Master of Science / Department of Biological and Agricultural Engineering / Stacy L. Hutchinson / The energy sector needs to transition to renewable energy to provide energy and economic security in the future (Murray & King, 2012). Liquid biofuels are an important renewable fuel in this transition because they are the preferred renewable energy source in the transportation sector (Lange, 2007), and the only renewable energy alternative for the aviation industry [International Air Transport Association (IATA), 2015]. Biofuels produced from food crops (first-generation biofuels) are being produced at an industrial scale, but they create several environmental and social conflicts (Mohr & Raman, 2013). Currently, there is a demand for the next generation of biofuels to resolve the environmental and social conflicts associated with first-generation biofuels. Salicornia, a salt tolerant oil seed crop (Panta et al., 2014), is one feedstock that might be able to resolve some of those conflicts because it can be irrigated with saline water (Warshay et al., 2017). The ability of Salicornia to tolerate saline environments suggests that it might be able to be cultivated in a hydroponic system designed to treat industrial wastewater. A hydroponic system designed to treat industrial wastewater and produce Salicornia as a biofuel feedstock could prevent some of the detrimental effects of industrial sources of saline water on terrestrial and aquatic ecosystems (Gerhart et al., 2006), and produce a feedstock that resolves some of the issues with first-generation biofuels. The first step in the development of the proposed hydroponic system is to determine if Salicornia can be cultivated with industrial wastewater in a hydroponic system. Studies were conducted with two sources of industrial wastewater, Flue Gas Desulfurization (FGD) wastewater and Cooling Tower Blowdown Water (CTBW), to determine how the composition of water affects the germination, survivability, early seedling growth, and lignocellulosic composition of Salicornia. The composition of water was shown to have no effect on seed germination and visual signs of phytotoxicity. These studies found that full strength CTBW and 20% FGD wastewater could be used to cultivate Salicornia in a hydroponic system if nutrients are added. Full strength FGD wastewater was shown to have a negative impact on seedling growth. These studies also found that Salicornia is not a good lignocellulosic biofuel feedstock because of its low lignocellulosic composition (e.g. 14.9-9.1% glucan, 13.2-6.7% xylan, 5.2-2.4% arabinan, and 9.8-6.2% lignin). However, a large percentage of the extractives content is unidentified and could have a monetary value. Additional research is needed to determine if a hydroponic system that cultivates Salicornia is able to provide any water quality treatment.

Thesis (MTech (Horticultural Sciences))--Cape Peninsula University of Technology, 2017. / The increasing demand for medicinal plants has led into serious over-harvesting of wild populations and presents an opportunity for potential profitable cultivation. Production of medicinal plants in controlled environments particularly hydroponic technology provides opportunities for high quality biomass accumulation and optimizes production of secondary metabolites. Water availability and supplies are becoming scarce, thus search for innovative irrigation practices is desirable and vital. The proper irrigation interval and growing media can play a major role in increasing the water use efficiency. Thus, Siphonochilus aethiopicus was cultivated by means of the hydroponic technique, under various substrate combinations and watering regimes.

The objective of this study was to optimize the cultural and environmental conditions necessary to produce high quality basil in a semi-arid climate during summer. Basil grown in a retractable roof greenhouse (RRGH) and full sun over two years using production systems including rockwool, containers, raised beds, vertical towers, and soil was evaluated based on biomass accumulation, morphological characteristics and quality. Photosynthetic response of basil to temperature and light was tested in a growth chamber to determine the optimum conditions that enhance photosynthesis and increase productivity. Biomass accumulation and quality of basil were affected by environment and cultural practices, with the largest quantities of highest quality basil produced in rockwool or raised beds in the RRGH. The response of basil to light and temperature indicated that highest photosynthesis during summer occurred between temperatures of 25 to 35 °C at a light intensity of 1500 μmol m⁻¹ s⁻¹.

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This thesis attempts to determine if food-producing plant growth can be incorporated within a building envelope to create an ideal plant growth environment while simultaneously enhancing the thermal properties of the building envelope. A window system was designed as a means of bringing food production into the built environment in an easily accessible fashion from the interior of a high-rise apartment complex. The Ya-Po-Ah Terrace in Eugene, Oregon, was chosen as a case study site for research on how a window could promote health, provide nutrition, and enhance the thermal comfort of the inhabitants. The design of the window unit is founded in precedent research on methods of plant growth in urban environments and systems for growing food in small and efficient ways. The design found that it is possible to create an ideal plant growth environment within a building assembly for use as a food production method for building inhabitants.

