Duration: 10/01/2003 to 09/30/2008

Administrative Advisor(s):

NIFA Reps:

Non-Technical Summary

Statement of Issues and Justification

The goal of this project is to make significant advances in greenhouse production by improving the utilization of water and nutrients with related reduction in negative environmental impact, developing a control strategy for natural ventilation of greenhouses, and improving the integration of automation, plant culture and environment into a cost effective, sustainable production system for vegetables, specialty and floricultural crops.

Greenhouse production, often called Controlled Environment Agriculture (CEA), is a high cost system for high-value crop production. This system allows production of plants out of season, provides for more efficient use of resources, and increases yields per unit area compared to tunnel or field crop production. It is also very dependent on advanced technologies and requires high-energy input. Detailed understanding of the interaction between physical and biological components within a CEA system is essential for successfully using advanced technologies.

Continued advancements are dependent on continued research to improve the understanding of the relationships and to use this information in improving the design and management of greenhouse systems. Decision-support models that link plant performance with environmental variables must be developed and then coupled with efficient, economic controls within an environmentally sustainable system. Because of the broad range of greenhouse designs, crops and differences in prevailing environmental conditions associated with different climatic zones, decision support systems are needed that are broadly applicable. Interdisciplinary cooperation of horticultural physiologists and agricultural engineers is needed to address this complex technology.

USDA Economic Research Service data (2001) show the size of the greenhouse/nursery industry in the US as $13,794,634,000, which was 6.8% of the value for all US commodities. Unfortunately, the data do not distinguish between greenhouse and nursery production. Nevertheless, the 2001 data shows that the greenhouse/nursery industry in the ten NE-164 member states generated approximately $2,418,738,000 in sales (approximately 17.5% of all sales in the greenhouse/nursery nationwide). Three of the ten member states (NJ, CT, NH) 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-164 member states.

Most state experiment stations are ill equipped to individually address all of the problems associated with complex CEA production systems and the wide range of crops produced in these systems. Because of the limit on expertise and resources associated with individual stations and individual Hatch projects, multi-state research collaboration is the most appropriate means for approaching the problem of developing useful CEA decision-support systems that require input from multiple disciplines and replication over different climatic zones. The regional approach also allows collaborative research to be conducted at individual institutions with expensive, complex, or unique facilities, e.g. open roof, flood floor greenhouse at Rutgers and the hydroponic lettuce greenhouse at Cornell.

The NE-164 group has a strong history of collaborative research programs and years of collective experience on all aspects of greenhouse systems. The initial focus was on structural design and glazing systems (Roberts and Mears, 1969; Roberts, et al., 1985; Roberts, et al., 1989; Aldrich and Bartok, 1994) and environmental control [heating, cooling, and ventilation] (Aldrich and Bartok, 1994; Elwell, et al., 1984a and 1984b; Short and Breuer, 1985; Short and Bauerle, 1989). The subsequent focus was on crop production systems (Both et al., 2001; Giacomelli and Gottdenker, 2000; Giacomelli, et al., 1994b). A recent focus has been on greenhouse lighting by NJ, NY, and NH (Donnelly and Fisher, 2002a; Fisher and Donnelly, 2002).

NE164 members have conducted needs assessment from the stakeholders through several methods, including individual observations and discussions at grower facilities, tracking the issues related to questions, and discussions at various meetings. Based on grower inputs and evaluation of the skills and interests of members and the available facilities, the committee has identified three high priority topics to address over the next 5 years. They are (1) managing nutrients and water in greenhouses, (2) managing the aerial environment for greenhouse plant production, and (3) integrating sustainable and economically profitable systems and processes for the greenhouse industry. These issues are discussed separately in each of the following proposal sections. The objectives for these topics are all technically feasible based on current knowledge, past work, and available facilities.

Topic No. 1, Managing nutrients and water in greenhouses: One fundamental component of Controlled Environmental Plant Production Systems (CEPPS) is the nutrient delivery system (NDS). The NDS consists 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, and be based proportionate to measured canopy solar radiation (Giacomelli and Ting, 1997) and plant responses to drought stress (Chen et al., 2002; Yang and Ling, 2002). Examples may include systems of drip irrigated rock wool culture for tomatoes or other large plants (Rorabaugh, et al., 2001; Ivey, et al., 2000), or aeroponic culture of small plants whereby the suspended plant root zone is irrigated with a nutrient spray (Hayden, et al., 2002).

Optimizing the management of nutrient concentrations, through control of electrical conductivity (EC), can ensure plants are only delivered the fertilizer concentration needed for healthy growth (Biernbaum, 1992), without risk of nutrient deficiencies or the potential for nutrient toxicities and fertilizer runoff that result from fertilizer over-application. Controlling nitrate-nitrogen runoff from greenhouses has been a primary focus of research (Biernbaum, 1992). The actual amount required by the crop is significantly less than is typically applied in commercial production (Yelanich and Biernbaum, 1994). Much of the excess nitrogen applied to crops grown with high fertilizer concentrations and heavy leaching can be lost into the environment. Soluble phosphate and heavy metal trace elements also are used extensively (Nelson, 1990).

