaf area index by 44 and 60% than those of perlite and clay pebbles, respectively. Based on these results, Lensli, a blend of fine Baltic and superfine black peat, is proving to be a promising organic alternative substrate for tomato production in the Dutch bucket hydroponic system.

Real-time nutrient management is crucial in controlled environment agriculture (CEA) for enhancing crop production, reducing fertilizer costs, and mitigating environmental impacts. Inadequate fertilization can reduce crop productivity and nutrient runoff. Sap-based sufficiency ranges could maintain balanced fertilization. The main objective of this study is to establish sap-based sufficiency ranges for lettuce (Lactuca sativa), tomatoes (Lycopersicon esculentum), and cucumbers (Cucumis sativus) across developmental stages and fertilizer levels in CEA. Lettuce was grown using a Randomized Complete Block Design (RCBD) with three cultivars (‘Casey,’ ‘Cherokee,’ ‘Chicarita’) and three fertilizer levels (low 50%, medium 100%, and high 200%) in a vertical farm and greenhouse. A split-plot in RCBD was used for tomatoes (‘Grandice,’ ‘Macxize,’ ‘Prodice’) and cucumbers (‘Georgia,’ ‘Verdon,’ ‘Camaro’) under the same fertilizer levels. Rockwool substrate was used for lettuce, and coco-coir for tomatoes and cucumbers. We monitored and maintained the environmental parameters: daily light integral (DLI) ranged from 17–23 mol/m²/day for tomatoes and cucumbers and 12–18 mol/m²/day for lettuce. Tomatoes received supplemental light from 1 AM to 10 AM. Temperature and relative humidity (RH) were maintained at 18–22°C and 70–80% RH for lettuce, and 22–25°C and 60–70% RH for tomatoes and cucumbers. We monitored pH and EC weekly. Sap samples were collected at half and final stages for lettuce and four stages for tomatoes and cucumbers. Chlorophyll and anthocyanin content, yield, number of fruit, soluble solids content (SSC), and titratable acidity (TA) were recorded, while fresh/dry weight, leaf area, SSC, and TA were measured for lettuce. The tissue crushing method was used to establish sap-based sufficiency ranges for nitrogen (NO₃⁻-N), phosphorus (PO₄³⁻-P), potassium (K⁺), calcium (Ca²⁺), magnesium (Mg²⁺), and sulfur (SO₄²⁻-S). Our results provide general sufficiency recommendations (in mg/L): For greenhouse lettuce, the sufficiency ranges were NO₃⁻-N (546–1027), PO₄³⁻-P (520–616), K⁺ (6250–7052), Ca²⁺ (690–899), Mg²⁺ (280–371), and SO₄²⁻-S (93–101). For lettuce in vertical farm, NO₃⁻-N (1122–1139), PO₄³⁻-P (524–629), K⁺ (5455–5672), Ca²⁺ (426–595), Mg²⁺ (173–205), and SO₄²⁻-S (102–129). For tomatoes, NO₃⁻-N (547–805), PO₄³⁻-P (730–927), K⁺ (5360–7151), Ca²⁺ (3139–3716), Mg²⁺ (1133–1427), and SO₄²⁻-S (2796–3127). For cucumbers, NO₃⁻-N (888–1081), PO₄³⁻-P (25–38), K⁺ (4291–5478), Ca²⁺ (2147–2493), Mg²⁺ (1458–1813), and SO₄²⁻-S (1615–1946). In conclusion, sap-based sufficiency ranges were established which enable real-time nutrient monitoring and support more efficient fertigation in CEA.

The Pour-through method is a recommended best management practice (BMP) for nurseries in Florida for managing nutrient levels in container-grown crops. An investigation into fertility management in container nurseries was conducted by comparing traditional methods of monitoring EC with more recently developed sensor-based technologies. A field experiment was conducted to establish a relationship between sensor-based EC measurements and the pour-through method under two different irrigation methods (sprinkler and drip irrigation) and fertilizer rates (low and high) under open field and high tunnel environments. A sensor system was designed for field deployment, and wireless communication was established to monitor sensor data remotely. Results showed that a correlation could be established under sprinkler irrigation, but no correlation could be established under drip irrigation. Salt stratification was shown to vary significantly with irrigation type, with results suggesting that sensor installation in the center of the container is an optimal choice for monitoring EC of the root zone under multiple irrigation methods. Finally, variation in the data was modeled to determine the minimum number of sensors needed to maintain the same precision as the pour-through method. It was estimated that four sensors per 1000 pots are necessary. However, more sensors may be required to maintain this precision at higher EC levels.

