Institut für Kulturpflanzenwissenschaften

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Lighting the Way: Disentangling the impact of light on yield, cannabinoids and terpenes in Cannabis sativa L.
(2024) Reichel, Philipp-Severin Alfons; Graeff-Hönninger, Simone
This thesis focuses on the evolving cultivation of C. sativa, which is rapidly changing due to increasing legalisation efforts. However, the main challenge is to bridge the gap between previously illegal knowledge and validated, accessible scientific evidence. There is still a notable lack of comprehensive government about the medicinal C. sativa sector, particularly with regard relation to the production of flowers. Knowledge of cultivation systems is proprietary. Scientific validation and stricter cultivation guidelines are urgently needed. Therefore, this thesis is dedicated to investigating the growth patterns of multiple C. sativa strains under different light spectra. The main objectives are to validate the efficacy of LED lighting systems, to determine the relationship between photosynthetic rates and flower yield, and to investigate the complex interactions in secondary metabolism. A major focus will be the investigation of changes in the heterogeneity of secondary metabolites and the development of strategies to mitigate this heterogeneity, emphasising the analysis of cannabinoids and terpenes. Ultimately, a comprehensive cultivation system will be established that demonstrates how light intensity, spectral composition, variety diversity, and plant density influence different flower positions within a C. sativa plant. This system will serve as a basis for the cultivation of medicinal C. sativa, bridging the gap between illegal practices and scientifically validated methods. The first step was to investigate parameters for optimising growth characteristics and secondary metabolite production in relation to specific strain characteristics by studying different C. sativa strains under different light spectra. Publication I addressed the following objectives: (1) to explore how different C. sativa strains adapt to various light spectra, studying growth patterns and overall morphology; (2) to investigate how distinct light spectra affect yield composition, revealing strain-specific responses to light exposure; and (3) to examine the influence of red to far-red light ratio on plant growth traits and biomass production. The publication Ⅰ involved three randomised light spectra (CHD, AP67 and SOL) and three different C. sativa strains (E19, A4 and KAN), each characterised by different growth habits. The primary objective was to estimate how these spectral variations affected plant morphology and yield. While most characteristics of the strains remained resilient to the effects of different light spectra, notable differences were observed in height and biomass distribution of main and side shoots. Plants grown under LED lamps showed a more compact growth pattern. Surprisingly, there were no discernible differences between light sources, spectra and C. sativa strains in total flower yield at 56 days after planting (DAP 56). However, changes in leaf fractions were observed as growth progressed, with sugar leaves emerging as a critical factor, particularly in the later stages of development. In the same experiment, the dried flower was divided into several flower positions to assess heterogeneity across the plant. These dried flowers from each strain were then analysed for cannabinoid and terpene composition. Detailed insights into these cannabinoid and terpene contents are provided in publication Ⅱ. The specific objectives of this thesis considered in this publication were (4) to study the impact of light spectra on the secondary metabolite development on different C. sativa strains and (5) to highlight the potential diversity of terpene and cannabinoid concentrations by identifying and comparing terpene profiles at different flower positions within each strain. Publication Ⅱ revealed a complex interaction between strain characteristics and light conditions, demonstrating that each strain retains its characteristic terpene profile regardless of light spectra. In particular, the research highlights the heterogeneity of secondary metabolites across different flower positions within the C. sativa plant, emphasising the critical role of light intensity and penetration in secondary metabolite production. Publication Ⅲ dealt with objective (6) to investigate how planting density affects individual yield, addressing competition dynamics among C. sativa to provide insights into optimal planting densities to maximise yield while considering space limitations and (7) to determine whether increased light intensity correlates with higher yields and concentrations of secondary metabolites. The main objective of publication Ⅲ was to understand the complex dynamics by which light-induced effects on individual plants can affect a high-density plant stock of 12 plants per m². The light intensity was increased from 680 PAR to 1200 PAR, a realistic level for C. sativa cultivation, and two experiments to achieve these objectives were conducted. The first experiment consisted of seven biomass sections to assess the influence of light on biomass distribution at a plant density of 2.66 plants per m². The results showed the potential of a low R: FR ratio to increase dry flower yield in the last ten days of flowering. The second experiment was designed to determine the impact of a light gradient on the distribution of secondary metabolites. Plant density remained constant throughout the experiment at 12 plants per m². The aim was to investigate if plant density correlated significantly with terpene and cannabinoid concentrations and if it induced variations in flower heterogeneity. The culmination of the findings from publications Ⅰ-Ⅲ and the ensuing discussion led to the development of an overall cultivation system consisting of three critical stages in the C. sativa growth cycle: 1) the vegetative phase under long-day conditions, 2) the initiation of flowers triggered by short-day photoperiods, and the subsequent biomass accumulation, culminating in 3) the ripening of flowers. The cultivation process begins with selecting a high-performance strain and producing healthy cuttings by propagation or hybrid seed. Rooted young plants are then placed in a suitable medium for the vegetative growth phase (stage one), characterised by long-day conditions (18:6). During this phase, the emphasis is on rapid development and biomass accumulation. In contrast, the plant structure is shaped by pruning. We recommend light defoliation of at least 20% and removal of lower lateral shoots. A gradual increase in light intensity from 400 to 950 PAR with an emphasis on 750 PAR is beneficial. Effective light spectra include SOL, AP67 and CHD, with 19%, 12% and 16% blue, respectively. Ideal conditions include CO2 levels of 900 ppm and temperatures around 25°C. In stage two (flowering), higher light levels and adapted fertilisation become important. Increased light intensity, especially at levels such as 1500 - 2000 PAR with 900 ppm CO2, will increase yield and potentially secondary metabolite production. Light spectra with a high share of green light around 510 nm and with an elevated green content can be beneficial under high intensities and densities. Controlled dimming strategies help maintain uniform light distribution, which is essential for homogenous terpene concentrations. Fertilisation should be dynamic with nitrogen concentrations below 240 mg N l-1 to avoid oxidative stress. In stage three (ripening), increasing FR (far red) can increase flower yield, making dynamic spectrum management valuable. Fertigation should be adjusted as biomass growth plateaus, gradually reducing nutrient levels in the final four weeks. At the same time, increasing the CO2 concentration to 1150 ppm at these lower N levels can benefit the final yield and secondary metabolite concentration. For this cultivation system to be successful, the fundamentals of precise environmental control, diverse strain selection and stable genetics are essential for medicinal C. sativa cultivation. Critical factors for cultivation include light intensity, distribution and penetration, and appropriate fertilisation. In addition, light uniformity and illumination within the canopy are essential for terpene standardisation. Pruning techniques and fertilisation should be adapted to the plant's growth stage. In summary, this thesis explores the dynamic field of C. sativa cultivation driven by legalisation. Recognising the key role of light in shaping successful cultivation techniques, this thesis contributes to a more comprehensive understanding of medicinal C. sativa cultivation.