Media pH has a major effect on nutrient availability and subsequent plant growth (Bailey, 1996; Peterson, 1981). Half of all nutritional disorders associated with bedding plant production can be attributed to pH-related problems (Nelson, 1994). Optimum pH varies among crop species, but is generally in the range of 5.8 to 6.2 (Warncke and Krauskopf, 1983). A low medium pH can lead to micronutrient toxicities, for example iron and manganese toxicity in geraniums (Nelson, 1994). Conversely, a high medium pH can lead to micronutrient deficiencies, for example, iron deficiency in petunias. Management of potting medium solution pH and micronutrient levels can reduce overall fertilizer load by ensuring that all applied nutrients are available for plant growth, and by avoiding the need to increase concentration of all nutrients (including NPK) in a complete blended fertilizer in order to correct deficiency of a single micronutrient (e.g., iron at high medium-pH; (Argo and Fisher, 2002)). Continued understanding of the relationships between pH and plant nutrient use is critical to optimizing the nutrient delivery to the plants.

Optimizing fertilizer and water management will reduce pesticide use. Excess fertilizer use and over watering often result in damage to plant roots, and provide ideal conditions for infestation with Pythium and other root-rot organisms, along with fungus gnat populations (Nelson, 1994). Infestations with these pest organisms can be devastating, and can require curative pesticide drenches. Application of fungicidal and insecticidal drenches is the current routine practice in greenhouse production, with monthly fungicidal drenches recommended for long-term crops such as poinsettia (Ecke et al., 1990). Management of the root zone environment (i.e., water and fertilizer) is recommended as the basis for integrated pest management approaches to this problem (Ecke et al., 1990; Styer and Koranski, 1997). The research to improve the plant root environment will reduce pesticide use while improving plant quality and growth.

In all watering systems, recycling of 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. Particularly, challenges (3) and (4) will be further investigated as part of this project.

Without research on managing nutrients and water, 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 limiting the use of nutrients and water, or be forced out of business.

Topic No. 2, Managing the aerial environment for greenhouse plant production: The aerial environment includes the temperature, light, relative humidity and airflow through the plant canopy. Ventilating greenhouses by replacing the warmer, higher humidity air with cooler, drier outside air is used as part of managing the aerial environment. The ventilation process is critical for cooling and for reducing humidity levels within the greenhouse. Reducing heat stress and the diseases caused by high humidity have a direct affect on the profitability of the greenhouse operation. Greenhouse cooling is essential for controlling the physiological response of a crop (MI, NY, NJ, CT). The process is more complex when insect screening is used (NJ). CO2 conservation is a dominant consideration (NY).

Early greenhouses used sidewall and ridge openings for natural ventilation to cool the air and reduce humidity. When energy was cheap, there was little concern about over ventilating since heat could be added to maintain temperature. As electricity became available, fan-ventilated greenhouses were developed. The control of the fans and heating systems has evolved as control technology has evolved. Today, several companies provide computer control systems that will operate the mechanical ventilation and heating system based on a variety of control strategies, sensor inputs from the plant area and weather station data.

The past few years have seen a major shift back to the installation of naturally ventilated greenhouses along with research to study proper design. OH is using a computational fluid dynamics program, FLUENT, to evaluate and illustrate the natural ventilation patterns and airflow rates of low cost, double poly, gutter connected greenhouse designs.

The modeling work has helped identify better designs for air inlets and outlets. The program requires too much time to run a simulation to be useful in the control of greenhouse openings. Ideally, the cross sectional area of the opening would vary in response to measured changes in wind direction and/or velocity and thermal buoyancy forces. Brocket and Albright (1987) developed a model for inlet control with natural ventilation based on the concept of neutral pressure level for animal housing. This model has the ability to make quick calculations. Therefore, it could be appropriate for control of natural ventilation systems for greenhouses. However, the model needs wind pressure coefficients for openings under various climatic conditions. These coefficients can be determined by using FLUENT. Combining FLUENT coefficients with the neutral buoyancy model will result in an improved model for natural ventilation control. Without this research, growers will continue to guess how to set greenhouse inlets with resulting decrease in plant performance from inadequate ventilation. They will also miss the opportunity for increased production from controlled airflow through the plant canopy.

Topic No. 3, Integrating sustainable and economically profitable systems and processes for the greenhouse industry: Sustainable, predictable crop quality can be achieved within efficient, cost effective well-designed greenhouses. There are many structural configurations, both in design and in dimensions, which encompass a wide range of environmental conditions. These systems contain many individual but interrelated components and processes. However, there are fundamental similarities in design requirements, physical components and production expectations that are necessary to establish an economically viable production system.

Light is a critical component of an optimum microclimate. The intensity of these wavelengths (400 - 700 nanometers) of photosynthetically active radiation (PAR) directly influences growth and development in green plants. Therefore, the properties of the greenhouse glazing and support structure are extremely important in greenhouse design. They are well understood and documented (Aldrich and Bartok, 1994; He et al., 1991; Lee et al., 2000).

