Institut für Tropische Agrarwissenschaften (Hans-Ruthenberg-Institut)

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A low-tech approach to mobilize nutrients from organic residues to produce bioponic stock solutions
(2024) Heintze, Sebastian; Beckett, Marc; Kriem, Lukas Simon; Germer, Jörn; Asch, Folkard; Liu, Guodong
Organic residues, as a nutrient source suitable of producing solutions for hydroponic crop production, have the potential to reduce the dependence on mineral fertilizers. Especially in remote and resource-constrained regions, organic residues might be the only option to produce hydroponic nutrient solutions. However, nutrient solutions made from organic residues, called bioponic solutions, are usually unbalanced in their nutrient composition, which leads to deficiencies and poor plant growth. This study aimed to experimentally develop a low-tech approach to produce bioponic stock solutions rich in NO3−, P, and K, to create a balanced bioponic solution. The mixed bioponic solution contained 58 mg L−1 NH4+-N, 43 mg L−1 NO3−-N, 50 mg L−1 PO43−-P, and 246 mg L−1 K+. This approach resulted in satisfactory levels of P, K and micronutrients. The solution was tested pure and spiked with Ca(NO3)2 on lettuce in comparison with a mineral Hoagland nutrient solution. Neither the bioponic nor the spiked bioponic solution achieved comparable lettuce yields to the Hoagland solution. The poor growth of the plants in the bioponic solution was attributed to an unfavorable NH4+:NO3− ratio, high microorganism load, and elevated pH levels. However, the approach of preparing bioponic stock solutions could be promising for future research into the production of balanced bioponic nutrient solutions from organic residues.
Abundance and symbiotic efficiency of indigenous rhizobia nodulating faba bean and common bean in southern Ethiopia
(2025) Geremu, Tadele; Abera, Girma; Lemma, Bekele; Rasche, Frank
The symbiotic association between legumes and indigenous rhizobia is crucial for enhancing legume productivity. However, inconsistent results and suboptimal performance of rhizobia inoculation in promoting legume production have been observed. In this regard, we assessed the abundance and symbiotic efficiency of indigenous rhizobia nodulating faba bean and common bean, as well as the soil factors affecting rhizobia abundance in southern Ethiopia. The study also compared the performance of indigenous rhizobia with commercial strains and mineral nitrogen treatment plants. A total of 132 soil samples were collected from barley, wheat, maize, potato, common bean, faba bean, intercropped common bean and maize, enset, and grazing land. Indigenous rhizobia were isolated and enumerated from these samples. Faba bean (FB) and common bean (CB) rhizobia population ranged from 0.0 to 1.7 x 10 4 and 1.7 x 10 1 to 1.7 x 10 7 cells g -1 soil, respectively. Rhizobia populations were significantly influenced by soil pH, EC, OC, TN, CEC, exchangeable acidity, aluminium, and the host crop occurrence. The isolated indigenous rhizobia demonstrated significant potential in enhancing nodulation, shoot dry weight, and TN accumulation in plants. Symbiotic efficiency indices revealed that over 95% of the indigenous rhizobia were effective in nodulation and shoot dry matter accumulation, indicating that naturally occurring rhizobia are efficient and may reduce the need for commercial inoculants in areas with abundant indigenous populations. However, in areas where rhizobia populations are low, strains isolated from faba bean (33FB, 84FB) and common bean (44CB, 102CB), which outperformed commercial strains should be further evaluated. The results suggest that soil rhizobia population levels should be assessed prior to inoculation to optimize nodulation and crop performance. To this end, it is emphasized to evaluate soil rhizobia strains to assess their stability and competitiveness relative to commercial inoculants across different agroecological conditions.
Assessing impacts of crop area expansion and crop-livestock integration on ecosystem functions in African savannas using the coupled LUCIA and LIVSIM models
(2025) Gutai, Benjamin; Marohn, Carsten; Bateki, Christian Adjogo; Asch, Folkard
Large-scale land use change (LUC) of African Guinea savannas to crop fields is expected to cause negative impacts on ecosystem functions (ESF) and long term land productivity. The complex interactions of key processes in savannas evoked by LUC calls for a process-based modelling approach. We employed the dynamically coupled Land Use Change Impact Assessment (LUCIA) model and the Livestock Simulator (LIVSIM) which represent LUC impacts on soil processes, landscape-scale matter fluxes, seasonal grass and crop growth, and livestock nutrition, production and reproduction, depending on seasonal feed availability and quality on accessible pastures. For a rangeland in Borana, Ethiopia, two different LUC scenarios were evaluated in comparison to the baseline of traditional pasture-based land use. In the intensive LUC scenario 52% of grassland was converted into unfertilized maize fields, inaccessible for livestock. The integrated LUC scenario of the same grassland conversion rate allowed feeding maize straw and provided high-quality feed reserves from seasonally managed pastures. LUC in the intensive LUC scenario led to declining yields in the second year after conversion. Feed production on the remaining rangeland patches was insufficient for livestock nutrition, causing drops of herd body weight and herd size particularly in drought years. Resilience of herd performance to LUC was enhanced in the integrated LUC scenario when feeding maize straw and high-quality feed reserves. In both LUC scenarios, topsoil organic carbon storage decreased after ploughing shrub grassland for cultivation, and so did soil water storage capacity due to soil pore destruction. Soil erosion of less than one cm after 10 years occurred under cultivation. The simulation results indicated that the well validated model framework could predict impacts of LUC and simple crop-livestock integration on savanna ESFs, grass growth dynamics and livestock production during seasonal and inter-annual rainfall variation. This study lays the foundation for further land use scenario simulations to improve the understanding of benefits and risks caused by savanna grassland conversion.