Timely detection of aqueous analytes is essential for informed decision-making in agriculture, particularly in controlled environments such as greenhouses, vertical farms, and space-based cultivation systems. Traditional aqueous sensing technologies typically depend on single-point measurements, capturing data at fixed times and locations. This constraint limits their ability to detect analytes that may emerge elsewhere in the system or at different intervals. In response, we present an innovative, low-cost sensor platform featuring a 3D-printed housing integrated with a mass-manufactured, nanotextured diffraction surface. This housing includes a lighting element and a camera sensor to enable continuous image-based analysis of water quality. Designed for seamless integration into hydroponic lines, the sensor units are both affordable and easily reproducible, allowing for deployment at multiple points within a system to provide real-time monitoring. Our results demonstrate the sensor’s capability to detect and quantify a range of aqueous analytes—including visible and UV-absorbing compounds, dust particles, and various microalgae species. Our sensor performs similarly to a commercial UV-Vis instrument, often used to measure contaminants present in water. Specifically, calibration curves derived from increased concentrations of a simulated contaminant had a calculated R2 value of 0.998 from the UV-Vis instrument and 0.996 from our device. Performance is further enhanced through machine learning algorithms that improve detection and classification. This scalable and cost-effective sensing system offers a practical solution for real-time water quality assessment across controlled environment agriculture, greenhouse systems, and extraterrestrial farming applications—particularly in contexts where labor is limited and rapid response is critical.

Capsicum annuum (pepper) is an emerging crop for controlled environment production that is susceptible to intumescence. Intumescence is a physiological disorder characterized by unrestricted cellular growth causing protruding lesions, ultimately leading to epidermal rupture. While the causative factor for this disorder remains unknown, water stress is commonly implicated and end-of-day (EOD) lighting has been identified as a potential strategy for mitigating intumescence development. However, the timing of pepper leaf area expansion and intumescence development as well as appropriate lighting strategies for their control have yet to be determined. The objectives of this work were to 1) determine the timing of leaf area expansion to better inform EOD or pre-dawn (PD) lighting applications for intumescence suppression; 2) quantify the impact of low-intensity lighting applications on pepper leaf morphology; and 3) determine the role of water stress in the occurrence of intumescence development for pepper. Pepper ‘Pot-a-Peño’, ‘Spicy Jane’, and ‘California Wonder’ were grown in 15-cm pots in a common greenhouse environment. For Objective 1, three weeks after transplant, one uniform leaf on each plant was tagged and plants were evaluated twice a day (0700 and 1900) for one week. For Objective 2, plants were subjected to 30-minute lighting treatments at an intensity of 25 μmol·m·−2·s−1 for two weeks provided at either EOD with blue (EOD-B; 447 nm), red (EOD-R; 659 nm), or far-red light (EOD-FR; 734 nm), or PD with blue light (PD-B; 447 nm). For Objective 3, plants were either maintained at 70% field capacity (control) or allowed a single event of reaching 40% field capacity prior to watering. Intumescence development was visually monitored twice a day (0900 and 1700) during the water stress event. For Objective 1, leaf area expansion was 46%, 34%, and 94% greater at night (1900-0700) compared to the day (0700-1900) for ‘Spicy Jane’, ‘Pot-a-Peño’, and ‘California Wonder’, respectively. For Objective 2, responses to lighting treatments were cultivar specific. For example, after two weeks, imaged leaf area was lowest under EOD-B for ‘Pot-a-Peño’ and greatest under EOD-FR for ‘Spicy Jane’. For Objective 3, intumescence development was observed on all cultivars subjected to water stress post returning to field capacity, with no incidence of the disorder for control plants. These results will help in the prediction of intumescence development for pepper produced in controlled environments and inform decisions regarding the timing of possible suppression methods to control this disorder.

