Author and affiliation:

• Roy Durlave, Bangladesh Open University

Marine red algae from the Bangladesh Bay of Bengal Hypnea Sp have been used as organic materials due to the presence of a number of plant growth-stimulating compounds. The effect of various seaweed species on plant growth and development with an emphasis on the use of this renewable bio-resource in sustainable agriculture of northern fertilizers raw materials system. Organically made fertilizers play an important role in increasing crop yield and the quality of crops promises improvements considering climate adaptation. Seaweed wastes compost was put in evaluation trials at Sreemangal, Bangladesh to evaluate its efficacy and find out the optimum dose for profitable Betel leaf production. This part of the study is directed toward the analysis of the future trend and performances of composting seaweed wastes. The science of seaweeds explores, how analysis of the future trend and performances of composting seaweed wastes. A field study was conducted at three sites at Khasia farmers of Sreemangal Khasia betel leaf cultivation community area of Bangladesh. Seaweed wastes mixed with compost organic fertilizer dose of 50g per support tree . The highest betel leaf yield was obtained from seaweed wastes mixed with compost organic fertilizer applied to plants. Table 1. (2880 leaf). Two people have not used it, but the one who has used it has had good results. This study suggests that seaweed wastes mixed with organic fertilizer are suitable for betel leaf cultivation. Area-based conservation is a key tool for delivering the SDG goal of responsible production and consumption. Providing a safe alternative to chemical fertilizers is a crying need of the present time. Marine red algae from the Bangladesh Bay of Bengal Hypnea Sp are often regarded as an underutilized bio-resource seaweed and have been used as organic materials due to the presence of a number of plant growth-stimulating compounds.The effect of various seaweed species on plant growth and development with an emphasis on the use of this renewable bio-resource in sustainable agriculture of northern fertilizers raw materials system. Organically made fertilizers play an important role in increasing crop yield and the quality of crops promises improvements considering climate adaptation. (www.northernfertilizer.com). Although chemical crop fertilizers boost crop yield, they are also responsible for environmental pollution all around the world. Northern organic and balanced fertilizers provide a safe alternative to chemical fertilizers while having more agricultural output and reducing chemical fertilizer usage. Technology-based circular economy model. Seaweeds or marine macroalgae are rich in diverse compounds like lipids, proteins, carbohydrates, phytohormones, amino acids, osmoprotectants, antimicrobial compounds and minerals. Their potential for agricultural applications has been used since antiquity, but recent demands of organic farming and organic food stimulated much the application of organic treatments like seaweed extracts in agriculture. Md. Mohidul Islam, Bangladesh Fisheries Research Institute (BFRI), Md. Shahzad Kuli Khan, Marine Fisheries & Technology Station. Bangladesh Fisheries Research Institute, Jakia Hasan, Bangladesh Fisheries Research Institute, Debbrota Mallick, Dauphin Island Sea Lab,Seaweed Hypnea sp. culture in Cox’s Bazar coast, Bangladesh October 2017, Bangladesh Journal of Zoology 45(1):37-46 DOI:10.3329/bjz.v45i1.34192. Project: Development of culture of seaweeds in south-eastern coast of Bangladesh. Seaweed wastes compost was put in evaluation trials at Sreemangal, Bangladesh to evaluate its efficacy and find out the optimum dose for profitable Betel leaf production. This part of the study is directed toward the analysis of the future trend and performances of composting seaweeds wastes and seaweeds can sequester carbon and reduce atmospheric carbon dioxide levels, thereby mitigating the effects of global warming. A field study was conducted at three sites at Khasia farmers of Sreemangal Khasia betel leaf cultivation community area of Bangladesh. Seaweed wastes mixed with compost organic fertilizer dose of 50g per support tree .

Table 1. Yield of betel leaf as influenced by seaweed wastes based organic fertilizer
Demo tree Farmers Name & Address Betel Leaf Plucking per day
1 Harun,Aliachhara, Habiganj, Bangladesh. 2780
2 Sonet,LongliaPunji , Sreemangal, Bangladesh. 2880
3 Victor Somer, Dubblechhara Punji, Moulvibazar, Bangladesh. 2780

Results:
The highest betel leaf yield was obtained from seaweed wastes mixed with compost organic fertilizer applied to plants. Table 1. (2880 leaf). Two people have not used it, but the one who has used it has had good result.