However, natural PAR light levels often limit the photosynthetic activity of plants. Supplemental lights have been added to greenhouses to increase the light intensity and the length of light periods. While, some work has been done to improve proper use of lights, more research is needed to optimize the design and management of lighting systems for economical plant growth. Without this research, electrical energy can be wasted by over lighting or under lighting; therefore, expected plant growth is not achieved. At other times, the solar irradiance intensity is so high that the greenhouse overheats and the plant temperatures get so hot that plant growth is reduced. Under these conditions, shading to diminish light intensity within the greenhouse and at the plant canopy may increase production. More research is needed on the optimization of shading so that the growing season can be extended into hotter, brighter times of the year. Using shading to lengthen the production time for vegetables, such as tomatoes, will allow the grower to obtain more income from the original investment that is required to grow the plant to the production stage.

Greenhouse production is generally considered more efficient in water usage than field production. For example, approximately 2,400 kg water (on average) was estimated to be consumed to produce 1,000 kg harvest of tomato fruits in greenhouse, while 13,900 kg water was used per 1,000 kg harvest in field production (Castillo, unpublished), showing that greenhouse water utilization efficiency is 5.8 times of that in the field. In addition, greenhouse enables longer production seasons with more intensive production, and thereby, the annual yield per hectare in greenhouse can be more than 10 times than that in the field production. However, despite the high water utilization efficiency in greenhouse, the total water consumption per hectare per year in greenhouse can exceed that in the field production. Water usage in greenhouses is important since it has a potential impact on water resources, especially in states where water supplies are limited.

Related, Current and Previous Work

Topic No. 1, Managing nutrients and water in greenhouses: AZ studied the effectiveness of a commercial fertigation control system that uses environmental parameters to control the EC and pH of a nutrient solution. Thirty minute sliding averages of the instantaneous light intensity were used to raise the EC under lower light conditions (when water uptake is reduced) and lower the EC under high light conditions (when water uptake is increased to maintain cooler leaf temperatures through the process of transpiration) (Kania and Giacomelli, 2001; Giacomelli, 2002).

AZ studied the effects of environmental conditions, rooting media, and fertigation treatments on hydroponic vegetable production (tomato and pepper) (Jensen, 1997; Giacomelli, 2002). NE studied the use of close-in canopy spectral analysis and color imaging in poinsettia nutrient management in a greenhouse (Meyer, et al., 1992).

CT investigated the seasonal changes of water and nutrient use in greenhouse tomato. The frequency and duration of watering was based on plant size and sunlight integral. Concentrations of nitrate and potassium were measured in the fertilizer solutions supplied to the plants and in the root medium. The dynamic uptake of water and nutrients was calculated from daily supply and drainage measurements. The data was used to model (curve fitting) seasonal changes with the goal of evaluating the effectiveness of the fertigation procedures (Gent, 2001).

CT investigated the effect of irradiance and solution composition on tissue composition of lettuce grown in hydroponic solution, particularly tissue nitrate concentration. A low solution EC lowered tissue nitrate, but a lower nitrate supply ratio by itself had no effect. However, under irradiance greater than 10 MJ-m-2-d-1, the lower EC also slowed growth. Due to selective uptake by the plants, the ratio of elements in the recirculating solution differed from the ratio in which they were supplied. Under irradiance of less than 10 MJ-m-2-d-1 and solution EC greater than 1.5 dS-m-1, nitrate accumulated in solution to a concentration greater than expected from simple dilution of concentrates. To prevent a rise in tissue and solution nitrate concentration under low irradiance, both solution EC and nitrate supply ratio had to be reduced by one-third, compared to the conditions required for rapid growth under high irradiance (Gent, 2000; Gent, 2003c).

CT investigated the effects of plant nutrition on the growth and development of poinsettia (Bible and McAvoy, 1997). CT also studied the mineral nutrition of tomato under diurnal temperature variation of root and shoot (Gent and Ma, 2000).

KY developed a crop-to-air vapor pressure deficit (VPD) control algorithm capable of controlling the VPD between the crop canopy and the surrounding air. This control algorithm can be used to indirectly control plant transpiration and may be particularly useful for sunlit plant propagation areas inside greenhouse structures (Gates and Mach, 2000; Mach et al, 1999, 2000).

NE proposed the use of a fuzzy logic based approach to crop water stress indices (FL-CWSI). The use of fuzzy inference systems may provide simpler, more reliable strategies to greenhouse control problems than traditional proportional, integral, and differential approaches. (A-Faraj, et al., 2001a)

KY developed fuzzy inference and neuro-fuzzy inference systems for single stem rose production (Chao, 1996; Chao et al, 1998a, 1998b), and a fuzzy-based environment controller to mimic either PI-control, or conventional staged ventilation control, or any combination as selected by the user (Chao et al., 2000; Gates et al., 1999, 2000, 2001).

KY developed dynamic misting control techniques for poinsettia propagation (Zolnier et al., 2001) as well as an empirical model for water uptake and root development of poinsettia cuttings (Wilkerson and Gates, 2001; Wilkerson et al., 2002).

NE developed dynamic plant temperature response functions through the use of short wave step input functions. Moderately stressed plants approached critical and under-damped response conditions. Severely stressed plants tended to respond closely to a first order model (Al-Faraj, et al., 2000).

MI studied root media and nutrient management strategies for various crops including poinsettia, impatiens, and chrysanthemum (Argo and Biernbaum 1995a, 1995b, 1995c and 1995d). In addition, MI studied nitrate and ammonia management strategies (Argo and Biernbaum, 1995c; Biernbaum et al., 1995a, 1995b, and 1995c; Yelanich and Biernbaum, 1995).