Global demand for high-quality onion bulbs is rising, and there is a need for innovative, resource-efficient cultivation systems that stabilize production while mitigating soil-related limitations. Hydroponic cultivation systems, widely adopted for high-value crops, offer a promising alternative by enabling precise environmental control, optimized nutrient management, and reduced exposure to soil-borne diseases and weed competition. However, hydroponic methods for onion bulb production remain underexplored despite their success in other vegetable crops. Knowledge gaps exist in root-zone aeration dynamics, nutrient uptake efficiency, and the economic scalability of hydroponic systems for onion production. The objective was to determine the growth performance, bulb quality, yield, and financial feasibility of growing onion varieties across these systems. This study evaluated the comparative performance of three onion varieties: Candy Onion (intermediate-day), Walla Walla Onion (long-day), and Yellow Sweet Spanish Onion (long-day), grown under three hydroponic systems (Deep Water Culture (DWC), Kratky, and Drip Irrigation) along with inground production. The study followed a randomized complete block design with three replications. Key growth parameters, such as plant height, leaf number, and chlorophyll content, were recorded each week. Yield attributes, including bulb diameter, weight, total fresh and dry biomass, and harvest index, were analyzed after harvest. Moreover, bulb quality parameters such as total soluble solids (TSS), sulfur content, and pungency (pyruvic acid concentration) were assessed for consumer acceptability. The economic evaluation considered were the cost of cultivation, gross and net returns, and the benefit-cost ratio to determine the financial viability of hydroponic onion production for small-scale farmers in Kentucky. Despite the higher initial setup cost, hydroponic systems are projected to provide about 25% greater financial returns by reducing labor, pesticide, and fertilizer expenses, making them a sustainable solution for onion production. This study provided insight for farmers, researchers, and policymakers on integrating hydroponic technology for enhanced onion production, economic profitability, and sustainable agricultural practices. Further studies are necessary to validate the findings and guide best-practice recommendations for optimizing onion cultivation and supporting year-round production in Kentucky and beyond.

In recent years, a technology called biopharming, in which plants are used to produce pharmaceuticals, enzymes, and other high-value proteins, has been commercialized. Infiltrating the plants via the stomata, with genes that encode for these proteins, is a critical step in biopharming, but there is limited research on how to manipulate plant morphology to optimise this process. In this study, we investigated how increasing the airflow in a hydroponic system under vertical farm condition affects the growth and morphology of Nicotiana benthamiana, the plant most commonly used in biopharming. The plants were grown in a hydroponic system under vertical farm condition equipped with LED lights, with a photoperiod of 16 hours light/8 hours dark, and a photosynthetic photon flux density of 160-180 µmol m-2 s-1. The growing beds were filled with liquid fertilizer with an electrical conductivity of 1.6 dS cm-1 and a pH of 6.0 ± 0.5. Seeds of Nicotiana benthamiana L. were sown in urethane cubes and transplanted onto the bed. In a preliminary experiment, the fresh weight, plant height, and number of leaves were measured to investigate the growth of Nicotiana benthamiana under hydroponic conditions, and at 30 days after transplanting was determined to be the optimum number of growing days for use as a control regime in the present study. The enhanced air-flow treatment employed a constant wind speed of 0.1 to 0.2 ms-1, and strategically placed air ducts were used to ensure that each plant was evenly exposed. Seven plants (each had 8 to 10 leaves) were harvested, of which the first, third, and fifth leaves were used to measure leaf area and perform stomatal observations. Applying the enhanced air-flow treatment increased the fresh weight and average stomatal aperture of the plants by 1.2 and 1.1-fold, respectively. Leaf area was also increased markedly by 1.8-fold, compared to the control regime. The same results were obtained after three replications, indicating that the method is reproducible. These results suggest that airflow is an important environmental factor that could influence the efficiency of the infiltration process in biopharming.