Long-term trends in yield variance of temperate managed grassland
(2023) Macholdt, Janna; Hadasch, Steffen; Macdonald, Andrew; Perryman, Sarah; Piepho, Hans-Peter; Scott, Tony; Styczen, Merete Elisabeth; Storkey, Jonathan; Macholdt, Janna; Professorship of Agronomy, Institute of Agriculture and Nutritional Sciences, Martin-Luther-University Halle-Wittenberg, Halle (Saale), Germany; Hadasch, Steffen; Biostatistics Unit, Institute of Crop Science, University of Hohenheim, Stuttgart, Germany; Macdonald, Andrew; Protecting Crops and Environment, Rothamsted Research, Harpenden, UK; Perryman, Sarah; Computational and Analytical Sciences Department, Rothamsted Research, Harpenden, UK; Piepho, Hans-Peter; Biostatistics Unit, Institute of Crop Science, University of Hohenheim, Stuttgart, Germany; Scott, Tony; Protecting Crops and Environment, Rothamsted Research, Harpenden, UK; Styczen, Merete Elisabeth; Section of Environmental Chemistry and Physics, Department of Plant and Environmental Sciences, University of Copenhagen, Copenhagen, Denmark; Storkey, Jonathan; Protecting Crops and Environment, Rothamsted Research, Harpenden, UK
The management of climate-resilient grassland systems is important for stable livestock fodder production. In the face of climate change, maintaining productivity while minimizing yield variance of grassland systems is increasingly challenging. To achieve climate-resilient and stable productivity of grasslands, a better understanding of the climatic drivers of long-term trends in yield variance and its dependence on agronomic inputs is required. Based on the Park Grass Experiment at Rothamsted (UK), we report for the first time the long-term trends in yield variance of grassland (1965–2018) in plots given different fertilizer and lime applications, with contrasting productivity and plant species diversity. We implemented a statistical model that allowed yield variance to be determined independently of yield level. Environmental abiotic covariates were included in a novel criss-cross regression approach to determine climatic drivers of yield variance and its dependence on agronomic management. Our findings highlight that sufficient liming and moderate fertilization can reduce yield variance while maintaining productivity and limiting loss of plant species diversity. Plots receiving the highest rate of nitrogen fertilizer or farmyard manure had the highest yield but were also more responsive to environmental variability and had less plant species diversity. We identified the days of water stress from March to October and temperature from July to August as the two main climatic drivers, explaining approximately one-third of the observed yield variance. These drivers helped explain consistent unimodal trends in yield variance—with a peak in approximately 1995, after which variance declined. Here, for the first time, we provide a novel statistical framework and a unique long-term dataset for understanding the trends in yield variance of managed grassland. The application of the criss-cross regression approach in other long-term agro-ecological trials could help identify climatic drivers of production risk and to derive agronomic strategies for improving the climate resilience of cropping systems.
A comparative life cycle assessment of a new cellulose-based composite and glass fibre reinforced composites
(2023) Liu, Yuanxi; Lask, Jan; Kupfer, Robert; Gude, Maik; Feldner, Alexander; Liu, Yuanxi; Neutral Lightweight Engineering, Institute of Lightweight Engineering and Polymer Technology, Technische Universität Dresden, Dresden, Germany; Lask, Jan; Department of Biobased Resources in the Bioeconomy, Institute of Crop Science, University of Hohenheim, Stuttgart, Germany; Kupfer, Robert; Neutral Lightweight Engineering, Institute of Lightweight Engineering and Polymer Technology, Technische Universität Dresden, Dresden, Germany; Gude, Maik; Neutral Lightweight Engineering, Institute of Lightweight Engineering and Polymer Technology, Technische Universität Dresden, Dresden, Germany; Feldner, Alexander; Fibres & Composites, Heidenau, Germany
The use of renewable lightweight materials and the adoption of cleaner production are two effective approaches to reduce resource consumption, which contributes to meeting the industry’s environmental impact targets. In a previous study we found, that a miscanthus fibre reinforced cellulose acetate (CA-Miscanthus, 25 wt.%) can be a bio-based alternative to glass fibre reinforced polypropylene (PP-GF, 20 wt.%), as both materials exhibit similar mechanical properties. However, only limited information on the environmental benefits of using bio-based composites instead of their petroleum-based counterparts are available. In this study, we compare the environmental impact of ready to use compound of both materials in the cradle to gate system boundaries, including fibre cultivation, fractionation and refining, fibre pretreatment, and compounding. The functional unit is chosen based on the equivalent function of both materials. The environmental impact is determined using the Product Environmental Footprint (PEF) methodology. The results reveal that the CA-Mis composite has a higher environmental impact than the PP-GF composite in all categories observed, despite its biomass origin. As the primary reason for the high impact, the acetic anhydride use during CA production is identified. The study indicates that, though the bio-composite CA-Mis has mechanical properties comparable to PP-GF composites, it is not as eco-friendly as we initially assumed it to be.
