ASHS 2024 Conference

Night Light Pollution Delays Flowering in Soybean and Cannabis - Madigan Eckels
Precise Moisture Control Promotes Optimal, Fast, and Uniform Spinach Seed Germination - Shem Msabila
Planting Density on the Growth and Production of Select Fruiting Crops in Aquaponic Systems - Teal Hendrickson
Global Sensitivity Analysis and Validation of the Modified Energy Cascade Crop Model for Controlled Environment Agriculture - Donald Coon
Planting Density and the Growth of Kale and Cilantro in Year-round Aquaponics - Teal Hendrickson
The Physiological Responses of Citrus Tree Roots to Soil Acidification - Duplicate Sambani
Towards Sustainable Controlled Environment Agriculture Systems: Developing An Intelligent Decision-Making Tool For Improved Resource Use Efficiency - Eshwar Ravishankar
Pre-breeding Leafy Green Watercress (Nasturtium officinale; Brassicaceae) In an Indoor Vertical Farm: A Discovery Trial - Yufei Qian

As urban centers encroach on agricultural land, it is increasingly important to study the effects of light pollution on sensitive short day flowering crops such as Glycine max (soybean) and Cannabis sativa. Common responses to light pollution include delayed flower initiation and development, and Cannabis growers additionally speculate a myriad of other detriments as a result of light pollution. We conducted a series of studies with three soybean and ten Cannabis cultivars to elucidate responses to light pollution. Plant were grown under full-night light pollution ranging from 0 to 150 nanomols m-2 s-1 of cool white light or 0 to 40 nmols m-2 s-1 of red light at 660 nm. We found that continuous light pollution as low as 10 nmol m-2 s-1 from cool white LEDs delayed inflorescence initiation and development of the most sensitive Cannabis cultivars, while red light pollution as low as 5 nmol m-2 s-1 caused similar effects. In cultivars that did not experience a delay in inflorescence initiation, other plant characteristics including height and inflorescence development rate were negatively impacted. In soybean, flower delay in response to light pollution varied by cultivar but was reduced or absent in more modern lines, indicating that breeding may have selected against light sensitivity. Future growers must consider tolerance to light pollution during cultivar selection in order to avoid the detrimental impacts to short day crops.

Traditionally, aquaponic systems are used to produce leafy greens and herbs, while fruits and fruiting vegetables have been considered more difficult to grow due to additional nutrient requirements. When nutrients are not a limiting factor, the possibility of producing more fruit per square foot by increasing planting density is tempting as global populations increase and agricultural land area decreases. This study examined the effects of two different densities on banana peppers (Capsicum annuum L. var ‘Goddess F1’) and pole beans (Phaseolus vulgaris L. ‘Seychelles OG’) in a 20 sq ft grow bed. High densities consisted of 14 and 22 pepper and bean plants respectively, while low densities were 7 and 11 pepper and bean plants. Higher densities of peppers and beans produced more fruits than lower densities, while plant dry biomass of higher densities appeared to be lower than higher densities. Results suggest that higher planting densities of peppers and beans may increase harvestable fruit.

Use of aquaponic systems has the potential to provide sustainable food production in a variety of environments year-round. Unfortunately, little is known about the limitations of aquaponics regarding planting density in a grow bed and year-round growing outside of tropical climates. This study evaluated two different planting densities of kale (Brassica oleracea var. acephala L. ‘Winterbor’) and cilantro (Coriandrum sativum L. ‘Cruiser’) in a 20 sq ft grow bed in a hoophouse grown during winter and early spring in Stillwater, OK, using bluegill (Lepomis macrochirus L.) as the fish species. High planting densities comprised of 54 kale plants and 68 cilantro plants. Low densities contained 36 kale plants and 48 cilantro plants. High planting density reduced fresh weight and chlorophyll content in kale, and chlorophyll content in cilantro. Additionally, total nitrogen content decreased at higher densities of kale while sulfur content increased. Cold weather mitigation was utilized in the form of a secondary plastic covering, extra light sources, and in-line heaters. Results suggest that higher planting density may be feasible for some leafy green and herb species while being detrimental to others and that year-round growing may be possible with the addition of inline water heaters.

Citrus tree roots are vital in nutrient uptake, water absorption, and overall plant health. Soil pH alters the availability and mobility of essential nutrients in the soil, thus influencing root physiological processes; like most plants, citrus trees are particularly vulnerable to changes in soil pH levels. The root apoplast is the plant component that first encounters adverse soil chemical conditions; hence, the conditions in the root apoplast determine a plant's response. This study aims to investigate the physiological responses of citrus tree roots to soil acidification, focusing on the impact of varying soil pH on root morphology, nutrient uptake, and overall root health. A controlled three-month greenhouse study was conducted at the Citrus Research and Education Center (CREC), hypothesizing that soil acidification will alter apoplast and phloem pH, reducing CLas population and root damage. This study was conducted utilizing citrus trees subjected to different soil pH levels. Forty trees were used and divided into four groups by pH treatment. These trees were irrigated thrice a week with pH treatments: 5.5, 6.5, 7.5, and 8.5. Soil acidity and alkalinity were routinely monitored with pH probe sticks. Once soil pH stabilized, feeder root samples were taken for apoplastic and phloem pH experiments. The pH-sensitive fluorescent stains were used for microscopy and vacuum infiltration to collect apoplastic fluids. Parameters such as root length, root surface area, and root diameter were measured to assess the morphological changes in citrus tree roots under different pH treatments. The concentration of essential macro- and micronutrients from the soil, plant tissue, and leachates was also analyzed weekly to evaluate nutrient uptake efficiency. Preliminary results indicate that soil acidification significantly improves fruit yield and feeder root density. By ascribing the specific mechanisms underlying root responses, this research provides valuable insights into the adaptive capabilities of citrus trees. It informs future practices to preserve the health and productivity of citrus groves.