Back to the roots: understanding banana below‐ground interactions is crucial for effective management of Fusarium wilt
(2022) Were, Evans; Viljoen, Altus; Rasche, Frank
Global banana production is affected by Fusarium wilt, a devastating disease caused by the soilborne root‐infecting fungus, Fusarium oxysporum f. sp. cubense (Foc). Fusarium wilt is notoriously difficult to manage because infection arises through complex below‐ground interactions between Foc, the plant, and the soil microbiome in the root–soil interface, defined as the rhizosphere. Interactions in the rhizosphere play a pivotal role in processes associated with pathogen development and plant health. Modulation of these processes through manipulation and management of the banana rhizosphere provides an auspicious prospect for management of Fusarium wilt. Yet, a fundamental understanding of interactions in the banana rhizosphere is still lacking. The objective of this review is to discuss the state‐of‐the‐art of the relatively scant data available on banana below‐ground interactions in relation to Fusarium wilt and, as a result, to highlight key research gaps. Specifically, we seek to understand (a) the biology of Foc and its interaction with banana; (b) the ecology of Foc, including the role of root‐exuded metabolites in rhizosphere interactions; and (c) soil management practices and how they modulate Fusarium wilt. A better understanding of molecular and ecological factors influencing banana below‐ground interactions has implications for the development of targeted interventions in the management of Fusarium wilt through manipulation of the banana rhizosphere.
The baobab (Adansonia digitata L.) in Southern Kenya–a study on status, distribution, use and importance in Taita–Taveta County
(2020) Fischer, Sahrah; Jäckering, Lisa; Kehlenbeck, Katja
Baobab (Adansonia digitata L.) is a multipurpose, drought resistant, wild fruit tree, endemic to arid and semi-arid lands of Sub-Saharan Africa. Baobab populations have been showing a lack of regeneration, and therefore causes concern for the species survival. This study investigated the state, distribution and use of baobabs in an under-researched population in Kenya, to identify the potential for further use and development of baobab resources. A baobab population was chosen in Taita–Taveta County, covering a sample area of 2015 km2. A systematic stratified transect survey was done to map baobab distribution using 49 transects (0.5 × 3 km each). The diameter at breast height and other indicators were measured on all baobabs in the transects to assess population status and health. A household survey (n = 46) and focus group discussions (n = 12) were done following the transect survey to gain an idea on the uses and distribution of baobab. In total, 432 baobab trees were measured and recorded in the research area of 2015 km2. The baobabs grew in two clusters (i.e., areas with a baobab density of ≥0.08 baobabs/ha). Both clusters showed rejuvenating populations. The main factors identified by the respondents, positively and negatively influencing baobab distribution were environmental factors, wildlife, human impact and commercial value. The study area shows a great potential for baobab to become an important part of the diet, due to its current use as an emergency food during food scarce times, and the relatively healthy and stable rejuvenating populations.
Biomonitoring via DNA metabarcoding and light microscopy of bee pollen in rainforest transformation landscapes of Sumatra
(2022) Carneiro de Melo Moura, Carina; Setyaningsih, Christina A.; Li, Kevin; Merk, Miryam Sarah; Schulze, Sonja; Raffiudin, Rika; Grass, Ingo; Behling, Hermann; Tscharntke, Teja; Westphal, Catrin; Gailing, Oliver
Background: Intense conversion of tropical forests into agricultural systems contributes to habitat loss and the decline of ecosystem functions. Plant-pollinator interactions buffer the process of forest fragmentation, ensuring gene flow across isolated patches of forests by pollen transfer. In this study, we identified the composition of pollen grains stored in pot-pollen of stingless bees, Tetragonula laeviceps , via dual-locus DNA metabarcoding (ITS2 and rbcL ) and light microscopy, and compared the taxonomic coverage of pollen sampled in distinct land-use systems categorized in four levels of management intensity (forest, shrub, rubber, and oil palm) for landscape characterization. Results: Plant composition differed significantly between DNA metabarcoding and light microscopy. The overlap in the plant families identified via light microscopy and DNA metabarcoding techniques was low and ranged from 22.6 to 27.8%. Taxonomic assignments showed a dominance of pollen from bee-pollinated plants, including oil-bearing crops such as the introduced species Elaeis guineensis (Arecaceae) as one of the predominant taxa in the pollen samples across all four land-use types. Native plant families Moraceae, Euphorbiaceae, and Cannabaceae appeared in high proportion in the analyzed pollen material. One-way ANOVA (p > 0.05), PERMANOVA (R² values range from 0.14003 to 0.17684, for all tests p-value > 0.5), and NMDS (stress values ranging from 0.1515 to 0.1859) indicated a lack of differentiation between the species composition and diversity of pollen type in the four distinct land-use types, supporting the influx of pollen from adjacent areas. Conclusions: Stingless bees collected pollen from a variety of agricultural crops, weeds, and wild plants. Plant composition detected at the family level from the pollen samples likely reflects the plant composition at the landscape level rather than the plot level. In our study, the plant diversity in pollen from colonies installed in land-use systems with distinct levels of forest transformation was highly homogeneous, reflecting a large influx of pollen transported by stingless bees through distinct land-use types. Dual-locus approach applied in metabarcoding studies and visual pollen identification showed great differences in the detection of the plant community, therefore a combination of both methods is recommended for performing biodiversity assessments via pollen identification.
Climate on the edge: impacts and adaptation in Ethiopia’s agriculture
(2025) Feleke, Hirut Getachew; Amdie, Tesfaye Abebe; Rasche, Frank; Mersha, Sintayehu Yigrem; Brandt, Christian; Younos, Tamim; Lee, Juneseok; Parece, Tammy E.