The challenge to achieve a balanced fertilization management in intensive organic vegetable production – approaches for improvement
(2024) Stein, Sophie; Möller, Kurt
The nutrient supply – especially in stockless farms – is a major challenge for organic vegetable farms. Due to the lack of animal husbandry, the nutrient cycle within the farm is limited. At the same time, the nutrient flows in vegetable growing are very high due to the high nitrogen (N) and potassium (K) requirements of the crops. If the nutrient flows are not adapted to the needs of the crops, severe nutrient imbalances, yield or quality losses can occur. Fertilization with basic fertilizers such as manure or compost, based on the N-demand of the crops, can lead to an accumulation of phosphorus (P) in the soil in the long term. Fertilization with N-rich organic commercial fertilizers, on the other hand, is to some extent contradictory to the principles of organic farming due to their origin – mostly from conventional animal husbandry. Another possibility for the exclusive N supply of the farm is the targeted use of legumes with the ability for biological N-fixation (BNF). However, since the cultivation of fodder legumes or grain legumes plays a minor role in vegetable production without livestock, their use for fertilizer management is limited. The aim of this thesis was to optimize fertilizer management in vegetable production based on balanced nutrient budgets of the three main nutrients N, P and K, as well as to increase the supply of N within the farm through the N-fixation of legumes. In a farm survey, the status quo of nutrient management was determined and analyzed using nutrient budgets. In two systemic field trials, the contribution of the strategies legume winter cover crop and living mulch to the on-farm N supply was tested. The status quo of the budgets on organic vegetable farms without livestock shows average budget surpluses of 67.5 kg N ha-1, 2.06 kg P ha-1 and 0.26 kg K ha-1. Another result is that an increase in the N content of base fertilizers such as solid manure or champost leads to an increase in the P and K balance. In the long term, such a strategy carries the risk of nutrient enrichment in the soil. Strategies based on the use of large amounts of keratin fertilizers, on the other hand, have the opposite effect, namely a long-term depletion of P and K. The integration of legumes into the vegetable crop rotation shows that both strategies – leguminous winter cover crops as a preceding crop to white cabbage and leguminous living mulch in combination with white cabbage – lead to similar or even slightly higher cabbage yields than cultivation without legumes or green cover. The direct N-effect of the leguminous winter cover crop on the first crop of white cabbage is about 2/3 of the total N-effect, the N-effect on the second crop of winter wheat is about 1/3 of the total N-effect of the BNF. In the case of the living mulch biomass, which is only incorporated after cabbage cultivation, the direct N effect of BNF on the first main crop is less than 40 %. The N effect on the subsequent winter wheat crop is over 60 %. The results of this thesis show that organic vegetable farms face at least two major challenges in terms of nutrient management: They must implement nutrient management that ensures a balanced nutrient budget in the soil and on the farm while reducing N surpluses through more efficient use of internal and external N sources. This thesis provides important figures for the characterization and balancing of nutrient management in vegetable production. These figures can be used to address the challenge of balanced fertilization management.
Optimizing pome fruits storage
(2024) Balkees, Basem Mahmoud; Zörb, Christian
Horticultural perishables are prone to fast deterioration and high losses. As the volume of production increases, further challenges are imposed to preserve these valuable foods in terms of quantity and quality. Accelerated development in science and applied technologies has helped to radically prolong the useful post-harvest life of horticultural produce. Notable success has been achieved with apples and pears as a result of their comparatively higher storability. Effective procedures and techniques have been developed to handle these fruits, including pre- and post-harvest physical and chemical treatments, in conjunction with the cutting-edge storage systems. However, certain procedures cannot be universally applicable. Considerations such as genotypic differences, climatic variations, and production factors necessitate adaptation of post-harvest practices to accommodate changing variables. This thesis describes the findings of experiments conducted as a contribution to advance preservation practices for apples and pears. Furthermore, we sought to investigate the biological actions underlying changes in fruit quality during storage and how these were influenced by various treatments. The first experiment was conducted to preserve the quality of late-harvested ‘Galaxy’ apples during extended storage. The effects of 1-methylcyclopropene (1 MCP) treatment and storage conditions on postharvest quality were analysed. Alongside quality measures, indicators like ethylene production, respiration rate, 1 aminocyclopropane-1-carboxylic acid oxidase (ACO) activity, and membrane permeability were assessed. After 7 months storage and 7 days shelf-life, apples subjected to 1-MCP and controlled atmosphere (CA) exhibited reduced ethylene production, respiration rate, and ACO activity compared to untreated or regular atmosphere counterparts. The combination of controlled atmosphere and pre-storage 1 MCP was the most effective in lowering ACO activity. Irrespective of conditions, 1 MCP curtailed ethylene production, respiration rate, and ACO activity during shelf-life, maintaining fruit firmness and slowing acidity loss. Only controlled atmosphere preserved quality and minimized disorders for optimally harvested apples, not late-harvested ones. None of the treatments maintained late-harvested apples quality after long-term storage plus shelf-life. The second experiment evaluated the effects of two ethanol vapor doses (250 or 500 ppm) or 1 MCP (650 ppb) with or without ethylene application (150 ppm) on the metabolism and quality of the apple cultivars ‘Elstar’ and ‘Nicoter’, over 14 d of