Institut für Kulturpflanzenwissenschaften

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Weaving knowledge, innovation, and learning: a transdisciplinary pathway to circular bioeconomy through BioBeo
(2025) Buruleanu, Claudia Lavinia; Chléirigh, Laoise Ní; Nic an Bhaird, Máire; Curran, Thomas P.; Reinmuth, Evelyn; Bîzoi, Mihai; Kyriakopoulos, Grigorios L.
The bioeconomy represents a new way of life for people, but also a responsibility towards the future of the planet. Generating a significant socio-economic impact, it could be viewed as a key element of sustainable development, as the current and future solution for economic processes, based on new development models compelled by climate changes and the economy’s resilience to potential crises. In this context, the paper presents in its first part the Circular Economy description and the Circular Bioeconomy discussion from an interdisciplinary perspective. The second part of the paper aims to explore education as a tool for facilitating systemic changes supporting a real transition to a sustainable bioeconomy. The key aspects discussed refer to the following: (1) European policies, strategies, and action plans for bioeconomy; (2) Circular Economy as a solution for sustainable food systems; (3) main requirements and challenges for developing a (Circular) Bioeconomy, including indicators of sustainability; (4) the links between Circular Bioeconomy and the Sustainable Development Goals; (5) possibilities for integrating the agri-food industry’s needs into bioeconomy education; and (6) pathways for teach bioeconomy concepts effectively.
Assessment of different methods to determine NH₃ emissions from small field plots after fertilization
(2025) Götze, Hannah; Brokötter, Julian; Frößl, Jonas; Kelsch, Alexander; Kukowski, Sina; Pacholski, Andreas Siegfried; Anderson, William A.
Ammonia (NH₃) emissions affect the environment, climate and human health and originate mainly from agricultural sources like synthetic nitrogen fertilizers. Accurate and replicable measurements of NH₃ emissions are crucial for research, inventories and evaluation of mitigation measures. There exist specific application limitations of NH₃ emission measurement techniques and a high variability in method performance between studies, in particular from small plots. Therefore, the aim of this study was the assessment of measurement methods for ammonia emissions from replicated small plots. Methods were evaluated in 18 trials on six sites in Germany (2021–2022). Urea was applied to winter wheat as an emission source. Two small-plot methods were employed: inverse dispersion modelling (IDM) with atmospheric concentrations obtained from Alpha samplers and the dynamic chamber Dräger tube method (DTM). Cumulative NH₃ losses assessed by each method were compared to the results of the integrated horizontal flux (IHF) method using Alpha samplers (Alpha IHF) as a micrometeorological reference method applied in parallel large-plot trials. For validation, Alpha IHF was also compared to IHF/ZINST with Leuning passive samplers. Cumulative NH₃ emissions assessed using Alpha IHF and DTM showed good agreement, with a relative root mean square error (rRMSE) of 11%. Cumulative emissions assessed by Leuning IHF/ZINST deviated from Alpha IHF, with an rRMSE of 21%. For low-wind-speed and high-temperature conditions, NH3 losses detected with Alpha IDM had to be corrected to give acceptable agreement (rRMSE 20%, MBE +2 kg N ha−1). The study shows that quantification of NH₃ emissions from small plots is feasible. Since DTM is constrained to specific conditions, we recommend Alpha IDM, but the approach needs further development.
Yield stability and weed dry matter in response to field-scale soil variability in pea-oat intercropping
(2025) Munz, Sebastian; Zachmann, Julian; Chongtham, Iman Raj; Dhamala, Nawa Raj; Hartung, Jens; Jensen, Erik Steen; Carlsson, Georg
Background and aims: Intercropping of grain legumes and cereals in European agriculture can provide benefits, such as an increase in yields, yield stability and weed suppression. Interactions between crops in intercropping may depend on spatial heterogeneity in soil conditions, which are present on farmers’ fields. Understanding the effect of within-field variation in soil conditions on interspecific interactions might increase the benefits of intercropping by within-field adjustment of the agronomic management. Methods: Crop performance and weed dry matter were assessed together with several soil properties in grids within three large field experiments at two sites (Germany and Sweden) and during two years. Each experiment was comprised of several strips sown either with the two sole crops oat ( Avena sativa L.) and field pea ( Pisum sativum L.) or an oat-pea intercrop. Results: The response of crop performance to within-field variability in soil conditions was mostly species-specific. Yield stability of intercropping was consistently higher compared with pea, but not compared to oat. The highest land equivalent ratio was found for an additive intercropping design under a higher water availability. In this experiment, yield stability of both intercropped pea and oat were lower, which might be expected as a result of within-field variation in interspecific interactions. Intercropping reduced weed dry matter compared to pea, for which one experiment indicated an increase in weed dry matter with nutrient availability. Conclusion: The experimental design and the developed statistical analysis can contribute to further research about spatial variations in interspecific interactions in intercropping, which will improve the understanding of plant-plant and plant-soil interactions.
