Participants

The team members represent multi-institutional and interdisciplinary collaborations. Our members include the following representatives for three main objectives:

Administrative Advisor: Adel Shirmohammadi

Objective 1. To optimize environmental management and control and reduce energy use for high-quality greenhouse and indoor crop production.

• Specific objective 1.1. Develop crop-specific guidelines for light quantity and quality in both supplemental and sole-source lighting applications.


• Specific objective 1.2. Investigate the conversion efficiency of electric light sources used for controlled environment crop production.


• Specific objective 1.3. Investigate environmental control strategies that incorporate artificial intelligence techniques.


• Specific objective 1.4. Investigate wavelength selective greenhouse coverings and CEAgrivoltaics applications for environmental controls and reduced resource use.


• Specific objective 1.5. Co-optimization of environmental variables and enhancing resource use efficiency in indoor crop production.

Qingwu Meng (University of Delaware)

Shuyang Zhen (Texas A&M University)

Jennifer Boldt (USDA-ARS)

Shamim Ahamed (UC Davis)

Ying Zhang (University of Florida)

Neil Mattson (Cornell University)

Genhua Niu (Texas A&M AgriLife Research)

Kellie Walters (University of Tennessee)

Meriam Karlsson (University of Alaska Fairbanks)

A.J. Both (Rutgers University)

Roberto Lopez (Michigan State University)

Murat Kacira (University of Arizona)

Objective 2. To improve root-zone management of biotic and abiotic factors for high-quality greenhouse and indoor crop production.

• Specific objective 2.1. Select new crops that may be grown all year round in soilless substrates and water culture or using novel production techniques.


• Specific objective 2.2. Improve the efficacy of organic fertilizer for hydroponic crop production using beneficial microorganisms and controlling rootzone environments (e.g., temperature, dissolved oxygen, and pH).


• Specific objective 2.3. Develop aquaponic production strategies that optimize plant productivity while improving nutrient use efficiency (e.g., decoupled aquaponics and aerobic/anaerobic digestion of fish waste solids).

Stephanie Burnett (University of Maine)

Yujin Park (Arizona State University)

Genhua Niu (Texas A&M AgriLife Research)

Youping Sun (Utah State University)

Neil Mattson (Cornell University)

Kellie Walters (University of Tennessee)

Roberto Lopez (Michigan State University)

Murat Kacira (University of Arizona

Objective 3. To train growers and students on new controlled-environment production and engineering knowledge.

• Specific objective 3.1. Develop and offer an online class in scouting for insects and diseases in controlled environment agriculture.


• Specific objective 3.2. Develop and share curricula for undergraduate and graduate courses in hydroponics and soilless crop production and controlled environment engineering applications for a new program in Agricultural and Environment Technology at UC Davis.


• Specific objective 3.3. Develop Scholarship of Teaching and Learning (SoTL) projects in CEA with university undergraduate students.


• Specific objective 3.4. Develop a hydroponics textbook that can be used for CEA industry members and for classroom use with contributions by many other team members.


• Specific objective 3.5. Develop a hydroponic training course for growers and organize an annual conference on urban agriculture - controlled environment.

Qingwu Meng (University of Delaware)

Stephanie Burnett (University of Maine)

Shuyang Zhen (Texas A&M University)

Shamim Ahamed (UC Davis)

Ying Zhang (University of Florida)

Kimberly Williams (Kansas State University)

Neil Mattson (Cornell University)

Joseph Masabni (Texas A&M AgriLife Extension)

Kellie Walters (University of Tennessee)

Meriam Karlsson (University of Alaska Fairbanks)

A.J. Both (Rutgers University)

Roberto Lopez (Michigan State University)

Gene Giacomelli (University of Arizona)

Murat Kacira (University of Arizona)

Statement of Issues

Objective 1.

Centralized open-field vegetable production suffers from low productivity, foodborne pathogens, extreme weather patterns, and seasonal disruptions. As an alternative, greenhouse and indoor vertical farming is emerging to meet consumers’ demand for safe, local, fresh, and nutritious vegetables all year round. However, this industry is limited by its high energy use, which is among the highest input costs for controlled environment agriculture (CEA, including greenhouses and vertical farms). Energy use for plant lighting, temperature control, and dehumidification is also associated with the largest share of carbon emissions from indoor farms. A range of energy-efficient technologies are available (LED lighting and smart climate control); however, successful adoption requires greater knowledge of complex plant interactions with the growing environment.