holding at room temperature (20 ± 2 °C). For both cultivars studied, ethanol vapor treatments, especially 500 ppm, slowed the ripening of apples and inhibited the effect of applied ethylene on the ethylene production and respiration, but not as much as the 1 MCP treatment in ‘Nicoter’ apples. Ethanol application also resulted in higher succinate, malate and total organic acids concentrations. Ethanol application significantly reduced the sucrose conversion to glucose and fructose, while the ethanol + ethylene treatment resulted in high total sugars, fructose and sorbitol concentration after 14 d at 20 °C. The ethanol application (500 ppm) also affected conversion of succinate to fumarate, suggesting the succinate dehydrogenase activity as one possible action point of ethanol on the apple fruit metabolism. The combination of ethanol + ethylene treatments had a different response as compared to their isolated application, affecting sugars and organic acids metabolism differently. Fruit treated with ethanol vapor maintained lower electrolyte leakage, higher flesh firmness, greener color and had more sound fruit. However, its application increased the pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) activity and also enhanced acetaldehyde and ethyl acetate accumulation, but in concentrations below the odor threshold reported in the literature. The 1-MCP treatment increased decay incidence compared to the other treatments, reducing the amount of sound fruit in ‘Nicoter’ apples, but allowed higher acidity maintenance after 14 d holding at room temperature. There was no incidence of external and internal physiological disorders in either of the cultivars. In a third experiment, we explored the effects of the interaction between controlled atmosphere and 1-MCP treatment on ‘Alexander Lucas’ pears in storage, aiming to minimize internal storage disorders. Following treatment with 1-MCP at 300 ppb, the fruit were stored either at -0.5 or 1.0 °C in regular air or in CA (2.0 kPa O2 plus <0.7 kPa CO2). After six months of storage, superficial scald did not develop in fruit. The highest occurrence of flesh browning (72.2 %) was observed in air-stored fruit at -0.5 °C without 1-MCP treatment. Storage in regular air at 1.0 °C combined with 1-MCP resulted in 88.8 % sound fruit. Conversely, 1-MCP increased the incidence of flesh and core browning under CA conditions. Both 1-MCP and CA maintained greener skin color and higher titratable acidity. No significant differences were found for fruit firmness, total soluble solids and ascorbic acid content between the treatments. In conclusion, the quality of ‘Alexander Lucas’ pear was best maintained during six months storage under regular air at 1.0 °C combined with 300 ppb 1-MCP treatment.
Limitations of soil-applied non-microbial and microbial biostimulants in enhancing soil P turnover and recycled P fertilizer utilization: A study with and without plants
(2024) Herrmann, Michelle Natalie; Griffin, Lydia Grace; John, Rebecca; Mosquera-Rodríguez, Sergio F.; Nkebiwe, Peteh Mehdi; Chen, Xinping; Yang, Huaiyu; Müller, Torsten
Introduction: Phosphorus recovery from waste streams is a global concern due to open nutrient cycles. However, the reliability and efficiency of recycled P fertilizers are often low. Biostimulants (BS), as a potential enhancer of P availability in soil, could help to overcome current barriers using recycled P fertilizers. For this, a deeper understanding of the influence of BSs on soil P turnover and the interaction of BSs with plants is needed. Methods: We conducted an incubation and a pot trial with maize in which we testednon-microbial (humic acids and plant extracts) and microbial BSs (microbial consortia) in combination with two recycled fertilizers for their impact on soil P turnover, plant available P, and plant growth. Results and discussion: BSs could not stimulate P turnover processes (phosphatase activity, microbial biomass P) and had a minor impact on calcium acetate-lactate extractable P (CAL-P) in the incubation trial. Even though stimulation of microbial P turnover by the microbial consortium and humic acids in combination with the sewage sludge ash could be identified in the plant trial with maize, this was not reflected in the plant performance and soil P turnover processes. Concerning the recycled P fertilizers, the CAL-P content in soil was not a reliable predictor of plant performance with both products resulting in competitive plant growth and P uptake. While this study questions the reliability of BSs, it also highlights the necessity toimprove our understanding and distinguish the mechanisms of P mobilization in soil and the stimulation of plant P acquisition to optimize future usage.
Loss of LaMATE impairs isoflavonoid release from cluster roots of phosphorus‐deficient white lupin
(2021) Zhou, Yaping; Olt, Philipp; Neuhäuser, Benjamin; Moradtalab, Narges; Bautista, William; Uhde‐Stone, Claudia; Neumann, Günter; Ludewig, Uwe
White lupin (Lupinus albus L.) forms brush‐like root structures called cluster roots under phosphorus‐deficient conditions. Clusters secrete citrate and other organic compounds to mobilize sparingly soluble soil phosphates. In the context of aluminum toxicity tolerance mechanisms in other species, citrate is released via a subgroup of MATE/DTX proteins (multidrug and toxic compound extrusion/detoxification). White lupin contains 56 MATE/DTX genes. Many of these are closely related to gene orthologs with known substrates in other species. LaMATE is a marker gene for functional, mature clusters and is, together with its close homolog LaMATE3, a candidate for the citrate release. Both were highest expressed in mature clusters and when expressed in oocytes, induced inward‐rectifying currents that were likely carried by endogenous channels. No citrate efflux was associated with LaMATE and LaMATE3 expression in oocytes. Furthermore, citrate secretion was largely unaffected in P‐deficient composite mutant plants with genome‐edited or RNAi‐silenced LaMATE in roots. Moderately lower concentrations of citrate and malate in the root tissue and consequently less organic acid anion secretion and lower malate in the xylem sap were identified. Interestingly, however, less genistein was consistently found in mutant exudates, opening the possibility that LaMATE is involved in isoflavonoid release.