Digestate composition affecting nitrogen fertilizer value, soil carbon mineralization, and nitrous oxide emissions
(2025) Häfner, Franziska; Möller, Kurt
The variety of organic feedstocks that can be used for anaerobic digestion leads to digestates with different physico-chemical compositions. Different feedstocks yield distinct digestate compositions, hence different fertilizer potential, which consequently may affect carbon (C) and nitrogen (N) cycling in soils. This present thesis aimed to explore the relationship between feedstocks used for anaerobic digestion, digestate composition and fertilizer properties, and their consequences for agricultural and environmental sustainability. It was investigated, how digestate properties can be related to its N fertilizer value, C storage potential, or greenhouse gas (GHG) emission potential. Two experiments were conducted to assess (i) differences in the N fertilizer value of seven digestates from different feedstocks in a practice-oriented 2-year field experiment with spring wheat on a silty loam, with two different application techniques and (ii) the degradability of organic matter (OM) in the digestates within an aerobic incubation experiment for 56 days. In addition, digestates were labeled with the stable isotope 15N, either in both NH4+-N and organic N, or only in NH4+-N. Those labeled digestates were examined in a 2-year field experiment to assess short-term nitrous oxide (N2O) emissions after application from the digestate and native soil-N pool. The labeled digestates were also examined in a pot study with a crop rotation of ryegrass and maize in a sandy and loamy soil. The 15N-labeling approach was applied to distinguish the N contribution in total N offtakes from the digestate, its solid and liquid fraction, and from the soil. In a first step, seven digestates from different feedstocks were collected from existing biogas plants either from farms or municipalities in Baden-Württemberg, Germany. The digestates showed differences in dry matter (DM), C/N ratio, ammonium (NH4+) concentration, macro nutrients, and salt content. The range was according to the literature, and no limits for heavy metals were exceeded. The food waste digestate stands out among the other digestates with lowest C/N ratio and raw fiber content, highest ammonium concentration and highest table salt (NaCl) content. In the field study, the mineral fertilizer equivalents (MFE) ranged from 18% to 60% in the 1st year and from 39% to 83% in the 2nd experimental year. Highest MFE in both years was exhibited with food waste (49-70%), while most other digestates from agricultural feedstocks showed MFE´s in the range of 28-49%. The fertilizer properties (C/N, lignin, acid detergent fiber (ADF), NH4+/N and organic C/organic N (Corg/Norg)) were found to predict 58.9-74.2% of the variance in N offtakes among the digestates. Incubation of the different digestates showed that 61% of the organic C added by food waste digestate had been mineralized after 56 days. In contrast, only 16-22% of the supplied organic C was decomposed for the other plant and manure-based digestates. The composition of the digestates could explain up to 90.4% of the CO2 evolution, with C/N being the predominant factor (35.5%), followed by ADF (26.5%), raw fiber content (9.2%), lignin (8.7%) Corg/Norg (6.7%) and Carbonate-C (1.2%). The pot study showed comparable N fertilizer replacement values (NFRV) as MFEs in the field, with 33.5-76.0% and 40.6-76.3%, in sand and loam, respectively. Highest NFRV was measured from sugar-beet and food-waste-based digestates, with on average 70% across the two soils. N offtakes and yield were affected by fertilizer, soil, and their interaction, meaning digestate performance among soils varied to different extents. Digestate`s N fertilizer value could be related to three main compositional parameters (C/N, Corg/Norg, NH4+/N), which accounted for 44.5% of the variance of total N offtakes. Digestate-15N recovery in aboveground biomass after five applications showed that between 28-78% of N was derived from the digestates. Total 15N-fertilizer recovery in biomass was 18-43% among digestates and did not correspond to higher total N offtakes or N use efficiency (NUE). The solid fraction within the raw digestate contributed only 4.0-8.3% to digestate-N offtakes, compared to 32.5-45.3% from the liquid fraction. N mineralization of the solids was estimated at 6-13% after five applications. Cumulative N2O emissions after application of the different digestates were higher in the 1st year (312–1580 g N2O-N ha⁻¹) compared to the emissions (133–690 g N2O-N ha⁻¹) in the 2nd year. Differences among digestates were only found in the 1st year, where sugar beet leaves had higher cumulative N2O than digestates from cattle slurry or food waste. Emission factors determined in the two years’ field study (0.21–0.75%) were all within the range of the IPCC default value. Based on 15N-labeling, it could be observed, that only 16–38% of N2O emissions originated from digestate N. From the results of field, pot, and incubation study, it can be concluded that differences in fertilizer value and OM stability are related to variations in digestate composition. Differences in C mineralization depend on the overall degradability of the digestates, as shown by C/N and fiber fractions. However, the relevance for yield, N recovery and C storage potential is in most cases rather low, except for digestates with very distinct properties, such as food waste or sugar beet digestates. The 15N labeling of digestates shows that the N taken up by the majority of digestate-treated crops derived more than 50% of N from the soil pool, underlining the significance of the soil for N supply via mineralization. After several crop cycles and applications of digestate, it appears that the impact of soil on digestate-derived 15N efficiency decreases. With repeated application and mineralization of Norg from the solids, the initially 2.4-4.6% lower N availability of the applied 15N from the solid fraction increased to a similar range as the NUE of the liquid fraction (~31-24%). The eight labeled digestates showed differences in NUE and 15N recovery rates, which indicate different impacts of the digestates on N immobilization and mineralization in the soil. Field application of the 15N-digestates shows that more than 60% of N2O emissions originate from the native soil N pool. The first peak following fertilization contained mainly soil N, presumably due to denitrification of soil nitrate, likely induced by the applied OM. Whereas later N2O peaks after rainfall events contained more denitrified digestate-N, as indicated by 15N signals in N2O, signifying that digestate derived N becomes the primary N source. It can be concluded that for N2O emissions that after digestate application, the main N source for emissions is the soil N pool, probably triggered by the supplied OM. Furthermore, the influence of environmental factors such as water-filled pore-space and soil N pool, on overall N2O emissions are of main relevance, and less the digestate type. In summary, while digestate composition does have some influence on its performance as fertilizer, the broader context of environmental conditions and the role of native soil N pools are of higher significance than the feedstock. Understanding these factors will be crucial for optimizing the use of digestates in agricultural and environmental management practice.
