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Joshua D. Butcher, Charles P. Laubscher, and Johannes C. Coetzee

Pelargonium tomentosum Jacq.; the peppermint-scented pelargonium, is an herbaceous groundcover indigenous to the Western Cape of South Africa. Volatile oils are produced by this plant, which are used in the fragrance industry. Studies on other Pelargonium species have shown chlorophyll content may affect the yield of essential oils. This study was carried out to investigate the viability of growing P. tomentosum in deep water culture (DWC) hydroponics and how best to aerate/oxygenate the nutrient solution to increase the chlorophyll content within leaves. The experiment was conducted over a period of 74 days, 16 different methods of oxygenation were applied to 9 replicates. The control had passive aeration; the treatments were made up of air-pumps, vortex oxygenators, and the application of hydrogen peroxide at various frequency intervals; these were combined with each other and run as separate oxygenation methods. The measurement of the chlorophyll content of plant leaves has been established to be an accurate way of establishing vigor, health, and levels of stress. It was found that the combination of high-frequency application (every third day) of hydrogen peroxide, vortex oxygenation, and air-pump injection (both operational for 24 hours/day) which formed treatment 11 (APVHa), yielded the highest production of chlorophyll within all the replicates differing significantly (P ≤ 0.001) from the control and other treatments.

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Daniel P. Gillespie, Gio Papio, and Chieri Kubota

grown leafy greens. Most leafy green hydroponics operations employ liquid-based cultivation systems such as nutrient film technique and deep water culture (DWC), which allow for efficient water and nutrient use and high productivity. However, although

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Marie Abbey, Neil O. Anderson, Chengyan Yue, Michele Schermann, Nicholas Phelps, Paul Venturelli, and Zata Vickers

production facility, such as controlled environment greenhouses or warehouses ( Love et al., 2015 ). Deep water culture (DWC) is the most popular commercial aquaponic system in which fish and plants are physically separated but coupled together; the plants

Open access

Chengyan Yue, Zata Vickers, Jingjing Wang, Neil O. Anderson, Lauren Wisdorf, Jenna Brady, Michele Schermann, Nicholas Phelps, and Paul Venturelli

The present study systematically investigated the effects of warehouse and greenhouse aquaponic growing conditions on consumer acceptability of different basil cultivars. A total of 105 consumers rated their liking of three basil cultivars (Nufar, Genovese, and Eleonora), each grown in three conditions (aquaponically in a greenhouse, aquaponically in a warehouse, both with Cyprinus carpio, Koi fish, and grown in soilless medium). We used linear random effect models to investigate consumer preferences for attributes of basil plants grown in different environments by controlling for individual-specific random effects. Participants generally liked the soilless medium–grown and greenhouse aquaponically grown basil plants more than the warehouse aquaponically grown plants. The soilless medium–grown basil had the highest appearance liking and flavor intensity, followed by the greenhouse aquaponic grown and then by the warehouse aquaponic grown. Aquaponically grown cultivars were rated less bitter than soilless medium–grown cultivars.

Open access

Samuel Doty, Ryan W. Dickson, and Michael Evans

important decision for bedding plant growers transitioning to edible crop production is whether to invest in new hydroponic equipment or modify existing culture systems ( Chidiac, 2017 ). Nutrient film technique (NFT) and deep water culture (DWC) are common

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M.A. Sherif, P.A. Loretan, A.A. Trotman, J.Y. Lu, and L.C. Garner

Nutrient technique (NFT) and deep water culture (DWC) hydroponic systems were used to grow sweetpotao to study the effect of four nutrient solution treatments on: translocation of nutrients and plant and microbial population growth in split-root channels. 'TU-155'cuttings (15 cm) were prerooted for 30 days in sand in 4 cm CPVC pipes 46 cm in length. A modified half Hoagland (MHH) solution was supplied ad libidum. After 30 days, plants were removed and the roots of each plant were cleaned and split evenly between two channels (15 cm deep by 15 cm wide by 1.2 m long). four plants per channel. Nutrient solution treatments (replicated) were: MHH-MHH: MHH-Air, MHH-deionized water (DIW); and monovalent (Mono) - divalent (Dival) anions and cations. Solution samples were continuously collected at 7-day intervals for microbial population profiling. Plants were harvested after growing for 120 days in a greenhouse. Storage roots, when produced, were similar in nutritive components. However, no storage roots were produced in Air or Mono channels and only a few in DIW. Fresh and dry weights for storage roots and foliage were highest in MHH-MHH in both NFT and DWC in repeated experiments. Population counts indicated that nutrient solution composition influenced the size of the microbial population in NFT. Population counts were highest in Dival channels. The microbial population counts (4.20-7.49 cfu/mL) were. relatively high in both NFT and DWC systems.

Open access

Daniel P. Gillespie, Chieri Kubota, and Sally A. Miller

Rootzone pH affects nutrient availability for plants. Hydroponic leafy greens are grown in nutrient solutions with pH 5.5 to 6.5. Lower pH may inhibit plant growth, whereas pathogenic oomycete growth and reproduction may be mitigated. General understanding of pH effects on nutrient availability suggests likely toxicity and deficiency of specific micronutrients. We hypothesized that if adjustments are made to the micronutrient concentrations in solution, plants will grow in lower-than-conventional pH without nutrient disorders, while oomycete disease incidence and severity may be reduced. To develop a new nutrient solution management strategy, we examined pH of 4.0, 4.5, 5.0, and 5.5 with or without micronutrient adjustments for growing two cultivars of basil plants Dolce Fresca and Nufar in a greenhouse hydroponic deep-water culture (DWC) system. Micronutrient adjustments included reduced concentrations of copper, zinc, manganese, and boron by one-half and doubled molybdenum concentration. Plants harvested 20 to 28 days after transplanting did not show significant effects of pH or the micronutrient adjustment. Phosphorus, calcium, magnesium, sulfur, boron, manganese, and zinc concentrations in leaves significantly declined, while potassium and aluminum concentrations increased with decreasing pH. However, these changes and therefore micronutrient adjustments did not affect basil plant growth significantly. ‘Nufar’ basil plants were then grown in a growth chamber DWC system at pH 4.0 or a conventional 5.5 with and without inoculation of Pythium aphanidermatum zoospores. Fourteen days after inoculation, P. aphanidermatum oospore production was confirmed only for the inoculated plants in pH 5.5 solution, where a significant reduction of plant growth was observed. The results of the present study indicate that maintaining nutrient solution pH at 4.0 can effectively suppress the severity of root rot caused by P. aphanidermatum initiated by zoospore inoculation without influencing basil growth.

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Philipp von Bieberstein, Ya-ming Xu, A.A. Leslie Gunatilaka, and Raphael Gruener

chamber kept at 28 °C with 16 h of fluorescent lighting. After ≈5 weeks (late summer), seedlings with an aerial length of ≈5 cm were transferred to a float system [deep water culture containing 50% modified Hoagland Nutrient Medium ( Hoagland and Arnon

Open access

Celina Gómez and Juan Jiménez

after sowing, three uniform seedlings per cultivar were transplanted into a single deep-water culture hydroponic system using 5-cm diameter net cups. Each cylindrical 7.6-L hydroponic system had a white plastic lid with three openings (25 cm apart) that

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Elisa Solis-Toapanta, Paul Fisher, and Celina Gómez

solution was not replaced, but the same mass of fertilizer as in the W treatment was added every 2 weeks (“W/O”). Each experimental unit (“replicate hydroponic system”) was an aerated deep-water culture hydroponic system with four basil plants. Water level