Climate change poses a significant threat to Ethiopian agriculture, impacting both cereal and livestock production through rising temperatures, erratic rainfall, prolonged droughts, and increased pest and disease outbreaks. These challenges intensify food insecurity, particularly for smallholder farmers and pastoralists who rely on climate-sensitive agricultural systems. This systematic review aims to synthesize the impacts of climate change on Ethiopian agriculture, with a specific focus on cereal production and livestock feed quality, while exploring effective adaptation strategies that can support resilience in the sector. The review synthesizes 50 peer-reviewed publications (2020–2024) from the Climate Change Effects on Food Security project, which supports young African academics and Higher Education Institutions (HEIs) in addressing Sustainable Development Goals (SDGs). Using PRISMA guidelines, the review assesses climate change impacts on major cereal crops and livestock feed in Ethiopia and explores adaptation strategies. Over the past 30 years, Ethiopia has experienced rising temperatures (0.3–0.66 °C), with future projections indicating increases of 0.6–0.8 °C per decade resulting in more frequent and severe droughts, floods, and landslides. These shifts have led to declining yields of wheat, maize, and barley, shrinking arable land, and deteriorating feed quality and water availability, severely affecting livestock health and productivity. The study identifies key on-the-ground adaptation strategies, including adjusted planting dates, crop diversification, drought-tolerant varieties, soil and water conservation, agroforestry, supplemental irrigation, and integrated fertilizer use. Livestock adaptations include improved breeding practices, fodder enhancement using legumes and local browse species, and seasonal climate forecasting. These results have significant practical implications: they offer a robust evidence base for policymakers, extension agents, and development practitioners to design and implement targeted, context-specific adaptation strategies. Moreover, the findings support the integration of climate resilience into national agricultural policies and food security planning. The Climate Change Effects on Food Security project’s role in generating scientific knowledge and fostering interdisciplinary collaboration is vital for building institutional and human capacity to confront climate challenges. Ultimately, this review contributes actionable insights for promoting sustainable, climate-resilient agriculture across Ethiopia.
Coffee berry borer control, but not coffee yield, is mediated by non-additive interaction between birds and ants across different cultivation systems
(2026) Cardona Tejada, Damaris A.; Parra, Juan L.; Grass, Ingo; Schurr, Frank M.
Coffee is one of the most traded tropical crops, cultivated in some of the most biodiverse regions on the planet. Coffee production can be seriously reduced by the coffee berry borer (CBB), a specialized beetle that feeds on the endosperm of coffee berries. Given the CBB's economic relevance, coffee-producing countries have developed extensive Integrated Pest Management programs. Nonetheless, most of these programs fail to incorporate CBB control by natural enemies such as birds and ants. While the effects of birds and ants on CBB suppression have been demonstrated to be positive when studied in isolation, their interactive effects have been little studied. To better understand the effects of the trophic interaction between birds and ants on CBB control, we conducted a full-factorial block experiment excluding birds and ants from coffee shrubs. We distributed 49 experimental blocks across three different coffee systems in a Colombian landscape: sun-exposed coffee, coffee-plantain intercropping, and shade coffee. We found birds to be key control agents of CBB: in the presence of ants, bird exclusion increased CBB infestation by 36 %. However, in the absence of ants, birds had little effect on CBB infestation, demonstrating that the effects of birds and ants were non-additive. This suggests that birds control CBB through a trophic cascade mediated by ants. We also found that the effects of exclusions were modified by the cultivation system, with the shade coffee system consistently reducing CBB infestation. Our experiment demonstrates that crop diversification is an effective measure for integrating local enemies into IPM strategies. Nonetheless, we acknowledge that trophic interactions are highly complex and exhibit a context-dependency that can result in the suppression of biological pest control. Therefore, we recommend conducting future analysis on evaluating the effects of predator´s community composition to encourage the development of IPM programs that leverage biodiversity in agroecosystems.
Combining improved mungbean cultivars with plant growth promoting rhizobacteria inoculation and regulated deficit irrigation to increase crop productivity
(2024) Pataczek, Lisa; Cadisch, Georg
The cultivation of legumes provides an approach to sustainably intensify agricultural production, since short-duration legumes can fit into existing cereal-based cropping systems, diversifying farm incomes and farmers diets, as well as providing environmental benefits through the fixation of atmospheric N2 and, thus, enhancing yields of following crops. Mungbean is a legume, which plays already an important role in the traditional nutrition of people in the Global South. Its nutritious seeds can improve food security and the short growing duration facilitates the diversification of mainly cereal-based crop rotations. However, yields are low and may even become lower in future in the face of climate change. Main constraints of mungbean cultivation include pest and diseases, as well as heat, drought and soil salinity due to inappropriate irrigation techniques or saline ground water. The main aim of this thesis was therefore to analyse the effects of more advanced cultivation techniques, i.e. the use of plant growth promoting rhizobacteria (PGPR) and regulated deficit irrigation (RDI), on the productivity and nitrogen (N) fixation capacity of improved mungbean (Vigna radiata L.) cultivars, resistant and/or tolerant to pests, diseases, heat and soil salinity. An extended literature review was conducted to summarize the current understanding of the use of PGPRs and the effect on crop productivity, especially on marginal land (Chapter 2). The use of PGPRs can on the one hand side increase plant growth through direct and indirect mechanisms, such as BNF, hormone production and nutrient solubilization or the production of antibiotics to suppress phytodiseases. Especially 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity plays a significant role to reduce the negative impact of stress environments. On the other side PGPRs can be used to remediate decontaminated sites, through metabolic capabilities, transforming for instance aromatic compounds into less toxic compounds, or the biodegradation of pesticides and organic pollutants. Since ACC deaminase-producing bacteria are also supposed to enhance root growth, it is assumed that they can potentially increase soil N uptake and/or infection sites for rhizobia to biologically fix atmospheric N2 (BNF). In order to test the effect of ACC deaminase-producing PGPRs on mungbean productivity and N accumulation, three strains were tested as single- or multistrain inoculation in the field: Rhizobium phaseoli, Bacillus subtilis and Pseudomonas fluorescens (Chapter 3). Their effect on one improved mungbean cultivar (NM11, resistant to the Mungbean Yellow Mosaic Disease) was assessed on two research sites in Faisalabad, Pakistan. The impact of the strains differed significantly, with no effect on productivity (total biomass, seed yield) or total N accumulation (BNF and soil-N uptake) with multi-strain inoculation of all strains and single-strain inoculation of P. fluorescens. Inoculation with B. subtilis did, however, result in significantly increased dry matter (roots: +211 kg ha-1, total dry matter: +1.7 t ha-1), and total plant-N (+36 kg ha-1), while R. phaseoli inoculation enhanced BNF (+24%). The results suggested that only the single strain inoculation of B. subtilis and R. phaseoli was promising in terms of productivity increase, however, the choice of the strain should be made according to the soil-N status: low soil-N favors R. phaseoli inoculation, while medium to high soil-N would rather point towards the use of B. subtilis. The improved mungbean cultivar NM11 was additionally tested together with three other improved cultivars (AVMU 1604, AVMU 1635 and KPS2, resistant/tolerant to powdery mildew, bruchids and heat and salt, respectively), in combination with RDI in a greenhouse trial at the University of Hohenheim (Chapter 4). The aim was to identify differences in drought adaptation strategies between the cultivars in terms of dry matter partitioning, yield, harvest index, pod harvest index, water use efficiency and carbon-13 isotope discrimination. Levels of water deficit as depletion fractions (%) of total available soil water were set to 0.45, 0.65 and 0.8, corresponding to recommended irrigation, moderate and severe water deficit, respectively. The cultivars differed in their drought resistance strategies, exhibiting either drought escape, avoidance, tolerance or a combination of several strategies. The cultivar KPS2 showed mainly a drought escape mechanism through faster development, stable yields and greatest harvest index/pod harvest index (36%/69%) across all RDI treatments and cultivars. The cultivar AVMU 1604 displayed mainly a mixture of drought avoidance and escape through increased remobilization of assimilates from vegetative plant parts to pods/seeds, resulting in greater yield under water deficit by 52%. The choice of a cultivar for the field should be based, thus, on the prevailing climatic conditions (season and region): KPS2 can grow in areas with terminate drought conditions, whereas AVMU 1604 can tolerate intermittent drought conditions. The results of this thesis showed that ACC deaminase-producing PGPRs can substantially affect N uptake, although this effect is barely discussed in literature. Moreover, improved mungbean cultivars, exhibiting already a range of tolerances and resistances to certain pests and diseases, showed a great potential in adapting to drought conditions, representing a viable option for cultivation under increasing abiotic and biotic stress factors in the face of climate change.
Complementary effects of pollination and biocontrol services enable ecological intensification in macadamia orchards
(2024) Anders, Mina; Westphal, Catrin; Linden, Valerie M. G.; Weier, Sina; Taylor, Peter J.; Grass, Ingo
In many crops, both pollination and biocontrol determine crop yield, whereby the relative importance of the two ecosystem services can be moderated by the landscape context. However, additive and interactive effects of pollination and biocontrol in different landscape contexts are still poorly understood. We examined both ecosystem services in South African macadamia orchards. Combining observations and experiments, we disentangled their relative additive and interactive effects on crop production with variation in orchard design and landscape context (i.e., cover of natural habitat and altitude). Insect pollination increased the nut set on average by 280% (initial nut set) and 525% (final nut set), while biocontrol provided by bats and birds reduced the insect damage on average by 40%. Pollination services increased in orchards where macadamia tree rows were positioned perpendicular to orchard edges facing natural habitat. Biocontrol services decreased with elevation. Pest damage was reduced by higher cover of natural habitat at landscape scale but increased with elevation. Pollination and biocontrol are both important ecosystem services and complementary in providing high macadamia crop yield. Smart orchard design and the retention of natural habitat can simultaneously enhance both services. Conjoint management of ecosystem services can thus enable the ecological intensification of agricultural production.
Design and development of an accessible open-source augmented reality learning authoring tool for applications in agroecological settings
(2024) Shidende, Deogratias; Treydte, Anna
Augmented Reality (AR) has emerged as a transformative educational technology, offering immersive, multisensory learning experiences that enhance engagement, conceptual understanding, and contextualization. In agroecology, where students must grasp complex ecological interactions and context-dependent knowledge, AR can bridge the gap between classroom instruction and field-based learning. However, the creation of AR content remains largely inaccessible to many educators in higher learning institutions (HLIs), particularly those without programming skills and individuals with disabilities such as the deaf and hard of hearing (DHH), and the blind and low vision (BLV). This dissertation addresses the central question: How can an accessible AR learning authoring tool enable non-technical educators and users with disabilities to create AR learning experiences for agroecology education in HLIs? To address this question, the study employed a design-based research (DBR) methodology, integrating Agile Scrum for iterative, inclusive tool development. Seven research questions (RQ1–RQ7) guided the investigation. First, a document-based analysis (RQ1) compared open-source software licenses (OSLs) to determine their suitability for academic–industry collaboration. Permissive licenses (e.g., MIT, BSD) were found to offer more flexibility in code reuse and integration, thereby promoting long-term project sustainability, although they require supplementary legal mechanisms to ensure reciprocity. Next, functional and non-functional software requirements (RQ2) were elicited through stakeholder workshops, interviews, surveys, and accessibility evaluations. These requirements informed the selection and redesign of MirageXR, an open-source AR platform. Key accessibility features were specified for DHH users, such as customizable captioning of audio augmentations, and for BLV users, such as voice navigation and spatial audio cues. These enhancements underscored the dual instructional and assistive roles of AR tools. In response to RQ3, a modular, component-based software architecture was designed using the C4 model. This enabled seamless integration of external services (e.g., 3D object repositories, learning management systems, and automatic speech recognition) and ensured that features could be added or updated without disrupting system stability. This modularity was essential given the evolving nature of AR technologies. The design and implementation phases (RQ4 & RQ5) employed participatory iterative prototyping with user feedback throughout the development process. Accessibility features were integrated into image, audio, and video augmentations, with functionalities such as caption editing, playback speed control, and 3D spatial positioning. These solutions directly addressed gaps in existing AR authoring