Brief Summary of Minutes of Annual Meeting

Topic 1: Energy conservation and alternative energy sources 1. Evaluate biomass derived fuels for greenhouse heating (NE, NJ, NY).

NE has secured two double poly grower-type greenhouses on campus - one is being heated by natural gas and cooled by ventilation and evaporative pads. It has been monitored and data recorded at 10-minute basis since January using a similar LabVIEW adaptive model and data acquisition system described in the report. We have an excellent record of spatial and diurnal quantum and total radiation during this production period, along with diurnal temperatures and the operational events for the Groton II controller used. We are also working with web cam technology to visually and through machine vision follow crop growth and development. The second campus house will be glazed with double poly this summer, instrumented, and will use a prototype portable greenhouse pellet burner built by Heat Source One of Beatrice, NE. The campus and the commercial houses are of similar size and design and in a NS orientation. These greenhouses are internet accessible. The plan for NE this fall is to investigate potential improvement in quantum availability to the canopy using reflective mulches and poly films. We also plan to develop a physiological (including sugar and nutraceutical properties), a production plan, a market plan and a database for growing 16 selected cultivars of day neutral strawberries. The software and model developed will allow us to capture the growth and development information and concurrently evaluate heating and ventilation operation, costs, and efficiencies in real time.

2. Develop decision support systems for alternative fuel heating systems (NJ, NE, NY, PA, CT).

Coordinated control of daily light integral and CO2 concentration (NY) In previous work at Cornell, a patented control algorithm was developed that demonstrates synergistic environmental control involving supplemental lights, moveable shades and CO2 supplementation. Outdoor air temperature and the expected solar integral for the next hour are predicted based on data collected in the previous several hours. An energy balance predicts the ventilation rate required to control temperature for the next hour. A growth model utilizing CO2 concentration and daily light integral is then utilized to develop costs associated with providing a consistent level of growth with varying levels of CO2 and supplemental light. For each combination the cost of supplemental CO2 is compared to savings of supplemental light and the least cost combination is chosen. This control algorithm was implemented in a greenhouse compartment at Cornell, and lettuce crops were grown under these conditions; CO2 use and lighting energy data were collected for 3 months. Over the course of the experiment the CO2 Light controller successfully produced consistent daily growth that used 37% less supplemental lighting than a light integral controller alone. The greenhouse used for this research was particularly dark (approximately 50% light transmission); we expect the percentage savings to be greater in a more typical commercial greenhouse.

Energy comparisons of several imported vs. locally-grown foods (NY) The impending probable shortage of liquid fuels has alerted policy makers and the public that we need to account for the energy needs of agricultural production and the energy costs of bringing food to our tables. It is for these reasons that energy budgets and types of energy used in food production are of great interest. In the following, the energy use being compared is only that part supplied by humans at a cost. The energy accounted for is that delivered as electricity and various fossil fuels used for crop production (called direct energy), and that required to manufacture building materials, tillage equipment, and supplies such as fertilizer and pesticides (called embodied energy). The energy to extract fossil fuels and generate electricity is also taken into account; it can be considered to be embodied energy. It requires money to acquire and manipulate the energy we are accounting for, and its use results in carbon dioxide and other greenhouse gas emissions.

Topic 2: Water and nutrient solution management

3. Develop protocols for irrigation that maximize water use efficiency while maintaining crop growth and quality (CT, ME, NE, PA, NY, OH, AZ).

Machine Vision Guided System for Plant Health and Growth Monitoring in Controlled Environment Agriculture Production (AZ) In progress: Dr. Kacira's lab has been working on development of a sensing and control lab at the University of Arizona Controlled Environment Agriculture Center (UA-CEAC) to assess plant growth, quality and health. A machine vision system has been designed, constructed and it is under operation. Machine vision system autonomously monitors textural, color, and temporal features of experimental plants to determine plant health, growth and early symptoms of stresses. The capability of the system is currently being evaluated for detection of tipburn on lettuce growing in a floating hydroponics setting. The monitoring system is capable of extracting plant morphological, textural and temporal features evaluated. The extracted plant parameters; top projected canopy area, entropy, energy, contrast, and homogeneity and these features showed promising signals for detection of lettuce tipburn occurrence. However, experiments are in progress to further evaluate these plant features and system capability on early tipburn detection. The ultimate goal of the system being developed is to establish a multi-sensor based plant monitoring platform for plant health/quality monitoring and resource savings in CE plant production.

