Daniel Crawford, an Agricultural and Biological Engineering B.S. student at the University of Florida, is researching climate sensors for propagation greenhouses. Production of seedlings, cuttings, and tissue culture transplants requires precise control of light, temperature, humidity, and mist irrigation. However, many greenhouses have few sensors inside their greenhouses and rely on a simple time clock and grower experience for mist timing. Commercially available sensors such as infra-red sensors for leaf temperature are being connected to a greenhouse control system at UF, to provide guidelines to growers on what sensors can be helpful. Climate data will also be used in a model of plant temperature and water loss to train growers on irrigation and climate control.

Harrison Meekins, a M.S in Environmental Horticulture, and Austin Erickson, a B.S in Chemistry, are researching heavy metal uptake and contamination in hemp. Heavy metals are heavily regulated by the EPA as a contaminant and pose a significant threat to hemp growers because of its tendency to accumulate heavy metals. Harrison and Austin are working to develop methods that growers can use to determine the presence of heavy metals in their crops accurately and reliably. One method that they are working on is developing a bioassay that can be used to track the uptake of heavy metals into plant tissue. Additionally, they are comparing different soil testing methods by their ability to extract and detect the presence of heavy metals in growing media. This will provide hemp growers with more knowledge to detect and combat heavy metal contamination to their plants.

Sofia Gomez (Laboratory technician), Peyton Beck, and Mario Molina (Agricultural and Biological Engineering B.S. students) are developing a third-generation automated environmental control system (light cart) for growing transplants to conduct research, modeling how factors such as vapor pressure deficit (VPD) affect leaf temperature and water loss during propagation. Vertical farming offers the ability to manipulate the propagation climate to optimize the growing environment of hard-to-root plants. However, this comes with an increased cost for growers that needs to be offset by reducing the propagation time and improving the quality of transplants compared to other propagation methods. The use of light carts as a research tool will enable to conduct several projects, modeling factors such as VPD, that play a key role on water loss of unrooted plats with the aim of optimizing the climate for indoor vertical farming propagation.

Annika Kohler is a Research Technician at Michigan State University and is investigating the daily light integral (DLI) for indoor seedling production on common bedding plants such as dianthus, geranium, petunia, salvia, and snapdragon. Previous research has shown that a moderate DLI is sufficient to produce young plants indoors. However, technology and production practices continue to advance, including better light sources to maximize plant growth and increasing interest in utilizing LED lighting for indoor young plant production. We are evaluating effects of DLI on seedling production and subsequent performance after transplant to determine positive and negative attributes that can affect a grower’s schedule, such as flowering time and plant size.

Dharti Thakulla, a research associate at the University of Florida and Ryan Fraser, a senior undergraduate researcher, are researching the implementation of ozone and non-thermal plasma technology for water treatment. Microbial contamination of the nutrient solution is a key challenge faced by hydroponic growers using recirculating systems. Ozone and non-thermal plasma technologies have been reported to aid in microbial sanitation and plant yield. However, it is important to consider and establish the correct method, dosage, and frequency of incorporating these technologies into hydroponic systems to avoid unwanted effect on plant growth or development. Through this project we aim to study the physio-chemical properties of ozone and plasma activated water and their effects on crop yield, sanitation, oxygen stability, and fertilizer interactions for hydroponic production.

Daniela Perez Lugones and Jansen Gedwed, both M.S. students in Environmental Horticulture at the University of Florida, are researching different rates of fertilizer, placement, and forms during production of containerized compact tomatoes (‘Siam’) and peppers (‘Basket of Fire’). Optimizing placement and fertilizer type (water soluble and controlled release) will allow growers and consumers to better manage inputs for higher nutrient uptake efficiency in plants. As well as placement and type, reducing and optimizing the amount of nitrogen provided up until the ‘point-of-sale’, or during the production phase, can cut costs by providing growers with increased production space, reducing fertilizer use, and minimizing shrinkage during shipping. Both growers and consumers could benefit from fertilization protocols that minimize fertilizer use while still producing compact, yet high-yielding container vegetables.