tools, particularly for DHH and BLV users. The sixth research question (RQ6) investigated usability and applicability through an AR creation workshop involving 24 agroecology educators. Findings revealed that although participants initially encountered difficulties, they gained proficiency over time. UMUX scores showed a correlation between AR experience and perceived usefulness. Participants highlighted AR's potential to visualize complex concepts and engage students in experiential learning. However, limitations in 3D content availability and customization highlighted the need for integrated 3D content creation and editing tools specifically tailored to agroecology. To answer RQ7, the study conducted a systematic literature review of 60 studies to identify current accessibility evaluation methods in AR. Most evaluations employed task-based scenarios, utilizing metrics such as time on task, error rate, and user satisfaction. The study's own evaluation validated that DHH users could independently author AR content using the developed tool. In contrast, BLV users could navigate the authoring functionalities but were unable to fully author AR content, indicating that further design improvements and assistive functionalities are required for full inclusion. Methodologically, this study contributes a novel integration of DBR and Agile Scrum for inclusive educational technology design. This hybrid framework facilitated rapid prototyping, iterative refinement, and participatory co-design, and is recommended for broader application in accessibility-focused educational innovation. Future research should document and validate this methodological approach across additional contexts and user groups. The study makes the following contributions: (1) provision of an open-source, extensible AR authoring interfaces and codebase for public use; (2) improved AR accessibility for AR for DHH and BLV users; (3) development of modular architectural and algorithmic solutions to enable multimodal accessibility; (4) empirical validation of AR’s pedagogical value in agroecology education; and (5) identification of optimal open-source licensing models for collaborative educational software development. In sum, the findings demonstrate that an accessible, open-source AR authoring tool can empower diverse educators, including those with disabilities, to create inclusive and contextually relevant learning experiences. The research affirms the importance of universal design, participatory development, and modularity in educational technology design and concludes with strategic recommendations: integrating AI-assisted 3D content generation, expanding accessibility to additional user groups, and establishing communities of practice to support sustainable AR content development in agroecology.
Determining the footprint of breeding in the seed microbiome of a perennial cereal
(2024) Michl, Kristina; David, Christophe; Dumont, Benjamin; Mårtensson, Linda-Maria Dimitrova; Rasche, Frank; Berg, Gabriele; Cernava, Tomislav
Background: Seed endophytes have a significant impact on plant health and fitness. They can be inherited and passed on to the next plant generation. However, the impact of breeding on their composition in seeds is less understood. Here, we studied the indigenous seed microbiome of a recently domesticated perennial grain crop (Intermediate wheatgrass, Thinopyrum intermedium L.) that promises great potential for harnessing microorganisms to enhance crop performance by a multiphasic approach, including amplicon and strain libraries, as well as molecular and physiological assays. Results: Intermediate wheatgrass seeds harvested from four field sites in Europe over three consecutive years were dominated by Proteobacteria (88%), followed by Firmicutes (10%). Pantoea was the most abundant genus and Pantoea agglomerans was identified as the only core taxon present in all samples. While bacterial diversity and species richness were similar across all accessions, the relative abundance varied especially in terms of low abundant and rare taxa. Seeds from four different breeding cycles (TLI C3, C5, C704, C801) showed significant differences in bacterial community composition and abundance. We found a decrease in the relative abundance of the functional genes nirK and nifH as well as a drop in bacterial diversity and richness. This was associated with a loss of amplicon sequence variants (ASVs) in Actinobacteria , Alphaproteobacteria , and Bacilli , which could be partially compensated in offspring seeds, which have been cultivated at a new site. Interestingly, only a subset assigned to potentially beneficial bacteria, e.g. Pantoea, Kosakonia , and Pseudomonas , was transmitted to the next plant generation or shared with offspring seeds. Conclusion: Overall, this study advances our understanding of the assembly and transmission of endophytic seed microorganisms in perennial intermediate wheatgrass and highlights the importance of considering the plant microbiome in future breeding programs.
Diacetoxyscirpenol, a Fusarium exometabolite, prevents efficiently the incidence of the parasitic weed Striga hermonthica
(2022) Anteyi, Williams Oyifioda; Klaiber, Iris; Rasche, Frank
Background: Certain Fusarium exometabolites have been reported to inhibit seed germination of the cereal-parasitizing witchweed, Striga hermonthica , in vitro . However, it is unknown if these exometabolites will consistently prevent S. hermonthica incidence in planta . The study screened a selection of known, highly phytotoxic Fusarium exometabolites, in identifying the most potent/efficient candidate (i.e., having the greatest effect at minimal concentration) to completely hinder S. hermonthica seed germination in vitro and incidence in planta , without affecting the host crop development and yield. Results: In vitro germination assays of the tested Fusarium exometabolites (i.e., 1,4-naphthoquinone, equisetin, fusaric acid, hymeglusin, neosolaniol (Neo), T-2 toxin (T-2) and diacetoxyscirpenol (DAS)) as pre- Striga seed conditioning treatments at 1, 5, 10, 20, 50 and 100 µM, revealed that only DAS, out of all tested exometabolites, completely inhibited S. hermonthica seed germination at each concentration. It was followed by T-2 and Neo, as from 10 to 20 µM respectively. The remaining exometabolites reduced S. hermonthica seed germination as from 20 µM ( P < 0. 0001). In planta assessment (in a S. hermonthica -sorghum parasitic system) of the exometabolites at 20 µM showed that, although, none of the tested exometabolites affected sorghum aboveground dry biomass ( P > 0.05), only DAS completely prevented S. hermonthica incidence. Following a 14-d incubation of DAS in the planting soil substrate, bacterial 16S ribosomal RNA (rRNA) and fungal 18S rRNA gene copy numbers of the soil microbial community were enhanced; which coincided with complete degradation of DAS in the substrate. Metabolic footprinting revealed that the S. hermonthica mycoherbicidal agent, Fusarium oxysporum f. sp. strigae (isolates Foxy-2, FK3), did not produce DAS; a discovery that corresponded with underexpression of key genes (Tri5, Tri4) necessary for Fusarium trichothecene biosynthesis ( P < 0.0001). Conclusions: Among the tested Fusarium exometabolites, DAS exhibited the most promising herbicidal potential against S. hermonthica . Thus, it could serve as a new biocontrol agent for efficient S. hermonthica management. Further examination of DAS specific mode of action against the target weed S. hermonthica at low concentrations (≤ 20 µM), as opposed to non-target soil organisms, is required.