Objective 2.

Hydroponic production, either nutrient solution or soilless substrate-based, is a preferred method for crop production under controlled environment like greenhouses and indoor farms. Hydroponics provides an opportunity to control the physical, chemical, and biological environment of the root zone. Physical and chemical environmental factors of root zone include nutrient composition (recipe) and concentration (electrical conductivity, EC), pH, temperature, and dissolved oxygen concentration. The biological factors are types of microorganisms (that is, microbiome) and their population. Under controlled environment in hydroponics, the microbiome in the root zone is completely different from that in soil rhizosphere.

Root zone temperature can influence plant growth and development. Greenhouse producers have been using root zone heating for decades by regulating media temperature during propagation and production of annual bedding plants and vegetable transplants. For solution-based hydroponics, root zone temperatures can be controlled through chilling and heating the nutrient reservoirs (Hooks et al., 2022; Miller et al., 2020; Sakamoto et al., 2015). The effect of root zone cooling and heating depends on air temperature and crops. However, available research-based information is limited for high-value leafy greens and culinary herbs.

As the demand for organic produce increases, interest in growing organic food crops under controlled environment using hydroponics is increasing as well. Nutrient management is more challenging with organic nutrient sources than inorganic fertilizers since organic nutrient sources often have imbalanced nutrient contents, high salinity and can introduce toxic pollutants and infectious agents and can decrease dissolved oxygen (Bergstrand et al., 2020; Kano et al., 2011; Williams, 2014). In addition, in organic fertilizer, many nutrients bound to organic substances are not immediately available for plant uptake and require microbially mediated mineralization processes (Bergstrand et al., 2020; Williams, 2014). However, current hydroponic rootzone environments are optimized principally for using inorganic fertilizer, and a significant knowledge gap exists regarding how biotic and abiotic factors of rootzone environment affect the efficacy of organic fertilizer for hydroponic crop production.

In recent years, application of bioproducts or plant biostimulants (PB) has gained recognition as a sustainable approach to boost plant growth and development under normal or stressed conditions (Askari-Khorasgani et al., 2019; Del Buono, 2021; Massa et al., 2017). PBs can be derived from a wide variety of materials: beneficial fungi such as arbuscular mycorrhizal fungi (AMF), beneficial bacteria such as plant growth-promoting rhizobacteria (PGPR), protein hydrolysate, humic substances, seaweed extract, and others (Del Buono, 2021; Shahrajabian et al., 2021). Thus, the effect of PBs largely depends on the type of PB.  Few studies have been  conducted to assess the efficacy of various PBs for (organic) crop production under controlled environments.

Aquaponics is a combination of aquaculture and hydroponics where fish waste is used as plant fertilizer and plants filter the water for fish. These production methods are land-use efficient and lend themselves well to urban production and to school science and agriculture classes. In the U.S., there are 5,350 aquaculture farms producing $1.8 billion wholesale annually (USDA, 2017). Aquaponics is an emerging industry, especially for urban agriculture.

Objective 3.

Controlled Environment Agriculture (CEA) is a rapidly changing field with high levels of technology. Growers and students working in CEA must understand topics including greenhouse engineering, irrigation and fertilization, business management and economics. Just in the past five to ten years, the tools and technology used in CEA have expanded to include an increased focus on LED lighting and other energy efficient technologies, hydroponic production of food, and improved sustainability of irrigation and fertilization practices. CEA technology will continue to change and evolve, making it critical to provide up to date, research-based training for growers. Highly skilled undergraduate and graduate students are needed to work in CEA; there are often more positions for graduates in this field than students to fill those positions. Our group is well positioned to train the next generation of growers and engineers as well as to connect students and the industry.

Since technology changes rapidly in this area, there is a strong need for research-based review articles and books on this topic. Currently, there are no student or grower-oriented books or review articles on the topic of hydroponics, which is a rapidly growing area of CEA. A hydroponics book would support the development of undergraduate and graduate hydroponic classes, which many members of our group either have developed or are planning to develop.