Controlled Environment Agriculture (CEA) systems significantly enhance crop yields per unit area in comparison to traditional open-field farming methods. Moreover, they contribute to reduced water consumption and offer extended and more predictable growing seasons. While CEA systems show promise in meeting urban vegetable demand, the question remains what the required inputs are (water, fertilizer, energy, labor) for different systems (vertical farm, greenhouses) in different climate locations. In this work, an easy-to-use transient energy model that simulates the internal microclimate of CEA systems is developed. The microclimate will include changes in temperature, humidity, water, nutrient, and carbon dioxide while also computing the energy costs associated with conditioning the space and electricity. This model will also accurately map the leaf temperature and hence compute the transpiration water loss accounting for the spectra of different artificial light sources. The energy model will be linked to a functional crop growth model that can simulate the yield of the plant over multiple growth cycles and quantify water and nutrient uptake. The potential of the developed model is demonstrated by performing simulations of year-around greenhouse operation within the U.S. Two climates categorized into hot, and cold based on annual temperature are selected for the simulation of tomato production. Results indicate that supplemental lighting energy requirement ranged between 128-160 kWh/m2-year across the selected climate zones to achieve target yield in a given duration. Overall energy consumption ranges from 200 - 400 kWh/m2-year. Overall, the supplemental lighting requirement makes upto 75 percent of the total required DLI and provides comparable improvements in biomass compared to yield in greenhouses without supplemental lighting. Finally, the model indicates that upto 90 percent of total supplemental lighting requirements require light intensities in the combination of 250 and 500 µmoles m-2 s-1 to satisfy the additional DLI requirement. However, a higher lighting intensity of 1000 µmoles m-2 s-1 is required sporadically at night during winter between October – March in the northern latitudes. Overall, this model integrates energy, temperature, nutrition, and crop yield considerations for various crops and acts as a useful predictive tool for assessing operational costs based on target yield and duration of growth for greenhouses operating in any given climate.

The Modified Energy Cascade (MEC) crop model was originally developed to predict the edible biomass production of bioregenerative life support systems (BLSS) along with BLSS consumption and production of O2 and CO2. Three distinct MEC versions support this original goal and controlled environment agriculture (CEA) on Earth. Cavazzoni built the first MEC for predicting crop growth, transpiration, and productivity of BLSS. Boscheri et al. and Amitrano et al. each developed versions building off Cavazzoni's work. While each of these model versions builds off each other, differences in methodology and assumptions of plant physiology impact the outputs of the model, necessitating a comparison between versions. To describe the effects of input variability and model structure on the outputs of the MEC versions before further development for BLSS and CEA production facilities, four research questions were chosen to guide this evaluation. 1) How much variation in transpiration and yield predictions can be attributed to the model version? 2) How are input variations propagated through the cascading nature of the models? 3) Which model components are highly sensitive or uncertain to which environmental conditions? 4) How well does each model version predict the outcome of lettuce yield and transpiration outcomes of data sets independent from model development? To answer the first three questions, a series of global sensitivity and uncertainty analyses were performed. They revealed that 1) for daily transpiration rate and edible biomass model version alone can explain between 69% and 82% with Amitranos representing the lowest values and Boscheris the highest typically. 2) Even in sequences of identical equations, where each subsequent calculation is identical, variability is gradually reduced with final output variations between 40% - 55% that can be attributed to the prior upstream differences. 3) The Cavazzoni and Boscheri edible yield predictions are highly sensitive to photosynthetic photon flux density (PPFD) and CO2 across calculations while Amitrano’s is more responsive to photoperiod rather than PPFD. 95% of Boscheris transpiration output is driven by relative humidity while the other two utilize a combination of that and photoperiod. Lastly, these models and their performance were evaluated using environmental and yield data from an indoor vertical farming facility and growth chamber experiments. Together these analyses provide the information necessary to continue the development of the MEC for the prediction of resource flows and yield of CEA and BLSS supporting the optimization of electricity usage and circularity processes within closed-loop agriculture.

Our research is to define and develop pre-breeding resources as foundational knowledge to underpin breeding of a specialty leafy green crop watercress (Nasturtium officinale; Brassicaceae). This is being achieved by screening a unique, worldwide collection of watercress population to discover and to enhance nutritional traits for health, morphology, and sensory of the indoor controlled environment agriculture (CEA) market. Watercress is a perennial semi-aquatic leafy green vegetable in the Brassicaceae family and is an understudied specialty crop that has important human health benefits. The most abundant secondary metabolite glucosinolate (GLS) in watercress is gluconasturiin, an aromatic GLS, which hydrolyses and releases phenethyl-isothiocyanates (PEITC). PETIC, specifically from watercress, has been proven to have chemo-preventative potentials. Wild germplasm collection harbours natural variations and useful trait discovery opportunities for introgression of novel traits into the existing gene pool. There is limited interdisciplinary research on crop nutrition and breeding for the CEA settings. We found that watercress is well-suited to indoor hydroponic growing. We established the first indoor vertical farm (VF), a controlled growth chamber in a shipping container, at University of California, Davis. Light quality and quantity both serve important roles in watercress growth and development, and a fully controllable vertical farm allows testing a suite of traits of interests with altered LED light regimes. Results showed that VF grown wild watercress possessed significant genotypic differences across treatments, indicating an abundant natural diversity. Altering red to blue LED light ratio and duration may further enhance the anti-cancer GLS compounds as well as nutritional quality profile of this leafy crop.