The diversity of quinoa morphological traits and seed metabolic composition
(2022) Tabatabaei, Iman; Alseekh, Saleh; Shahid, Mohammad; Leniak, Ewa; Wagner, Mateusz; Mahmoudi, Henda; Thushar, Sumitha; Fernie, Alisdair R.; Murphy, Kevin M.; Schmöckel, Sandra M.; Tester, Mark; Mueller-Roeber, Bernd; Skirycz, Aleksandra; Balazadeh, Salma
Quinoa (Chenopodium quinoa Willd.) is an herbaceous annual crop of the amaranth family (Amaranthaceae). It is increasingly cultivated for its nutritious grains, which are rich in protein and essential amino acids, lipids, and minerals. Quinoa exhibits a high tolerance towards various abiotic stresses including drought and salinity, which supports its agricultural cultivation under climate change conditions. The use of quinoa grains is compromised by anti-nutritional saponins, a terpenoid class of secondary metabolites deposited in the seed coat; their removal before consumption requires extensive washing, an economically and environmentally unfavorable process; or their accumulation can be reduced through breeding. In this study, we analyzed the seed metabolomes, including amino acids, fatty acids, and saponins, from 471 quinoa cultivars, including two related species, by liquid chromatography – mass spectrometry. Additionally, we determined a large number of agronomic traits including biomass, flowering time, and seed yield. The results revealed considerable diversity between genotypes and provide a knowledge base for future breeding or genome editing of quinoa.
Fiber hemp biomass yield and quality on shallow stony soil in Southwest Germany
(2025) Greiner, Beatrice E.; Kunisch, Jana; Krauße, Galina; Thiel, Theresa; Schwadorf, Klaus; von Cossel, Moritz; Kabala, Cezary
Shallow arable soils (<35 cm depth) are classified as marginal for common agriculture but may still support biomass production from industrial crops like fiber hemp, which has a low indirect land-use change risk. However, little is known about hemp’s performance under such conditions. Therefore, this study investigated the biomass yield and quality of fiber hemp and other crops on a shallow (<35 cm), stony (>15% stone content), and clay-rich (>50% clay content) soil at 800 m above sea level in Southwest Germany (2018–2021). A randomized field trial tested different row widths and nitrogen (N) fertilization levels to assess low-input options for the given type of marginal land. Across years and row widths, hemp achieved average grain dry matter (DM) yields of 1.3 Mg/ha at a fertilization rate of 40 kg N/ha and 1.6 Mg/ha at 120 kg N/ha (with on average 30.9 ± 1.4% crude fat content across treatments). The average stem DM yields accounted for 5.11 Mg/ha (40 kg N/ha) and 6.08 Mg/ha (120 kg N/ha), respectively. Reduced N fertilization (40 kg/ha) lowered DM yields by up to 16% compared to full fertilization (120 kg/ha), but the effect was not significant and weaker at wider row spacing (45 cm). Additionally, maize reached acceptable DM yields (>17 Mg/ha). These findings suggest that shallow soils classified as marginal require reassessment, as they may offer viable opportunities for sustainable industrial hemp cultivation and contribute to a bio-based economy.
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.