Fernanda Trientini is a Ph.D. student at the University of Florida studying mass and charge balance of recirculating nutrient solutions. Recirculating nutrient solutions are hard to manage due to multiple factors affecting the system concomitantly. Many growers use a standard nutrient solution for reservoir filling and replenishment without considering the effects of factors such as water quality, water treatment, solution pH, and acid-injection type. Fernanda's project aims to develop a mass balance model and easy-to-use decision-support tool that can customize solutions according to grower conditions to reduce fertilizer and water costs and the environmental impact of nutrient solution drainage.

Caleb Spall, is an M.S. student at Michigan State University and is currently investigating how light quality, DLI, and photoperiod influence flowering and morphological responses of greenhouse-grown specialty cut flowers during the young plant and finishing stages. Consumer and market demand for locally sourced, sustainably produced fresh specialty cut flowers continues to increase in the U.S. Growers across northern latitudes cannot produce specialty cut flowers in field or high tunnel cropping systems year-round due to the extreme temperatures and low DLIs characteristic of winter months. As a result, they must utilize greenhouses to produce high-quality specialty cut flowers during the winter to satisfy demand. The results of this research could be adapted into cultural guidelines for Midwestern and northern growers who are already utilizing or plan to utilize greenhouses for year-round specialty cut flower production.

Anthony Soster, is an M.S. student at Michigan State University and is currently investigating how daily light integral (DLI), day and night temperature, photoperiod, and plant growth regulators impact production time, leaf unfolding rate, excessive stretch, and flower development of succulents. Consumer demand for potted succulents continues to increase in the U.S. due to their diverse colors, forms, and flowers. However, when grown in greenhouses located in Northern latitudes, the production cycle of some succulent genera can be greater than 16 weeks, especially during winter months. Unfortunately, little research based information is available regarding how temperature, light, and photoperiod interact to and potentially reduce production time and promote flowering. The goal of this research is to develop models and identify critical photoperiods for several genera and cultivars of commonly grown succulents to reduce production costs and increase profitability. Additionally, we are investigating if a pre-shipment high rate PGR substrate drench can effectively reduce excessive stretch under low light environments such as consumer homes and offices.  

Kellie Walters, a Ph.D. student at Michigan State University, is working on the production, flavor and color enhancement of leafy greens and culinary herbs in controlled environments. She is evaluating how light intensity and quality, short wavelength radiation, carbon dioxide, and temperature interact and influence leafy green and herb flavor, volatile oil content, anthocyanins, growth, and development. Additionally, she has several side projects that include 1) quantifying the impact of carrier water alkalinity and air temperature at application on the efficacy of various plant growth regulators (PGRs) including ethephon and 2) determining the photoperiodic flowering responses of several specialty crops. 

The plant growth regulator (PGR) ethephon [(2-chloroethyl) phosphonic acid] breaks down to release ethylene (C₂H₄) and can be sprayed on floriculture crops to reduce cell elongation, inhibit internode elongation, reduce apical dominance, increase lateral branching, and abort flower buds and flowers. However, the efficacy of ethephon applications is influenced by a variety of environmental and cultural factors. For example, As pH or ambient temperature increases, ethephon efficacy decreases. This is due to ethephon breaking down into ethylene more quickly before it is absorbed by the plant. Since carrier water alkalinity affects solution pH, Kellie is quantifying how ethephon efficacy is influenced by carrier water alkalinity and air temperature at application. With increased efficacy comes the potential for lower chemical inputs, increased uniformity, and higher quality plants. Kellie is also determining the photoperiodic flowering responses of several foliage annual plants, herbs, and hop vines. Growers are increasingly incorporating foliage annuals into mixed combination planters due to their brightly colored or patterned leaves. However, the flowers of these foliage annuals are often unattractive and stall the desired vegetative growth. Therefore, our goal is to provide photoperiodic lighting recommendations to prevent flowering in foliage crops and herbs and enhance cone production of hop vines grown in controlled environments.

