Newest publications
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.
Potential pitfalls when using popular chemical extractions to characterize Al‐ and Fe‐containing soil constituents
(2025) Rennert, Thilo; Lenhardt, Katharina R.; Rennert, Thilo; Department of Soil Chemistry and Pedology, Institute of Soil Science and Land Evaluation, University of Hohenheim, Stuttgart, Germany; Lenhardt, Katharina R.; Department of Soil Chemistry and Pedology, Institute of Soil Science and Land Evaluation, University of Hohenheim, Stuttgart, Germany
Wet‐chemical extraction of soil to quantify pedogenic species or to remove specific compounds prior to other analyses is an established approach in analytical soil mineralogy and soil chemistry. Interpretation and informational value of data derived from long‐established and frequently used extractions, for instance involving dithionite, oxalate/oxalic acid in the dark (AOD), and pyrophosphate (PYR), suffers from nonuniform practical regulation and missing knowledge about potential methodical limitations. In this review, we analyzed potential pitfalls of these frequently used extractions, with the focus on selectivity and completeness of the methods as derived from effects of time dependency and of phase separation. Major problems we identified comprised that time‐dependency of extraction differed between analytical targets, that a multitude of species is attacked, reducing the selectivity for the original analytical target, and that studies on extraction from model compounds, including analytical targets and nontargets, are not universally present. The latter aspect is crucial for the completeness of AOD and PYR extraction that has not been proven for all potential analytical targets of the methods yet. We practically tested citrate (CIT) extraction of aluminum (Al) and iron (Fe) in organic association, using selected models of soil constituents. Apart from a synthesized poorly ordered Si‐rich short‐range ordered aluminosilicate, CIT did not extract Al from nontarget phases, confirming previous studies, but did extract Al and Fe completely from organic associations. In addition to recommendations on the practical use of dithionite‐based, AOD, citrate‐ascorbate (CA), and CIT extraction, we suggest replacing highly problematic PYR extraction by CIT extraction for metals in organic association in soil and using AOD extraction in combination with CA and CIT extraction to avoid potential misinterpretation of ambiguous data.
Mitigating phytotoxicity of hydrothermal liquefaction hydrochar toward potential agricultural applications
(2026) Batista, Gabriel F.; Kruse, Andrea; Becker, Gero C.
Valorizing hydrothermal liquefaction (HTL) by-products is essential to improve process sustainability and support its industrial-scale implementation. However, the direct agricultural application of HTL-derived hydrochar remains limited due to reported phytotoxic effects. By studying and mitigating phytotoxicity, this work evaluates the potential suitability for agricultural use of hydrochar, the solid by-product from continuous HTL of a 50/50 wt. % cattle manure and wheat straw mixture at 325 °C, separated with an in-line filter. Phytotoxicity was assessed using seed germination assays with Barley (Hordeum vulgare) and Cress (Lepidium sativum) seeds. Two hydrochar post-treatments, washing (hydrochloric acid and water) and pyrolysis (300 °C and 500 °C), were examined to mitigate hydrochar phytotoxicity. Raw HTL-hydrochar significantly hindered plant growth, reducing the root lengths of barley and cress by 37 % and 70 %, respectively, compared to the control. Water-washed post-treatment eliminated hydrochar phytotoxicity and enhanced Barley root growth by 42 % compared to control at a 15 ton ha⁻¹ application rate, indicating a possible growth-stimulating effect. Pyrolysis also mitigated hydrochar phytotoxic effects, with cress root lengths statistically similar to the control. No uptake of heavy metals by the plants were observed in the germination assays. These results suggest that phytotoxicity originates from water-soluble organic compounds, likely phenols, short-chain organic acids and aldehydes, produced during HTL process and adsorbed in the hydrochar surface. The novelty of this work lies in demonstrating the complete removal of phytotoxicity from HTL hydrochar using technologically mature and scalable post-treatments. Therefore, a barrier to hydrochar valorization is removed, enabling further investigations into agronomic applications. This work contributes to a circular biomass valorization strategy.
From farm to table: uncovering narratives of agency and responsibility for change among actors along agri-food value chains in Germany
(2025) Hector, Veronica; Friedrich, Jonathan; Schlaile, Michael P.; Panagiotou, Anna; Bieling, Claudia
Given the complex nature of agri-food value chains and related sustainability challenges, the question arises who has the agency and responsibility to address these challenges and facilitate systemic change. We address this question through a mixed method approach and examine experiences with agriculture among different actors along the agricultural value chains in Germany. Based on this, we explore how various actors make sense of current agri-food topics as well as of their perceived responsibility and agency to change practices. While our study shows weak signals for the favoring of collective and collaborative approaches to change, there is a dominant narrative of externalizing responsibility to other actors, mainly consumers, state actors, and to a lesser extent farmers; upstream market actors such as retailers are barely mentioned, indicating a lack of awareness of the power dynamics within agri-food systems. We discuss how these findings can inform appropriate governance mechanisms at different levels and future research to address the prospective responsibility of value chain actors and power dynamics within agri-food transitions.
Effect of thermal treatment on the extraction and antioxidant and antiglycation activities of (poly)phenols from Ribes magellanicum
(2025) Ávila, Felipe; Martinez, Natalia; Mora, Nicolás; Márquez, Katherine; Jiménez-Aspee, Felipe; Rupasinghe, H. P. Vasantha
Phenolic compounds have antiglycation activity, but the changes occurring during thermal treatment (TT) in these activities are not completely understood. The effects of the extraction conditions of (poly)phenols from Ribes magellanicum fruits, before and after TT, on their antioxidant and antiglycation effects were assessed. (Poly)phenol-enriched extracts (PEEs) from raw and TT (90 °C, 1 h) Ribes magellanicum were extracted using three solvent mixtures (ethanol/water/acetic acid) with increasing water content (0, 24, and 49%) and three solvent-to-solid ratios (5, 10, and 20 mL/g). PEEs of raw samples showed increased values of total (poly)phenols (TPC), TEAC, and FRAP and decreased IC50 values of fluorescent advanced glycation end products (AGEs) with increasing water content. An increase in TPC and FRAP values was observed for TT samples, but an increase in the IC50 values of fluorescent AGEs for PEEs with increasing water content was observed. Antiglycation activity (IC50 raw/IC50 TT) depended on the solvent-to-solid ratio and the extracting solvent. HPLC-DAD-MS analysis of raw and TT samples showed degradation of anthocyanins, flavonoid fragmentation, and oxidation as the main changes in the phenolic composition of TT samples. We show that TT affects the (poly)phenolic composition of R. magellanicum, producing a decrease in the antiglycation activity when extractions are performed with increasing water content, despite increasing TPC and FRAP activity.