NH developed a computer database program called FloraSoil to help growers monitor plant nutrient status. Commercial growers, educators, and researchers have been testing tissue samples and entering nutrient composition data into the database. The software user establishes nutrient thresholds, which can be fine-tuned to individual crops (e.g., a higher target pH range for geraniums than petunias). The software displays nutritional trends in graphs in order to identify problem trends and allow crop comparisons. This software has been expanded to include graphical tracking of insect pest counts for integrated pest management, and also monitoring of plant height (Argo and Fisher, 2002).

NH has undertaken research on management of media pH, and correction of pH-related problems, in collaboration with OH and MI (Argo and Fisher, 2002; Fisher et al., 2003). The research has shown that in research conditions when pH is in the optimum range, and micronutrient levels (especially iron) are adequately supplied, it is possible to reduce NPK fertilizer concentration by up to 50% over current practices and still produce vigorous floricultural crops. Improved recommendations have also been developed for correcting media pH problems with use of lime and acid materials. NH and OH are collaborating in developing a series of extension presentations and publications in English and Spanish languages in order to deliver this research to the industry.

NJ constructed and is testing an ebb and flood floor irrigation system with underground nutrient solution storage tanks for the study of closed irrigation systems. Two identical but independent floor sections (100 m2 each) can be used for nutrition and/or contamination (e.g., disease organisms) studies (Both et al., 2001).

NY developed an instrumentation protocol (using LabVIEW) for monitoring pH, EC, Dissolved Oxygen (DO), temperature, and nitrate concentration in floating hydroponic systems. Lysimeters were used to measure evapotranspiration. In addition, nitrate uptake measurements were conducted using a continuous nitrate analyzer. Despite the fact that the analyzer required continuous maintenance and calibration, the measurements showed that changes in nitrate uptake are a reasonable indicator of potential plant stress. This system was sensitive enough to detect short-term (hourly) plant responses (Mathieu and Albright, 2002).

NY developed a feed forward neural network simulation model with nine input variables (pH, EC, nutrient solution temperature, air temperature, relative humidity, light intensity, plant age, amount of acid added, amount of base added), and two output variables (pH and EC at the next time step). The model is capable of predicting pH at the next 20-minute time step within 0.01 pH units and EC within 5 5S-cm-1. The model is capable of accurate predictions when relatively rapid changes occurred due to system failures.

NY developed and is testing a water-conditioning system that can be used for alkalinity and pH control in recirculating nutrient solutions (Spinu et al., 1997; Spinu and Albright, 1997).

OH has studied various sensing techniques for early, non-destructive detection of plant drought stress. Drought stress in New Guinea Impatiens was detected one day before human observation of the stress symptoms (Kacira and Ling, 2001). A prototype sensing apparatus has been built for applications in a greenhouse environment (Chen et al., 2002. A different sensing approach using visible, near infrared, and mid-infrared spectral information has also been investigated (Yang and Ling, 2002).

OH studied the evapotranspiration (ET) of four mini-rose plants and correlated ET with moisture tensions measured with tensiometers. Commercial control software and hardware permitted irrigation events to be independently initiated and stopped according to tension levels for any of the four plants. The effects of tensiometer location within a container were evaluated and various levels of tension used to start and stop irrigation were studied (Hansen and Pasian, 1999). Measured ET was compared to calculated ET using Stanghellini, Denman, Denman-Montieth, and Fynn ET models (Prenger et al., 2002). NY is currently completing a study of factors contributing to ET in hydroponic lettuce crops and coordinating results with the OH study. NE used inexpensive mini-pot lysimeters to study water use (Al-Faraj, et al., 2001b).

OH studied the automation of water and fertilizer delivery systems based on crop and environmental conditions (Fynn et al., 1994a and 1994b; Hansen et al., 2000). The research includes study of microirrigation for delivery of water and nutrients to container-grown trees located on an outdoor gravel bed.

Topic No. 2, Managing the aerial environment for greenhouse plant production:

NJ has developed a simple simulation tool to model natural ventilation in open-roof greenhouses (Sase et al., 2002). Additional data collection and model refinement are continuing.

Experiments have been conducted at NH, NJ, Clemson University, Univ. of California Davis, and commercial operations in NH and NJ to provide data on production response to supplemental lighting (Donnelly and Fisher, 2002a and 2002b). Preliminary economic analysis of lighting for cutting production has used a financial investment model (Lighten Up) developed at NH (Fisher and Donnelly, 2002a). This financial model is being adapted to lighting of other crops, and will be particularly useful for industry when combined with the crop budgeting methodology and information developed by NJ (Brumfield, 1993).

Topic No. 3, Integrating sustainable and economically profitable systems and processes for the greenhouse industry: MI has developed control procedures for quantification of daily light integral and air temperature on the rate of development and plant quality of floriculture crops (including bedding plants and herbaceous perennials). MI has also developed a poinsettia plant shoot tip temperature model based on environmental parameters.

MI has developed an energy consumption and crop-timing model to predict consequences to changing greenhouse air temperatures. Inputs to the model include weather data, various greenhouse characteristics (e.g., glazing type, venting parameters, and heating characteristics), energy cost, and plant developmental rates. The model predicts energy consumption at a given growing temperature for the duration of the crop cycle. Work is in progress to determine plant specific developmental rates.