Digital agriculture: socio-technical-physical interactions and the transformation of the rural world(s)
(2024) Hidalgo Jaramillo, Francisco Javier; Regina, Birner
The social and environmental challenges that humanity faces today to produce food, fuel, and fibers in a sustainable and fair way call for a transformation. Digital agriculture has been embraced with much enthusiasm by many as the contour of such transformation. Proponents of these technologies, including international organizations as well as numerous researchers focused on innovations, describe this innovation as a paradigm shift. Associated with increased efficiencies and enhanced communication, digital agriculture is commonly depicted by these groups as the advent of a more sustainable and ‘smart’ future. Other groups, including grassroots organizations, socio-environmental activists, and critical scholars, on the other hand, see digital agriculture with skepticism and concern. They refer to the entrenchment of digital agriculture in productivist, capitalist, and extractivist forms of production, and a linkage with the consolidation of corporate power and state surveillance. Using a critical and systems approach, this thesis scrutinizes these arguments, examining the socio-technical transitions that emerge from agricultural digitalization, and discerns their societal and environmental consequences. This examination is relevant given that despite digital agriculture can transform the face of agricultural systems, it is not yet clear in what way. The emergent condition of digitalization requires this analysis to inform responsible governance of this innovation. Critical studies have made important contributions to this understanding. However, the complexity of digital agriculture calls for additional conceptual frameworks to be incorporated. The coffee production system has been selected as a case study in this thesis. This selection responds to the global scope of this system and the relevance that it represents for rural development. To set the picture: coffee is one of the most traded agricultural products in the world. Yet, more than 70% of it is produced by smallholder farmers who receive less than 10% of its final value. Meanwhile, coffee farmers experience manifold social and environmental challenges that threaten their livelihoods and the sustainability of the whole system. Poverty, power and information asymmetries, and climate change are among them. Against this background, this thesis takes the perspective of coffee as a crop, a cultural system, and a value chain. Following a qualitative research approach, the analysis is informed by a theoretical literature review and data from semi-structured interviews with developers and users of digital technologies. The thesis is divided into three studies (chapters 2, 3, and 4) which together present a critical analysis applied at three scales: 1) global, 2) value chain, and 3) local. Across these studies, three main socio-technical aspects of digital agriculture are addressed. First, global governance of digital agriculture and its consequences for farmers’ rights and capabilities. Second, the consequences of different technical assemblages for the sustainability of agricultural systems. Third, local forms of interaction with digital technologies. After presenting and introduction in Chapter 1, Chapter 2 presents a literature review on the political dynamics of digital agriculture. Drawing upon an emancipatory conceptualization of agency and sovereignty, this chapter is focused on describing two main forms of governance: governance through and governance of digital technologies in the context of agriculture. This description is followed by an analysis of the multiple effects of these two forms of governance on farmer’s sovereignty and agency. The analysis revealed that the governance of digital agriculture is an assemblage of multiple agencies of human and cyber agents (smart devices, automated machines, algorithms). Socio-technical interactions in this assemblage result simultaneously in sovereignty and agency gains and losses for farmers - a complex set of power transactions in which farmers participate many times inadvertently. Together with oppressive forms of governance associated with corporate technological lock-in, data extractivism, and a surveilling state, there is evidence also of a democratic facet of digitalization. This facet is integrated by open-collaborative networks, data cooperatives, cyberactivism, and open-source software. With this analysis, the study aimed to understand how the political position of farmers is affected by digitalization, understanding that this process is occurring in a context of structural power imbalance. A socio-technical perspective is applied in Chapter 3 to explore 20 digital tools designed for the coffee value chain, examining the pathways toward sustainability (environmental, social, and economic) promoted by these tools. The socio-technical perspective mainly proposes that social and technical systems shape each other in reciprocal interactions. Building on this idea, the chapter examines the technical attributes of these tools (functionality, technologies included, operation rules, information flow). Subsequently, it analyzes the consequences of these attributes in terms of three broad social dynamics: 1) knowledge and value systems represented, 2) power structures, and 3) possibilities for using these tools effectively. The forms in which these social dynamics are shaped by these tools, in turn, yield specific sustainability outcomes. These include the kind of production systems that are endorsed - and not endorsed -, the access to these technologies and their benefits, and the way in which social inequalities and power asymmetries are addressed - or not addressed -. The data for this analysis comes from interviews with 15 developers of these tools and secondary information. The analysis shows that technical attributes play a fundamental role in directing the kinds of pathways toward sustainability that are made available for agricultural systems. Additionally, it shows that in some cases, rather than a revolution, digital agriculture can look like business as usual but tweaked. Chapter 4 presents a local perspective on digitalization. Using data from interviews with 73 households in two selected coffee growing communities in Colombia, this chapter explores how they engage with digital technologies. The study parts from the idea that important reality-design gaps in digital agriculture result from a lack of understanding and inclusion of local worldviews around digital technologies and farming. Amartya Sen’s capabilities approach was adopted as the conceptual framework for the analysis. This framework posits that resources only become assets when they can be used by individuals to accomplish the life they value. For that reason, the analysis in this chapter was focused on first, understanding the elements that configure a valuable life for these communities, and next, understanding how they use digital technologies to support the accomplishment of this life. The underlying values of this local process of technological appropriation were compared with the values represented by broader narratives of digital agriculture. This offered a picture of the negotiations and tensions that occur when contrasting visions of farming, digitalization, and a desirable future, interface. Drawing upon a relational perspective, the local appropriation process is characterized by multiple negotiations between farmers’ personal and collective goals, situated knowledge, institutional programs, and the agency of non-humans (e.g. land, plants, animals, machines). From these interactions emerge distinctive forms of digitalization and non-digitalization. This process of local appropriation revealed the critical view of farmers and agency, for example, by following a digitalization pathway that profoundly diverges from dominant imaginaries and discourses around digital agriculture. By applying a systems approach and by integrating three frameworks into critical scholarship - (1) emancipatory conceptualization of agency and sovereignty, (2) Sen´s capabilities approach, and (3) a relational approach - this thesis presents evidence of the complexity of socio-technical-physical interactions that lead to certain broad-mainstream and local-everyday digitalization pathways. These pathways, in turn, present particular societal consequences, such as the kind of agricultural worlds that are made possible, the interests that are represented in them, and the possibilities of participation for different social groups. More than a single trajectory, digital agriculture is a space of multiplicity and permanent emergence, also for reproducing current – not necessarily sustainable - models. For this reason, this thesis calls for abandoning notions of immutability, universality, and uniformity in development discourses, perspectives of rurality, and the generation of new technologies. Instead, it proposes to integrate a critical and systems-relational perspective into inclusionary innovation research and practice.
