Browsing by Subject "Cannabis sativa L."

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The bioeconomy potential of hemp (Cannabis sativa L.)
challenges of new genotypes and cultivation systems to meet the rising demand for phytocannabinoids
(2021) Burgel, Lisa; Graeff-Hönninger, Simone
Cannabis sativa L. as a prime example of a multifunctional crop is excellently suited for recycling management due to its versatility and the usability of the whole plant. Cannabis currently experiences a boom due to its rich phytochemical repertoire, its fibres and valuable oil required in numerous products, and its unique agricultural properties. The medical benefits of C. sativa, based on the phytocannabinoids available in flowers and leaves, are the main focus of attention worldwide. Innovative markets in the food, cosmetics and pharma industry are growing fast, with a focus on cannabidiol (CBD), which is the leading cannabinoid of the cannabis plant. Basically, it is important to differentiate between industrial hemp genotypes and phytocannabinoid-rich (PCR) cannabis genotypes. Industrial hemp meet the 0.2% THC limit mandated by the EU legislation, and therefore, can be legally cultivated by farmers on a field scale. PCR genotypes contain high amounts of non-psychoactive cannabinoids such as CBD and cannabigerol (CBG) in the range of 10 – 30% while their THC content is also below 0.2%. These genotypes are currently being bred but are still barely available on the market. Cannabinoid extraction from industrial hemp cultivated on a field scale could provide a decisive advantage as the harvested biomass quantities could be significantly increased through better land use and cost management, compared to an indoor system. The multi-functionality of the industrial hemp can provide added economic value. Therefore, existing cultivation systems for fibre and oilseed production have to be modified as the harvesting time and harvested organ are expected to differ greatly from those of the present systems. In order to achieve this, publication I dealt with the objective, to determine the yield potential of different EU-registered hemp genotypes with regard to inflorescence and biomass yield as well as cannabinoid content, depending on genotype, growth stage and biomass fraction in an outdoor cultivation system. The cultivation of seven industrial hemp genotypes (Finola, Fédora17, Ferimon, Félina32, Futura75, USO 31 and Santhica27) was carried out in a two-year field experiment. Sampling of leaves and inflorescence, took place at four specific growth stages: vegetative leaf stage, bud stage, full-flowering stage, and seed maturity stage. Dry matter was recorded, and cannabinoids were analysed. The results indicated that the content of cannabinoids highly depended on the genotype and the growth stage. Thus, biomass and inflorescence yields must be considered for an optimized harvest result. Genotype Santhica27 indicated the highest contents of CBG/A. Further, it was found that genotypes such as Futura75, Fédora17, Félina32, Ferimon, Finola and Santhica27, which were highlighted to have a higher CBD/A or CBG/A content compared to other evaluated genotypes, reached the highest yields of threshing residues after seed maturity, and thus a higher CBD/A and CBG/A yield per area. In conclusion, harvesting after seed maturity seems to be economically beneficial. These findings make selected industrial hemp genotypes excellent candidates for multipurpose cropping. Additionally, the thesis aimed at further standardization of PCR genotypes in indoor cultivation systems. Due to the prescribed requirement of high-quality medical cannabis material, indoor cultivation is in focus as under the system all production parameters can be standardized. The production of cannabinoids under indoor conditions is expensive due to processing costs and regulatory limitations, thus there is an increasing interest in using the available space requirements efficiently. Publication II evaluated the adaptation of the plant architecture, through the targeted use of synthetic phytohormones, aiming for a small and compact plant morphology for various indoor systems. The objective was, to test the impact of exogenously applied plant growth regulators (PGRs), such as NAA, BAP and a mixture (NAA/BAP-mix) of both on the plant architecture of different PCR genotypes. Therefore, genotypes were treated with synthetic phytohormones in various concentrations in a greenhouse experiment. Furthermore, the differences in leaf and flower yields resulting from morphological changes in these genotypes and their CBD/A content was investigated. A genotype-specific impact of applied PGRs on the plant architecture was determined. NAA led to more compact plants with a consistently high floral yield for genotype KANADA, whereas CBD/A content was not affected. Genotypes 0.2x and FED showed reduced floral yields due to the PGRs applications. Publication III dealt with the evaluation of the growth performance of PCR genotypes grown in different substrate compositions substituted with peat alternatives in an indoor cultivation system. The impacts of the following substrate compositions: peat-mix growth media (PM); peat-mix substituted with 30% of green fibres (G30) consisting of coniferous wood and wood chips from pine and spruce wood growth media, and coco coir fibres (CC), on growth performance, biomass and flower yields, biomass nitrogen (N) content as well as CBD/A contents were tested. The results showed that the different substrates had significant impacts on the growth, biomass and floral yields, root development and N tissue content of the tested genotypes. A genotype-specific reaction on floral yield was investigated. While genotype KANADA had the highest floral yields when grown in PM, 0.2x showed no significant differences, with higher floral yields grown in G30 and CC. For both genotypes, no limiting effect on CBD/A content was enacted. It can be concluded, that organic peat alternatives such as green fibres, partly replacing peat in standard growing media, offers a genotype-specific option.