Drought stress during anthesis alters grain protein composition and improves bread quality in field-grown Iranian and German wheat genotypes
(2021) Rekowski, Azin; Wimmer, Monika A.; Tahmasebi, Sirous; Dier, Markus; Kalmbach, Sarah; Hitzmann, Bernd; Zörb, Christian
Drought stress is playing an increasingly important role in crop production due to climate change. To investigate the effects of drought stress on protein quantity and quality of wheat, two Iranian (Alvand, Mihan) and four German (Impression, Discus, Rumor, Hybery) winter wheat genotypes, representing different quality classes and grain protein levels, were grown under field conditions in Eqlid (Iran) during the 2018–2019 growing season. Drought stress was initiated by interrupting field irrigation during the anthesis phase at two different stress levels. Drought stress at anthesis did not significantly change total grain protein concentration in any of the wheat genotypes. Similarly, concentrations of grain storage protein sub-fractions of albumin/globulin, gliadin and glutenin were unaltered in five of the six genotypes. However, analysis of protein sub-fractions by SDS polyacrylamide gel electrophoresis revealed a consistent significant increase in ω-gliadins with increasing drought stress. Higher levels of HMW glutenins and a reduction in LMW-C glutenins were observed exclusively under severe drought stress in German genotypes. The drought-induced compositional change correlated positively with the specific bread volume, and was mainly associated with an increase in ω-gliadins and with a slight increase in HMW glutenins. Despite the generally lower HMW glutenin concentrations of the Iranian genotypes and no effect of drought on the concentration of HMW sub-fraction, there was still high specific bread volume under drought. It is suggested that for the development of new wheat cultivars adapted to these challenging climatic conditions, the protein composition should be considered in addition to the yield and grain protein concentration.
Estimation of the P fertilizer demand of China using the LePA model
(2021) Yu, Wenjia; Li, Haigang; Nkebiwe, Peteh Mehdi; Li, Guohua; Müller, Torsten; Zhang, Junling; Shen, Jianbo
Modern phosphate (P) fertilizers are sourced from P rock reserves, a finite and dwindling resource. Globally, China is the largest producer and consumer of P fertilizer and will deplete its domestic reserves within 80 years. It is necessary to avoid excess P input in agriculture through estimating P demand. We used the legacy P assessment model (LePA) to estimate P demand based on soil P management at the county, regional, and country scales according to six P application rate scenarios: (1) rate in 2012 maintained; (2) current rate maintained in low-P counties and P input stopped in high-P counties until critical Olsen-P level (CP) is reached, after which rate equals P-removal; (3) rate decreased to 1–1.5 kg ha−1 year−1 in low-P counties after CP is reached and in high-P counties; (4) rate in each county decreased to 1–8 kg ha−1 year−1 after soil Olsen-P reached CP in low P counties; (5) rate in each county was kept at P-removal rate after reduction; (6) P input was kept at the rate lower than P-offtake rate after reduction. The results showed that the total P fertilizer demand of China was 750 MT P2O5, 54% of P fertilizer can be saved from 2013 to 2080 in China, and soil Olsen-P of all counties can satisfy the demand for high crop yields. The greatest potential to decrease P input was in Yangtze Plain and South China, which reached 60%. Our results provide a firm basis to analyze the depletion of P reserves in other countries.
Organic matter composition of digestates has a stronger influence on N2O emissions than the supply of ammoniacal nitrogen
(2021) Petrova, Ioana Petrova; Pekrun, Carola; Möller, Kurt
Manures can be treated by solid–liquid separation and more sophisticated, subsequent approaches. These processes generate fertilizers, which may differ in composition and N2O release potential. The aim of the study was to investigate the influence of processing-related changes in digestate composition on soil-derived N2O emissions after application to soil. For that purpose, N2O emissions within the first 7 weeks after fertilization with two raw and eight processed digestates (derived from solid–liquid separation, drying and pelletizing of separated solid, and vacuum evaporation of separated liquid) were measured in the field in 2015 and 2016. Additionally, an incubation experiment was run for 51 days to further investigate the effect of subsequent solid and liquid processing on soil-derived N2O release. The results showed that, only in 2016, the separation of digestate into solid and liquid fractions led to a decrease in N2O emissions in the following order: raw digestate > separated liquid > separated solid. N removal during subsequent processing of separated solid and liquid did not significantly influence the N2O emissions after fertilization. In contrast, the concentrated application of the final products led to contradictory results. Within the solid processing chain, utilization of pellets considerably increased the N2O emissions by factors of 2.7 (field, 2015), 3.5 (field, 2016), and 7.3 (incubation) compared to separated solid. Fertilization with N-rich ammonium sulfate solution led to the lowest emissions within the liquid processing chain. It can be concluded that the input of less recalcitrant organic C into the soil plays a greater role in N2O release after fertilization than the input of ammoniacal N. Digestate processing did not generally reduce emissions but apparently has the potential to mitigate N2O emissions substantially if managed properly.