CT has optimized nutrient ratios for production of greenhouse tomatoes. In this work it was noted that shade had a significant effect on production and quality (Gent, 2003a and 2003b).

AZ continues to evaluate a commercial fertigation control system for automated control of the EC and pH of a nutrient solution within a rockwool substrate, drip-irrigated commercial tomato system. Thirty minute sliding averages of the instantaneous light intensity were used to raise the EC under lower light conditions and lower the EC under high light conditions (Giacomelli, 2002).

AZ continues arid climate evaluation of cultivars within rockwool substrate, drip-irrigated commercial tomato systems for pepper and tomato. They studied the effects of environmental conditions, rooting media, and fertigation treatments on hydroponic vegetable production (tomato and pepper) (Giacomelli, 2002).

AZ studied the temproral variations in the concentrations of nitrate, potassium, and manganese under four nutrient regimes used for sweetpotato hudroponics. The reesults showed that the decline in nitrate concentrations over time resulted infairly reasonable r-squares and thus fairly reasonable reularity both for the standard soultions and the double-N by nitrate treatment (Ono, et al., 2001; 2002).

AZ has studied various strategies for composite lighting, the lighting profile that results when combining solar lighting and supplemental lighting systems. The adoption of composite lighting for controlled environment crop production rests on the principal premise that, depending on the lighting profile employed, equal moldes of photons delivered to two crop treatments do not necessarily result in equal growths for the two treatments (Cuello, 2002).

Keyword searches of CRIS were conducted. The searches identified many projects with key words that relate to the proposed research objectives. A review of these projects showed that many did not relate to the specific greenhouse research proposed in this project. For example, most of the projects that showed up with the keyword of fertigation were for field production. Others were projects that have terminated. Most of the remaining projects were being conducted by the researchers participating in this multistate research project. Here is a summary of related projects by non-NE  164 participants:

SC-1700059 is investigating the affect of light quality as related to different types of plastics on plant performance. In contrast, NE - 164 stations are looking at total light and management of supplemental light.

NC-06547 is looking at refining the pour-through method for nutrient extraction form the potting medium as compared to the SME substrate test and is developing procedures for using the pour-through method by growers. The multistate projects work is related to methods for reducing and/or recycling the nutrients.

SC-1700135 is studying shading and hanging baskets as they relate to light management strategies in greenhouses. The multistate project pertains more to efficient use of supplemental lighting and some shade management to improve greenhouse production.

NC  06662 is developing models capable of predicting nutrient uptake and transpiration rates for tomatoes in greenhouse canopies in both naturally and mechanically ventilated greenhouse. The focus of this research is tomato production. The multistate projects focus is application of models to a variety of crops.

ALK-00-09 is looking at the importance of natural and artificial light energies and spectral distributions for high latitude crop production and photoperiodic control. The multistate projects focus is on completely different geographic locations.

Objectives

1. Develop and evaluate methodologies such as evapotranspiration modeling, non-contact sensing of plant responses to drought stress, and measurement of root zone water tension for plant water status assessment and compare these assessments to actual water and nutrient use for tomato, salad greens and potted ornamental plants, as a part of managing delivery of nutrients and water in greenhouses (CT, NY, NE, OH, AZ, KY, NJ).
   
2. Evaluate the entire fertigation system, including water delivery, plant uptake, and runoff, while accounting for optimization of micronutrient, media pH, and EC levels. (AZ, CT, NE, NH, NY, OH, PA).
   
3. Improve design of water and nutrient recirculation systems (NJ, NY, KY, OH, AZ, PA).
   
4. Develop design and control recommendations for naturally ventilated greenhouses (OH, NE, NY, NJ).
   
5. Enhance technology transfer and research in light integral control (CT, MI, NH, NY, AZ).
   
6. Develop an economic analysis of the costs and benefits of supplemental lighting for seedling plugs, other greenhouse crop types, and photoperiodic lighting (AZ, CT, KY, MI, NE, NH, NY, NJ, OH).
   
7. Improve the understanding of using shade to optimize production of high-quality greenhouse tomato for spring and early summer production (AZ, CT, KY, MI, NE, NH, NY, NJ, OH).
   
