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Paul R. Fisher and Royal D. Heins

A methodology based on process-control approaches used in industrial production is introduced to control the height of poinsettia (Euphorbia pulcherrima L.). Graphical control charts of actual vs. target process data are intuitive and easy to use, rapidly identify trends, and provide a guideline to growers. Target reference values in the poinsettia height control chart accommodate the biological and industrial constraints of a stemelongation model and market specifications, respectively. A control algorithm (proportional-derivative control) provides a link between the control chart and a knowledge-based or expert computer system. A knowledge-based system can be used to encapsulate research information and production expertise and provide management recommendations to growers.

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P.R. Fisher and R.D. Heins

A graphical control chart was developed to monitor leaf count of Easter lily (Lilium longiflorum Thunb.) and make temperature recommendations based on predictions of a leaf unfolding rate (LUR) model. The graph allows observed and target leaf count to be compared visually over time. Timing of the visible bud stage, when flower buds are visible externally on the plant, is important to time flowering for the Easter sales period. The optimum LUR and average daily temperature required to achieve a target visible bud date can be read directly from the chart. The approach provides an intuitive method for transferring quantitative models to growers.

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Thomas Graham and Michael A. Dixon

(concentration multiplied by the time of exposure) as a process control parameter for liverwort management; 2) establish initial aqueous ozone toxicity thresholds for liverwort; and 3) evaluate the response of liverwort to aqueous ozone at exposure levels and

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P.R. Fisher and R.D. Heins

Timing of Easter lily (Lilium longiflorum Thunb.) for sales is complex because the date of Easter and the number of leaves formed on plants before flower bud initiation vary from year to year. A process control chart was developed that uses a leaf unfolding rate model of Easter lily to control development rate towards flowering. The technique allows observed and target leaf count to be tracked on a graph and compared visually over time. The optimum leaf unfolding rate and average temperature can be read directly from the chart without the need for mathematical calculation. The approach provides an intuitive method for transferring quantitative models to growers and can be applied to other management problem areas.

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Maynard E. Bates

Increased production and reduced costs are goals of all plant growers. As a rule, introduction of computer-based control of the plant environment in a well-designed greenhouse will result in yield increases of thirty percent (30%) over other control techniques. A simple model will show how these changes impact profitability.

New technologies in sensors, interfaces, computers, software, and plant growth knowledge are being applied to management of the crop environment. Examples of direct canopy temperature measurement, online plant weight measurement, integration and control of photosynthetic photon flux, and nutrition control will be presented. Integrated process control is replacing setpoint maintenance. Models are being developed for incorporation into environmental control systems. Examples for solar irradiance and crop growth will be demonstrated.

Ultimately expert systems based on artificial intelligence technology will manage crop production in controlled environments. These systems will incorporate information on crop genome, local climate, cultural practices, pests and diseases, economics, and markets, in addition to environmental control. A possible configuration of the hardware and software for such a system will be discussed.

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Changhoo Chun and Cary A. Mitchell

`Waldmann's Green' leaf lettuce (Lactuca sativa L.) is being used as a model leafy vegetable crop to develop a protocol for variable control of photosynthetic photon flux (PPF) during crop production. Feedback from real-time photosynthetic gas exchange rates by lettuce canopies is used to modulate electronic dimming ballasts of lamp banks. Algorithms within process-control software are being fine tuned to maximize increments of photosynthetic output relative to increments of photon input. Dynamic optimization of PPF was 21% more efficient than constant high PPF saturating photosynthesis with respect to biomass accumulated per photons absorbed. Dynamic optimization also is being combined with principles of phasic control, in which environmental resources such as photosynthetically active radiation (PAR) and carbon dioxide (CO2) are deliberatively limited in input during specific phases of crop development when plants are less sensitive to inputs (e.g., lag, plateau, and senescence phases) but optimized for the responsive exponential phase. Preliminary results indicate that leaf lettuce growth benefits from optimizing environments for no more than 4 or 5 days during a 20-day production cycle. Dynamic optimization of CO2 level is achieved by controlling the injection of CO2 into the inlet air stream of Minitron II crop canopy cuvette/growth chambers. Algorithms are being modified to simultaneously vary PPF and CO2 for optimum photosynthesis.

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Brianna L. Ewing and Barbara A. Rasco

(USFDA, 2004). Cider processing steps to control identified hazards Both apple growers and cider producers should ensure that microorganisms of public health concern are adequately reduced by a minimum of a 5-log reduction, the process control standard

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James P. Syvertsen, Juan C. Melgar, and Francisco García-Sánchez

) and trees ( Levy and Syvertsen, 2004 ), attempts to improve the salt tolerance of plants have met with very limited success. Progress in improving salinity tolerance will come through an understanding of processes controlling the uptake and transport

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Christopher J. Currey and Roberto G. Lopez

process-control approach to poinsettia height control HortTechnology 5 57 63 Fisher, P.R. Heins, R.D. 2002 UNH FloraTrack for poinsettia: Graphical tracking plant height on computer Univ. New Hampshire Coop. Ext Durham, NC Gent, M.P.N. McAvoy, R.J. 2000

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James J. Luby and Douglas V. Shaw

effects is a more difficult situation that can be overcome only when alternative biochemical pathways or physiological processes controlled by other genes are brought together in an outlier genotype. Novel germplasm or parental combinations may be