Role of benzoic acid and lettucenin A in the defense response of lettuce against soil-borne pathogens
(2021) Windisch, Saskia; Walter, Anja; Moradtalab, Narges; Walker, Frank; Höglinger, Birgit; El-Hasan, Abbas; Ludewig, Uwe; Neumann, Günter; Grosch, Rita
Soil-borne pathogens can severely limit plant productivity. Induced defense responses are plant strategies to counteract pathogen-related damage and yield loss. In this study, we hypothesized that benzoic acid and lettucenin A are involved as defense compounds against Rhizoctonia solani and Olpidium virulentus in lettuce. To address this hypothesis, we conducted growth chamber experiments using hydroponics, peat culture substrate and soil culture in pots and minirhizotrons. Benzoic acid was identified as root exudate released from lettuce plants upon pathogen infection, with pre-accumulation of benzoic acid esters in the root tissue. The amounts were sufficient to inhibit hyphal growth of R. solani in vitro (30%), to mitigate growth retardation (51%) and damage of fine roots (130%) in lettuce plants caused by R. solani, but were not able to overcome plant growth suppression induced by Olpidium infection. Additionally, lettucenin A was identified as major phytoalexin, with local accumulation in affected plant tissues upon infection with pathogens or chemical elicitation (CuSO4) and detected in trace amounts in root exudates. The results suggest a two-stage defense mechanism with pathogen-induced benzoic acid exudation initially located in the rhizosphere followed by accumulation of lettucenin A locally restricted to affected root and leaf tissues.
Characterization of epidermal bladder cells in Chenopodium quinoa
(2021) Otterbach, Sophie L.; Khoury, Holly; Rupasinghe, Thusitha; Mendis, Himasha; Kwan, Kim H.; Lui, Veronica; Natera, Siria H. A.; Klaiber, Iris; Allen, Nathaniel M.; Jarvis, David E.; Tester, Mark; Roessner, Ute; Schmöckel, Sandra M.
Chenopodium quinoa (quinoa) is considered a superfood with its favourable nutrient composition and being gluten free. Quinoa has high tolerance to abiotic stresses, such as salinity, water deficit (drought) and cold. The tolerance mechanisms are yet to be elucidated. Quinoa has epidermal bladder cells (EBCs) that densely cover the shoot surface, particularly the younger parts of the plant. Here, we report on the EBC's primary and secondary metabolomes, as well as the lipidome in control conditions and in response to abiotic stresses. EBCs were isolated from plants after cold, heat, high‐light, water deficit and salt treatments. We used untargeted gas chromatography–mass spectrometry (GC–MS) to analyse metabolites and untargeted and targeted liquid chromatography‐MS (LC–MS) for lipids and secondary metabolite analyses. We identified 64 primary metabolites, including sugars, organic acids and amino acids, 19 secondary metabolites, including phenolic compounds, betanin and saponins and 240 lipids categorized in five groups including glycerolipids and phospholipids. We found only few changes in the metabolic composition of EBCs in response to abiotic stresses; these were metabolites related with heat, cold and high‐light treatments but not salt stress. Na+ concentrations were low in EBCs with all treatments and approximately two orders of magnitude lower than K+ concentrations.
Assessment of a postharvest treatment with pyrimethanil via thermo-nebulization in controlling storage rots of apples
(2021) Büchele, Felix; Neuwald, Daniel A.; Scheer, Christian; Wood, Rachael M.; Vögele, Ralf T.; Wünsche, Jens N.
Apples are very susceptible to infections from various fungal pathogens during the growing season due to prolonged exposure to environmental influences in the field. Therefore, a strict and targeted fungicide strategy is essential to protect fruit and trees. Increased environmental and health concerns and pathogen resistance have resulted in a rising demand to reduce fungicide usage and residues on marketed fruit. Thus, producers must develop new plant protection strategies to conform to the legal and social demands while still offering high-quality apples. This study assessed the efficacy of a post-harvest fungicide treatment with pyrimethanil via thermo-nebulization for controlling storage rots and compared the results to those of standard pre-harvest fungicide strategies. The results showed that a single post-harvest application of pyrimethanil successfully controlled storage rots and is comparable to strategies using multiple pre-harvest fungicide applications. The control of fungal rot was sustained even after 5 months of storage and 2 weeks of shelf life. Thermo-nebulization into the storage facility allowed for a lower dosage of fungicide to be used compared to pre-harvest applications, while still maintaining optimal rot control. Residue analyses showed that the post-harvest fungicide treatment did not exceed legal or retailer’s standards.
Impacts of carbon dioxide enrichment on landrace and released Ethiopian barley (Hordeum vulgare L.) cultivars
(2021) Gardi, Mekides Woldegiorgis; Malik, Waqas Ahmed; Haussmann, Bettina I. G.