Sustainable Resource Management and Year Round Production of Fresh Green Salad Crops With Automated and Remotely Monitored Controlled Environment Plant Production Systems (AZ) An automated and remotely monitored three floating hydroponic system (FHS) was designed and constructed at the CEAC for research. The potential sustainable management of reduced and reused water and fertilizer in this hydroponic systems is being evaluated for production of fresh green salad crops. The automated FHS units are remotely monitored using LabView platform for parameters including EC, pH, dissolved oxygen and nutrient temperature in the root zone, and air temperature, relative humidity, light intensity, and CO2 concentration in the aerial environment. Currently, strategies were also developed to control the temperature and pH in the nutrient zone. Research is continuing on the dynamics of the system, and the effects of electrical conductivity, pH and water temperature on plant growth, quality and phytochemical yield, and energy input-output analysis in the production system.

Integrative Farming Practices for Sustainable Food Production (AZ) A state of the art controlled environment aquaponics research greenhouse was designed and engineered for intensive fish and vegetable production. Aquaponics is the integration of recirculating aquaculture and hydroponic plant systems. This system allows for reuse of water to produce lettuce in an efficient and sustainable manner. Research goals of the project include determining the biomass production (fish and plants) that can be achieved per unit of resources (water, nutrients, space), exploring the physiological interactions in a controlled environment aquaponics system, determining the water use efficiency of aquaponic systems, and developing production techniques for large scale applications. System output is determined by the overall biomass production of fish and plants. The Feed Conversion Ratio (FCR) is used to measure the production efficiency of fish. Plant biomass and Chlorophyll Concentration Indices are used to determine plant growth and quality. Environmental monitoring and control consists of air temperature, relative humidity and photosynthetic active radiation (PAR). Water temperature, pH, electrical conductivity, and dissolved oxygen are monitored and controlled. The complete water chemistry of the system is analyzed on a biweekly basis. The research greenhouse has been operating for one year and has established a synergistic relationship between the fish component, the filtration (biological, mechanical and chemical) component, and the hydroponic plant component. Current research has focused on Oreochromis niloticus spp. (Tilapia) and Lactuca sativa cultivars (lettuce). Fish effluent is a sustainable and efficient nutrient source for plant production and plant uptake and deposition of nutrients is an environmentally friendly means of filtration.

ME and GA are collaborating with Jonathan Frantz from the USDA-ARS to develop predictive models that will estimate water use of Euphorbia pulcherrima and Petunia × hybrida based on changes in vapor pressure deficit, temperature, and photosynthetic photon flux density. This model, once developed, will be included in the USDA-ARS program, Virtual Grower, which is available free to growers (http://www.ars.usda.gov/services/software/download.htm?softwareid=108). In ME Heuchera americana 'Dale's Strain' were grown in a capacitance automated irrigation system at volumetric water contents (VWC) set points of 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, or 0.50 L L-1. The volume of water applied to plants ranged from 2.5 to 5 L over a 50 d cropping cycle. Water use efficiency (g of shoot biomass/L of water applied) decreased as plants were irrigated at higher VWC set points. Of morphological variables measured (height, width, length of petiole, and number of leaves), VWC only significantly affected leaf area at the end of the cropping cycle. Leaf area increased with increasing VWC set point (range = 800 to 1600 cm2). A minimum VWC of 0.3 L L-1 is recommended for irrigation of Heuchera americana 'Dale's Strain' to avoid this reduction in leaf area.

