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Chlorophyll fluorescence is interesting for phenotyping applications as it is rich in biological information and can be measured remotely and non-destructively. There are several techniques for measuring and analysing this signal. However, the standard methods use rather extreme conditions, e.g., saturating light and dark adaption, which are difficult to accommodate in the field or in a greenhouse and, hence, limit their use for high-throughput phenotyping. In this article, we use a different approach, extracting plant health information from the dynamics of the chlorophyll fluorescence induced by a weak light excitation and no dark adaption, to classify plants as healthy or unhealthy. To evaluate the method, we scanned over a number of species (lettuce, lemon balm, tomato, basil, and strawberries) exposed to either abiotic stress (drought and salt) or biotic stress factors (root infection using Pythium ultimum and leaf infection using Powdery mildew Podosphaera aphanis). Our conclusions are that, for abiotic stress, the proposed method was very successful, while, for powdery mildew, a method with spatial resolution would be desirable due to the nature of the infection, i.e., point-wise spread. Pythium infection on the roots is not visually detectable in the same way as powdery mildew; however, it affects the whole plant, making the method an interesting option for Pythium detection. However, further research is necessary to determine the limit of infection needed to detect the stress with the proposed method.
Linnéa Ahlman; Daniel Bånkestad; Sammar Khalil; Karl-Johan Bergstrand; Torsten Wik. Stress Detection Using Proximal Sensing of Chlorophyll Fluorescence on the Canopy Level. AgriEngineering 2021, 3, 648 -668.
AMA StyleLinnéa Ahlman, Daniel Bånkestad, Sammar Khalil, Karl-Johan Bergstrand, Torsten Wik. Stress Detection Using Proximal Sensing of Chlorophyll Fluorescence on the Canopy Level. AgriEngineering. 2021; 3 (3):648-668.
Chicago/Turabian StyleLinnéa Ahlman; Daniel Bånkestad; Sammar Khalil; Karl-Johan Bergstrand; Torsten Wik. 2021. "Stress Detection Using Proximal Sensing of Chlorophyll Fluorescence on the Canopy Level." AgriEngineering 3, no. 3: 648-668.
Moving food production into the urban and peri-urban areas is one way of facilitating a closed-loop approach, integrating waste handling with food production in order to recirculate nutrients and at the same time reduce the use of mined and fossil resources in the production. Using anaerobic digestion as a way of converting urban wastes to an energy source (methane) and a nutrient-rich biodigestate with subsequent use as fertilizer for food production seems like a feasible approach. However, utilizing urban wastes in plant production systems implies some challenges, such as high salinity of the waste, imbalanced composition of nutrients, and abundance of less favorable forms of nitrogen. In a series of experiments, these problems were addressed. Vegetables (Pak Choi) were cultivated hydroponically in a controlled climate. Experiments included increased salinity, elevated levels of nitrite, and different concentrations of the biogas digestate-based nutrient solution, with mineral based solutions as controls. In general, the mineral controls yielded around 50% higher fresh biomass than the organic solutions. However, the quality of the produce with respect to content of secondary metabolites such as vitamins was enhanced when the plants were cultivated with organic nutrient solutions. Increasing the concentration of NaCl to 241 mg Cl L−1 did not negatively affect plant performance. Increasing the concentration of nitrite negatively affected plant growth, with reductions in biomass production by up to 50%. Given this well-functioning nitrification process that did not result in high nitrite concentrations, the use of anaerobic digestates seems feasible for hydroponic production of vegetables.
Karl-Johan Bergstrand; Håkan Asp; Malin Hultberg. Utilizing Anaerobic Digestates as Nutrient Solutions in Hydroponic Production Systems. Sustainability 2020, 12, 10076 .
AMA StyleKarl-Johan Bergstrand, Håkan Asp, Malin Hultberg. Utilizing Anaerobic Digestates as Nutrient Solutions in Hydroponic Production Systems. Sustainability. 2020; 12 (23):10076.