8. Quantitatively evaluate seasonal and annual water balances for greenhouses (AZ, CT, KY, MI, NE, NH, NY, NJ, OH).
   

Methods

Objective 1, Plant Transpiration Modeling: Particular emphasis will be placed on the development of plant transpiration simulation models for vegetables (e.g., tomato and lettuce) and container crops (e.g., chrysanthemum, impatiens and poinsettia) grown under common greenhouse environment conditions. These simulation models can be used as decision support tools by growers to help them manage the use of water and nutrients. At the same time, these models can be used to predict water and nutrient usage for various crops grown under a range of environment conditions. These predictions can be used to decide which crops to grow when limited amounts of water are available. Finally, accurate transpiration models will help growers stay ahead of the expected future environmental regulations dealing with water use and nutrient solution discharge. The identified states will examine the effect of plant development and greenhouse environment on water uptake and nutrient use (AZ, CT, NJ, NY: greenhouse tomato, NY: leafy vegetables, KY, NJ, OH: flowering pot plants). Water and nutrient uptake, and yield and crop quality will be compared when plants are grown in greenhouses with different environmental conditions (e.g., with and without shade screens, air movement, various humidity ranges, temperature ranges, EC strategies, etc.) and at different locations. Methods and instruments for direct measurement of substrate water status while monitoring plant stress with digital imaging and other non-contact sensing will be evaluated (OH). Time domain reflectometry instruments and tensiometers will be tested as means for controlling the frequency and duration of irrigation and fertigation events while monitoring volumetric water content in container-grown greenhouse crops in indoor environments and landscape nursery plants in outdoor environments (OH). Fertilization will be altered to more exactly match the crop nutrient requirements, as a function of environment conditions. Optimized nutrient supply regimes will be identified for greenhouse crops commonly grown in the northeastern United States. Objective 2, Plant Water and Nutrient Management: This objective will investigate traditional and new nutrient management techniques used for greenhouse crop production. There will be two focus areas: (a) evaluation of the entire fertigation system, including water delivery, plant uptake, runoff, and recirculation, especially with regard to the fate of nitrate-nitrogen, and (b) optimization of micronutrient, media pH, and EC levels. For the first focus area of this objective, a conceptual and quantitative model will be developed for the flows of nutrients and water within and through the overall greenhouse system. The greenhouse will be conceptualized as a mini water shed, and the model will show the potential and sensitivity of the system to different technologies and management options that could reduce runoff. The research will require significant collaboration between the NE-164 members, because it needs to include microclimate (evapotranspiration), engineering (environment control), biology (plant physiology), and economic (investment and operating cost) components. For the second focus area, optimum pH ranges, micronutrient demands, and macronutrient demands will be quantified by NH and OH for different plant species by growing plants with varying levels of pH, iron, and NPK fertilizer. New fertilizer formulations will be evaluated, particularly with regard to the type of iron chelate, the iron: manganese ratio, and the iron: N ratio. Optimizing these variables has potential to broaden the range of acceptable media pH for healthy growth and thereby reduce plant health problems associated with media pH. This will also allow growers to use micronutrients in a targeted way to avoid or correct deficiencies, in place of the current common practice whereby growers increase the overall fertilizer concentration of all nutrients when only iron or other micronutrients are limiting. Objective 3, Water and crop nutrient Recirculation Systems: The emphasis will be placed on the study of closed irrigation system (i.e., with no or very minimal discharge to the outside environment). The systems of interest include hydroponic systems (e.g., NFT, floating hydroponics, and aeroponics) and ebb and flood systems (both on benches and on specially designed floors). Plant nutrients in liquid form can be delivered from a bulk solution (e.g., with a concentrate injector or with a so-called A and B tank system) or from a series of individual solutions that contain one or two plant nutrients. Depending on the type of system, these delivery systems and their associated (computer) control algorithms range from simple to more complex. The more complex delivery systems allow for control of individual nutrients, but are also more expensive and require more maintenance. Several nutrient delivery systems are in use at various NE-164 member stations. Research will continue in an effort to understand and optimize each system with the goal of providing optimized nutrient solutions throughout the various stages of the crop life cycle. Objective 4, Natural Ventilation System Control: A computational fluid dynamics (CFD) program has been used in OH for studying natural ventilation rates of double poly, gutter connected greenhouses. Air exchanges were predicted with the CFD model and compared to an energy balance model. Very good agreement was achieved on sunny days with significant wind. There was generally poor agreement, however, on low wind, cloudy days as the CFD model was mainly influenced by wind speed and the energy balance model was mainly influenced by solar radiation. A contrasting computer model for natural ventilation in greenhouses has been developed in NY, a model based on the concept of the neutral pressure level and resulting ventilation rates arising from thermal buoyancy and wind effects. The model has a limited background of testing, but appears to be successful in predicting ventilation rates. However, the most severe restriction to using the model for design is to know how winds will generate pressures around the shell of a greenhouse, especially at vent openings. The CFD work at OH provides a means to develop rules for estimating wind pressure coefficients, and that will be a central focus of this objective. The CFD program will be used to generate wind pressure coefficient predictions for a variety of greenhouse shapes, vent placements, and wind directions. Those results will then be used in the neutral pressure level model to calculate expected ventilation rates. The predictions generated by these two approaches to greenhouse natural ventilation (OH and NY) will be compared and contrasted with the goal of identifying where they differ, why they differ, and what can be done to bring the predictions closer. Moreover, designs and resulting natural ventilation rates will be evaluated in commercial and research greenhouses in cooperating states, primarily OH and NY. Portable data loggers with temperature, humidity, solar radiation, wind and vent opening sensors will be installed and monitored via modems. Ultimately, when the subtleties of natural ventilation are better understood, computer-based control programs can be developed to provide more consistent temperature control in naturally ventilated greenhouses, as well as more consistent temperature uniformity through optimized air distribution. Objective 5, Light Integral Control: A computer algorithm to control supplemental lights and movable shade systems to achieve a consistent daily integral of light, and use off-peak electric rates to the maximum extent, has been patent protected (NY). The algorithm is currently being incorporated into two commercial computer control systems through licensing arrangements. Continued research (NY, in cooperation with other stations) will develop light integral goals for a variety of conventional and unconventional greenhouse crops. The next step is to develop lighting rules that consider carbon dioxide levels other that ambient. The integration and coordination of light, carbon dioxide concentration, and ventilation (infiltration or slight ventilation) will be tested in NY to develop rules to optimize the combination of daily light integral and carbon dioxide concentration on a dynamic basis throughout the day. The algorithm to be developed will be freely shared with the other research stations in the project, but will be patent protected and extended to the commercial sector through licenses. Objective 6, Costs and Benefits of Supplemental Lighting: Lighting studies will be conducted at both commercial operations and in research facilities. Supplemental light intensities and electricity usage will be carefully monitored. When possible, off-peak power usage will be promoted. Light uniformity data will be collected and compared to plant development and quality. Plant quality will be monitored at the time of shipment, as well as, in the case of plug production, at the time the plants are grown out to final market size. Materials and labor costs will be tracked so that a careful economical analysis can be preformed comparing lit and unlit treatments. Results of the economic evaluations will be shared with the commercial greenhouse industry. The first step of this project is to quantify the effects of daily light integral on plant growth and development. This has already been determined for some major vegetable and flower crops, but information on many economically important crops has not yet been published. For floriculture crops, the primary benefits of supplemental lighting are increased plant quality and more rapid plant development, while for vegetable production, the primary benefit is an increase in harvest index. Plants will be grown under different light intensities in greenhouses and growth chambers to determine the benefit of increased photosynthetic lighting. Experiments will be performed on young plants (e.g., plugs) and mature, flowering plants. Light quantum sensors and thermocouples will be connected to dataloggers to record light intensity and air and plant temperature. Once the benefit of supplemental lighting has been determined for a variety of crops, then an economic cost-benefit analysis will be performed. NY will contribute to this effort through sharing of its research data and computer algorithm for controlling light to a consistent daily integral. The algorithm has been implemented in a simulation program in addition to a control program. The simulation program will be made available to all research stations for their use in evaluating light control strategies specific to local conditions. Advice on using the program will be readily shared. Objective 7, Using Shade to Optimize Production: Experiments will be conducted in four identical greenhouses. The environment in individual houses will be altered using reflective aluminized shade cloth (Aluminet) stretched across the ridge along the length of the greenhouse. Three levels of shading will be applied: shade cloth of 30 and 50% transmittance, or 30% shade cloth partially shredded to give 15% shade. One house will not be covered with shade cloth. All houses will have roll-up sides during the summer to minimize temperature variation among treatments. There will be four adjacent rows extending the length of the greenhouse. Watering will be adjusted between greenhouses according to daily light integral to maintain an adequate water status in the root medium. The supply of fertilizer will be varied by shade regime to maintain similar concentrations in the root medium. Nutrient regimes will be modified using proportioners with suitable concentrate solutions to maintain the target nutrient concentration in the root medium. A range of cultivars will be included in this test. Modern hybrids will be compared to older, open-pollinated cultivars, whose fruit quality is sensitive to environmental conditions. Objective 8, Quantitatively Evaluate of Water Balances: A major problem in producing greenhouse lettuce is to avoid tip burn and edge burn. They are two different phenomena and it appears that each is related to relative humidity. If the relative humidity is too high, tip burn appears. If too low, edge burn can occur. However, the mechanisms and interactions of other environmental parameters are not well understood. As part of the projects effort to focus on water balances, the impacts of relative humidity on each of these physiological disorders for lettuce will be researched in NY for applications to colder regions of the U. S. Seasonal and annual water balances of semiarid greenhouses (AZ) will be quantitatively understood for the three cooling methods: 1) traditional fan-and-pad cooling, 2) high pressure fog cooling with natural ventilation, and 3) high pressure fog cooling and fan (forced) ventilation. Environmental variables and plant responses (evapotranspiration and plant photosynthetic rates) will be continuously monitored, and water utilization efficiency using a portable gas exchange measurement system (CIRAS2, PPSystems) for assimilation (mole carbohydrate fixed per mole water transpired) will be obtained. Amount of water utilized for irrigation and evaporative cooling will be monitored and systems water utilization efficiency (yield harvested per total water usage for irrigation and cooling) will be estimated.