Brown seaweed extracts, particularly Ascophyllum nodosum (AN), have shown beneficial effects on improving plant physiology, flower development and abiotic stress tolerance in various crops. However, limited research has been conducted on other seaweed species, such as Ecklonia maxima (EM) and Macrocystis pyrifera (MP). This study aimed to evaluate the thermotolerance of tomato (Solanum lycopersicum L.) seedlings in response to the application of three seaweed extracts, AN, EM and MP (1% v/v). ‘Big Beef’ tomato seedlings were root-drenched with seaweed extracts at transplanting and grown for 35 days with weekly foliar application in growth chambers set at 26/19°C (day/night, 16/8 h) for control and 33/26°C for mild heat stress treatments. Under heat stress, AN and EM treatments significantly increased shoot fresh weight by 12.5% and 10.8%, respectively, compared to the control, while MP treatments showed no significant differences. Also, seedlings treated with MP showed a numerical increase in chlorophyll fluorescence (Fv’/Fm’) by 12.8% and a reduction in leaf electrolyte leakage by 19.8% compared to the control under heat stress. However, no significant thermotolerance effects of seaweed extracts were observed in SPAD, net photosynthetic rate (Pn), pollen count and viability. In conclusion, the application of seaweed extracts provided differential response to thermotolerance benefits of tomato seedlings under mild heat stress conditions, with AN and EM enhancing shoot biomass and MP showing potential in mitigating physiological heat stress damage.

Open field cultivation of specialty crops such as tomato is challenging in Oklahoma due to unpredictable weather. In open fields, early planting of tomato seedlings during spring is hampered due to damaging chill weather conditions. On the other hand, higher temperatures during the summer months severely limit productivity. Furthermore, insect pests and disease pressure are high in open field conditions. As a result, the production cost per unit area is high. With the objective to develop cost effective and profitable production systems, tomato production in high tunnel was evaluated in Oklahoma. Six tomato cultivars including beefsteak and cherry types were evaluated in high tunnel at Langston University, OK during spring-summer season in 2023. High tunnel kept warm during the early seedlings establishment period and allowed early planting in spring by six weeks compared to open field cultivation. Similarly, by covering the roof with 45% shade cloth, a continuous harvest was achieved throughout the summer until third week of September. Study revealed the beefsteak tomato cultivars produced higher marketable fruit yield compared to cherry types. The marketable fruit yield of six evaluated tomato cultivars were in the range of 44.3 ton/ha - 77.12 ton/ha. Similarly, total soluble solid (brix %) content in high tunnel grown tomatoes were in the range of 5.1 % - 6.1%. Our study shows the early growth, season extension, and high yield of tomatoes due to use of high tunnels, and small - medium or limited resources farmers could benefit from it.

Heating cost and low light limit greenhouse winter production in the north. Improved technologies can now support more efficient light delivery and interception. The greenhouse bell pepper cultivars Brocanto (yellow), Milena (orange) and Olly (red) were chosen to assess inter-canopy lighting with overhead high-pressure sodium irradiance. In addition to HPS, LED fixtures for in canopy placement were evaluated (GE current Arize® Integral). Plants were grown in a high-wire drip irrigation system using dutch bato buckets (17.7 L volume). The photoperiod was 16-h, day temperature 22 ± 2°C and reduced to 18 ± 2°C during the night. One or two horizontal LED bars were positioned and adjusted within 30 cm of the top of the plants throughout the study. In treatments with two LED bars, the bars were placed 30 cm (12 inches) apart. The intensity (400-700 nm) horizontally from the LEDs and measured at the location of the plant stems averaged 195 ± 30 µmol m-2s-1. Overhead HPS provided ~130 ± 20 µmol m-2s-1, 100 cm below the fixtures. Natural light was seasonally limited during the study. Seeds were sown on 29 Aug and one plant was transplanted into each container 50 d later (17 Oct). Lower leaves were removed as fruit ripened and the study was terminated at a plant height of ~180 to 200 cm. Colored peppers were first harvested 79 d from transplant (4 Jan) and the study was discontinued 8 weeks later. Plants grown with two LED bars produced higher yields than those with one bar or only HPS lighting. Olly produced 1.3 ± 0.09 kg under HPS, 2.2 ± 0.16 kg (one bar) and 3.2 ± 0.02 kg (2 bars) per plant while both Brocanto and Milena yielded 1.6 ± 0.19 kg under HPS, 2.3 ± 0.19 kg with one bar and 2.7 ± 0.09 kg (Milena) or 2.9 ± 0.10 kg (Brocanto) with two LED bars. The LEDs also increased the number of harvested peppers. For Olly, ten peppers were harvested on plants with only HPS and increased to 15 and 20 peppers with the LED bars. Six more peppers per plant were harvested with interlighting for Brocanto and Milena. The pepper size remained similar across treatments for Brocanto (197 ± 12.4 g) and Milena (170 ± 10.0 g). For Olly, the pepper size increased from 129 ± 6.0 g (HPS) to 161 ± 5.4 g with two LED inter-canopy bars.