About 150 rhizobacteria and 49 rhizosphere fungi were isolated from the rhizosphere of grasses and sedges at Nylsvley Nature Reserve, Limpopo Province, South Africa. The rhizobacterial isolated were mostly Gram negative (72%) and rod shaped (73%). The dominant fungal genera were Trichoderma, Aspergillus, Pencillium, Neosartorya and Fusarium. The antagonistic activity of the above isolates were determined in a dual culture assay against a range of plant pathogens namely Colletotrichum gloeosporioides, Pythium irregulare, Penicillium digitatum, Fusarium solani and Geotrichum candidum. All rhizosphere fungal isolates showed positive antagonism against G. candidum (100%) and F. solani (100%). The rhizobacterial isolates showed positive antagonism against G. candidum (71%) and C. gloeosporioides (76%). The growth promotion and biocontrol activity of the rhizosphere isolates that showed broad-spectrum antagonistic activity against the fore mentioned pathogens were further evaluated on Canadian peat substrate under greenhouse condition. Although most of the rhizosphere isolates resulted in improved fresh leaf weight in comparison with the non-inoculated control in final growth promotion experiments, no statistical difference could be found in increasing leaf weight by one of the tested isolates. Some isolates and BactolifeTM prevented root infection by Pythium. However, only isolate 68B showed significant prevention of root infection compared to the Pythium inoculated control. The selected rhizobacteria, fungal and commercial biocontrol products that showed the most effective growth promotion and biocontrol activities were further evaluated in a re-circulating hydroponic system. Overall, isolate BSB (Bacillus subtilis) consistently enhanced the fresh leaf and root weight by 29.82 and 24.31% compared to the untreated control. Treatments with rhizobacteria isolate 91B and 43B significantly increased fresh leaf weight and suppressed Pythium root infection of lettuce. Isolate 91B and 121B significantly decreased the incidence of Pythium after the 1st and 2nd week of inoculation respectively. The combination of rhizobacteria BSB and 43B showed a synergistic effect as reflected in increased fresh leaf weight and total biomass per plant whilst suppressing root rot caused by Pythium group-F. Copyright 2003, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Begashaw, L 2003, Utilisation of rhizosphere microflora in the biocontrol of root rot and growth enhancement of lettuce under hydroponic systems, MSc dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-05092005-103113 / > E642/ag</gm> / Dissertation (MSc (Agric))--University of Pretoria, 2006. / Microbiology and Plant Pathology / unrestricted

Hydroponic production was initially explored as an alternative to field production due to the ease of plant growth control and the hopes of preventing the majority of disease causing agents known to be present in general soil environments. Of primary concern in terms of pathogens are the water-borne and water-motile zoosporic fungi (especially Pythium spp.) which are able to spread easily throughout the system and cause root-rot and wilting. Few pesticides are currently registered for use in hydroponic systems due to the high costs of registration, while registered pesticides carry a high cost to the grower. Recent legislative moves by numerous countries are also resulting in a trend towards the re-use of hydroponic nutrient solution. As a result such hydroponic solutions require a greater level of disinfection to prevent disease outbreaks but without resulting in chemical buildup of phytotoxic and environmental concern. Sanitiser formulation has seen significant changes over the last few years resulting in sanitisers being used in many new areas and in a more environmentally friendly nature. Although sanitisers are not designed to have specific action against micro-organisms (as is the case with fungicides and anti-microbial agents such as antibiotics), most sanitisers are able to act on cell membranes due to the inherent surfactant properties. This study attempted to determine the suitability of various sanitisers and chemicals as alternate means of control of Pythium in recirculating gravel hydroponic systems by: 1). Exposing Pythium zoospores in a water suspension to the sanitisers Actsol®, Agral 90®, Fitosan®, Prasin®, Purogene®, TecsaClor®, Sporekill® and copper (as copper (I) sulphate) which all managed to eliminate 80% or more of the viable inoculum within a 10 minute exposure time at relatively low concentrations. 2). Testing the above sanitisers for phytotoxicity effects on cucumber plants in a static hydroculture system under laboratory conditions and lettuce plants in a gravel bed hydroponic system under greenhouse conditions. Purogene® and TecsaClor® exhibited a slight growth promotion effect at low concentrations, yet still caused negative phytotoxic effects when dosed at high concentrations. All other sanitisers exhibited some measure of phytotoxicity, observed as growth retardation and leaf discolouration, with phytotoxic effects increasing with increasing concentrations. Copper sulphate was found to be the most phytotoxic chemical tested. 3). Addition of the sanitisers to a small scale hydroponic system (greenhouse), as well as to a semi-commercial scale (field) gravel bed hydroponic system artificially infested with Pythium and cultivated with lettuce. The sanitisers were also compared to a commercially available fungicide, Phytex®. Only Phytex® and Purogene® managed to effectively reduce disease incidence and promote growth over an untreated, Pythium infested control. The results indicated that Purogene® was the most effective for application into a gravel bed hydroponic system cultivated with lettuce, while no sanitiser treatment was able to equal the improved growth and disease control recorded with treatment of the commercial fungicide Phytex®. Although all the sanitisers were able to reduce levels of Pythium inoculum in the hydroponic nutrient solution, this beneficial effect did not translate into increased yields, due to the growth retardation due to phytotoxic effects. / Dissertation (MSc (Plant Pathology))--University of Pretoria, 2008. / Microbiology and Plant Pathology / unrestricted