Recurrent drought stress in grapevines
(2025) Lehr, Patrick Pascal; Zörb, Christian
Climate change is expected to increase the frequency and intensity of drought, impacting global agricultural production. To maintain food production under these changing conditions, it is crucial to understand how plants respond to drought and the mechanisms they use to cope with water deficit. Drought events frequently occur multiple times during a growing season, potentially leading to stress memory in plants, where responses of primed plants to subsequent droughts are modified. The regulation of transpiration by controlling the stomata is of great relevance under drought stress. Therefore, it is of particular interest to investigate the metabolic processes occurring in guard cells. The role of guard cells in stress memory and the signals involved in stomatal regulation remain under active investigation. A possible signal from root to shoot under drought conditions, leading to stomatal closure via abscisic acid biosynthesis is an increased sulfate concentrations in xylem sap. Therefor three questions were investigated: (i) How does the metabolic acclimation of guard cells in grapevine and maize under recurrent drought stress differ from the acclimation of mesophyll cells? (ii) Can additional sulfate application modify the drought response of these crops? (iii) What are the drought stress strategies of grapevine and maize, and how can agricultural production utilise these strategies? The analysis of metabolites of grapevine and maize mesophyll cells showed that the metabolite profiles of plants that have been subjected to repeated drought stress showed less alteration than those of unprimed plants, indicating that primed plants were less stressed. The metabolome of grapevine and maize guard cells was less affected by drought stress than that of mesophyll cells. This suggests that plants prioritize the stability of guard cell metabolomes to maintain stomatal function during stress. In contrast, grapevine and maize guard cells showed a similar increase in sugar concentrations during drought compared to mesophyll cells. It is debated whether sugars like sucrose, glucose, and fructose have an osmotic effect on guard cells or if they are sensed by hexokinases within the guard cells, which may trigger stomatal closure, thus coordinating sugar levels and photosynthesis with transpiration. Phosphorylated hexoses can be metabolized to pyruvate, which can feed into the citrate cycle and provide energy in the guard cells. They can also be used for the synthesis of metabolites such as malate, which influence stomatal opening. The distinct regulation of sugar concentrations in guard cells of grapevine and maize, in contrast to other metabolite classes, like amino acids, highlights that sugar concentrations in guard cells play a pivotal role during drought stress. In conclusion, the acclimation of the guard cell metabolomes in grapevine and maize differs from that of the mesophyll cells. Sulfate is discussed as a xylem-derived chemical signal for abscisic acid-dependent stomatal closure during early drought stress. Therefore, additional sulfate application may improve sulfate availability under drought conditions, enhancing the drought response, as investigated in this study. The results show that both grapevine and maize leaf sulfate concentrations were increased under drought stress, but only when additional sulfate was applied. This increase in leaf sulfate with supplemental sulfate suggests that increased sulfate availability enhances the drought response, leading to improved metabolic acclimation in leaves. This underscores the importance of adequate sulfate supply for optimal drought stress response and suggests that sulfate fertilization could enhance drought acclimation in crops. The results also show that changes in sulfate availability have a faded impact on the metabolome of guard cells compared to mesophyll cells. This, combined with the reduced metabolic acclimation of guard cells under drought conditions, suggests that guard cells maintain higher metabolic stability against external stress factors. The comparison between grapevine and maize drought stress response revealed that maize shows a more intense metabolic reorganization in response to drought stress, which may enhance its stress resilience and improve survival chances during droughts. However, this rapid reorganization comes at a cost, as it requires resources such as energy and nutrients to synthesize stress-defence molecules. These resources are diverted from other plant functions, potentially reducing yield and product quality. Additionally, the process of re-acclimating to well-watered conditions following a drought event also demands energy investment. In some cases, secondary metabolites such as carotenoids or anthocyanins accumulate in plants during drought and can remain even after the drought ends, altering the quality of harvested products, as seen in grapevine. This suggests that genotypes with a reduced response to drought may have advantages for agricultural production, especially in environments with more favourable conditions. Nevertheless, a rapid and intense metabolic response can be beneficial in cases of severe or prolonged drought, or when combined with other stress factors like heat. In such situations, quick acclimation can be vital for crop survival, allowing the plant to resume growth once the drought ends. A cell type-specific reaction, as seen in guard cells, in which only certain cells adapt metabolically, offers the chance of a resource-saving adaptation. The concept of increased acclimation to drought improving fitness during stress but potentially reducing yield applies to priming effects as well. Stress memory, where drought stress induces lasting effects beyond the drought period, may lead to higher costs or lower yields during favourable conditions. However, if another drought occurs, plants with stress memory are better adapted and show increased fitness during the unfavourable period. For crops, priming is advantageous in regions with frequent drought, while reduced stress memory may be beneficial in areas with optimal conditions.