Towards standardized medicinal cannabis production systems: development of agronomic strategies and automated tools for plant growth monitoring and prediction in controlled environments
(2025) Schober, Torsten; Graeff-Hönninger, Simone
Medicinal cannabis producers are once again in a highly competitive market, which, despite good prospects, has had to contend with price erosion due to overproduction and rising production costs in recent years. Meanwhile, there is a growing awareness of the need for standardized cultivation systems and methods that enable a consistent and homogeneous quality of the flower material regarding cannabinoid and terpene profiles. Cultivation in indoor systems is therefore coming into focus, as these systems allow the plant life cycle, relevant environmental parameters (e.g., light, temperature, humidity, CO2 content of the air), and nutrient and water supply to be freely controlled. However, these systems often require a high input of energy and resources. Therefore, indoor growers face a multivariate optimization problem because the optimal interplay of genotype, environment, and plant management must be found regarding the target triangle of yield optimization, cost efficiency, and sustainability. Although agronomic research on cannabis has been on the rise in recent years, many practices and strategies in the industry are still based on anecdotal evidence and personal belief systems. Even basic agronomic principles vary widely across the industry and in research papers. At the same time, the influences of individual environmental parameters are often only considered separately without being able to integrate them into the complex overall picture. The development of standardized, controlled cultivation systems requires implementing “decision support systems” to incorporate the existing complexity of influencing factors. This involves monitoring systems that enable conclusions about the actual condition of the plant in real-time, as well as dynamic models that will allow the prediction of future growth behavior of the plant in response to changing environmental parameters. The main focus of this work was to investigate the influence of fundamental agronomic management decisions on the temporal course of plant growth and yield formation. The factors studied were to be evaluated regarding their effect on biomass production and cannabinoid homogeneity. The focus was on investigating different growing media, plant densities, and vegetation lengths. The data collected was used to create a basic concept for a real-time monitoring system and to calibrate a process-oriented growth model. Publication I describes two experiments comparing the most common growing media in the cannabis industry, namely rockwool, peat, and coco-coir mixtures. One experiment simulated the entire cultivation cycle, while the parallel experiment was designed to simulate an extended vegetative growth phase. A fertigation system was set up that allowed for an integrative, i.e., medium-specific, root zone management. Weekly destructive and non-destructive measurements were taken to generate a data set that was as detailed as possible to record plant growth. Likewise, environmental parameters such as light, temperature, and humidity were recorded in close temporal and spatial intervals. The comparison of the growing media was based on the estimated functional parameters of adjusted growth functions. The results showed that the effect of the growing medium on biomass production was primarily due to the ratio of transpiration area to available water. Furthermore, differences in nutrient uptake and assimilate distribution were observed, which had no significant effect on plant growth. The growing media only plays a minor role in the production and homogeneity of the secondary metabolites. In publication II, two further elementary management parameters were varied: planting density and the length of the vegetative phase. The aim was to develop empirical models for the effects of both factors on relevant growth parameters and, if possible, to derive recommendations for optimal canopy management. A strong linear correlation between yield per unit area and CBD production was demonstrated in both cases. Surprisingly, there was no yield saturation per unit area at high planting densities. However, the results illustrated how systems with high planting densities significantly increase the proportion of biomass in the upper half of the crop and, thus, the proportion of the desired inflorescence fractions. For standardized cultivation systems, it is, therefore, essential to optimize the planting density for the growth behavior of the genotypes used, whereby the possible planting densities can be significantly higher than the industry standards currently in place. The experiments served as the primary data basis for establishing an HSI system for quantifying plant nutrient status, which is presented in publication III. With the help of a self-built mobile camera frame, images were taken on a single-leaf and whole-plant basis using a hyperspectral camera. A chemometric model correlated the extracted spectra with the observed foliar concentrations of N, P, and K. This study was designed as a proof of concept. It showed that the system could accurately predict N and P concentrations under non-standardized light conditions in the greenhouse. The results of publications I - III were used in the subsequent discussion to outline a baseline for a standardized cultivation system for medicinal cannabis. The vertical gradient of the secondary metabolite concentration in inflorescences from the different canopy layers proves particularly problematic for standardized flower material. Maximizing plant density while considering microclimatic aspects is a key means of minimizing these gradients. At the same time, the duration of the vegetative phase, associated with height and side shoot growth, can be minimized. This allows the position of the inflorescences to be controlled as well as possible while minimizing the need for human intervention. The smaller plant size also simplifies fertigation management. It is a prerequisite for introducing vertical cultivation systems, significantly increasing indoor productivity and resource efficiency. Plant-based monitoring systems, such as the HSI system presented, can be expanded to capture further plant parameters in real-time. These can provide essential input data, especially in automated control systems for fertigation control. Due to the high acquisition rate, they also allow monitoring of the cultivation area with high spatial resolution. Thus, they can be used for the early detection of disease outbreaks and to reduce horizontal variability. In addition, the generated data sets were used to calibrate the CROPGRO model for the potential biomass production of medicinal cannabis in semi-controlled conditions. The model provided good predictions for the temporal course of height growth, leaf formation rate, biomass gain, and N mobilization. CROPGRO has the necessary interfaces to integrate further growth-limiting processes. The future of indoor cannabis cultivation is closely linked to developing smart greenhouses with intelligent, model-based control systems. This work provided important insights into agronomic conditions while creating the basic tools for future decision support systems.