Barley (Hordeum vulgare L.) is an important food security crop due to its high-stress tolerance. This study explored the effects of CO2 enrichment (eCO2) on the growth, yield, and water-use efficiency of Ethiopian barley cultivars (15 landraces, 15 released). Cultivars were grown under two levels of CO2 concentration (400 and 550 ppm) in climate chambers, and each level was replicated three times. A significant positive effect of eCO2 enrichment was observed on plant height by 9.5 and 6.7%, vegetative biomass by 7.6 and 9.4%, and grain yield by 34.1 and 40.6% in landraces and released cultivars, respectively. The observed increment of grain yield mainly resulted from the significant positive effect of eCO2 on grain number per plant. The water-use efficiency of vegetative biomass and grain yield significantly increased by 7.9 and 33.3% in landraces, with 9.5 and 42.9% improvement in released cultivars, respectively. Pearson’s correlation analysis revealed positive relationships between grain yield and grain number (r = 0.95), harvest index (r = 0.86), and ear biomass (r = 0.85). The response of barley to eCO2 was cultivar dependent, i.e., the highest grain yield response to eCO2 was observed for Lan_15 (122.3%) and Rel_10 (140.2%). However, Lan_13, Land_14, and Rel_3 showed reduced grain yield by 16, 25, and 42%, respectively, in response to eCO2 enrichment. While the released cultivars benefited more from higher levels of CO2 in relative terms, some landraces displayed better actual values. Under future climate conditions, i.e., future CO2 concentrations, grain yield production could benefit from the promotion of landrace and released cultivars with higher grain numbers and higher levels of water-use efficiency of the grain. The superior cultivars that were identified in the present study represent valuable genetic resources for future barley breeding.
High-throughput field phenotyping reveals genetic variation in photosynthetic traits in durum wheat under drought
(2021) Zendonadi dos Santos, Nícolas; Piepho, Hans‐Peter; Condorelli, Giuseppe Emanuele; Licieri Groli, Eder; Newcomb, Maria; Ward, Richard; Tuberosa, Roberto; Maccaferri, Marco; Fiorani, Fabio; Rascher, Uwe; Muller, Onno
Chlorophyll fluorescence (ChlF) is a powerful non‐invasive technique for probing photosynthesis. Although proposed as a method for drought tolerance screening, ChlF has not yet been fully adopted in physiological breeding, mainly due to limitations in high‐throughput field phenotyping capabilities. The light‐induced fluorescence transient (LIFT) sensor has recently been shown to reliably provide active ChlF data for rapid and remote characterisation of plant photosynthetic performance. We used the LIFT sensor to quantify photosynthesis traits across time in a large panel of durum wheat genotypes subjected to a progressive drought in replicated field trials over two growing seasons. The photosynthetic performance was measured at the canopy level by means of the operating efficiency of Photosystem II (Fq′/Fm′) and the kinetics of electron transport measured by reoxidation rates (Fr1′ and Fr2′). Short‐ and long‐term changes in ChlF traits were found in response to soil water availability and due to interactions with weather fluctuations. In mild drought, Fq′/Fm′ and Fr2′ were little affected, while Fr1′ was consistently accelerated in water‐limited compared to well‐watered plants, increasingly so with rising vapour pressure deficit. This high‐throughput approach allowed assessment of the native genetic diversity in ChlF traits while considering the diurnal dynamics of photosynthesis.
Potential of impedance flow cytometry to assess the viability and quantity of Cannabis sativa L. pollen
(2021) Rafiq, Hamza; Hartung, Jens; Burgel, Lisa; Röll, Georg; Graeff-Hönninger, Simone
Over the last decade, efforts to breed new Cannabis sativa L. cultivars with high Cannabidiol (CBD) and other non-psychoactive cannabinoids with low tetrahydrocannabinol (THC) levels have increased. In this context, the identification of the viability and quantity of pollen, which represents the fitness of male gametophytes, to accomplish successful pollination is of high importance. The present study aims to evaluate the potential of impedance flow cytometry (IFC) for the assessment of pollen viability (PV) and total number of pollen cells (TPC) in two phytocannabinoid-rich cannabis genotypes, KANADA (KAN) and A4 treated with two different chemical solutions, silver thiosulfate solution (STS) and gibberellic acid (GA3). Pollen was collected over a period of 8 to 24 days after flowering (DAF) in a greenhouse experiment. Impedance flow cytometry (IFC) technology was used with Cannabis sativa to assess the viability and quantity of pollen. The results showed that the number of flowers per plant was highest at 24 DAF for both genotypes, A4 (317.78) and KAN (189.74). TPC induced by STS was significantly higher compared to GA3 over the collection period of 8 to 24 DAF with the highest mean TPC of 1.54 × 105 at 14 DAF. STS showed significantly higher viability of pollen compared to GA3 in genotype KAN, with the highest PV of 78.18% 11 DAF. Genotype A4 also showed significantly higher PV with STS at 8 (45.66%), 14 (77.88%), 18 (79.37%), and 24 (51.92%) DAF compared to GA3. Furthermore, counting the numbers of flowers did not provide insights into the quality and quantity of pollen; the results showed that PV was highest at 18 DAF with A4; however, the number of flowers per plant was 150.33 at 18 DAF and was thus not the maximum of produced flowers within the experiment. IFC technology successfully estimated the TPC and differentiated between viable and non-viable cells over a period of 8 to 24 DAF in tested genotypes of Cannabis sativa. IFC seems to be an efficient and reliable method to estimate PV, opening new chances for plant breeding and plant production processes in cannabis.