Drought impacts on plant–soil carbon allocation - integrating future mean climatic conditions
(2025) Leyrer, Vinzent; Blum, Juliette; Marhan, Sven; Kandeler, Ellen; Zimmermann, Telse; Berauer, Bernd J.; Schweiger, Andreas H.; Canarini, Alberto; Richter, Andreas; Poll, Christian
Droughts affect soil microbial abundance and functions—key parameters of plant–soil carbon (C) allocation dynamics. However, the impact of drought may be modified by the mean climatic conditions to which the soil microbiome has previously been exposed. In a future warmer and drier world, effects of drought may therefore differ from those observed in studies that simulate drought under current climatic conditions. To investigate this, we used the field experiment ‘Hohenheim Climate Change,’ an arable field where predicted drier and warmer mean climatic conditions had been simulated for 12 years. In April 2021, we exposed this agroecosystem to 8 weeks of drought with subsequent rewetting. Before drought, at peak drought, and after rewetting, we pulse‐labelled winter wheat in situ with 13CO2 to trace recently assimilated C from plants to soil microorganisms and back to the atmosphere. Severe drought decreased soil respiration (−35%) and abundance of gram‐positive bacteria (−15%) but had no effect on gram‐negative bacteria, fungi, and total microbial biomass C. This pattern was not affected by the mean precipitation regime to which the microbes had been pre‐exposed. Reduced mean precipitation had, however, a legacy effect by decreasing the proportion of recently assimilated C allocated to the microbial biomass C pool (−50%). Apart from that, continuous soil warming was an important driver of C fluxes throughout our experiment, increasing plant biomass, root sugar concentration, labile C, and respiration. Warming also shifted microorganisms toward utilizing soil organic matter as a C source instead of recently assimilated compounds. Our study found that moderate shifts in mean precipitation patterns can impose a legacy on how plant‐derived C is allocated in the microbial biomass of a temperate agroecosystem during drought. The overarching effect of soil warming, however, suggests that how temperate agroecosystems respond to drought will mainly be affected by future temperature increases.
Lentils can absorb amino acids as a nitrogen source supporting early growth
(2025) Kröper, Alex A.; Zikeli, Sabine; Wimmer, Monika A.; Zörb, Christian
Background: Lentils ( Lens culinaris Medik.) are a valuable crop due to their high nutritional content, low environmental impact, and nitrogen‐fixing ability via rhizobacteria. Early in development, before this symbiosis is established, lentils require external nitrogen, typically supplied through fertilizers or already present in soils. Aim: This study explores whether lentils can utilize amino acids as a nitrogen source and how amino acid supplementation affects growth and nitrate uptake. Results: The findings show that lentils can absorb amino acids from soil, with no adverse effects on growth compared to mineral N fertilizers. The amino acid patterns show only slight changes in individual amino acids. NPF/NRT1, NRT2, AMT2, and DUR3 were expressed in all treatments in root tissue. LHT1 plays a minor role in the distribution of N in the shoots of lentil plants. Conclusion: Although amino acid uptake is less efficient than that of nitrate, it may still benefit young plants in organic farming until rhizobacterial symbiosis is established.
Urban waste fertilizer: effects on yield, nutrient dynamics, and potentially toxic element accumulation
(2025) Reimer, Marie; Möller, Kurt; Magid, Jakob; Bruun, Sander
Recycling nutrients contained in urban wastes to agriculture is essential in a circular economy. This study simultaneously compares different recycled fertilizers (household waste compost, sewage sludge, human urine) with mineral fertilization and animal manures. Tested were their long-term effects on yield, nutrient budgets, potentially toxic element (PTE) accumulation, and nitrogen (N)/carbon (C) cycle (among others N efficiency, N losses, soil C). Therefore, data from a long-term field trial and predictions from the soil–plant-atmosphere model Daisy were evaluated. Based on trial data, human urine performed similar to the mineral fertilization for yield, N efficiency (mineral fertilizer equivalent (MFE) = 81%), and nutrient budget, while sewage sludge and compost were comparable to animal manures in terms of having lower yields, N efficiencies (MFE 70% and 19% respectively) and higher nutrient imbalances, especially P and S surpluses. Compost and sewage sludge applications resulted in net PTE inputs. Yet, plant uptake and soil accumulation seemed neglectable. Model outputs predicted N losses of 34–55% of supplied N. Losses were highest for compost, followed by deep litter, manure, sewage sludge, human urine, mineral fertilization, and slurry. Nitrate leaching was the main loss pathway (14–41% of N input). Within the compost and straw-rich manure fertilization, about 25% of applied N was stored in the soil which was accompanied by an increase in soil C. The study suggests substitution of established fertilizers with recycled ones is feasible. Thereby each fertilizer has advantages and disadvantages and thus should be utilized according to its strength or in mixtures.
Comprehensive evaluation of the DSSAT‐CSM‐CERES‐Wheat for simulating winter rye against multi‐environment data in Germany
(2024) Shawon, Ashifur Rahman; Memic, Emir; Kottmann, Lorenz; Uptmoor, Ralf; Hackauf, Bernd; Feike, Til
Crop models are valuable tools for simulating and assessing genotype‐by‐environment interactions. In most studies, these models are parameterized based on crop data from a few sites and years, which often limits their applicability to a broader geographic context. Therefore, we utilize countrywide multi‐environment variety trial data in this study to implement a genotype‐specific model parameterization for winter rye ( Secale cereale L.) in Germany. We use the Crop and Environment REsource Synthesis (CERES) model originally used for wheat available in the decision support system for agrotechnology transfer (DSSAT) framework and adapt and evaluate it for rye. Calibration and evaluation involved a comprehensive agronomic trial datasets for the rye cultivar Palazzo, encompassing 194 site‐years of experiments covering various cereal production regions in Germany. The parameterization followed a structured approach, encompassing phenology, growth, and yield‐specific coefficients. The parameterized CSM‐CERES‐Rye (where CSM is cropping system model) demonstrated reasonable accuracy in simulating critical crop parameters, including aboveground biomass, leaf area index, tiller, grain number, unit seed weight, and grain yield. The model is available for diverse model‐based assessments of rye cultivation, including evaluating crop management, analyzing crop rotations, and assessing rye's suitability across varied environments, making it valuable for sustainable agriculture and decision‐making.