Quality Analysis of Bitter Acids in Hops (Humulus lupulus L.) from a Controlled Environment Versus Field Production System - Katie Stenmark
The Affect of High pH on Hydroponic Lettuce in a Controlled Environment - Alexander Speck
Drought Stress Responses of North American Native Bog Birch and Sweetgale in a Sensor-automated System - Jessica Hutchinson
Effects of Plant Growth Promoting Rhizobacteria on Yield of Amaranth viridis Linn. Grown in a Growth Chamber and Greenhouse - Zachary Williams
Shade-Avoidance Responses of Kale and Lettuce Elicited by Far-Red Light Can Persist Under High-Light Intensity - Jiyong Shin
Does Intermittent and Continuous Nutrient Flow Affect the Growth and Phytochemicals of Culinary Herbs in NFT Hydroponics - Abishkar Regmi
Adjusting Supplemental LED Light Intensities Based on Real-time Chlorophyll Fluorescence Measurements in a Greenhouse - Suyun Nam
Interactions of Far-Red Photons with Orange Photons or Red Photons: Photosynthetic Response, Morphology and Fruit Yield - Seonghwan Kang

Hop plants are produced for harvest of mature hop cones that are utilized in the medicinal, agricultural, cosmetic and craft beer industries. Hop plants are vigorously climbing perennials that require shorter than 15-hour days for flowering induction, and a trellis structure (3-6m annual height) for seasonal support. In the United States, the majority of hops are grown in field production systems in the Pacific Northwest where summer day lengths are long. The demand for hops has increased due to a boom in the craft beer industry which has led growers in southern states to seek alternative methods for producing hops outside of their traditional commercial growing region. Hop performance in greenhouse systems has not been evaluated in Oklahoma before, but controlled environments offer an alternative for hop producers in the south to limit pests, reduce contact with Downy Mildew (Pseudoperonospora humuli), and harvest multiple crops per year. Four cultivars of hops (‘Cascade’, ‘Comet’, ‘Newport’, ‘Tahoma’) were grown on a 3m trellis using a Dutch bucket hydroponic system with one rhizome per bucket spaced 0.5m apart without supplemental lighting in the USDA research greenhouses at Oklahoma State University. Four identical cultivars of hops were grown in a field system using a V-style trellis (5m height) at the Cimarron Valley Research Station in Perkins, OK. Mature hop cones were hand harvested at 80% moisture and dried at ambient temperature to 8-10% moisture. Hops were stored for up to six months frozen under nitrogen in vacuum sealed bags until analysis was performed. Hop bitter acids (α-acids and β-acids) were extracted using a 0.1% formic acid solvent, and hop quality was determined by HPLC. Bitter acids of greenhouse hops were determined to be highest in cultivars ‘Comet’ (α- 2.12%, β- 0.73%), ‘Cascade’ (α- 2.00%, β- 1.04%), and ‘Tahoma’ (α- 1.92%, β- 1.23%), where ‘Newport’ had a notably lower α and β-acid content (α- 0.71%, β- 0.81%). Bitter acid quality in field hops were comparable to hops produced in the greenhouse (‘Cascade’ α- 2.99%, β- 1.77%; ‘Newport’ α- 2.95%, β- 1.56%; ‘Tahoma’ α- 1.42%, β- 1.56%; ‘Comet’ α- 1.95%, β- 0.71%). With the information from this research, local greenhouse growers will be able to determine if hops are a viable option for their region.

In North Dakota, indoor-grown lettuce faces water pH levels higher than the ideal 5.5 to 6.5 range, with Fargo's water averaging a pH of 9.2 from 2018 to 2022. Addressing the gap in research on high pH's impact on lettuce, this study, running from 2023 to 2024, explored the effects of pH levels on the yield of lettuce grown in deep water culture (DWC) hydroponic systems. We tested three lettuce varieties (Casey, Gladius, and Tendita) under four pH conditions (6.3, 7.0, 8.3, and an unbuffered level), with each setup replicated four times. Th initial growth was in rock wool cubes under a clear dome for a month before transferring to DWC for another month. The results indicated significant differences in yield and size across pH levels and varieties. Gladius yielded the highest at pH 6.3 (86.0 g/plant), while Casey showed the lowest yield at pH 7.0 (9.6 g/plant). Gladius also achieved the largest diameter (25.1 cm) at pH 6.3, contrasting with Casey's smallest at 7.0 pH (10.2 cm). Notably, high pH (8.3) still produced reasonable yields and sizes, especially with the Gladius variety, highlighting the potential for selecting suitable varieties to mitigate adverse pH effects. This study underscores the importance of variety selection in hydroponic systems with non-ideal water pH, providing crucial insights for optimizing indoor lettuce production.