KY developed a photosynthesis-based irrigation model for Hibiscus 'Cashmere Wind' under controlled-environment conditions. This model was based on the relationship between substrate moisture content and photosynthetic rate. A sigmoidal equation best fit the curve (r2=0.62). Photosynthesis was maintained at or near maximum rates from 100% container capacity to 62% container capacity. A distinct decrease in photosynthesis was apparent at 61% container capacity and this was used as an irrigation set point. Subsequent experiments showed that biomass and quality could be maintained equally among irrigation treatments so long as substrate moisture content was maintained above this set point.

Precise Nursery Water and Nutrient Delivery System (OH) Over a four-year period, a new water and nutrient delivery system was designed and constructed to accurately and precisely deliver nutrient solutions during relatively short irrigation events (5 to 10 min) in small volumes (10 to 50 L) to small numbers of container-grown plants typically required for specified treatments in research plots. The system was delivered to the Ohio Agricultural Research and Development Center (OARDC), Wooster, Ohio, for beta testing by Argus Control Systems Limited, White Rock, British Columbia on December 15, 2006. The unit was tested summer 2008 and summer 2009. Current results indicate the accuracy of nutrient delivery for the Argus Nutrient Delivery System is equal to or better than +/- 3% of specified target concentrations. These conclusions are based on a precise, nutrient system calibration procedure developed at the OARDC followed by daily pH and EC measurements.

Willoway Nurseries, Inc., Avon, Ohio, Bill Bauerle and Robert Hansen agreed to set up experiments to measure volumetric water content (VWC) and EC in container-grown plants as a basis for understanding leaching, water and nutrient delivery efficiencies, and optimizing systems for recycling water and nutrients. Twenty VWC sensors for making these measurements (Decagon ECH20-TE) and four data loggers (Decagon Em50) were purchased and tested in preparation for installation, summer 2009. The capability of these sensors to decide when and how much to irrigate pot-in-pot, container-grown trees will be evaluated and compared to growers' current practices for scheduling irrigation. In addition, ground up pine bark and hard wood chips are being evaluated as replacement components for container mediums since Canadian Sphagnum Peat Moss has tripled in price during the last year or so. The evaluation will be based on particle size, container capacity, porosity and durability. Newly designed platforms for doing flow-though measurements in the field were designed and constructed and will also be available for measuring EC and pH during summer 2009 and comparing results to the ECH20-TE pore water measurements.

Development of a Simple Test to Determine Capillary Flow in Different Types of Growing Media (PA) We propose to develop a simple and easy to conduct test that will compare capillary flow in various types of growing media. The test method evaluated was based on capillary uptake of a growing medium over a specific time course. Peat was brought to 4 moisture content values (160%, 250%, 390%, and 470%) and pots of moistened peat were placed in contact with water for 30 minutes in a container with the water depth of 1/4-inch. The cumulative water uptake was calculated by subtracting the previous weight from the current weight. The peat with the highest mass wetness values (390 and 470) had similar uptake patterns and the intercepts were similar, but the slope of the 390 moisture content line was 0.42 where as the slope of the 470 moisture content line was 0.29. Peat with an initial moisture content of 250% had a substantially higher slope and a lower intercept while the peat with the lowest moisture content had a steeper slope and a smaller intercept. It is clear that the initial moisture content of the peat will affect measured unsaturated water flow so any test for capillary flow must standardize the starting conditions. Subsequent test development trials when peat was a component of the mix used moisture content standardized to a constant value. In trial 2 moist peat was compared with perlite and a mixture of 50% peat and 50% perlite. The slope and the intercept of cumulative water uptake of peat was similar to that reported in Trial 1. Perlite had a much different intercept and a different slope to the regression line. The mixture of peat and perlite provided an intermediate water uptake. Trial 3 was conducted to provide a comparison of peat, sand and a mixture of peat and sand. The slope and the intercept for peat was different from the first two trials and there is no explanation for that difference at this point. The slope and intercept for sand is much different from either peat or perlite. The water uptake in sand is extremely rapid in that in the first minute all the water that could be taken up was taken up. The mixture of peat and sand has a much different slope that was evident for the other materials. The conclusion at this point is that different materials do have different slopes and intercepts so that it should be possible to develop a laboratory test that will permit the characterization of unsaturated water flow in commercial growing media.