Grower perspectives on perennial wild plant mixtures for biogas production in Germany
(2024) Becker, David; Ilic, Anna-Maria; Reichardt, Franziska Julia; Hartung, Jens; Beck, Janna; Jablonowski, Nicolai David; Lewin, Eva; von Cossel, Moritz
‘Perennial wild plant mixtures’ (WPM) cultivation is a novel approach to combine biomass provisioning for biogas production with biodiversity enhancement at field scale in Germany. But the methane yield is about 40% lower compared with silage maize. Therefore, the cultivation of WPM is incentivized with about 250–927 Euro per hectare and year. However, agronomic and best management practices of WPM cultivation are unclear, so that large parts of the yield potential of WPM are likely to remain untapped. Hence, this study aims to shed light on farmers’ current perspectives and experiences with WPM cultivation by carrying out a nationwide survey in 2021. The feasibility of inferential statistics was examined in detail, but was not possible due to an insufficient number of responses. Nevertheless, the descriptive analysis revealed valuable information on farmers’ experiences with and their motives for cultivating WPM such as biodiversity enhancement and landscape beauty. Generally, WPM were proven to be much less productive compared with common biogas crops such as maize. Nevertheless, 59% of the farmers cultivated WPM on less favorable soil, and 67% of the farmers used nitrogen fertilization rates of less than or equal to 50 kg ha−1, resulting in generally higher yields compared with results from unfertilized areas. However, while there is common agreement on the positive effects of WPM cultivation on agrobiodiversity, more agronomic research on best management practices is required to make WPM more competitive to common biogas crops without additional subsidies.
Absorption of¹⁵N enriched ammonia by winter wheat at different growth stages
(2025) Frößl, Jonas; Ruser, Reiner; Müller, Torsten
BackgroundLoss of gaseous reactive nitrogen in the form of aerosols may impact human health, and its deposition leads to eutrophication and acidification of natural ecosystems. In order to reduce ammonia (NH3) emissions, which are a main pathway of nitrogen loss to the environment, accurate monitoring and understanding of the factors involved is required.AimsAs information on the absorption of NH3 by wheat plants in central Europe is scarce, we conducted a field experiment to quantify NH3 absorption by a winter wheat canopy in May and June with each two emission scenarios (5 and 12 kg NH3‐N ha−1).MethodsTo induce NH3 emissions, a 15N enriched ammonium sulfate solution (pH 9) was applied in trays between the wheat rows.ResultsAbsorption of the volatilized NH3 of the aboveground plant biomass ranged between 23 and 181 mg NH3‐N m−2 (corresponding to 14.8% and 20.0% of the emitted NH3) and was significantly higher during the first sampling in May, when compared to the second sampling in June. A higher emission led to a higher absolute amount absorbed.ConclusionsThe results indicate that wheat will indeed absorb significant amounts of NH3 emitted at ground level. They will be useful for further improving NH3 emission factors and the understanding of the NH3 emission pathway.
An adapted indicator framework for evaluating the potential contribution of bioeconomy approaches to agricultural systems resilience
(2024) Lewandowski, Iris; von Cossel, Moritz; Winkler, Bastian; Bauerle, Andrea; Gaudet, Nicole; Kiesel, Andreas; Lewin, Eva; Magenau, Elena; Marting Vidaurre, Nirvana Angela; Müller, Benedikt; Schlecht, Valentin; Thumm, Ulrich; Trenkner, Marielle; Vargas‐Carpintero, Ricardo; Weickert, Sebastian; Weik, Jan; Reinmuth, Evelyn
This study reviews a variety of “bioeconomy approaches” (BAs) to assess their potential contribution to resilience in agricultural systems, focusing on benefits that can improve multi‐functionality regarding private and public goods. It is based on Meuwissen et al.'s framework to assess the resilience of farming systems. Drawing on literature and expert knowledge, this indicator framework is adapted to develop a new framework which is then applied to seven contrasting BAs (miscanthus, perennial flowering wild plant mixtures, permanent grassland, nutrient recycling, agrivoltaics, urban agriculture, and microalgae). The major outcomes are: 1) the extended indicator framework can help evaluate BAs for their potential to foster resilience in future agricultural systems, 2) all BAs are characterized by their ability to provide multiple private and public goods simultaneously, 3) the strongest contribution of BAs to public goods is their function in maintaining the good condition of natural resources and resource‐use efficiency, 4) all BAs can enhance resilience in agricultural systems by contributing diversity, multifunctionality, environmental sustainability, and autonomy, 5) the mitigation of potential drawbacks of BAs implementation requires ex‐ante assessment, favorable BAs combinations, and stakeholder involvement, 6) context‐specific analysis of each BAs is required to assess their qualitative and quantitative contribution to resilience.