Climate change in the Northern United States is causing less consistent rain events that pressure horticulturists to mitigate the negative impacts of drought stress in ornamental plants. Selecting ornamental native plants that can adapt to predicted changes in climate is a way to preserve and strengthen landscape biodiversity and resilience. Bog birch (Betula pumila) and sweetgale (Myrica gale) are native, colony-forming shrubs indigenous to bogs across the Northern regions of North America with aesthetic features that merit their introduction as ornamental plants. The successful introduction of wetland plants into the nursery industry depends upon their tolerances to variation in water availability typical of managed landscapes. Our 8-week study assessed physiological responses to gradual declines in substrate volumetric water content (VWC) for both shrubs, as water stress intolerance may be a constraint in horticultural landscapes. To model a severe water deficit, we built an automated irrigation system using Arduino microcontrollers connected to soil moisture sensors and solenoid valves that allowed us to track and control VWC. Control plants were maintained at 40% throughout the 8-week period, while drought was simulated by decreasing VWC by 5% each week. Water potential, stomatal conductance, and rate of leaf photosynthesis declined in the plants experiencing drought, with symptoms of leaf dieback and yellowing. In contrast, plants held at 40% VWC maintained physiological functions and had minimal aesthetic decline. By week 8, droughted bog birch and sweetgale reduced their leaf dry masses by 20% and 28%, respectively, relative to control plants. Plants held at 5% VWC had lower stomatal conductance and photosynthetic rates compared to those held at 40%, with sweet gale showing a steeper decline compared to bog birch. During the experiment, stomatal conductance of drought-stressed bog birch and sweetgale decreased by 93% and 77% respectively, and increased for control plants. Similarly, bog birch and sweetgale experienced photosynthetic declines, with respective average decreases of 68% and 62%. At the end of the experiment bog birch maintained a higher leaf retention after severe drought. Most plants of both species retained some living leaf tissue under severe drought. Despite their natural habitats in waterlogged areas, bog birch and sweetgale have potential as drought tolerant, native ornamental shrubs for gardens and landscapes.

Amaranth viridis Linn. (amaranth), commonly referred to as Callaloo, is highly nutritious, drought tolerant, and require few inputs to grow. Amaranth is also known to have pharmacological properties. However, this crop is susceptible to pest damage, which hinders the crops growth, development, and marketable yield. Plant growth promoting rhizobacteria (PGPR) are naturally occurring soil microorganisms that live in the rhizosphere, aggressively colonize plant roots, and provide many benefits to plants. PGPR can promote plant growth, improve plant tolerance to biotic and abiotic stresses, increase nutrient and water uptake, and cause induced systematic resistance. This study was conducted to investigated the application of PGPR on yield and development of amaranth grown in a growth chamber and greenhouse. The study was conducted at the University of Maryland Eastern Shore Agricultural Experiment Station in a complete randomized design with four treatments (T1: Control, T2: Strand 209 (single strand), T3: Blend 5 (double strand), T4: Blend 8 (triple strand)), and six replications in the growth chamber study and nine replications in the greenhouse studies. One growth chamber study (duration for 5 weeks) and three greenhouse studies (summer 2022, fall 2022, and summer 2023) were conducted for ten weeks. Amaranth shoots grown in the greenhouse were harvested biweekly, and fresh weight and dry weight were measured. In both PGPR studies, height data and chlorophyll content were collected weekly, and fresh and dry weight of the whole plant (shoots and roots) were collected at the final harvest. Blend 5 was shown to significantly increase shoot growth when compared to the other treatments in the growth chamber study. In the 2022 summer greenhouse, Strand 209 and Blend 8 significantly increased root biomass, while Blend 5 significantly increased fresh weight of the whole plant. In the 2023 summer study, Strand 209 was significantly higher in average shoot dry weight and whole plant fresh weight when compared to the other treatments. The results of both studies showed that the application of PGPR increased amaranth growth and development. Future studies will evaluate the effects of the PGPR on systemic resistance of amaranth against the pigweed beetle.

Far-red (FR; 700–750 nm) light induces shade-avoidance responses such as stem and leaf elongation and an increase in specific leaf area (SLA). Previous studies have reported that a high photon flux density (PFD) can mitigate the effects of FR light. However, limited research has explored the impacts of individual waveband PFDs on the effects of high total PFD (TPFD) in regulating FR-light responses. To address this gap, we conducted an experiment hypothesizing that the effects of a high FR fraction [FR-PFD divided by the sum of red (R; 600–699 nm) and FR PFD] on shade-avoidance responses would persist when the TPFD increases were solely from increases in R and FR PFDs. We grew kale (Brassica oleracea var. sabellica) ‘Red Russian’ and lettuce (Lactuca sativa) ‘Rex’ and ‘Rouxai’ under 12 lighting treatments with a 24 h∙d−1 photoperiod, TPFDs of 85, 170, 255, or 340 µmol∙m−2∙s−1, and FR fractions of 0.00, 0.17, or 0.33. The blue (400-499 nm) PFD was constant in all treatments and the alterations in the TPFDs were solely due to R and FR PFDs. Based on preliminary results, high FR fractions increased the leaf length of kale to a similar degree at all TPFDs except for no increase at the TPFD of 85 µmol∙m−2∙s−1. High FR fractions increased the leaf length of lettuce ‘Rex’ and ‘Rouxai’ to a similar degree at all TPFDs. In contrast, the SLA of kale did not respond to the FR fraction at any of the TPFDs. The SLA of lettuce ‘Rex’ and ‘Rouxai’ was increased by high FR fractions to a similar degree at all TPFDs except for no increase at the TPFD of 85 µmol∙m−2∙s−1. Contrary to the paradigm, our results suggest that FR-fraction effects can persist under a high TPFD when R and FR PFDs are elevated. Moreover, the lack of response of kale leaf length and lettuce SLA to the FR fraction at the lowest TPFD implies that a low R and FR PFD attenuates the effect of the FR fraction in eliciting shade-avoidance responses.