Fertilization Strategies to Reduce Substrate Salt Accumulation in Sub-Irrigation Systems (NY) The objective of this project was to determine the influence of fertilizer concentration and irrigation method (sub- versus overhead irrigation) on the growth of several bedding plant species. Seedlings were transplanted into ten centimeter pots with a peat-based medium. Irrigation provided via ebb and flow benches (subirrigation) or hand watering (overhead). Within each greenhouse plants received a complete fertilizer solution provided at a concentration of 0.25, 0.50, 1.0, 1.75, and 2.5 dS/m. By the end of the nine week period container medium EC varied from 0.9 to 6.2 dS/m. For plants that received overhead irrigation optimal shoot dry mass (DM) was achieved at: 0.5 dS/m for pepper; 1.0 dS/m for tomato, Antirrhinum, Impatiens, and Torenia; and at 1.75 dS/m for the rest of the species. For the subirrigated plants optimal DM was achieved at: 0.5 dS/m for Antirrhinum, Gazania, Impatiens, and Torenia; 1.0 dS/m for kale, lettuce, pepper, and tomato; and 1.75 dS/m for collards. Our results corroborate previous reports that optimal plant growth often requires lower fertilizer concentrations when subirrigation is used. In several cases DM was negatively affected by high fertilizer concentrations with subirrigation. For example, DM of subirrigated Impatiens declined from 11.6 to 3.4 g/plant as fertilizer concentration increased from 1.0 to 2.5 dS/m.

Silicon Supplementation to Enhance Abiotic Stress Resistance (NY) Twenty popular bedding plant species were screened for silicon response; half of the species showed enhanced tissue silicon levels when potassium silicate supplementation was added to the fertilizer regime. Dry weight (DW) of three species increased when supplemented with Si, these were Bracteantha (+16%), Lobelia (+19%), and Verbena (+19%). Our results demonstrate that common floriculture species grown in a peat-based substrate do absorb silicon; and that Si supplementation from potassium silicate drenches was effective at increasing leaf Si concentration for about one-half of these crops. More work is needed to determine the appropriate rate of Si supplementation and to examine possible Si benefits under conditions of abiotic stress.

Silicon Supplementation and Regulated Deficit Irrigation of Poinsettia (NY) To investigate possible beneficial effects of substrate applied Si and Ca in Poinsettia (Euphorbia pulcherrima Willd. ex Klotzsch) production. The treatment design was a factorial arrangement having 2 Ca concentrations, 2 Si concentrations, and 3 irrigation regimes. We applied 0 and 56 mg·L-1 Si , 0 and 100 mg·L-1 Ca, as part of regular fertigation.  In addition, plants were given 100, 80 and 60% regulated deficit irrigation (RDI).  Regulated deficit volumes were established gravimetrically using several well watered (100%) reference plants. We observed a significant improvement in postharvest water stress tolerance, as measured by degree of wilt, when plants were supplemented with silicon. Leaf wilt angle was reduced 31% after 5 days of simulated postharvest storage without water. Regardless of nutrition regime, plants subjected to 60 and 80% optimal irrigation exhibited reduced postharvest wilting compared to well watered plants.

  4. Develop irrigation protocols and filtration or sterilization methods for nutrient solution recirculation that minimize the effects of pathogens or toxic metabolites (CT, NY, OH)

Partial Saturation Ebb and Flow Irrigation (CT) Sub-irrigation for production of potted ornamental plants combats the waste of water and fertilizer in traditional overhead watering systems used in greenhouses. However, current ebb and flow watering systems for flooded floors operate slowly. The root medium takes up water to near saturation during each watering cycle. There is no ability to restrict the water provided to the plants. We have examined a system to rapidly deliver and remove water. Less water is absorbed by the root medium and little if any water drains out of the pots. This improves plant quality and prevents spread of disease. We examined several parameters that vary between this partial saturation ebb and flow watering on a flooded floor compared to full saturation watering. Plants took up 20 to 30% less water and fertilizer. Biomass until flower development and bloom, and stem height, were also reduced by 10 to 20% under partial saturation. In one experiment with Poinsettia, inoculation of some plants with Pythium resulted in wilting of 20 of 240 non-inoculated plants grown under full saturation. No plants were affected under partial saturation. Post harvest quality of leaves and flowers in a controlled environment were similar under the two watering regimes.