Authors and affiliation:

• Bella Tsachidou, Université libre de Bruxelles
• Philippe Delfosse, University of Luxembourg

To provide sufficient quantities of food, feed and other products, farming systems have to overcome limiting factors such as the nutrient depletion of arable soils. Nitrogen being the main mineral element required for plant growth, has led to the extensive use of chemical fertilizers causing nitrogen pollution of the ecosystems. To prevent further acceleration of environmental pollution emanating from agriculture, the agricultural sector has shifted its attention to alternative eco-friendly approaches. Anaerobic digestion is an environmentally sound multipurpose process that has the capacity to turn waste into a resource, by generating both cost competitive bioenergy in the form of biogas and biofertilizer as digestate (also knows as biogas residues) which contains all the nutrients initially present in the organic substrates utilized. Therefore, the recycling of biogas residues resulting from the anaerobic digestion of organic waste on agricultural land is among the means to reduce chemical fertilizer use, combat climate change and advance circular economy. However, the long-term effect of biogas residues on soil properties remains an unexplored field of research and therefore, despite their potential, the use of biogas residues as biofertilizers is limited due to a lack of confidence in their quality and safety.

 
Given the importance of grassland agroecosystems in Europe, this investigation focused on the agricultural and environmental benefits of different biogas residue fractions when utilized as biofertilizers on the grassland soils of the Greater Region with the ultimate aim to provide scientific evidence for the EU policy making and modification with respect to agricultural sustainability under climate change. More specifically, in this in sacco decomposition study we investigated the potential of the granulated biogas residue fraction to provide nutrients and enhance soil carbon sequestration when utilized as exogenous organic matter in grassland soils, and assessed the impact of different nitrogen fertilizers on the organic matter decomposition and nutrient release processes. The experiment was conducted in two permanent grasslands of the Greater Region over one management period using rooibos tea as a comparator material. The decomposition and chemical changes of the two materials after incubation in the soil were assessed by measuring the mass loss, total carbon and nitrogen status, and fibre composition in cellulose, hemicellulose and lignin.

 
Overall, after the incubation period, granulated biogas residue maintained up to 68% of its total mass, organic matter and total carbon; increased its content in recalcitrant organic matter by up to 45% and released 45% of its total nitrogen. Granulated biogas residue demonstrated resilience and a higher response uniformity when exposed to different nitrogen fertilizers, as opposed to the comparator material of rooibos tea. However, the magnitude of fertilizer-type effect varied, with ammonium nitrate and the combinatorial treatment of raw biogas residue mixed with urea leading to the highest organic matter loss from the bags. Finally, following decomposition, we observed the formation of lignin-like substances, which were analytically recorded as acid-insoluble substances. This may be an indication that recalcitrant C and N were carried into the bags via the resilient compounds of chitin and glomalin originating from fungi, such as arbuscular mycorrhizal fungi, which might have invaded the bags to absorb nutrients, particularly phosphorus, from the granulated biogas residue.
The findings of this study suggest that granulated biogas residue is a biofertilizer with the potential to supply nutrients to soil biota over time and promote carbon sequestration in grassland soils in several ways. Overall, these results strongly advocate for the environmental benefits of biogas residues and their capacity to compete favorably with chemical fertilizers, thereby advancing agricultural sustainability while contributing to climate change mitigation.

Authors and affiliations

Agroscope

• Francesco Argento
• Frank Liebisch

Carbon sequestration in agricultural soils is increasingly seen as an effective way to mitigate climate change. Soil organic carbon also plays a crucial role in maintaining soil fertility, water retention, and nutrient cycling and thus is a key element of soil health. However, the frequent use of high amounts of organic fertilizers increases the stored (total) nitrogen pool and subsequent mineralization of soil organic matter contributes to leaching of nitrates into groundwater, degrading drinking water quality and ecosystems.