Snow peas (Pisum sativum) are a flavorful crop that can be eaten raw or cooked. Diversified farmers often grow them to provide diverse crops for local markets. Controlled environment agriculture allows for fresh harvest and sale in markets that may not otherwise have access to them, such as early or late in the season. This research aims to increase crop diversity for growers. In this research, three cultivars of snow pea were grown including, Oregon Giant, Royal Snow, and Golden Sweet. These varieties were grown using a high (200 mg/L N) or low rate (100 mg/L N) of fertilizer in three different systems. The systems were drip irrigated 3:1 coconut coir: parboiled rice husks, drip irrigated 3:1 sphagnum peat: parboiled rice husks, and hydroponic nutrient film technique (NFT). The pods were harvested every two days for two weeks. Data collected included germination rate, number and weight of pods, and dry weight of shoot biomass per experimental unit. Two trials occurred, the first in winter 2024-2025 and the second in spring 2025. Golden Sweet and Royal Snow had the highest germination rate at over 80% in both trials and Oregon Giant performed poorly at less than 60%. In total harvestable yield, there was no significance in rate of fertilizer by itself, but the interaction between system and fertilizer was significant. In NFT, plants produced more peas with a high rate of fertilizer while in sphagnum peat, they produced more peas with a low rate of fertilizer. Regardless of fertilizer, plants in coconut coir produced very little and experienced a high rate of fruit abortion. In the interaction between system and cultivar, Golden Sweet in NFT produced more than any other combination. In this comparison, when grown in coconut coir, all three cultivars produced significantly less than all other combinations. The production cycle from seed to final harvest was approximately 80 days in both trials. It is feasible to produce a marketable crop of snow peas in controlled environment agriculture. NFT systems with 200 mg/L N of fertilizer produced the highest yield and biomass and could offer hydroponic growers a new crop option.

Maximizing crop yield is essential for the economic viability of indoor vertical farming, where operational costs are high. Among the many factors influencing productivity, planting density stands out as a manageable and cost-effective variable. Optimizing planting density offers a practical approach to improving yields without requiring major structural or technological changes. In this study, we evaluated the effects of planting density on lettuce (Lactuca sativa) yield and individual plant growth characteristics. Two cultivars with contrasting growth habits were used: butterhead lettuce ‘Rex’, known for its compact form, and green leaf lettuce ‘Fusion’, which exhibits an upright growth habit. Plants were cultivated for 24 days after transplanting in a controlled indoor environment maintained at 22 °C, under a photosynthetic photon flux density of 200 μmol∙m-2∙s-1 with an 18-hour photoperiod. Using a deep-water culture hydroponic system, we tested five planting densities: 21, 42, 82, 109 and 131 plants∙m-2. The nutrient solution was prepared with deionized water and a water-soluble fertilizer (12N–1.75P–13.3K; Jack’s Nutrients FeED 12–4–16 RO), providing 150 mg∙L⁻¹ of nitrogen. As planting density increased from 21 to 131 plants∙m-2, total shoot fresh mass per unit growing area rose from 1.6 to 7.2 kg∙m-2 in ‘Rex’ and from 2.6 to 10.9 kg∙m⁻² in ‘Fusion’. However, in ‘Fusion’, increasing density led to a 29% reduction in plant diameter, 19% in leaf number, 25% in leaf area, 33% in shoot fresh mass, and 5% in root fresh mass. Similarly, in ‘Rex’, leaf area and shoot fresh mass decreased by 23% and 26%, respectively, while root fresh mass, plant diameter and leaf number remained relatively consistent across densities. Our results suggest that while increasing planting density from 21 to 131 plants∙m-2 reduces individual plant growth, it increases overall lettuce crop yield per growing area in indoor lettuce production.