Nursery Water Cleansing System (W. Bauerle, OH) A complete irrigation and water cleansing system was designed and constructed at a large commercial nursery facility. The irrigation and nutrient delivery system featured a special multi headed injection system designed by Bauerle. This Controlled Nutrient Delivery System (CNDS) injects essential, individual plant nutrients that result in the optimization of plant growth and development. The nutrients also result in the increased production of phytoalexins which stimulates the natural plant immune system against pathogenic infections. The water cleansing system was incorporated to control plant pathogens in the recycled effluent water. It was accomplished with the injection of chlorine dioxide into the system.

Topic 3: Sensors and control systems

5. Improve volumetric water content sensor efficacy (ME, NY, OH).

Physical Characterization of a New Substrate for Automated Irrigation Management by Using Microtensiometers (AZ) The objective of this project is to characterize foam glass substrate which is highly porous substrate and the use of a microtensiometer to trigger irrigation, when the matric potential is lower than desired. Experiments with this substrate and stone fibers were conducted at the CEAC-University of Arizona resulting in similar yields with 95% confidence interval. This research involves physical characterization of the foam glass which particle size is < 1.25 cm and the development of a microtensiometer to measure matric potential. The microtensiometer consists on a pressure transducer, stainless steel tubing, stainless steel porous cap and a solid block of the foam glass. The microtensiometer is going to be placed on the substrate bag and it is going to trigger irrigation when the matric potential is less than the desired. Finally, the water movement inside the foam glass growing bag (size: length= 100cm width = 15 cm and height = 15 cm) is going to be simulated by using the software packet Hydrus 3D. The simulation of water flow and the duration of each irrigation are going to be manipulated to have the ideal scenario to maximize water efficiency. The simulations of irrigations are going to be tested in a growing bag with mature tomatoes plants in a greenhouse located at the CEAC-University of Arizona. Plant water status measurements such as lysimeter are going to be conducted in order to avoid plant stress.

6. Improve sensor control of the greenhouse aerial environment (light, carbon dioxide, temperature, and moisture) (NJ, OH, NY, NE, AZ).

Greenhouse crop production for local sustainability and self-reliance (AK) Producing greenhouse crops in high latitude locations is demanding. Large seasonal variations in natural day lengths and temperatures require continuous modifications in the greenhouse climate to best conform to outside conditions. There is a demand for suitable greenhouse management procedures to be developed and disseminated to producers in northern and other challenging locations.

In OH sensors have been installed in a research greenhouse located on Wooster campus, OARDC to validate a model developed for estimating ventilation requirements of a greenhouse to improve CO2 enrichment efficiency. A semi-closed greenhouse is proposed to improve energy and CO2 enrichment efficiency of plant production in greenhouses.

Topic 4: Environmental effects on plant composition

7. Develop greenhouse design and management protocols to maintain high nutrition values of vegetable crops grown under various environments (AZ, CT, NJ).

Effects of Supplemental Light Quality on Growth and Phytochemicals of Baby Leaf Lettuce Grown under White Light (AZ) Using UV-A, blue, green, red, and far-red light-emitting diodes (LEDs), we investigated the effects of different supplemental light qualities on phytochemicals and growth of 'Red Cross' baby leaf lettuce (Lactuca sativa L.) grown at a high planting density under white fluorescent lamps as the main light source inside a growth chamber. After 12 days of light quality treatment (22 days after germination), phytochemical concentration and growth of lettuce plants were significant affected by light treatments. Anthocyanins concentration increased with supplemental UV-A and blue respectively, carotenoids concentration increased with supplemental blue, phenolics concentration increased with supplemental red while supplemental far-red decreased anthocyanins, carotenoids and chlorophyll concentration, compared to those under in the white light control. The fresh weight, dry weight, stem length, leaf length and leaf width significantly increased with supplemental far-red light compared to white light, presumably due to enhanced light interception by enlarged leaf area under supplemental far-red light. The results demonstrated that supplemental light quality could be strategically used to enhance nutritional value and growth of baby leaf lettuce grown under white light.