Justification

Objective 1.

The photon spectrum and intensity influence photosynthesis, plant shape, and accumulation of mineral nutrients. Light use efficiency of indoor crops also depends on other environmental factors (e.g., temperature, humidity, and carbon dioxide concentration) and cultural factors (e.g., nutrient solution concentration and composition). Therefore, optimizing the light environment based on key environmental and cultural factors has the potential to improve crop growth and nutritional value while saving electrical costs.

Optimal control of the environment in plant production facilities is a complex task due to the multiple interactions of the parameters involved. Traditional environment controls rely on sensor feedback from aerial or rootzone environment without information and data from crop growth as well as an approach considering entire production system in decision making. Integration of artificial intelligence (AI) can assist growers in making more logical, data-driven, site-specific management decisions which influence crop productivity, quality, as well as use of labor and other resources. An AI framework consists of models, controllers, and real-time data, that combined with domain knowledge can optimize decisions for selected outcomes (e.g., profitability, resource use efficiency).

Objective 2.

Traditional food crops grown in greenhouses include tomatoes, peppers, eggplant, strawberries, leafy greens, and culinary herbs. Additional novel food crops will be explored to find the high-yielding and profitable crops in greenhouse and indoor hydroponic systems to justify the high crop production cost in indoors.

Realizing year-round production under controlled environment is economically important to provide constant supply of fresh produce and increase the efficiency of the facility use. Greenhouse hydroponic crop production is energy intensive. In hot summers in southern region, cooling the air temperature of a greenhouse to optimal temperatures for many cool-season leafy greens and herbs is challenging. In cold winters, heating the entire greenhouse to the optimal level is costly. To reduce energy cost, root zone temperature control under suboptimal air temperature may be a solution. Quantifying the interaction between air and nutrient solution (root zone) temperatures is crucial to optimize crop yield, nutritional quality, and post-harvest longevity. The lack of this information limits the full utilization of the major advantage of controlled environments, which is the ability to manipulate the production environment. Consequently, there are significant gaps in economic feasibility, and the potential to provide high-quality, flavorful food to people from all socioeconomic backgrounds is diminished.

Greenhouse gas emissions associated with chemical fertilizer production, the global phosphorus shortage, and soil and water pollution caused by over application and mismanagement have all been recognized as severe threats to sustainable food production (Nosheen et al., 2021; Oelkers and Valsami-Jones, 2008). In addition, recent inorganic fertilizer shortage raised fears of a global food crisis. The use of organic materials as fertilizers has multiple advantages, such as recycling nutrients, supplying beneficial organic biostimulants, and decreasing the demand for mined minerals (Bergstrand et al., 2020).

Organic farming is one of the fastest growing segments in the U.S. agriculture. Increasing organically grown fresh produce such as fruiting vegetables, leafy greens and herbs under controlled environment is essential. Therefore, information on how to manage organic fertilizers in soilless substrate and organic hydroponics is urgently needed. In addition, the demand for organic seedlings for open field production far exceeds the supply. Controlled environment is an ideal facility for producing organic seedlings and transplants. Research-based information on how to best utilize available organic fertilizers amended with PBs to produce quality transplants will reduce transplant shock, and thus economic losses, and increase transplant tolerance to biotic and abiotic stresses after transplanting. Therefore, it is imperative to evaluate the effectiveness of PB products in tandem with organic fertilizers with optimal application rates and timings to organic farmers/stakeholders.

Aquaponics is one of the most popular systems for urban agriculture and for science classes in high schools and agriculture colleges. Although aquaponics concept is not new, there are many areas that need more research work. Cornell University research will address issues faced by aquaculture and aquaponics operators: the large volumes of solid waste that must be frequently removed and cleaned from their systems.

Objective 3.

Our group includes greenhouse engineers, horticulturists, and economists working in CEA. We are well suited to provide education and training on a broad range of topics. Many members of our team provide education in CEA through undergraduate instruction, mentoring of undergraduate and/or graduate students working on research projects, or Extension programming with CEA growers. The collaborative nature of our group allows us to broaden our programming so that our individual efforts coalesce for greater regional and national impact.