In season estimation of economic optimum nitrogen rate with remote sensing multispectral indices and historical telematics field-operation data
(2025) Abdipourchenarestansofla, Morteza; Piepho, Hans-Peter
Accurate estimation and spatial allocation of economic optimum nitrogen (N) rates (EONR) can support sustainable crop production systems by reducing chemical compounds to be applied to the ground while preserving the optimum yield and profitability Smart Farming (SF) techniques such as historical precision agriculture (PA) machinery data, satellite multispectral imagery, and on-machine nitrogen adjustment sensors can bring together state-of-the-art precision in determining EONR. The novelty of this study is in introducing an efficient optimization framework using SF technology to enable real-time and prescription based EONR application execution. An optimization strategy called response surface modelling (RSM) was implemented to support decision making by fusing multiple sources of information while keeping the underlying computation simple and interpretable. Here, a field of winter wheat with an area of 7 ha was used to prove the proposed concept of determining EONR for each location in the field using auxiliary variables called multispectral indices (MSIs) derived from Sentinel 2. Three different image acquisition dates before the actual N application were considered to find the best time combination of MSIs along with the best MSIs to model yield. The best MSIs were filtered out through three phases of feature selection using analysis of variance (ANOVA), Lasso regression, and model reduction of RSM. For the date 2020.03.25, 14 out of 21 MSIs exhibited a significant interaction with the N applied as determined through an on-machine N sensor. For dates 2020.03.30 and 2020.04.04, the numbers of significant indices were identified as 6 and 10, respectively. Some of the MSIs were no longer significant after five days of the growth period (5-day interval between Sentinel 2 revisits). The best model demonstrated an average prediction error of 14.5%. Utilizing the model’s coefficients, the EONR was computed to be between 43 kg/ha and 75 kg/ha for the target field. By incorporating MSIs into the fitted model for a given N range, it was demonstrated that the shape of the yield-N relation (RSM) varied due to field heterogeneity. The proposed analytical approach integrates farmer engagement by participatory annual post-mortem analysis. Using the determined RSM approach, retrospective assessment compares economically optimal N input, based on observed MSIs values to each location, with the actual applied rates.
Highlighting the potential of multilevel statistical models for analysis of individual agroforestry systems
(2023) Golicz, Karolina; Piepho, Hans-Peter; Minarsch, Eva-Maria L.; Niether, Wiebke; Große-Stoltenberg, André; Oldeland, Jens; Breuer, Lutz; Gattinger, Andreas; Jacobs, Suzanne
Agroforestry is a land-use system that combines arable and/or livestock management with tree cultivation, which has been shown to provide a wide range of socio-economic and ecological benefits. It is considered a promising strategy for enhancing resilience of agricultural systems that must remain productive despite increasing environmental and societal pressures. However, agroforestry systems pose a number of challenges for experimental research and scientific hypothesis testing because of their inherent spatiotemporal complexity. We reviewed current approaches to data analysis and sampling strategies of bio-physico-chemical indicators, including crop yield, in European temperate agroforestry systems to examine the existing statistical methods used in agroforestry experiments. We found multilevel models, which are commonly employed in ecology, to be underused and under-described in agroforestry system analysis. This Short Communication together with a companion R script are designed to act as an introduction to multilevel models and to promote their use in agroforestry research.
Carry‐over effect of leguminous winter cover crops and living mulches on winter wheat as a second main crop following white cabbage
(2024) Stein, Sophie; Zikeli, Sabine; Möller, Kurt
Background: The direct effect of winter cover crops (WCCs) or living mulches (LMs) on a first vegetable crop has already been investigated. However, little is known about the effect on growth and yield of a second cash crop in the rotation. Aims: The aim of the study was to assess the carry‐over effect of legumes grown as WCC or LM on winter wheat as a second crop after cabbage, measured in yield and nitrogen release. Methods: Two field trials were carried out in Germany between 2019 and 2022. In the WCC trial, rye, rye with vetch, vetch, pea, and faba bean were used as WCC and compared to bare soil. The WCC biomass was incorporated before cabbage planting in late spring. For the LM trial, perennial ryegrass or white clover was used as LM during cabbage cultivation and compared to bare soil. The LM biomass was incorporated with the cabbage residues and compared to an early incorporation of LM biomass before cabbage planting. In both trials, winter wheat was sown in the fall as the second following main crop in the rotation. Results: Leguminous WCC species had significant higher wheat yield compared to non‐legumes but not compared to the control without WCC. Late incorporation of LM biomass resulted in increased wheat yield at 10.1–10.4 Mg ha −1 compared to an early incorporation before cabbage planting at 9.35 Mg ha −1 . Net N releases show that for WCC, the main effect of legume nitrogen fixation is achieved in the first crop cabbage immediately after incorporation of WCC biomass. In the case of leguminous LM, the effects of legume nitrogen fixation are of much higher relevance in the second main crop, winter wheat, due to LM biomass incorporation after cabbage cultivation. Conclusion: Therefore, we suggest to consider not only the direct but also the carry‐over effects of leguminous cover cropping in vegetable crop rotations.