Evaluation of Yields and Quality of Baby Salad Leaves (AZ) As part of the on-going collaboration with Dr. Cynthia Thomson at the Department of Nutritional Sciences and Arizona Cancer Center, the Kubota lab is in charge of year-round production of baby leaves (mix of two lettuces and komatsuna). A total of 45 post-menopausal over-weight women are recruited and consuming greenhouse vegetables at three different doses (2, 5, and 10 servings a day) to examine human body response in terms of mitigating oxidative stress by consuming more vegetables. In the Kubota lab, while producing sufficient amounts of study vegetables (baby leaf mix, red pepper, and tomato), we evaluate seasonal changes in yield and the major phytochemical compounds in leaves (carotenoids, anthocyanins, phenolics, and ascorbic acid).

8. Develop greenhouse design and management protocols to maximize production of beneficial compounds such as phytochemicals and biopharmaceuticals (NY, AZ, CT, MI, NJ).

Biopharmaceutical Protein Production under Controlled Environments: Growth, Development and Vaccine Productivity of Transgenic Tomato Plants Grown Hydroponically in a Greenhouse (AZ) As the first step toward optimization of greenhouse-based production of plant-made high-value protein, growth and development of transgenic tomato plants were evaluated as well as their fruit and protein productivities. Transgenic tomato expressing a predominant antigen fusion protein F1-V against plague was used as a model system. Transgenic T2 lines, 'F1-V', its background wild-type cultivar, 'TA234',and a commercial greenhouse cultivar, 'Durinta', were grown hydroponically in a greenhouse equipped with a heating and an evaporative cooling system from September 2007 to March 2008. When comparing 'F1-V' with 'Durinta', 'Durinta' yielded more fruit than 'F1-V', although final vegetative biomass of the two genotypes was not significantly different. Cumulative fruit yield per plant of 'Durinta' for 13 weeks of harvests was almost twice that of 'F1-V'. However, total soluble-protein (TSP) concentration of fruits of 'Durinta' was significantly lower than that of 'F1-V', making the estimated cumulative TSP production by fruits lower in 'Durinta'. On the other hand, when comparing 'F1-V' with 'TA234', there were no significant differences neither in vegetative biomass, fruit yield, fruit TSP concentration nor cumulative TSP production between the two genotypes, suggesting that the differences between 'F1-V' and 'Durinta' are related to the difference between the baseline genotypes rather than the transgenic event. Our results suggest that biomass productivity is not necessarily the high priority trait in selecting cultivars for high-value protein production.

Lighting effects on active metabolite production in St. John's wort (NY) Hypericum perforatum or St. John's wort is a plant grown commercially for use as a medicinal plant. The consistency of secondary metabolites that act as active ingredients in H. perforatum preparations is a constant problem and is attributed partially to environmental conditions experienced by the plants during growth. Controlling the light provided to plants has been an effective way to manipulate plant growth in other crops. The effects of light intensity, quantity and quality on biomass and secondary metabolites hyperforin, pseudohypericin and hypericin over time were investigated in four experiments. Light intensities from 90 to 340 umol m-2 s-1 were investigated while daily light integral was held constant. Effects of daily light integral were demonstrated by holding the light intensity constant and varying the light integral from 8.6 to 20 mol m-2 d-1. The response of metabolite production to the presence or absence of UV-A and UV-B was also explored. Finally, the usefulness of stressing the plants with supplemental UV-B light just prior to harvest was determined. Results showed a very small or no significant increase in the secondary metabolites quantified in response to increasing light intensity, light integral or the addition of UV-A or UV-B light. Biomass production was shown to increase with exposure to increased light intensity and light integral. It was demonstrated that all of the metabolites increased their concentrations as plants transitioned from a vegetative to reproductive state. For growth in controlled environments, increased light integral did increase metabolite production indirectly as biomass increases led to a more rapid time to flowering. Since metabolite concentrations were shown to rise so dramatically when plants were flowering, the best protocol for maximizing metabolite production per square meter of growing space is to furnish plants with as much total light as possible which would hasten the time to flowering, then harvest plant material at the full bloom stage.

