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Effects of Low Nutrient Solution pH on Hydroponic Leafy Green Plant Growth, Nutrient Concentration of Leaf Tissue, and Pythium Zoospore Infection

Gillespie, Daniel Patrick
http://rave.ohiolink.edu/etdc/view?acc_num=osu1563205720634412

Abstract Details

2019, Master of Science, Ohio State University, Horticulture and Crop Science.
In recent years, the increased demand for locally grown produce and outbreaks of E. coli linked to leafy greens has led to hydroponic leafy green production in controlled environments becoming a viable addition to the fresh produce food supply. Prevention of plant pathogen introduction in hydroponics is critical, as effective control agents for root diseases of edible crops are limited and may not be registered for use in greenhouses or indoors. This study examined lowering nutrient solution pH as a new management strategy to mitigate the risk of oomycete root disease incidence without negatively influencing plant growth. Although pH below 5.0 has been shown to negatively affect oomycete pathogen growth and reproduction, hydroponic nutrient solution is typically maintained within pH 5.5-6.5, as plants tend to exhibit growth inhibition outside of this range. Nevertheless, growth inhibition can typically be attributed to pH-dependent factors affecting nutrient uptake and availability, which may be mitigated if precautionary measures are considered. We hypothesized that if plants can be grown in pH below 5.0, the risk of oomycete disease incidence may be reduced. As first steps towards the development of a new nutrient solution management strategy, we determined if adjusting micronutrient concentrations in nutrient solution based on reported availability levels were effective in mitigating nutrient disorders and plant growth inhibition typically experienced at low pH. Basil and spinach plants were grown in deep-water hydroponic systems with pH maintained at 4.0, 4.5, 5.0, or 5.5. Two nutrient solutions (with and without micronutrient adjustments) were applied at each pH level, where concentrations of copper, zinc, manganese, and boron were decreased by one-half and molybdenum concentration was doubled in the adjusted solution. To our surprise, even though most elemental concentrations of leaf tissue decreased with decreasing pH, basil plant growth was not affected by pH for a range of 4.0-5.5 or nutrient solution adjustment. Alternatively, spinach plant growth was significantly reduced in pH below 5.0. Using basil plants, we then examined the efficacy of lowering pH in preventing Pythium infection. Nutrient solution pH was maintained at 4.0 or a conventional range (pH 5.5-6.5) and inoculated with Pythium aphanidermatum zoospores five days subsequent to transplanting. Disease symptomology was almost exclusively limited to pH 5.5-inoculated treatments. In addition, fresh plant mass was significantly reduced in pH 5.5-inoculated treatments. The results of this study indicate that low pH (pH 4.0) can effectively suppress Pythium aphanidermatum disease incidence after zoospore inoculation without influencing basil plant growth. For spinach, further nutrient adjustments or precautionary measures may alleviate growth reductions observed at low pH. These results indicate that low nutrient solution pH is an effective, low cost, and environmentally sustainable root disease management strategy if crops can tolerate continuous exposure to low pH.
Chieri Kubota, PhD (Advisor)
Sally Miller, PhD (Committee Member)
Michelle Jones, PhD (Committee Member)
152 p.
Agricultural Chemicals; Agricultural Economics; Agricultural Education; Agriculture; Horticulture; Plant Pathology
hydroponic; pH; pythium; leafy greens; nutrient solution; herbs; basil; spinach; controlled environment agriculture; plant pathology; plant physiology; horticulture; nutrient uptake; nutrient concentration

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Citations

  • Gillespie, D. P. (2019). Effects of Low Nutrient Solution pH on Hydroponic Leafy Green Plant Growth, Nutrient Concentration of Leaf Tissue, and Pythium Zoospore Infection [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1563205720634412

    APA Style (7th edition)

  • Gillespie, Daniel. Effects of Low Nutrient Solution pH on Hydroponic Leafy Green Plant Growth, Nutrient Concentration of Leaf Tissue, and Pythium Zoospore Infection . 2019. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1563205720634412.

    MLA Style (8th edition)

  • Gillespie, Daniel. "Effects of Low Nutrient Solution pH on Hydroponic Leafy Green Plant Growth, Nutrient Concentration of Leaf Tissue, and Pythium Zoospore Infection ." Master's thesis, Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1563205720634412

    Chicago Manual of Style (17th edition)

osu1563205720634412
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© 2019, some rights reserved.Creative Commons License Effects of Low Nutrient Solution pH on Hydroponic Leafy Green Plant Growth, Nutrient Concentration of Leaf Tissue, and Pythium Zoospore Infection by Daniel Patrick Gillespie is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by The Ohio State University and OhioLINK.