Page 171 - PC2019 Program & Proceedings

PLANT CANADA 2019

S127. Comparative analysis between conventional and novel water treatment technologies in
recirculating hydroponics
*1
1
1
2
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Levesque, S. ; T. Graham ; D. Bejan ; P. Zhang ; J. Lawson ; M. Dixon
1
1 University of Guelph
2 Environmental Technology Consultant
Fertigation water, irrigation water with fertilizer dissolved in it, is commonly employed in hydroponic
cropping systems. Capturing fertigation run-off and reapplying it to the crop conserves fertilizer and
water resources while limiting the discharge of these nutrient rich solutions to the environment. Although
an efficient use of resources, recirculating fertigation water does pose a risk in terms of pathogen
proliferation. Pathogens can be picked up from infected plants and other sources and inadvertently
directly applied to the crop during solution re-use. There are many conventional technologies, such as
ozone (O3) or Advanced Oxidation Processes (AOPs) that can eliminate pathogens and prevent their
proliferation in fertigation water. There are also emerging electrochemical technologies, such as the use
of Dimensionally Stable Anodes (DSA), that can inactivate pathogens using in situ regenerative
hypochlorination. These emerging electrochemical chlorination processes are superior to conventional
chlorination in that disinfectant does not need to be continually added, a process that can sour the solution
making it unfit for crop production. The regenerative electrochemical chlorination technology is
evaluated against ozone and AOP technologies for pathogen control during Cyclamen persicum
production. Fertigation solutions spiked with Fusarium oxysporum f. sp. cyclaminis were treated with the
three technologies and then allowed to recirculate through the crop. After 6 weeks of growth, plants were
harvested and evaluated for disease symptoms. Results of the study will be presented.

Serge Levesque (serge@uoguelph.ca)

S128. Focusing on natural changes in solar spectrum to better understand plant light responses
Marie, T.R.J.G. ; B.J. Micallef; B. Grodzinski
*
University of Guelph

Portions of the solar spectrum are filtered out through the Earth’s atmosphere. This filtering can be
attributed to Rayleigh scattering, Mie scattering, and absorption by atmospheric gases. Rayleigh
scattering preferentially diminishes short wavelength blue light while Mie scattering evenly dissipates
PAR. The circular nature of the Earth’s atmosphere makes solar radiation path-length through the air
mass longer in lower solar elevations which enhances light scattering. Dusk/Dawn, winter solstice, and
high latitudes each manifest a change in spectrum due to their inherent lower solar elevations. The
presentation will discuss data on ratios, absolute irradiance, and rates of spectral changes in these
situations. Furthermore, recommendations for the horticultural LED lighting industry and plant
photobiological research community will be emphasized. The take home message is; when we assess
plant physiological responses to light, we should factor and correlate light intensity, photoperiod duration,
and spectral quality as it would naturally change in a day, season, and geographic latitude. Once natural
lighting scenarios can be standardized artificially, then we can modify it for yield, morphology, and
phytonutrient content. It is believed that fundamental responses to natural changes in solar spectrum is
ubiquitous among land plants.

Telesphore Marie (mariet@uoguelph.ca)

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