Melissa Muñoz Agudelo, Ph.D. student at Clemson University.

Botrytis cinerea is the fungal pathogen responsible for Botrytis blight in several crops including commercial cut roses. This disease is usually acquired during the production stage, but disease symptoms are more often seen in the post-harvest, especially when infected flowers are exposed to high humidity conditions during transportation. Fungicide applications as single-site or multisite products have been one of the main strategies for Botrytis blight management. However, during our previous research we were able to prove that several B. cinerea isolates are resistant to different fungicide modes of action, which means a challenge for disease management especially considering that environmental conditions in the commercial greenhouses like leaf wetness, temperature and relative humidity are favorable for disease development most of the time.

Current research focusses on the evaluation pre- and post-harvest applications of calcium in roses and assessment of different BCAs as management strategies for Botrytis blight alternative to the traditional fungicides. The integration of this strategies as part of an integrated disease management might allow a better rotation of fungicides and hopefully reduce Botrytis blight incidence and severity.

Mary Vargo is an M.S. Student at Clemson University and is currently evaluating stock plant management techniques on the effects of post-harvest flower development of Impatiens xhybrida. One of the principle strategies for producing many cuttings from stock plants involves the weekly application of ethephon, however, high rates of ethephon can cause significant delays in flowering for cuttings grown in the post-harvest environment.

We are assisting stock plant growers by evaluating daily light integral levels, ethephon rates, and cutting harvest position on the stock plant to create guidelines for producing high quality, uniform cuttings that flower in 5-6 weeks in the post-harvest production. We are also creating a bud meter that tracks flower development from visible bud to open flower at various temperatures so growers can utilize this resource as a means to keep the crop on schedule for the timely success of uniform flowering crops.

Melissa Muñoz Agudelo, M.S. en route to Ph.D student at Clemson University, is currently evaluating traditional and alternative management strategies for Botrytis control in cut rose production greenhouses. Botrytis cinerea is a significant problem affecting cut rose production in both pre-and post-harvest conditions which leads to losses for both growers and wholesalers. One of the principal strategies for disease management is fungicide applications including multisite and site-specific fungicides. However, the development of resistance is becoming more problematic especially in the case of the site-specific fungicides, making them less effective.

We are helping growers by evaluating fungicide resistance development, monitoring cultural practices and environmental factors that are associated with disease development to create a risk model that lead to better strategies for fungicide applications and we are evaluating alternative management strategies for disease management using post-harvest calcium dips.

M.S. student at Clemson University, Jiwoo Park, is working on growing petunias for improved consumer performance.

Consumer performance is critical to the success of greenhouse businesses. In recent years, greenhouse growers have reduced the amount of fertilizer applied to their spring bedding plant crops. This has resulted in concern about the performance of these plants once the consumer has purchased them. This experiment was designed to determine the effect of different fertilizer delivery methods and fertilizer concentrations on the growth of petunias (Petunia x hybrida) in the consumer environment. We focused on three fertilizer delivery strategies: Constant Liquid Fertilization Program, Controlled Release Fertilization Program and Post-Production Fertilizer Pulse Treatment. This study also examines the fertilizer cost efficacy associated with different fertilizer application techniques.

M.S. student at Clemson University, Katherine Bennett, is investigating calcium as an alternative to fungicides for Botrytis control.

Petunia Flower Meltdown, or rapid necrosis of petunia flowers, is a problem during transport of flowering plants from the greenhouse to retail locations. This phenomenon is a result of Botrytis infection in the greenhouse, and the disease expression occurs when the plants are placed into a humidity environment during transport. We are looking at alternative compounds for control as fungicides are becoming less effective due to resistance development. Initial studies demonstrated the potential value of calcium to inhibit Botrytis infection in petunia flowers. So, we are conducting experiments to determine the best strategies for applying calcium to reduce the postharvest losses that occur due to Botrytis infection.