NE1035: Commercial Greenhouse Production: Component and System Development
Statement of Issues and Justification
Issues and JustificationUSDA Economic Research Service data (2006) show the size of the greenhouse/nursery industry in the US as $16,891,934,000, which was 7.1% of the value for all US commodities. Unfortunately, the data do not distinguish between greenhouse and nursery production. Nevertheless, the 2006 data shows that the greenhouse/nursery industry in the current twelve NE-1017 member states (AK, AZ, CT, GA, KY, ME, NE, NJ, NY, OH, PA, and TX) generated approximately $4,239,580,000 in sales (approximately 25.2% of all sales in greenhouse/nursery nationwide). Three of the twelve member states (AK, NJ, and CT) have greenhouse/nursery sales ranked the highest of all agricultural commodities within that state. It is clear that this segment of the agricultural industry is of significant importance throughout the NE-1017 member states.
Academic support for commercial greenhouse production (also known as controlled environment agriculture) has, through NE-1017, brought together a unique mix of plant scientist and engineers interested in improving the economic viability of this important segment of agricultural production in the US. The challenges faced by individual researchers include limited funding sources, limited availability of (expensive) research facilities, and limited support through individual Experiment Stations. Through collaborating in a Multi-State project, researchers are able to work on subcomponents of larger research questions and later combine their results to provide solutions to the greenhouse industry.
NE-1017 members continue to conduct needs assessment from their stakeholders through several methods, including grower input, observations at grower operations, tracking issues related to grower questions, and presentations and discussions at various state, regional and national meetings. Based on grower inputs, evaluation of skills and interests of project members, and the available facilities, the project members have identified five high priority topics to address over the next 5 years. They are (1) energy conservation and alternative energy sources, (2) water and nutrient solution management, (3) sensors and control systems, (4) environmental effects on plant composition, and (5) natural ventilation design and control. These issues are discussed separately in each of the following paragraphs. The objectives for these topics are all technically feasible based on current knowledge, past work, and available expertise and facilities.
Topic 1: Energy conservation and alternative energy sources
Justification: As oil prices approach $100 per barrel, rising energy costs are clearly a concern for greenhouse growers. Strategies to reduce energy consumption, particularly for heating, include management, maintenance and, where justified, investment for upgrades of facilities and equipment. Potential conservation practices include: (1) management strategies that enable growers to lower air temperature without compromising their crops, (2) maintenance of structures and equipment, (3) mechanization or other measures that increase space utilization within the greenhouse, (4) upgrading control systems and strategies that improve uniformity and reduce unwanted fluctuations in temperature, and (5) insulation of greenhouse structures in areas where light reduction will not impact production, as well as insulating heating pipes in the boiler room and where they transport heat through areas that do not require heating. Continued research and guidance is needed to assist growers in implementing the most appropriate and economical conservation methods.
In addition to energy conservation measures, growers are increasingly interested in the use of alternative fuel sources (biomass, waste, wind, solar, etc.). New technologies and applications are becoming available continuously and new research is needed to evaluate these technologies for commercial greenhouse applications.
Topic 2: Water and nutrient solution management
Justification: Nutrient delivery systems consist of the hardware components that transport nutrient solution (water and soluble fertilizer) from a central location to each individual plant according to predetermined specifications. Irrigation frequency and duration may be based on fixed time intervals determined from past grower experiences, or be more specific to plant demands. Examples of nutrient delivery systems include drip, ebb and flood, overhead, capillary mat, aeroponics, and hydroponics. Optimizing the management of nutrient delivery systems, through control of electrical conductivity, can ensure plants are only provided the fertilizer concentration needed for healthy growth, without risk of nutrient deficiencies or the potential for nutrient toxicities and fertilizer runoff that result from fertilizer over-application.
In all nutrient delivery systems, recycling of the nutrient solution to eliminate contamination of the environment is possible, but such practices require a high level of management of nutrient concentrations and water supply. Closed irrigation systems pose several unique challenges: (1) a large storage container is needed to collect the drain water and to store the solution volume needed for the next irrigation cycle, (2) the system needs to be properly designed to prevent any leaks, (3) the potential exists for disease organisms to spread rapidly throughout the entire solution volume, (4) unwanted residues (e.g., from chemical applications) can accumulate over time, (5) nutrient settling and aeration, and (6) closed systems may be more expensive to install and maintain. Despite these challenges, many growers are highly interested in closed irrigation systems because of the belief that future regulations will restrict the practice of uncontrolled discharge of nutrient solutions to the environment. Growers are asking for systems that will recycle the nutrient solutions without risking the spread of disease while maintaining good nutrition management and avoiding toxicity.
Without continued research on managing water and nutrients, growers are going to be forced into expensive waste water treatment systems, are going to face challenges of growing plants in less than ideal conditions because of limited availability of water, or be forced out of business.
Topic 3: Sensors and control systems
Justification: It is important to accurately measure and interpret the greenhouse environment in order to provide an optimum environment throughout a cropping cycle. Growers use a range of sensors and control systems, from manual control all the way to sophisticated computer control. Sensors and control systems are continuously developing and their installation and use often require a significant investment in time and money. As a result, many growers would benefit from improved sensors and control systems at their operations if they had the appropriate decision tools that help them determine what the best options are for their operations. Such decision tools (e.g., summaries of evaluations and/or trials) can be generated by research projects conducted by NE-1017 members.