In the United States, illnesses associated with fresh produce are increasing in frequency.  While contamination risks are present at every aspect of the farm to fork continuum, post-harvest practices holds the potential for cross-contamination of large amounts of product.  Post-harvest contamination risks for hydroponically grown lettuce packaged with intact roots and sold as "living lettuce"" are poorly understood.  In this study, transmission of Salmonella enterica serotype Enteritidis to the roots and leaves of butterhead lettuce was studied when contamination was introduced during typical handling practices.  The effectiveness of random sampling strategies for selection of Salmonella contaminated leaves was assessed by co-inoculating the Salmonella solution with Glo Germ™ and comparing recovery from blacklight selected leaves.  The recovery of Salmonella was improved by only 0.5 log CFU/g when blacklight was used to select Glo Germ™ contaminated leaves (P=0.05). This suggests random leaf selection as described by current FDA protocols is adequate. In addition, this study showed rapid transfer of Salmonella from liquid to the roots and sub-sequentially to the leaves of living lettuce.  Salmonella persisted but did not grow on leaves when stored at 4˚C for 18-days. Storage at 12˚C was associated with 2 log CFU/g increases in Salmonella on roots after 18-days storage (P=0.0002), while 4˚C storage was associated with a decrease of 0.4 log CFU/g Salmonella on roots (P=0.0001). Growth occurred only under temperature abuse conditions.  This reinforces the need for maintaining temperature control and highlights the importance of identifying risks associated with post-harvest handling during hydroponic production and distribution. / Master of Science in Life Sciences

Halogeton (Halogeton glomeratus) is a halophytic, invasive species that displaces Gardner’s saltbush (Atriplex gardneri) on saline rangelands. Forage kochia (Bassia prostrata) is a potential species to rehabilitate these ecosystems. This study compared the salinity tolerance of these species and tall wheatgrass (Thinopyrum ponticum) and alfalfa (Medicago sativa). Plants were evaluated for 28 days in hydroponics where they were maintained at 0, 150, 200, 300, 400, 600, and 800 mM NaCl. Shoot growth and ion accumulation were determined. Alfalfa and tall wheatgrass were severely affected by salt with both species’ shoot mass just 32% of control at 150 mM NaCl. Alfalfa did not survive above 300 mM NaCl, while, tall wheatgrass did not survive at salt levels above 400 mM NaCl. In contrast, forage kochia survived to 600 mM, but produced little shoot mass at that level. Halogeton exhibited ‘halophytic’ shoot growth, reaching maximum mass at 141 mM, and not less mass than the control until salinity reached 400 mM. Gardner’s saltbush did not show a dramatic decrease in dry mass produced until it reached salt levels of 600 and 800 mM NaCl. Forage kochia yielded high amounts of dry mass in the absence of salt, but also managed to survive up to 600 mM NaCl. Salt tolerance ranking (GR50 = 50% reduction in shoot mass) was Gardner’s saltbush=halogeton>forage kochia> alfalfa>tall wheatgrass. Both halogeton and Gardner’s saltbush actively accumulated sodium in shoots, indicating that Na+ was the principle ion in osmotic adjustment. In contrast, forage kochia exhibited a linear increase (e.g. passive uptake) in Na+ accumulation as salinity increased. This study confirmed that halogeton is a halophytic species and thus well adapted to salt-desert shrubland ecosystems. Gardner’s saltbush, also a halophyte, was equally salt tolerant, suggesting other factors are responsible for halogeton displacement of Gardner’s saltbush. Forage kochia is a halophytic species that can survive salinity equal to seawater, but is not as salt tolerant as Gardner’s saltbush and halogeton.