Impact of harvest time and pruning technique on total CBD concentration and yield of medicinal cannabis
(2022) Crispim Massuela, Danilo; Hartung, Jens; Munz, Sebastian; Erpenbach, Federico; Graeff-Hönninger, Simone
The definition of optimum harvest and pruning interventions are important factors varying inflorescence yield and cannabinoid composition. This study investigated the impact of (i) harvest time (HT) and (ii) pruning techniques (PT) on plant biomass accumulation, CBD and CBDA-concentrations and total CBD yield of a chemotype III medical cannabis genotype under indoor cultivation. The experiment consisted of four HTs between 5 and 11 weeks of flowering and three PTs-apical cut (T); removal of side shoots (L) and control (C), not pruned plants. Results showed that inflorescence dry weight increased continuously, while the total CBD concentration did not differ significantly over time. For the studied genotype, optimum harvest time defined by highest total CBD yield was found at 9 weeks of flowering. Total CBD-concentration of inflorescences in different fractions of the plant’s height was significantly higher in the top (9.9%) in comparison with mid (8.2%) and low (7.7%) fractions. The T plants produced significantly higher dry weight of inflorescences and leaves than L and C. Total CBD yield of inflorescences for PTs were significantly different among pruned groups, but do not differ from the control group. However, a trend for higher yields was observed (T > C > L).
Wood-ash fertiliser and distance from drainage ditch affect the succession and biodiversity of vascular plant species in tree plantings on marginal organic soil
(2022) Zuševica, Austra; Celma, Santa; Neimane, Santa; von Cossel, Moritz; Lazdina, Dagnija
Cutaway peatland is a marginal land, which without further management is an unfavourable environment for plant growth due to low bearing capacity, high acidity and unbalanced nutrient composition of the soil. After wood-ash application, the soil becomes enriched with P and K, creating better conditions for tree growth. In addition to being economically viable, tree plantations ensure long-term carbon storage and promote habitat restoration. In a three-year term, we studied how distance from a drainage ditch and three different doses of wood-ash—5, 10, and 15 tons per hectare—affect the diversity of vascular plants in a tree plantation on a cutaway peatland. Plant species richness, vegetation cover and composition were positively affected by the distance from the drainage ditch and application with fertiliser, but in most cases, fertiliser dose had no significant effect. Both cover and species diversity were not affected by the planted tree species. In a tree plantation, herbaceous plants provide soil fertility by decay and recycling, and reduce mineral leaching in the long term. Since vascular plants play an important role in both the development of habitats and tree growth, it is important to know how multiple factors influence the development of vegetation in tree plantations.
Efficiency of phosphorus fertilizers derived from recycled biogas digestate as applied to maize and ryegrass in soils with different pH
(2022) Bach, Inga-Mareike; Essich, Lisa; Bauerle, Andrea; Müller, Torsten
Three phosphorus (P) fertilizer fractions recycled from biogas digestates were tested alone and in combination for their efficiency in two agricultural surface soils with different pH: a silty sandy loam and a clay loam. The experiments were carried out in pots under greenhouse conditions, using mineral triple superphosphate (TSP) as a reference. Maize was cultivated for 50 days, followed by ryegrass cultivation for an additional 84 days in the same soil, without additional fertilization. The variables investigated were above-ground plant biomass production, plant phosphorus concentration and content, and plant available phosphorus concentration in soil. The dry matter (DM) yield of maize was increased by the organic P fertilizers equal to or more than TSP in both soils. In the neutral soil, biomass was almost doubled compared to TSP when using one of the fractions (Struvite containing P-Salt) alone or in combination with dried solid fractions. P concentration in maize cultivated in the neutral soil was not significantly different between the P fertilization treatments. However, associated with biomass increase, the total P content in maize plants was equal to or higher than that with TSP. In the acidic soil, P concentration and total P content in maize plants, as well as the calcium-acetate-lactate extractable P (CAL-P) concentration in soil, were equal to or even higher than TSP. Ryegrass DM yield was unaffected by all P fertilizers, independent of the soil, although P concentration and total P content increased in the acidic soil with all fertilizers. Our results show that recycled P fertilizers from biogas digestates are effective P fertilizer alternatives to mineral TSP for maize cultivation under acidic and neutral soil conditions. The lack of growth effects in ryegrass indicates that recycled P fertilizers do not require changes in weed control. On the other hand, P extraction by ryegrass in overfertilized acidic soils as an option for soil remediation also works in soils fertilized with biogas digestate fractions.
A global network meta-analysis of the promotion of crop growth, yield, and quality by bioeffectors
(2022) Herrmann, Michelle Natalie; Wang, Yuan; Hartung, Jens; Hartmann, Tobias; Zhang, Wei; Nkebiwe, Peteh Mehdi; Chen, Xinping; Müller, Torsten; Yang, Huaiyu
Bioeffector (BE) application is emerging as a strategy for achieving sustainable agricultural practices worldwide. However, the effect of BE on crop growth and quality is still controversial and there is still no adequate impact assessment that determines factors on the efficiency of BE application. Therefore, we carried out a network metaanalysis on the effect of BEs using 1,791 global observations from 186 studies to summarize influencing factors and the impact of BEs on crop growth, quality, and nutrient contents. The results show that BEs did not only improve plant growth by around 25% and yield by 30%, but also enhanced crop quality, e.g., protein (55% increase) and soluble solids content (75% increase) as well as aboveground nitrogen (N) and phosphate (P) content by 28 and 40%, respectively. The comparisons among BE types demonstrated that especially non-microbial products, such as extracts and humic/amino acids, have the potential to increase biomass growth by 40–60% and aboveground P content by 54–110%. The soil pH strongly influenced the efficiency of the applied BE with the highest effects in acidic soils. Our results showed that BEs are most suitable for promoting the quality of legumes and increasing the yield of fruits, herbs, and legumes. We illustrate that it is crucial to optimize the application of BEs with respect to the right application time and technique (e.g., placement, foliar). Our results provide an important basis for future research on the mechanisms underlying crop improvement by the application of BEs and on the development of new BE products.

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