Gene A Giacomelli

Abstract:

Innovations in greenhouse engineering are technical developments which help evolve the state-of-the-art in CEA (Controlled Environment Agriculture). They occur in response to the operational demands on the system, and to strategic changes in expectations of the production system. Influential operational factors include availability of labor, cost for energy, logistics of transport, etc. Influential strategic factors result from broader, regional issues such as environmental impact, product safety and consistency, and consumer demand. These are industry-wide concerns that have the effect of changing the production system in the long term. Global issues are becoming more influential on greenhouse production sustainability, and include less tangible issues such as social acceptance, political stability, quality of life benefits, and environmental stewardship. These offer much more complex challenges and are generally beyond the realm of engineering. However global issues do affect greenhouse engineering innovation. The most effective innovations in greenhouse engineering design, operations and management, will incorporate input from partnerships with the academic, private and public sectors of society. Furthermore, successful applications include, at least to some degree a multi-disciplinary approach of the sciences, engineering and economics, while for ultimate success and sustainability, societal and political support must also be attained. For this overview of innovation in greenhouse engineering a list of influential factors, or "driving forces" affecting the development, application, evolution and acceptance of greenhouse systems have been described. The factors are similar for all greenhouse systems around the world, as they include the plant biology of the crop, the physical components of the structure and production system hardware, the management and logistics of labor and materials, and the mechanism of marketing the crop. Each greenhouse system, wherever located, must resolve similar problems for its specific application. The magnitude of the factors and their relative local importance are different for the specific sites. The design response will be introduced and related to the factors, as examples of innovation.

Abstract:

The ultimate goal of this collaborative project is to develop an effective environmental control strategy to cool the greenhouses for plant production and minimize the water use in semiarid climate. Using a single-span double-polyethylene greenhouse with tomato plant canopy at The University of Arizona, the canopy transpiration rate and the water balance of greenhouse were investigated. The greenhouse was equipped with high-pressure fog nozzles, roll-up side vents with insect screens, and a roof vent. Fogging was operated cyclically with an air temperature set point of 24°C. Under different vent configurations, the transpiration rate was measured using a stem gage. The amounts of generated fog and non-evaporated water droplets were collected and measured. The natural ventilation rate was measured continuously using SF 6 gas as a tracer. Preliminary results showed that the transpiration rate increased linearly with an increase in vapor pressure deficit (VPD) of the air. When the ventilation rate was decreased by reducing the vent openings, the total water use in the greenhouse decreased by 13% and relative humidity increased as expected from simulation based on the steady-state energy balance. The decrease in canopy transpiration was driven by the decrease in VPD, and was at a greater magnitude than that of fog evaporation rate under the present experimental conditions with relatively high humidity ranging 70-94%. These results suggest that by optimizing natural ventilation rate, we could effectively cool the greenhouse with less water use.

Abstract:

Spectral and dynamic morphological features were investigated for plant health monitoring using machine vision techniques. The plants were stressed by withholding all nutrient salts. The spectral reflectance of healthy and stressed lettuce leaves (Latuca sativa cv. `Ostinata') was measured to determine at which wavelength(s) a stressed condition would be apparent. The measured wavebands were between 400 and 1000 nm. A reference waveband was utilized to account for photometric variables such as lighting and surface geometry differences during image acquisition. The expansion of the top projected leaf area (TPLA) was found to be an effective feature to identify stressed plants. The nutrient stressed plant was identifiable within two days after nutrients were withheld from a healthy plant. This was determined by a clearly measurable reduction in TPLA expansion.

Abstract:

Newly formulated aqueous foam was tested in the field. The foam demonstrated the longevity necessary for practical field use. Soil temperatures beneath an insulation layer of aqueous foam were measured to determine the effectiveness of foam as soil mulch. Leaf temperature within a canopy was monitored to observe the modification of plant leaf temperature, and to evaluate the phytotoxic effects of foam applied directly to the leaf canopy. Leaves were not damaged after being covered with the foam for two weeks. The foam-protected soil was effectively insulated, and the aqueous foam proved to be an effective radiation shield against the cold night sky. Temperature differences as high as 5 °C (9 °F) were measured between the foam-covered and uncovered copper metal plates, which were used to simulate plant leaves. The foam covered plates were ≃80% as effective as the aluminum foil covered plates in reducing radiation heat transfer.

Abstract:

Ginger (Zingiber officinale Rosc.) rhizomes are popular as a spice and an herbal dietary supplement. The anti-inflammatory and anti-nausea qualities of ginger have applications in the pharmaceutical industry. Conventionally grown as a tropical field crop, ginger is plagued by soil-borne disease and nematode problems. Aeroponic cultivation of ginger can provide high-quality rhizomes that are free from pesticides and nematodes and can be produced in mild-winter greenhouses. An experiment involving 34 ginger plants grown in aeroponics was performed in a temperature controlled greenhouse in Tucson, Arizona. The unique aeroponic growing units incorporated a "rhizome compartment" separated and elevated above an aeroponic spray chamber. Bottom heat was supplied to one half of the plants. Accelerated growth was observed in plants receiving bottom heat. One third of the plants were grown in units where the rhizome compartment was filled with perlite, one third in sphagnum moss, and one third without any aggregate medium. Those plants grown in perlite matured faster than the other treatments. The aeroponic units without aggregate medium provided an opportunity to photograph the growth habit of rhizomes over a three month period. Those images were incorporated into a 60-second digital movie that dramatically illustrates how underground rhizomes develop and grow.