Digital innovations and institutional barriers in agricultural input subsidy programmes in sub‐Saharan Africa: evidence from Nigeria
(2026) Adetoyinbo, Ayobami; Gupta, Saurabh; Okoruwa, Victor; Adetoyinbo, Ayobami; Department of Agricultural Economics, Agrifood Chain Management, Humboldt Universität zu Berlin, Berlin, Germany; Gupta, Saurabh; Centre for Development Policy and Management (CDPM), Indian Institute of Management, Udaipur (IIMU), Udaipur, India; Okoruwa, Victor; Department of Agricultural Economics, University of Ibadan, Ibadan, Nigeria
Motivation: Agricultural input subsidy programmes are crucial for improving agricultural productivity in sub‐Saharan Africa (SSA). However, there is little empirical evidence on how second‐generation input subsidy programmes (SISPs) based on information and communication technology (ICT) are implemented and the institutional challenges that undermine their effectiveness. Purpose: This article assesses the implementation of ICT‐based SISPs and their challenges in SSA using the Nigerian e‐wallet input subsidy programme as a case study. We draw on a conceptual framework that integrates the national innovation system (NIS), contingency theory, and new institutional economics. Approach and methods: We analysed expert interviews and participatory qualitative data from Process Net‐Maps and focus group discussions (FGDs) using content and Process Net‐Map analyses. Findings: The results show that over 20 public, private and community actors were involved in implementing the e‐wallet SISP across five stages. The programme increased private‐sector participation, reduced corruption, improved recipient targeting, and speeded up input delivery compared to first‐generation input programmes. However, weak institutional arrangements (such as poor funding, restricted institutional collaborations, and stakeholder capability gaps) undermined the innovation aspect of the e‐wallet SISP. The programme also faced five main challenges: policy inconsistency, poor information flow and weak reporting, moral hazards such as “round‐tripping,” input leakage and diversion, and elite capture. The study concludes that institutional constraints, rigid organizational structures, and a narrow focus on solving first‐generation programme challenges limited the ability of actors to adapt to new and evolving challenges. Policy implications: Effective SISPs and input policies require supportive institutional environments that allow actors from all sectors to function effectively. Programmes should thus be designed and managed with flexible and organic structures that foster collaboration among private, public, and community stakeholders. Continuous, stage‐specific evaluations and smart governance tools, such as real‐time mobile data collection and buy‐back initiatives, can strengthen monitoring, input tracking, accountability, and input use incentives.
Do we need post-tree thinning management? Prescribed fire and goat browsing to control woody encroacher species in an Ethiopian savanna
(2024) Abate, Teshome; Abebe, Tesfaye; Treydte, Anna
Worldwide, bush encroachment threatens rangeland ecosystem services, including plant biodiversity and forage for livestock. Various control methods for encroaching woody species and restoring herbaceous vegetation exist but have rarely been explored experimentally. We assessed the impact of post-tree thinning management on tree mortality, the herbaceous community, and overall rangeland condition in Borana, an Ethiopian savanna ecosystem. At two 1.4 ha areas of encroached mono-specific Vachellia drepanolobium (whistling thorn) stands, we set up twenty-four 20 × 10 m experimental plots with four post-tree-thinning treatments (goat browsing only (1), prescribed fire (2), fire and goat browsing (3), and control (4) (i.e., no management after tree cutting), with three replications in a complete block design. Over two growing periods, we monitored resulting tree mortality, coppicing, seedling mortality and recruitment, as well as herbaceous layer attributes (diversity, biomass) and overall rangeland condition. All three post-tree thinning management scenarios significantly enhanced tree mortalities, reduced seedling recruitment and increased the abundance of the dominant desirable grass species. Prescribed fire and fire and goat-browsing treatments resulted in significantly greater grass and forb species richness, forb diversity, and biomass, as well as the overall rangeland condition compared to goat browsing only and the control treatment. However, grass species diversity did not respond to treatments. Post-tree management significantly increased tree mortality, reduced seedling recruitment, and increased the abundance of desirable grass species. Our findings strongly suggest that post-thinning management, particularly prescribed fire or a combination of fire and browsing, is highly effective in suppressing woody encroachment and improving biomass and overall rangeland condition.