Environmental control to increase genetic expression of valuable chemicals in tobacco (NY) Continuing research uses chloroplast-transformed tobacco cultivars expressing cellulase as model crops with which to determine how to produce pharmaceuticals in controlled environments (CEs) most cost effectively. It was thought unlikely that cellulase enzymes would be a major target chemical for commercial CE production, but it was expected knowledge of the factors affecting the performance of chloroplast transformants expressing cellulase would generalize to transformants expressing other chemicals requiring or benefiting from greenhouse containment/production, that would be commercially viable. We have made good progress on the generation of transplastomic tobacco lines containing the gene for the high value human protein interleukin-2 (IL2) for CEA evaluation. Although protein expression in the chloroplast does not result in the production of properly glycosylated IL2, there is a market for non-glycosylated IL2. To date, there are no published reports of IL2 production in transplastomic plants.

Topic 5: Natural ventilation design and control

9. Improve control strategies as an alternative to existing vent control systems (AZ, NJ).

No accomplishments during this reporting period.

10. Continue our efforts to use CFD techniques to evaluate greenhouse natural ventilation systems (AZ, NY, OH, IL).

Validation of CFD Simulations for Three Dimensional Temperature Distributions of a Naturally Ventilated Multispan Greenhouse obtained by Wind Tunnel Measurement (AZ) As a continuation of the experimental wind tunnel research (Kacira et al., 2007) on the effect of vent configurations on greenhouse ventilation and spatial temperature distributions, the main focus of this study was to compare 3D temperature distributions obtained for different ventilation cases from wind tunnel study with CFD simulations to validate the developed model. Three different turbulence models (standard k-E, RNG and Realizable) were evaluated to determine the effect on the agreement with experimental results. It was found that standard k-E model agreed well with the experimental results. However, the RNG model results were in good agreement with experimental results when the external wind speed was zero m/s (under full buoyancy conditions) in the cases evaluated. The study showed that the selection of the turbulence model was critical depending on the conditions evaluated.

11. Continue efforts to improve the efficiency and effectiveness of greenhouse fog cooling systems (AZ, IL, NJ, OH, NY).

Enhanced Climate Control of Semi-arid and Arid Greenhouses Equipped with Fogging Systems (AZ) The primary objective of this project is to develop and validate high-performance control strategies for fogging systems that will enable or improve year-round cultivation in greenhouses located in arid and semi-arid regions. The research includes two main tasks. The first task focuses on the development and validation of climate control algorithms capable of maintaining the air temperature and humidity at levels suitable for crop growth throughout the year. The experiments at the UA-CEAC examines natural ventilation system equipped with variable pressure fogging system using different approaches that take into account the capabilities and limitations of the system. The second task will investigate the influence of the system flexibility on the performance of the fogging system. Operational flexibility will be represented by the number of fogging levels achievable by separate activation of different nozzle lines and/or pressure change in the lines, and the control time-step. To conduct this research, a variable pressure fogging system was installed for the experimental greenhouse. This 300 m2 naturally ventilated greenhouse equipped with both roof and side vents is instrumented with a sensor network enabling 3D scanning of the greenhouse aerial parameters as well as plant parameters (transpiration, leaf temperature) to evaluate the spatial uniformity of interior climate and study plant responses under various conditions. The experiments are in progress to develop the control strategies for the variable pressure fogging system. This project is a collaborative effort with Rafael Linker of Technion and Avraham Arbel of ARO-Volcani Research Center in Israel.