While increasing soil organic carbon can lead to improved soil fertility and water retention, high levels of soil organic carbon, given the right conditions, can lead to increased microbial activity, which can increase nitrogen mineralization and intensify nitrate leaching. In recent studies, it has been shown that nitrate leaching is often largely fed from the soil reserves of organic matter. Furthermore, the composition of humus can vary depending on the source material used for organic fertilization and thus affects subsequent decomposition rate, leading to differences in nutrient availability and stability. Therefore, management practices that promote carbon storage via humus accumulation should be carefully balanced with measures to prevent excessive build up and nitrate losses to ensure optimal soil function and health.

The trade-off between carbon storage and nitrate pollution highlights the need for site-adapted approaches that consider both factors simultaneously, while providing the base for crop production. Traditional site-adapted approaches such as crop rotation, cover cropping, and organic amendments have been shown to increase soil organic carbon while reducing nitrogen leaching. Additionally, the use of site-adapted fertilizer recommendations and precision agriculture tools such as soil- and model-based fertilizer recommendations, variable-rate fertilizer application and soil mapping can help optimize nitrogen fertilizer application to maximize yield while minimizing nitrogen leaching and other losses. Understanding the role of mineralization in the seasonal nitrogen supply and matching it with the crop nitrogen demand is of fundamental importance for balancing strategies.
In conclusion, increasing soil organic carbon is an important strategy for mitigating climate change and improving soil fertility and crop production, but must be balanced with efforts to maintain water quality and prevent soil degradation. Site-adapted approaches that consider environmental factors such as soil type, topography, water and nutrient availability can help optimize fertilizer management practices to achieve both goals simultaneously. By balancing soil fertility and soil services, we can achieve systems that benefit both the environment and crop production.

Authors and affiliations:

Lidia Marcińska-Mazur (1),  Renata Jarosz (1), Justyna Szerement (1, 2), Jakub Mokrzycki (1), Monika Mierzwa-Hersztek (1). 

1. AGH University of Science and Technology
2. Maria Curie-Skłodowska University

Nowadays, we observe continuous soil degradation caused by erosion, salinity, loss of biodiversity, reduction of organic matter, or the accumulation of toxic compounds. It becomes evident to use the right indicators to assess and monitor soil condition. Among the various biological indicators commonly proposed for soil health monitoring, the activity of soil enzymes has great potential to assessment soil quality.
The aim of the study was to investigate the effect of the addition of the mineral-organic fertilizer compositions composed of zeolite-vermiculite composite (NaX-Ver) or zeolite-carbon composite (NaX-C) enriched with lignite or leonardite to the mineral salts (NPK) on the enzymatic activity of soil. The 2-year pot experiment was carried out in 2020 and 2021 in the vegetation hall of the University of Agriculture, located in Krakow-Mydlniki. In total, the pot experiment design for investigated plant – spring wheat, comprised 10 sets of treatments, and each set included 4 replications. The control objects were soil without fertilisation (C) and an object with mineral fertilization (NPK).

Conductive to assess the impact of mineral-organic mixtures on the soil’s enzymatic activity, analyses of the activity of dehydrogenases (DhA), ureases (Ure) as well as an acid (AcP) and alkaline phosphatases (AlP) were carried out. On the basis of the obtained results, the value of the soil quality index was assessed using the geometric mean of enzyme activity (GMea). The obtained results indicate that both the type of applied mineral-organic mixtures and their dose significantly impact the soil’s enzymatic activity. The highest level of enzymatic activity was found in the soil with the addition of NaX-Ver with 3% of lignite, and the lowest in the soil with the addition of NPK. Based upon the results of the research, it can be concluded that the addition of zeolite-carbon composite contributed to a greater extent to the improvement of enzymatic activity in the soil compared to the addition of zeolite-vermiculite composite.