Chicago/Turabian StyleKarl-Johan Bergstrand; Håkan Asp; Malin Hultberg. 2020. "Utilizing Anaerobic Digestates as Nutrient Solutions in Hydroponic Production Systems." Sustainability 12, no. 23: 10076.
In greenhouse organic horticulture there is a great challenge in supplying the crop with adequate amounts of nutrients at the right stage of crop development. This has been identified as one of the main factors compromising yields in organic systems as compared with conventional hydroponic systems based on the use of synthetic fertilisers. In organic systems, the supply of nutrients is reliant on microbial degradation of organic complexes, a process that is dependent on factors such as temperature, soil water content and pH. Different organic fertilisers will also have different characteristics with respect to mineralisation of nutrients. In order to evaluate different strategies for organic fertilisation in long-term greenhouse crops such as high-wire tomato crops, an experiment with three different treatments was performed. The different strategies evaluated were one based on blood meal, kalimagnesia and the commercial product Baralith Enslow (composed of clay and ground lucerne), one with poultry manure and kalimagnesia, and one with solid biogas digestate and kalimagnesia. A five-month tomato crop was grown. Lysimeter samples were taken from the growing media biweekly for monitoring of plant available nutrients. The results suggested that nitrogen was likely to have been the limiting factor for plant growth, however, the biogas digestate delivered mineralised nitrogen throughout the experiment.
Karl-Johan Bergstrand; Klara Löfkvist; Håkan Asp. Dynamics of nutrient availability in tomato production with organic fertilisers. Biological Agriculture & Horticulture 2020, 36, 200 -212.
AMA StyleKarl-Johan Bergstrand, Klara Löfkvist, Håkan Asp. Dynamics of nutrient availability in tomato production with organic fertilisers. Biological Agriculture & Horticulture. 2020; 36 (3):200-212.
Chicago/Turabian StyleKarl-Johan Bergstrand; Klara Löfkvist; Håkan Asp. 2020. "Dynamics of nutrient availability in tomato production with organic fertilisers." Biological Agriculture & Horticulture 36, no. 3: 200-212.
Horticultural greenhouse production in circumpolar regions (>60° N latitude), but also at lower latitudes, is dependent on artificial assimilation lighting to improve plant performance and the profitability of ornamental crops, and to secure production of greenhouse vegetables and berries all year round. In order to reduce energy consumption and energy costs, alternative technologies for lighting have been introduced, including light-emitting diodes (LED). This technology is also well-established within urban farming, especially plant factories. Different light technologies influence biotic and abiotic conditions in the plant environment. This review focuses on the impact of light quality on plant–microbe interactions, especially non-phototrophic organisms. Bacterial and fungal pathogens, biocontrol agents, and the phyllobiome are considered. Relevant molecular mechanisms regulating light-quality-related processes in bacteria are described and knowledge gaps are discussed with reference to ecological theories.
Beatrix Alsanius; Maria Karlsson; Anna Rosberg; Martine Dorais; Most Naznin; Sammar Khalil; Karl-Johan Bergstrand. Light and Microbial Lifestyle: The Impact of Light Quality on Plant–Microbe Interactions in Horticultural Production Systems—A Review. Horticulturae 2019, 5, 41 .
AMA StyleBeatrix Alsanius, Maria Karlsson, Anna Rosberg, Martine Dorais, Most Naznin, Sammar Khalil, Karl-Johan Bergstrand. Light and Microbial Lifestyle: The Impact of Light Quality on Plant–Microbe Interactions in Horticultural Production Systems—A Review. Horticulturae. 2019; 5 (2):41.
Chicago/Turabian StyleBeatrix Alsanius; Maria Karlsson; Anna Rosberg; Martine Dorais; Most Naznin; Sammar Khalil; Karl-Johan Bergstrand. 2019. "Light and Microbial Lifestyle: The Impact of Light Quality on Plant–Microbe Interactions in Horticultural Production Systems—A Review." Horticulturae 5, no. 2: 41.