Hydroponic cultivation has emerged as an innovative method for efficient and sustainable production of different crops because of year-round production and precise nutrient delivery. Light plays a major role when plants are grown in a controlled environment. Supplemental light is necessary for the physiological function of crops when grown in a hydroponics system. In nutrient film technique (NFT) hydroponic production, crops are usually produced with continuously flowing nutrient solutions. However, intermittent flow, where nutrient solutions are paused for periods of time instead of continuous cycling, has been proposed as a more efficient hydroponic system. Intermittent flow of nutrients increases the efficiency of hydroponic systems as it reduces the cost of running pumps continuously. Culinary herbs can be grown easily in NFT hydroponic systems. These herbs are a high-value crop and are a rich source of vitamins, nutrients, fibers, and phytochemicals that are known to fluctuate in concentration in different production systems. Yet it is not known if intermittent irrigation will impact phytochemicals in culinary herbs with or without supplemental lights in NFT production. This experiment investigated the effect of intermittent and continuous flow of nutrients in two culinary herbs, cilantro (Coriandrum sativum) and parsley (Petroselinum crispum) with or without supplemental lights. To regulate nutrient solution flow, the pump was turned on continuously in the continuous flow treatment, whereas it was turned on and off periodically for 30-minute intervals in the intermittent flow system. The herbs were grown for a month and different plant growth parameters like plant height, plant fresh weight, dry weight, root length (RL), total phenolic content (TPC), total flavonoid content (TFC) and proline were measured. Interestingly, nutrient delivery only affected plant height and plant fresh weight in cilantro. Plant height was greater in intermittent flow whereas plant fresh weight was greater in continuous flow. However, nutrient flow did not show any differences in other studied growth parameters in both herbs. Supplemental light significantly increased the root length, plant fresh weight, and dry weight of both herbs. TFC of cilantro was affected by the interaction of supplemental light and nutrient flow system with greater flavonoids in a continuous flow without supplemental light. In parsley, supplemental light increased the proline content. These findings suggest that cilantro and parsley can be grown easily in intermittent flow by reducing the associated cost of production. However, supplemental lighting is necessary to increase the yield of herbs.

Precise and efficient control of supplemental lighting is vital to minimize electrical energy costs in controlled environment agriculture. Even though various environmental factors such as temperature, vapor pressure deficit, CO2 concentrations, and water status influence photosynthetic capacity, current supplemental light control strategies are controlled only based on ambient sunlight conditions. Meanwhile, chlorophyll fluorescence is widely used as an indicator of environmental stress and photosynthetic capacity on account of its easy and non-invasive measurement. A chlorophyll fluorescence-based biofeedback system has been proposed as an innovative approach for precise control of supplemental LED light intensities. The biofeedback system can dynamically optimize LED light intensities based on real-time measurements of chlorophyll fluorescence while allowing plants to decide the amount of supplemental light they need. The biofeedback system has been previously validated in a growth chamber, but its application in an actual greenhouse condition remains unexplored. The objective of this research was to implement the biofeedback system in a greenhouse environment for real-time control of supplemental light intensities based on photosynthetic activity. Additionally, the productivity and energy efficiency of the biofeedback strategy were evaluated and compared to conventional light control strategies. Two fluorometers (MINI-PAM; Heinz Walz, Effeltrich, Germany) were used to monitor the electron transport rate (ETR) and quantum yield of photosystem II (ΦPSII) every 10 minutes, and the Biofeedback system adjusted supplemental LED light intensities until the predefined target ETR and ΦPSII were achieved. Three popular greenhouse crops [lettuce (Lactuca sativa), sweet basil (Ocimum basilicum), and spinach (Spinacia oleracea L.)] were grown under five supplemental light conditions. Specific targets of 1) electron transport rate (ETR), 2) quantum yield of photosystem II (ΦPSII), 3) photosynthetic photon flux density (PPFD), 4) daily light integral (DLI), and 5) no control (ambient sunlight) were used to control supplemental light intensities. In contrast to conventional lighting control methods, the biofeedback system tailored supplemental light intensities according to not only sunlight levels but also temperature and humidity. The result underlines the effectiveness and energy efficiency of the biofeedback system that could integrate variable environmental factors in the greenhouse and apply them to adjust supplemental light intensities precisely.