It is likely that both consumers and legislators will continue to be interested in sustainable and organic plant production. In greenhouses, sustainability should include efficiently utilizing resources including electricity, fuel for heating systems, water, and nutrient systems. One method to do this is to improve sensor technology and design and improve grower decision making capability with respect to greenhouse heating, lighting, irrigation, and fertilization.
Topic 4: Environmental effects on plant composition
Justification: Research conducted by NE-1017 members has the potential to make contributions to the fields of genetic engineering and human health. By manipulating the plant environment, it may be possible to stimulate specific gene expressions in plants, or increase the production and/or the quality of compounds important for the nutritional value of specific plants. In some cases, research in these areas is more easily fundable, resulting in new collaborations and new knowledge generation. Some NE-1017 members have already collaborated in such research projects and additional projects are in the planning stages. Developments in these research areas have the potential to significantly increase the economic returns for greenhouse operations involved in crop production for plant compound generation.
By manipulating the plant environment, it is possible to increase the production and/or the quality of specific compounds important for the nutritional or industrial value of specific plants. In some cases, research in these emerging areas is more easily fundable, resulting in new collaborations and new knowledge generation. Some NE-1017 members have already collaborated in such research projects and additional projects are in the planning stages. Developments in these research areas have the potential to significantly increase the economic returns for greenhouse operations involved in crop production for plant compound generation.
Controlled environments provide a unique opportunity to modify product quality attributes or more specifically, concentrations of selected phytochemicals in plants. An example of such approach is lycopene in tomato. It has been reported that light quality and intensity (e.g., Alba et al., 2000), air temperature (e.g., Krumbein et al., 2006), nutrient concentration (e.g., Fanasca et al., 2006), and salinity level of nutrient concentration (e.g., Krauss et al., 2006) affected lycopene concentration in fruit. Another example in enhancing secondary metabolites of Hypericum perforatum or St John's wort, a medicinal crop produced worldwide, and the reported factors affecting its active medicinal compounds include light quality and intensity (Briskin and Gawienowski, 2001), air temperature (Couceiro et al., 2006), and others (Murch et al., 2003). In floriculture, it has been observed that flower pigment concentrations were affected by greenhouse environments, but limited amount of research has been conducted for environmental factors on flower color, also driven by altered concentrations of phytochemicals. However, practical information on manipulating various phytochemicals as affected by environmental conditions and cultural system/practices is limited.
Another emerging area relevant to this approach is biopharmaceutical and other high value protein production using plants and other photoautotrophic organisms (algae and bacteria) including transgenic organisms. Specifically, whole plant based production is advantageous over more traditional systems using microbes or mammalian cells (Twyman et al., 2003). However, genetic, cultural and environmental factors to enhance biopharmaceutical production have not been well investigated, although optimization of the production is critical in commercialization of such products. Such effort of optimization must be done in a collaborative format including fundamental and applied researchers consisting of biologists, applied horticulturists, and engineers through strong linkage between academic researchers and industry R&D groups.
The controlled environment agriculture (CEA) is an integrated technology to maximize the productivity of plants and considered as a sustainable platform of producing phytochemicals, biopharmceuticals and other high value products. In CEA, all growth parameters can be controlled and the plants can be kept free of pesticides since most pathogens and diseases can be addressed using integrated pest management techniques in the contained environment. We propose to take advantage of this combined expertise of horticultural sciences, plant biotechnology, and greenhouse engineering to develop a potential foundation for a new industry, and greenhouse design and technology suitable for high quality products and plant high value compound production such as phytochemicals and biopharmaceuticals.
Topic 5: Natural ventilation design and control
Justification: Natural ventilation of greenhouses involves the use of sidewall and/or roof vents to cool the air and reduce humidity. Reducing heat stress and diseases caused by high temperature and humidity have a direct effect on the profitability of the greenhouse operation. The control of the ventilation vents and heating systems has evolved as control technology has evolved. Today, several companies provide computer control systems that will operate natural ventilation and heating systems based on a variety of control strategies, sensor inputs from the plant area as well as weather conditions.
Today's advanced greenhouse industry is developing into sustainable crop production systems with reduced energy consumption, and higher crop yields and quality. Properly designed ventilation systems are essential for the optimal control of air temperature, humidity and maintaining optimum concentrations of gases in greenhouse environment. Thus, photosynthetic and transpiration processes of plants are regulated properly and the quality of crops is improved. The ventilation process is critical for cooling and for reducing humidity levels within the greenhouse. Reducing heat stress and diseases that are caused by high humidity levels has a direct effect on the profitability of a greenhouse operation. Greenhouse cooling is essential for controlling the physiological response of a crop which is directly related to yield and production quality. Due to advantages such as low energy consumption, less operational cost, less maintenance, less noise, there has been a major shift back to the utilization of natural ventilation. However, the physical phenomena involved in natural ventilation and designing a naturally ventilated greenhouse are complex and appropriate control strategies are needed to ensure uniformity, production quality and energy efficiency.
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