Effect of irrigation canal conveyance efficiency enhancement on crop productivity under climate change in Nepal
(2024) Basukala, Amit Kumar; Eschenbach, Annette; Rasche, Livia
Nepal is expanding its irrigation facilities as an adaptive measure to climate change; however, the current canal conveyance efficiency (CCE) is low with significant water losses. In this study, we assess the potential impact of increasing CCE on the productivity of rice, maize, and wheat under different climate change scenarios (SSP1-2.6, SSP3-7.0, and SSP5-8.5), utilizing three bias-adjusted general circulation models. The study simulates potential yields at ecoregion levels for two periods: near future (2023 to 2050) and end-century (2075 to 2100). Management scenarios include the following: (1) business as usual, (2) CCE at 30%, (3) CCE at 50%, and (4) CCE at 70%. The results indicate that increasing CCE to 30%, coupled with expanded irrigated areas and adjusted fertilization rates, could boost yields by three tons per hectare across all three crops at the national level. Further increasing CCE to 50% could yield additional increases of up to 0.6 t/ha of maize and 1.2 t/ha of rice in the terai region. A CCE of 70% results in further increases of up to 2.1 t/ha of rice and 1.2 t/ha of maize. The benefits of improved CCE vary by location, with the subtropical terai region experiencing the most and the mountain regions showing the least. We conclude that there is potential to increase yields by increasing CCE to 70% in the terai region, 50% in the hill region, and 30% in the mountains. Wheat appears to benefit the least from improved CCE. This work highlights efficient irrigation as a reliable adaptive measure for future climate change in Nepal.
Enhancing weed suppression in plants by artificial stress induction
(2025) Merkle, Michael; Petschenka, Georg; Belz, Regina; Gerhards, Roland
Various plant species from the Poaceae, Cannabaceae, and Brassicaceae families are used as cover crops to suppress weeds and volunteer crops through competition and allelopathy. This study examined the effects of artificially induced stress on the physiological processes, total phenolic content (TPC), and allelopathic potential of the plant species Avena strigosa, Cannabis sativa , and Sinapis alba at an early growth stage with the aim to increase their weed suppression abilities. Stress was induced at the 3–4 leaf stage in greenhouse-grown plants via harrowing, methyl jasmonate (MeJA) application, insect stress simulation, or a combination of insect stress and harrowing. Maximum quantum yield of photosystem II and shoot dry matter in the three plant species were only minimally or not affected a few days after treatment (DAT). Insect stress caused visible symptoms on treated leaves in all plants. The TPC in the shoot extracts of combined stress-treated C. sativa and insect-stressed S. alba was significantly higher by 1.7 and 1.9 times, respectively, five DAT compared to the shoot extracts from untreated control plants. Additionally, laboratory bioassays with aqueous shoot extracts from the untreated and treated plants were conducted to identify changes in allelopathic potential within the shoot tissues. The application of shoot extracts from MeJA-treated C. sativa and S. alba resulted in the lowest seed germination rates for the two weed species Alopecurus myosuroides and Stellaria media , as well as for the volunteer wheat Triticum aestivum , which were up to 65% lower 10 DAT compared to seeds treated with shoot extracts from non-stressed plants. However, the root-suppressing effect of the shoot extracts on weeds was not influenced by the stress treatments. This study reveals that artificial stress induction can be a suitable management strategy to enhance weed and volunteer cereal suppression in plants in an early growth stage but may vary between stress types and plant species, and requires further optimization and field testing.
Evaluating the protein value of fresh tropical forage grasses and forage legumes using in vitro and chemical fractionation methods
(2021) Salazar-Cubillas, Khaterine C.; Dickhöfer, Uta
The objectives of the present study were (1) to assess the adequacy of the in vitro and chemical methods to predict post-ruminal crude protein supply (PRCP) from fresh tropical forage, and (2) to identify PRCP supply predictors. Twenty-three fresh forage grasses and 15 forage legumes commonly used in domestic cattle feeding in the tropics and subtropics were incubated in the rumen of cows to determine ruminal crude protein (CP) degradation. The PRCP supply was calculated from in situ rumen-undegraded CP and in vitro organic matter digestibility (i.e., reference method), from ammonia-nitrogen release during in vitro incubation (i.e., in vitro method), and from the concentrations of chemical CP fractions (i.e., chemical method). The adequacy was evaluated using error-index and dimensionless parameters, and stepwise regression was used to select PRCP predictors. Adequacy ranged from poor to moderate (0.53 to 0.74) for the in vitro method being lower for forage legumes at a slow rumen passage rate (0.20), and even poorer (0.02 to 0.13) for the chemical method. Hence, the in vitro method can estimate PRCP supply in tropical forages with moderate to high but not with slow passage rates. Equations developed in the present study appear to predict PRCP supply with reasonable adequacy.
Exploring the plausibility of inoculated cowpeas as a climate adaptation strategy for Namibian smallholder farmers
(2025) Rasche, Livia; Katjana, Johannes; Jantke, Kerstin; Uchezuba, David; Schneider, Uwe A.; Lombardi, Mariarosaria
Increased cultivation of cowpeas is a possible adaptation option for Namibian farmers under changing climatic conditions. Using inoculated cowpeas can potentially double the yields under favorable climate conditions. But is such a potentially beneficial agricultural adaptation technique likely to be adopted? We surveyed 90 cowpea farmers from 30 villages in the Kavango region of northern Namibia on their households and farms, access to institutions and services, food consumption and preferences, and perceptions of climate change. Our survey reveals that smallholder farmers will not readily adopt the new technology. At most, about 50% of farmers can be convinced by new information to change their agricultural activities. When specifically asked about their willingness to grow inoculated cowpeas, almost all farmers responded that they would be willing to do so. However, the farmers are reluctant to allocate more land for cowpea cultivation, mainly because harvesting is very time and labor-intensive. The study shows that technology assessments should be conducted in combination with socio-economic assessments to realistically assess the potential success of proposed adaptation measures, as the extent to which a new technology may be adopted is an essential indicator for justifying funding of new technologies or adaptation programs.

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