Pot grown herbs are often cultivated as certified organic products, and there is an increasing demand for organically certified ornamental plants. Supplying the required nutrients using organic fertilizers is a challenge with respect to matching the mineralization and thus the availability of dissolved nutrients in the growing medium with plant demand. In experiments, sweet basil and Pelargonium × hortorum were cultivated using two different organic fertilizer strategies and controlled-release mineral nutrients as control treatment. The two organic strategies were, i) blood meal + Baralith® Enslow (a plant-based organic fertilizer), and ii) poultry manure. The availability of dissolved nitrogen was monitored during the crop cycle by under-pressure lysimeter sampling. Plant development parameters were measured along with chlorophyll fluorescence and chlorophyll concentration of leaves. For both organic treatments, nitrate-N availability was low at the beginning of the experiment, whereas ammonium-N was high. During the experiment, ammonium availability decreased at the same time as nitrate availability increased after a few weeks and then declined again by the end of the experiment. The blood meal + Enslow treatment caused poor germination and slow growth in basil. Plant height and fresh weight was also affected by this treatment for basil but not for Pelargonium. Chlorophyll concentration was affected by treatment, with also visually detectable paler leaves in the treatment with poultry manure. There were no differences in chlorophyll fluorescence (Fv/Fm) between treatments, indicating that plants were not stressed in any of the treatments.
Karl-Johan Bergstrand; Klara Löfkvist; Håkan Asp. Dynamics of nitrogen availability in pot grown crops with organic fertilization. Biological Agriculture & Horticulture 2018, 35, 143 -150.
AMA StyleKarl-Johan Bergstrand, Klara Löfkvist, Håkan Asp. Dynamics of nitrogen availability in pot grown crops with organic fertilization. Biological Agriculture & Horticulture. 2018; 35 (3):143-150.
Chicago/Turabian StyleKarl-Johan Bergstrand; Klara Löfkvist; Håkan Asp. 2018. "Dynamics of nitrogen availability in pot grown crops with organic fertilization." Biological Agriculture & Horticulture 35, no. 3: 143-150.
Chemical plant growth regulators (PGRs) are used in the production of ornamental potted and bedding plants. Growth control is needed for maximizing production per unit area, reducing transportation costs and to obtain a desired visual quality. However, the use of PGRs is associated with toxicity risks to humans and the environment. In many countries the availability of PGRs is restricted as few substances are registered for use. A number of alternative methods have been suggested. The methods include genetic methods (breeding) and crop cultivation practices such as fertigation, temperature and light management. A lot of research into “alternative” growth regulation was performed during the 1980-1990s, revealing several possible ways of using different climatic factors to optimize plant growth with respect to plant height. In recent years, the interest in climatic growth regulation has been resurrected, not least due to the coming phase-out of the plant growth regulator chlormequat chloride (CCC). Today, authorities in many countries are aiming towards reducing the use of agrochemicals. At the same time, there is a strong demand from consumers for products produced without chemicals. This article provides a broad overview of available methods for non-chemical growth control. It is concluded that a combination of plant breeding and management of temperature, fertigation and light management has the potential of replacing chemical growth regulators in the commercial production of ornamental pot- and bedding plants.
Karl-Johan I. Bergstrand. Methods for growth regulation of greenhouse produced ornamental pot- and bedding plants – a current review. Folia Horticulturae 2017, 29, 63 -74.
AMA StyleKarl-Johan I. Bergstrand. Methods for growth regulation of greenhouse produced ornamental pot- and bedding plants – a current review. Folia Horticulturae. 2017; 29 (1):63-74.
Chicago/Turabian StyleKarl-Johan I. Bergstrand. 2017. "Methods for growth regulation of greenhouse produced ornamental pot- and bedding plants – a current review." Folia Horticulturae 29, no. 1: 63-74.