Efficient nutrient management is critical for optimizing hydroponic production. However, limited research exists on optimizing nutrient solution volume for various leafy green vegetables in recirculating hydroponic cultivation. To address this gap, we evaluated the growth and nutrient responses of four leafy green vegetables: butterhead lettuce (Lactuca sativa ‘Salanova Red Butter’), arugula (Eruca sativa ‘Standard’), kale (Brassica oleracea ‘Red Russian’), and red Malabar spinach (Basella alba ‘Rubra’). These crops were grown in a nutrient film technique (NFT) hydroponic system under two nutrient solution volumes, Low (76 liters) and High (151 liters), in a greenhouse during both summer and fall. Electrical conductivity (EC) of 1.8 mS/cm was maintained across treatments. Results indicated that leaf nitrogen (N) and potassium (K) content significantly increased with High nutrient solution volume while phosphorous (P) and K followed a similar trend in the fall. Low nutrient solution volume reduced nitrate levels in arugula tissue during both seasons, suggesting that lower volume may help minimize excessive nitrate levels in plant tissues. In summer, nitrate levels in red Malabar spinach (Low volume) and red butter lettuce (High volume) slightly exceeded recommended limits, while kale consistently surpassed safe nitrate levels regardless of treatment. Additionally, nutrient solution volume influenced key postharvest attributes such as color, texture, vitamin C, and anthocyanin content, with species-specific responses. These findings highlight the importance of crop-specific nutrient solution management to optimize plant health, improve nutrient use efficiency, minimize nitrate accumulation and nutrient waste, and support sustainable hydroponic production.

Adequate aeration in deep-water culture (DWC) sustains high dissolved oxygen (DO) levels, promoting nutrient uptake and root development. In multi-layered DWC systems, where a single reservoir supplies multiple trays, strategic aeration placement is essential for uniform oxygen distribution. This study examines how aeration location (reservoir vs. growing tray) and oxygenation method (air pump vs. oxygen concentrator) affect root zone DO levels and the growth of arugula (Eruca sativa ‘Astro’) and spinach (Spinacia oleracea ‘Auroch’). Plants were grown for 25 days in an indoor vertical farm at the air temperature of 22 °C under sole-source LED lighting (18-h photoperiod, 215 µmol∙m⁻²∙s⁻¹). Six aeration treatments were applied in a DWC system comprising a reservoir and a growing tray: no aeration (control), air pump aeration (reservoir, tray, or both), and oxygen concentrator aeration (reservoir or tray). The average DO level in the rootzone without aeration was 5.6 ppm. Aeration using the air pump increased DO to 6.0 ppm when placed in the reservoir, 7.3 ppm when placed in the tray, and 7.3 ppm when applied to both the reservoir and the tray. The oxygen concentrator treatment resulted in a higher increase in DO in the root zone, reaching 9.5 ppm when aeration was applied in the reservoir and 19.7 ppm when applied in the growing tray. Regardless of the oxygenation method, aeration in the reservoir had no effect on the growth of arugula or spinach compared to no aeration. Air pump aeration in the growing tray or both locations similarly increased leaf area, shoot fresh mass, and shoot dry mass in both species. In arugula, leaf area, shoot fresh mass, and shoot dry mass increased by 294%, 227%, and 120%, respectively. In spinach, leaf area, shoot fresh mass, and shoot dry mass increased by 184%, 216%, and 100%, respectively. Oxygen concentrator aeration in the growing tray increased leaf area by 217%, shoot fresh mass by 224%, and shoot dry mass by 73% in arugula, while having minimal effects on spinach. Our findings indicate that aerating the growing tray is more effective at increasing DO concentration than aerating the reservoir. Additionally, oxygen concentrators were more efficient than air pumps at elevating DO levels. However, regardless of DO concentration, aeration in the growing tray with the air pump was most effective at promoting growth in both arugula and spinach.