Plant response from the interaction between far-red and orange photons were rarely known, compared to that of far-red and red photons. Recent previous studies have found application of supplemental orange photons increases the openness of tomato plant architecture, resulting in improved dry weight than supplemental blue, green and red photons. However, limited information is available on the effects of orange photons on plant growth, morphology, and photosynthetic efficiency. Thus, our objective was to quantify the effects of orange photons on growth and photosynthetic responses during long term crop cultivation, compared to red photons. Dwarf tomatoes ‘Red Robin’ were grown in a walk-in chamber with controlled environmental conditions for 96 days after sowing (day temp. 24.3 ± 0.4℃ / night temp. 19.8 ± 0.5℃ and RH 60.5 ± 3.5%). Four light spectral treatments were applied as follows: 1) B25G25O200 (orange), 2) B25G25R200 (red), 3) B25G25O165FR35 (O FR), and 4) B25G25R165FR35 (R FR) (subscripts denote photon flux densities in µmol m² s-1). All spectral treatments had the same total light intensity of 250 µmol m² s-1 with a 18-h photoperiod. Leaf photosynthetic rate was measured before the fruit stage under sole-source orange or red light, as well as under combination lights (RGB or OGB), in a random order. Plant height and main stem length significantly increased under the two spectral treatments with far-red photons (i.e., O FR or R FR), compared to treatments without far-red photons (i.e., orange and red treatments). In comparison between orange and red treatments (without far-red), total dry weight of orange treatment was significantly higher than in red. However, the trend was opposite in the treatments with far-red photons (O FR treatment was lower than R FR treatment). In comparison between with and without far-red photons, total leaf area and fruit dry weight under far-red photons were significantly higher than those in the treatments without far-red photons, whereas stem weight was lower. Brix° under with far-red photons was higher than the treatment without far-red, and that of orange treatment was higher than in the red. Photosynthesis rate under sole-source orange photons was higher than under red photons, but no significant difference was observed among under combination lights. Overall, our results indicated that application of orange photons instead of red photons led to improved biomass and fruit yields in dwarf tomato, resulting in enhanced openness in the canopy structure; however, the trends were reversed with the application of far-red photons.

Timing Kale Growth for Peak Nutrition and Energy Efficiency in a Vertical, Hydroponic Indoor Container Farm - Skyler Brazel
Effects of Beneficial Bacterial Endophytes on Growth of Lettuce Plants, Transcriptome, and Root Microbiome in Hydroponic Systems - Chuansheng Mei
Soybean Speed Breeding: Optimizing Photoperiod for Maximizing Yield and Minimizing Time - Cristiane da Silva
Energy Modeling and Management to Improve the Sustainability of Indoor Farming - Ying Zhang
Increasing Circularity in Controlled Environment Agriculture using Anaerobic Digester Effluent as an Organic Fertilizer - Ana Martin Ryals
Utilizing Deep Learning for Hydroponic NFT Channel Spacing Optimization - Azlan Zahid
Modeling Evapotranspiration in Greenhouse and Indoor Cutting Propagation - Daniel Crawford
The Impact of Extreme Low Irradiance on the Wholesale Market Volume of Major Horticultural Crops in Korea - Jinhyun Kim

As entrepreneurs look to find new ways to shorten the gap between farm and table in urban communities, many are considering vertical farming as an answer to the problem of limited growing space. The aim of this experiment is to determine the optimal harvest time in weeks for vertically grown, hydroponic kale (Brassica oleracea var. acephala cv. ‘Toscano’) based on morphological data, phytonutrient concentrations, energy, and yield. After a four-week germination period, kale was grown for up to eight weeks and harvested at eight different stages of growth, based on the number of weeks spent in the vertical system. When harvested, morphological parameters were measured, and samples were collected to analyze mineral nutrient content. Electrical Energy usage data was collected and presented as: Lighting, HVAC, and Other. Data was analyzed as a Randomized Complete Block Design with three blocks. Mean plant height, fresh leaf mass, and leaf dry mass all increased with growth stage, with the largest plants being observed at stage eight. Additionally, the greatest mean quantity of dead, diseased, or unconsumable leaves of 3.27 leaves per plant was observed at stage eight. Mineral nutrient concentrations of calcium, sulfur, and manganese increased through seven weeks (stage seven), after which a decrease was observed in stage eight. Decreases in concentration during stage eight was also observed for phosphorus, potassium, and magnesium, with negligible differences in the younger stages. No differences in energy data existed for the daily mean lighting, HVAC, and Other electrical consumption across all eight stages. Harvest data collected indicates that plants should be harvested prior to stage eight to maintain mineral nutrient content and minimize dead leaves and should be considered with total energy consumption to optimize farm productivity, energy efficiency, and nutritional content of plants. Further analysis of other primary and secondary metabolites alongside total energy consumption cost is necessary to identify the best stage of harvest maturity and nutritional quality for consumers relative to energy usage and production cost.

Controlled environment agriculture will play an important role in feeding the increasing world population as urbanization is expanding, and arable land is decreasing. Higher yields will help offset the initial high cost for building hydroponic production facilities. Beneficial bacterial endophytes have been receiving more attention in sustainable agriculture practices because they can promote plant growth, enhance nutrient uptake, and inhibit pathogen growth. The Institute for Advanced Learning and Research has established a bacterial endophyte library of more than 2000 strains and found that some bacterial endophytes significantly increased the growth of tall fescue KY31 in vitro, up to 8-fold compared with untreated control plants. In previous paper, we reported that Pseudomonas psychrotolerans IALR632 significantly promote lettuce growth in hydroponic systems. In this study, we investigated the molecular and microbiological mechanisms these bacteria exhibit for plant growth promotion in hydroponic systems through plant gene expression with RNAseq and root bacterial community changes through microbiome analysis after bacterial inoculation. Lettuce (Lactuca sativa) cultivar ‘Green Oakleaf’ was inoculated with Pseudomonas psychrotolerans IALR632 one week after seeds were sown and transplanted to nutrient film technique (NFT) hydroponic units one week after bacterial inoculation. Samples were taken at 4, 10, and 15 days after lettuce seedlings were transplanted for gene expression analysis. Root samples were taken 15 days after transplantation for microbiome analysis. Anosim, NMDS, and PCoA analyses indicated bacterial community changes in inoculated plants. The top genus relative abundance was unclassified bacteria with 87% in IALR632 treatment and 85% in control (p=0.0136). In the next top 24 genus’s relative abundance, IALR632 inoculation dramatically increased Sediminibacterium, Hyphomicrobium, Sphingobium, Devosia, Mycobacterium, Rhodoplanes, and Runella by 68%, 114%, 72%, 158%, 513%, 103% and 1920%, respectively, and reduced Methylotenera, Rhizobium, and Sphingomonas by 68%, 62% and 45%, respectively. RNAseq data showed that there were 135, 2059, and 9319 DEG between the control and bacterial treatment at 4, 10, and 15 days, respectively. These DEG are being analyzed for pathways involved in plant growth promotion.