Resumo: Devido a mudanças no hábito alimentar o consumo de alface vem aumentando, sendo seu fornecimento diário, o ano todo. Sendo assim, o cultivo hidropônico tem sido adotado por muitos produtores. Apesar disso, muitas cultivares ainda não são adaptadas a essa tecnologia. O objetivo deste trabalho foi avaliar o desempenho de cinco cultivares de alface em dois ambientes de cultivo no sistema hidropônico, tipo NFT, no período de 06/02 a 07/04 de 2006 em Ribeirão Preto, estado de São Paulo, Brasil. Para isso as cultivares Pira Roxa, Pira Vermelha, Locarno, Crespona gigante e Verônica foram avaliadas em casa de vegetação convencional e climatizada em sistema NFT (Técnica do fluxo laminar de nutrientes). O delineamento experimental foi em blocos casualizados, sendo cinco cultivares em três blocos. A colheita foi realizada aos 61 dias da semeadura sendo avaliadas a massa fresca e seca da parte aérea, caule e raízes; número de folhas maiores que 10 cm e número total de folhas. A cultivar Crespona gigante não diferiu da cv. Verônica em massas fresca e seca da parte aérea, mas foi superior às cultivares Pira Vermelha, Pira Roxa e Locarno. As cultivares Pira Roxa e Pira Vermelha sugeriram melhor adaptação, indicando maior resistência ao pendoamento. Não houve efeito significativo para a interação, cultivares e ambientes, mostrando que as cultivares comportaram-se de forma semelhante nos dois ambientes. Houve um maior consumo de água pelas plantas de alface na casa de vegetação convencional em relação à climatizada, provavelmente devido às maiores temperaturas e à menor umidade relativa do ar. A extração de nutrientes pelas folhas de alface (média de cinco cultivares) obedeceu a seguinte ordem decrescente: K>N>Ca>Mg>P>S>Fe>Mn>Zn>Cu. / Abstract: Due to changes in feeding habits, lettuce consumption has been increasing and must be supplied daily throughout the year. As a result, many producers have adopted hydroponics’ cultivation. In spite of this, many cultivars are not yet adapted to this technology. The objective of this study was to evaluate the performance of five lettuce cultivars grown in two environmentals in NFT (Nutrient Film Technique) hydroponic system in the period from Feb/06 to Apr/07 2006 in Ribeirão Preto, state of São Paulo, Brazil. To accomplish this, cultivars Pira Roxa, Pira Vermelha, Locarno, Crespona gigante, and Verônica were evaluated in conventional and climatizated greenhouse in the NFT system. A randomized-block experimental design was used, consisting of five cultivars in three blocks. Harvest was performed 61 days after seeding. Evaluations were made for fresh and dry mass of the aerial part, stem, and roots; number of leaves larger than 10 cm; and total number of leaves. Cultivar Crespona gigante in fresh weight and dry matter of the aerial part did not differ from cultivar Verônica, but it was superior to them cultivars Pira Roxa, Pira Vermelha and Locarno.The cultivars Pira Roxa and Pira Vermelha suggested a better adaptation, showing better resistance to bolting. There was no significant effect of the cultivars OE environments interaction, demonstrating that the cultivars had similar behaviors in both environments. There was a larger consumption of water by the lettuce plants under the conventional greenhouse conditions in comparison to the acclimated one, probably due to their higher temperatures and lower air relative humidities. The extraction of nutrients by leaves lettuce plants (average five to cultivate) obeyed to the followed the decreasing order: K>N>Ca>Mg>P>S>Fe>Mn>Zn>Cu. / Orientador: Jairo Augusto Campos de Araújo / Coorientadora: Sally Ferreira Blat / Banca: Glauco Eduardo Pereira Cortez / Banca: Luiz Vitor Egas Villela Junior / Mestre