Soybeans play a crucial role in global agriculture, serving as a primary source of protein and oil, which supports food security, livestock feed, and renewable energy worldwide. The growing demand for food and fuel has intensified the need for soybean production, driving research into soybean cultivation in controlled environments. Manipulating light conditions using specialized LED lights in soybean production is particularly promising, as soybeans are highly responsive to light variations, including changes in the light spectrum. Our objective was to develop compact soybean plants optimized for controlled environments and enhance seed yield by exposing them to various light spectra. Soybean plants (varieties CZ 75 70LL and S16-14801C) were cultivated from seeds in growth chambers (27 °C/26 °C, day/night; 68% relative humidity; 590 µmol mol⁻1 CO₂) in 11 L plastic pots containing peat-moss substrate. One week after germination, the plants were exposed to one of four light spectrum treatments with 700 μmol m−2 s−1 photon flux density. These treatments had different percentages of photon flux ratios of blue (B: 400–500 nm), green (G: 500–600 nm), red (R: 600–700 nm), and far-red (FR: 700–750 nm) wavelengths: 1) 22B:50G:26R:2FR (White light), 2) 20B:80R, 3) 50B:50R, and 4) 40B:40R:20FR. Seed yield evaluations showed that the 40B:40R:20FR treatment resulted in a 10% higher 100-seed weight compared with the other treatments for both varieties. The number of seeds per plant increased by 21% in S16-14801C and 11% in CZ 75 70LL under the same treatment. Seed weight per plant was also higher in both varieties under this treatment, with increases of 26% for S16-14801C and 19% for CZ 75 70LL. Morphological evaluations revealed that the shortest plants were in the 50B:50R treatment, with a 2.4-fold reduction in height for S16-14801C and a 1.7-fold reduction for CZ 75 70LL compared to White light. Plants under the 40B:40R:20FR treatment were 33% shorter than those in the white light treatment for both varieties. Additionally, plants exposed to 40B:40R:20FR had 27% fewer branches but exhibited a 19% thicker stem diameter and a 29% higher shoot dry weight than other treatments. These findings confirm that the light spectrum can be adjusted to meet specific goals and enhance soybean cultivation in controlled environments, particularly by increasing seed yield and promoting plant compactness.

Strawberry (Fragaria × ananassa) production in the United States is a $2.5 billion industry, traditionally dominated by field cultivation. Controlled Environment Agriculture (CEA) is emerging as a promising alternative, offering year-round production and greater control over growing conditions. Despite its potential, strawberry cultivation in CEA systems remains cost-intensive, primarily due to high labor requirements. Additionally, strawberry production follows a cyclical pattern, with fruit developing in discrete peaks known as flushes. These fluctuations present challenges for consistent resource management, labor planning, and market supply, highlighting the need for predictive tools to optimize production efficiency. Our primary research objective is to develop a strawberry growers’ decision support tool for crop management through yield prediction based on flower mapping, a method of describing floral developmental stages through meristem dissection. Using a soilless hanging gutter system designed to mimic a commercial greenhouse production system, we grew a widely used cultivar Albion. The greenhouse maintained average daytime and nighttime air temperatures of 22.5 ± 3.1°C and 18.2 ± 2.8°C, respectively. Daily light integral (DLI) averaged 20.0 ± 3.0 mol·m⁻²·d⁻¹, daytime CO₂ concentration averaged 580 ± 207 ppm, and vapor pressure deficit (VPD) averaged 1.0 ± 0.6 kPa. Supplemental lighting provided a 16-hour photoperiod with a photosynthetic photon flux density (PPFD) of ~250 μmol·m⁻²·s⁻¹. Plants were fertigated through a drip irrigation system and grown in a commercial strawberry substrate composed of 100% coconut coir fiber. We performed weekly flower mapping on randomly sampled plants and yield measurements for the rest of plants for 19 weeks. We hypothesized that yield of a future week can be predicted based on counts of floral buds at each of 11 developmental stages. We found that floral meristem stages 4 and 5 (when calyx and trichomes differentiate on the floral bud) exhibit significant positive correlations with yield occurring nine weeks later. In addition, stage 11 meristems (anthesis) showed a significant positive correlation with yield occurring three weeks later. The remaining developmental stages exhibited weaker correlations and were less reliable predictors of upcoming yield. By using these key developmental stages, we will develop a methodology for forecasting near-future yield. This will help U.S. greenhouse strawberry growers to make informed decisions about resource allocation, labor scheduling, and market planning, ultimately optimizing yield and production efficiency in CEA systems. Our research outcomes lay the groundwork for more comprehensive yield predictions in the future.