Speed breeding is a cutting-edge technology, that utilizes controlled environments to significantly reduce plant generation time, thereby accelerating breeding and research programs. The manipulation of temperature, irrigation, phytohormones, and light are the main ways to reduce plant cycles in speed breeding programs. However, changing these factors can result in decreased yield efficiency, which can also affect the quality of a speed-breeding program. This study aimed to increase seed production without increasing harvest time in soybean plants, a short-day plant, by using different photoperiod regimes. Two soybean (Glycine max) varieties, S16-14801C and CZ7570LL, were grown from seeds in 11-L pots containing peat moss-based substrate in growth chambers with controlled temperature (27 ± 0.5 ˚C), CO2 (475 ± 15 µmol mol-1), humidity (70 ± 5.0%), and light (300 ± 5 µmol m-2 s-1 at table; 20% blue, 10% green, 70% red). One week after germination, seedlings were exposed to four different photoperiod regimes: i) 10 h (0 w at 18 h); ii) two weeks at 18 h and then 10 h (2 w at 18 h); iii) four weeks at 18 h and then 10 h (4 w at 18 h) and iv) six weeks at 18 h and then 10 h (6 w at 18 h). The light fixtures were not adjusted over plant height following industry practices. The plants were harvested ten days after 95% of the pods had attained maturity (R8 stage). For both varieties, the number of pods and seeds and seed weight per plant increased linearly, with the increase in the number of weeks at 18 h. Thus, the number of pods, seeds, and seed weight of plants at 6 w at 18 h were at least 5-fold higher than in plants at 0 w at 18 h. Similarly, plants grown at 6 w at 18 h presented 4-fold higher biomass than plants grown at 0 w at 18 h. However, the increased seed yield and biomass accumulation did not result in a longer plant cycle; plants of both varieties at 6 w at 18 h were harvested 32 days before plants at 0 w at 18 h. Here, we demonstrated that seed yield can be increased and harvest time decreased by manipulating the photoperiod. These findings can help plant breeders in identifying the most suitable method for growing soybean plants in a shorter period, while also ensuring high seed production.

Controlled environment agriculture (CEA) is considered one of the most efficient ways of crop production. CEAs have the ability to control environmental conditions to maximize crop production. Indoor farms are considered one of the CEA systems that precisely control the environment, leading to high energy consumption in lighting, heating, cooling, and humidity control requirements. Enhancing the energy use efficiency (EUE) of indoor farms requires a better understanding of the energy characteristics of the system and crop production is needed. In this study, a steady state energy model and a machine learning based crop growth model were developed to evaluate energy-saving strategies for indoor lettuce production. The strategies included shifting photoperiod, utilizing heat tolerant crops, and adjusting air temperature settings at four different locations (Phoenix, AZ, Los Angeles, CA, Jacksonville, FL, and Boston, MA). The results showed that cultivar selection plays an important role in EUE improvement. Using high temperature settings with heat tolerant cultivars can increase the EUE of the system. However, increasing temperature setting alone does not significantly reduce energy consumption because of the increasing amount of energy needed for dehumidification. The geographical location of the indoor farm also affects energy consumption because of the different outdoor climate conditions. Boston, MA, which has the coldest outdoor air temperature, had the lowest energy consumption overall compared to the other three locations. Lastly, changing the photoperiod schedule from daytime to nighttime can reduce the electricity costs dramatically by avoiding the peak rate of electricity despite not having a significant reduction in energy consumption.

As global population and stress on our natural resources increases, we need to rethink how/where we produce food with emphasis on recycling resources such as carbon, water, and nutrients. Controlled environment agriculture (CEA) is gaining increasing attention due to its potential for improving resource use efficiency compared to traditional field-based agriculture. This project investigated a novel approach for treating hydroponics irrigation water and recovering nutrients from vegetable waste for reuse in CEA systems. An integrated anaerobic/aerobic biological treatment process was investigated. Anaerobic digester effluent was nitrified via an aerobic membrane bioreactor process to produce a liquid organic fertilizer supplement (nADE). The nADE was evaluated as a nutrient source for indoor hydroponic and greenhouse soilless drip-irrigation lettuce cultivation. Lettuce yield, tissue nutrient content, water quality, and nutrient uptake efficiency were compared between the nADE treatment and a commercial fertilizer control for each CEA system. The lettuce grown on nADE demonstrated similar or higher yields, more leaves, and elevated tissue nutrient content than the control. The nADE media improved N and P uptake efficiency in the drip-irrigation system but decreased K, Ca, and Mg uptake efficiency, possibly from the over-application of these nutrients. Further research is needed to optimize the integrated treatment system as well as nADE dosing. The study demonstrates a circular bioeconomy approach to decrease dependency on inorganic fertilizers while benefiting crop yield and quality.