Biostimulant and arbuscular mycorrhizae application on four major biomass crops as the base of phytomanagement strategies in metal-contaminated soils
(2024) Peroni, Pietro; Liu, Qiao; Lizarazu, Walter Zegada; Xue, Shuai; Yi, Zili; von Cossel, Moritz; Mastroberardino, Rossella; Papazoglou, Eleni G.; Monti, Andrea; Iqbal, Yasir; Latowski, Dariusz; Kumar, Adarsh
Using contaminated land to grow lignocellulosic crops can deliver biomass and, in the long term, improve soil quality. Biostimulants and microorganisms are nowadays an innovative approach to define appropriate phytomanagement strategies to promote plant growth and metal uptake. This study evaluated biostimulants and mycorrhizae application on biomass production and phytoextraction potential of four lignocellulosic crops grown under two metal-contaminated soils. Two greenhouse pot trials were setup to evaluate two annual species (sorghum, hemp) in Italy and two perennial ones (miscanthus, switchgrass) in China, under mycorrhizae (M), root (B2) and foliar (B1) biostimulants treatments, based on humic substances and protein hydrolysates, respectively, applied both alone and in combination (MB1, MB2). MB2 increased the shoot dry weight (DW) yield in hemp (1.9 times more), sorghum (3.6 times more) and miscanthus (tripled) with additional positive effects on sorghum and miscanthus Zn and Cd accumulation, respectively, but no effects on hemp metal accumulation. No treatment promoted switchgrass shoot DW, but M enhanced Cd and Cr shoot concentrations (+84%, 1.6 times more, respectively) and the phytoextraction efficiency. Root biostimulants and mycorrhizae were demonstrated to be more efficient inputs than foliar biostimulants to enhance plant development and productivity in order to design effective phytomanagement strategies in metal-contaminated soil.
Combination of silicate-based soil conditioners with plant growth-promoting microorganisms to improve drought stress resilience in potato
(2024) Mamun, Abdullah Al; Neumann, Günter; Moradtalab, Narges; Ahmed, Aneesh; Nawaz, Fahim; Tenbohlen, Timotheus; Feng, Jingyu; Zhang, Yongbin; Xie, Xiaochan; Zhifang, Li; Ludewig, Uwe; Bradáčová, Klára; Weinmann, Markus; Li, Huixin
Due to shallow root systems, potato is a particularly drought-sensitive crop. To counteract these limitations, the application of plant growth-promoting microorganisms (PGPMs) is discussed as a strategy to improve nutrient acquisition and biotic and abiotic stress resilience. However, initial root colonization by PGPMs, in particular, can be affected by stress factors that negatively impact root growth and activity or the survival of PGPMs in the rhizosphere. In this study, perspectives for the use of commercial silicate-based soil conditioners (SCs) supposed to improve soil water retention were investigated. The SC products were based on combinations with lignocellulose polysaccharides (Sanoplant® = SP) or polyacrylate (Geohumus® = GH). It was hypothesized that SC applications would support beneficial plant–inoculant interactions (arbuscular mycorrhiza, AM: Rhizophagus irregularis MUCL41833, and Pseudomonas brassicacearum 3Re2-7) on a silty loam soil–sand mixture under water-deficit conditions (6–12 weeks at 15–20% substrate water-holding capacity, WHC). Although no significant SC effects on WHC and total plant biomass were detectable, the SC-inoculant combinations increased the proportion of leaf biomass not affected by drought stress symptoms (chlorosis, necrosis) by 66% (SP) and 91% (GH). Accordingly, osmotic adjustment (proline, glycine betaine accumulation) and ROS detoxification (ascorbate peroxidase, total antioxidants) were increased. This was associated with elevated levels of phytohormones involved in stress adaptations (abscisic, jasmonic, salicylic acids, IAA) and reduced ROS (H2O2) accumulation in the leaf tissue. In contrast to GH, the SP treatments additionally stimulated AM root colonization. Finally, the SP-inoculant combination significantly increased tuber biomass (82%) under well-watered conditions, and a similar trend was observed under drought stress, reaching 81% of the well-watered control. The P status was sufficient for all treatments, and no treatment differences were observed for stress-protective nutrients, such as Zn, Mn, or Si. By contrast, GH treatments had negative effects on tuber biomass, associated with excess accumulation of Mn and Fe in the leaf tissue close to toxicity levels. The findings suggest that inoculation with the PGPMs in combination with SC products (SP) can promote physiological stress adaptations and AM colonization to improve potato tuber yield, independent of effects on soil water retention. However, this does not apply to SC products in general.

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