Measurement of Progress and Results

Outputs

• Transpiration rate data as a function of sunlight, temperature, and applied shade, and as a function of crop development.
• Plant transpiration models will be developed or refined for several vegetables and container crops.
• Non-contact sensing techniques will be evaluated for assessing plant drought stress levels.
• Procedures for using tensiometers to control irrigation and to monitor root zone potting medium water tension.
• Optimized (i.e., all-time on-time delivery) nutrient management strategies for several greenhouse vegetables and container crops.
• New and redesigned nutrient delivery systems, which reduce water and nutrient usage and reduce the discharge of nutrient solutions to the outside environment.
• Improved natural ventilation models that will lead to adopting control strategies for naturally ventilated greenhouses.
• A report discussing economic returns of lighting several greenhouse crops, including seedling plugs and vegetative cuttings.
• An industry publication (book and CD) on greenhouse lighting will provide a means of transferring research to growers and will serve as a study guide for university greenhouse courses. Topics in this publication will include fundamental concepts of light and lighting for crops ranging from plug seedlings to vegetables.
• Data on the effect of shading levels on tomato yield and quality under different climatic conditions.
• Data on the daily light integral effects on various floriculture crops, including bedding plants and herbaceous perennials. Data measured will include production time and plant quality (flower number, dry weight accumulation, lateral branching, etc.)