In controlled environment agriculture (CEA), maintaining effective plant spacing throughout the crop growth cycle is crucial for efficient resource (light, water, space, and nutrients) utilization to achieve optimal crop yield and quality. Overcrowded or overlapping plant leaves could cause inefficient light exposure to plants/parts of plants, negatively affecting their growth. Additionally, reduced airflow makes overcrowded plants prone to diseases and foliage damage. Meanwhile, sparse plant spacing could result in inefficient space and light utilization. Traditional plant spacing adjustment relies on expert knowledge and manual labor, which is time-consuming, labor-intensive, and costly. Computer vision-based automatic plant space adjustment could help with data-driven decision-making and reduce labor dependency. This study aims to develop a deep learning-based computer vision approach to estimate the effective plant spacing by extracting the morphological characteristics of plants and NFT (nutrient film technique) channels during different plant growth stages. A total of 576 lettuce plants were grown in an NFT channel-based hydroponics system in a controlled environment. Then, RGB-D information of these plants and NFT channels was collected each day for three weeks from planting to harvesting. Then, CNN (convolutional neural network) was employed to extract the plant and NFT channel feature information. Then, the spatial pyramid pooling approach was used to encode and decode the contextual information and segment the plants and NFT channels. This approach helped to achieve an F1-score of 0.90 on the test dataset to estimate space between plants and NFT channels. These results show the potential of the proposed approach for automated plant space adjustment for efficient resource utilization.

Current mist irrigation practices in plant propagation do not represent the variable rate of water loss experienced in a greenhouse environment and often rely on grower experience for adjusting irrigation settings. Automated control logic for these systems can be improved by considering climate data to predict the real-time water loss in the propagation environment. The objectives of this study were to 1) identify the impacts of environmental parameters on the water loss of young plants in greenhouses and indoor environments and 2) develop an evapotranspiration model based on the key parameters identified to achieve weather-based mist irrigation control for resource-efficient plant propagation in controlled environment agriculture. Data sets that include climate data, water applied, and water loss were collected in greenhouse sunlight and indoor sole-source LED environments with unrooted chrysanthemum cuttings. Trials were completed in June and September in 2023 and February in 2024 to collect diverse minute-by-minute data in each environment. Measurements using load cells indicated highly variable water loss in the greenhouse environment. Conversely, in the indoor environment with lower and constant photosynthetic photon flux density (PPFD) and reduced vapor pressure deficit via a fog system, rate of water loss was lower and consistent over time. The key parameters for modeling water loss, found using stepwise regression, were PPFD, leaf temperature, and air vapor pressure (temperature and relative humidity). These climate parameters were correlated with water loss data over time to yield a simple evapotranspiration equation that could be programmed into commercial environmental control systems to improve current irrigation scheduling programs. By improving the control of mist irrigation to take climate data into account, growers have the potential to reduce crop losses (“shrinkage”), reduce rooting time, and improve water use efficiency.

 The recent loss of our colleague Marc van Iersel reminds us of the reasons our work in horticulture is so important. Marc's career was devoted to developing processes that judiciously utilized sensors to create efficient strategies to optimize crop quality and production for the grower. By examining the path of van Iersel’s work, we can understand how directed, mindful research can move quickly from the hands of the researcher to the farmer. Marc’s early work centered around developing smart irrigation systems utilizing biofeedback to measure soil moisture, with the goal of reducing water usage. More recently, Marc’s work integrated LED lighting with sensors including light sensors, moisture sensors, and low cost canopy and fluorescence detection to generate strategies for precise, energy efficient control of lighting in greenhouse and vertical growing platforms. Marc frequently consulted with growers to understand their needs and challenges, allowing the grower’s needs to frame his research. Marc also mentored the development of students, fellows, and colleagues in their own research, helping them discover how their programs could unfold in directions which would be most valuable. In this session we will examine the history of Marc’s research and continued work by colleagues, to ensure his lessons in how to provide practical answers for commercial horticulture are not lost. This two-hour session will include presentations from Marc's students and colleagues, and conclude with a 30-minute moderated Q&A/discussion.

Coordinator(s)

• Jennifer Boldt, United States Department of Agriculture, Agricultural Research Service, Toledo, OH, United States
• Neil Mattson, Cornell University, Ithaca, New York, United States
• Melanie Yelton, Grow Big, United States

• Bruce Bugbee, Utah State University, Plants, Soils, and Climate, Logan, Utah, United States
  A Life Filled with People, Plants, Photons, and Perseverance (15 mins)
• Stephanie Burnett, University of Maine, School of Food and Agriculture, Orono, Maine, United States
  Impact on Sensor Automated Irrigation and Student Mentoring (15 mins)
• Rhuanito Ferrarezi, University of Georgia, Horticulture, Athens, Georgia, United States
  The Man Behind the Legend (15 mins)
• Andrew Ogden, University of Georgia, Griffin, Georgia, United States
• Shuyang Zhen, Texas A&M University, United States
  The Light He Shined: Translating Plant Physiology into Smart Lighting Control Strategies (15 mins)
• Leonardo Lombardini, University of Georgia, Horticulture, Athens, Georgia, United States
  Honoring Marc's Legacy (15 mins)