Outcomes or Projected Impacts

• Computer control software that incorporates the improved plant transpiration models will reduce the use of nutrients and reduce the discharge of nutrients to the environment.
• New sensor based irrigation management strategies will improve the use of water and nutrients and improve the plant quality.
• Better control of pH and other growth media parameters to improve plant use of nutrients.
• Extension publications on how to integrate management of pH, EC, and micronutrients will result in improved crop quality and will reduce the concentration of NPK required to produce crops efficiently.
• Improved micronutrient fertilizer formulations that increase plant quality and will also reduce the concentration of NPK required to produce plants efficiently.
• Improved nutrient delivery systems that effectively incorporate recycling of nutrient solutions while maintaining plant health and quality.
• Improved CFD and neutral pressure models useful for real time control of natural ventilation of greenhouses.
• Improve grower investment decisions and energy efficient use of supplemental lighting for seedling plugs, cuttings, and other greenhouse crops.
• Collaborative publication that summarizes fundamental concepts of light and lighting for crops ranging from plug seedlings to vegetables.
• Improve quantity and quality of tomato production by using new management recommendations on shading for spring and early summer seasons.
• Improved understanding of water use to allow for future research at reducing water as an input to greenhouse production, especially in semiarid regions.
• Improved liaison with commercial greenhouse manufacturers through the NGMA, the primary organization of greenhouse manufacturers.

Milestones

(2004): Multi-state plant transpiration data collection on greenhouse vegetable and container crops. Review of existing transpiration models and drought stress detection techniques. CT Set up greenhouses with shade. Optimize systems that differ in delivery of water and nutrients to a tomato crop. Multi-state data collection on nitrate uptake dynamics for target crop species. Experimentation begins on micronutrient and pH research by NH and OH. Multi-state data collection on water and nutrient usage for target crop species. Development of optimum usage strategies. Coordinate the model work with respect to types of structures and related issues. Reprogram the neutral pressure level model from Turbo Pascal into a computer language to be decided. Lighting report to be published by MI, NH, NJ. Experimentation begins on supplemental lighting by NH, MI and NJ. Measure yields and fruit quality of a tomato crop grown under different levels of shade (CT).

(2005): Development of appropriate ET models, non-contact drought stress sensing techniques, and tensiometer based irrigation strategies. CT continues experiments in 2nd year and compares cultivars of greenhouse tomato that differ in fruit quality in response to shade. Trials of nitrate uptake under various nutrient concentrations and environmental parameters. Research trials of developed optimum usage strategies. Develop and refine CFD models and start buoyancy models by NY and OH. CT continues experiments in 2nd year and compares cultivars of greenhouse tomato that differ in fruit quality in response to shade.

(2006): Testing of the plant water status assessment methods. CT compares cultivars that vary substantially in research trials. Development of optimized water and nutrient delivery strategies and use in response to minimize nitrate run-off. Research trials of the fate of residues (chemicals) in recirculating systems. Continue model development and refinement by NY and OH. Economic analyses completed for lighting of different crops by NH and NJ.

(2007): Testing of the plant water status assessment methods in industry trials. CT will vary nutrient and water supply to optimize fruit quality under different levels of shade. Testing of new delivery strategies in industry trials. Extension publication summarizes micronutrient and pH research by NH and OH, including recommended formulations and overall strategy. Research trials of the fate of residues (chemicals) in recirculating systems. Compare model results with data and start implementation of control from model results by NY and OH.

(2008): Evaluation and fine-tuning of the plant water status assessment methodologies. Sharing of results with scientific and industry communities. Evaluation and fine-tuning of the plant water status assessment methodologies. Sharing of results with scientific and industry communities. Evaluation of the effectiveness and fine-tuning of the developed delivery strategies. Sharing of results with scientific and industry communities. Development of optimized management strategies. Sharing of the results with scientific and industry communities. Continue the implementation of the natural ventilation control based on model results.

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Projected Participation

View Appendix E: Participation

Outreach Plan

Results of this research will be made available through several means: refereed publications; conference papers; proceedings; project reports; on-line sources (web); presentations in local, regional, and national grower meetings and greenhouse engineering workshops; and industry reports. Several participants have partial extension appointments and therefore will develop outreach materials through fact sheets and other extension publications.

A book and series of web site and industry articles will be developed on micronutrient and overall fertilizer management. Extension publications will be in both English and Spanish, and results will be presented in industry conferences.

A publication including text book and study guide will be prepared suitable for university student and grower audiences, and will be distributed by a national greenhouse industry publisher. A mini-conference for industry will be organized on greenhouse lighting, either at a national meeting or major regional meeting.

Organization/Governance

The standard organization and governance model will be used. The officers will be a chair, chair elect, and secretary with each serving two-year terms.

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Attachments

Land Grant Participating States/Institutions

AZ, CT, GA, IA, KY, ME, MI, NE, NJ, NY, OH, PA, TX

Non Land Grant Participating States/Institutions