Authors and affiliation

• Oehl, Fritz, Agroscope                      
• Corazon-Guivin, Mike Anderson, Universidad Nacional de San Martín
• Tchabi, Atti, Université de Lomé                   
• Coyne, Danny, International Institute of Tropical Agriculture          
• Sieverding, Ewald, Universität Hohenheim

Arbuscular mycorrhizal fungi (AMF) deliver important ecosystem services and play a key role for major soil and plant functions, including root health and plant nutrition, soil health and fertility, as well as preventing soil erosion and facilitating water infiltration. Importantly, they contribute to climate smart agriculture. Living collections of indigenous AMF have been developed by the authors since 1980 at: I) CIAT (International Center for Tropical Agriculture), Colombia, ii) IITA (International Institute of Tropical Agriculture), Benin/Nigeria (together with the University of Basel, UNIBAS), iii) at UNIBAS a tri-national collection from the countries surrounding Basel), iv) the Swiss Agroscope collection of AMF (SAF), into which the trinational collection was integrated. Recently another collection was initiated at the National University of San Martín in Peru. These collections contain ~350 AMF isolates, belonging to over 50 species, most of which have been screened for their beneficial effects on crop growth, nutrient uptake and soil health on various crops: e.g. cassava, beans, white yam, coffee, inka nut, soybean, wheat, strawberry, and leek. Some outstanding results from those screening activities will be presented, and the isolates that proved the most beneficial in terms of crop growth and soil health are highlighted. The special properties of some AMF species, their phylogeny, life cycle strategies and their protective effects against root pests and diseases (e.g. nematodes or pathogens) will also be presented and the drawbacks for their implementation in agriculture discussed.

From experiments performed in the Tropics, isolates belonging to Rhizoglomus, Funneliformis, Sclerocystis, Entrophospora, Diversispora and Acaulospora, proved most effective, while species in the early ancestral clades, Archaeospora and Paraglomus, rarely showed a positive effect. In experiments performed in Europe, isolates of Funneliformis, Rhizoglomus, Entrophospora and Diversispora were among the most effective, while species from Archaeospora and Paraglomus were least effective on crop growth. However, there were species and genera within Glomeraceae, which also had no effect on plant growth, while others had short-term (few months) or long-term (several to multiple months) effects, but rarely both. For example, within the Glomeraceae and Entrophosporaceae, Rhizoglomus spp., Funneliformis mosseae and Entrophospora claroidea promote crop growth for a few months only, while Dominikia aurea and Septoglomus constrictum impact plant growth over several crop cycles. This may be linked to their life cycle and survival strategies.

For the magnitude of effects on plant growth and for the greatest diversity of species having a positive impact on plant growth, Rhizoglomus stands out as the genus providing the most beneficial effects, from species such as R. intraradices, R. irregulare, R. clarum and R. manihotis, in addition to R. variabile and R. invermaium, which were only recently found to be highly beneficial for crops. Species from the ancestral AMF orders, however, have rarely been found to be beneficial (e.g. Archaeospora myriocarpa and Paraglomus occultum). There are only limited data for effects by species of Gigasporales, which is the youngest of the six AMF orders. Gigasporales appear to be most prevalent in warmer, subtropical and tropical climates, and where they have the most promising effect on plant growth, health and soil fertility, most probably in the long-term.
Within our collections, ~100 AMF isolates that positively stimulate plant growth and/or improve plant health have been identified. Occasionally, negative but never strongly negative effects were observed, although negative effects have been reported elsewhere. Most isolates demonstrating beneficial effects belong to the Glomeraceae, which is opportune for their use in agricultural settings, as these tend to be easiest to propagate, and to scale up. Using combinations of AMF isolates/species also offers promise but knowledge on their combined effects needs first to be assessed, as some combinations can be antagonistic and their mutual benefits not necessarily additive.
In conclusion, the living collections of AMF offer potentially colossal benefits to agriculture and beyond. This is particularly pertinent under the current sociopolitical climate with rising fertilizer and synthetic input costs, as well as the challenges that climate change presents, and the need to more efficiently use our water resources. The maintenance of these living reservoirs is therefore critical, but requires an equally colossal effort to keep them alive and available.

Authors and affiliation

University of Agronomic Sciences and Veterinary Medicine of Bucharest

• IOSUB, Laura Mihaela
• Teodorescu, Razvan Ionut
• Gidea, Mihai

In the conditions of the continuous growth of the population and implicitly the demand for food, the increase of agricultural production becomes a necessity. This increase can be achieved first of all by increasing the production capacity of the cultivars used, but also through a soil management that harmonizes the local pedoclimatic conditions with the requirements of the cultivated plant. The implementation of the requirements of a sustainable agriculture system manages to meet the requirements of increasing the productivity of the soil combined with the reduction of environmental pollution, the reduction of the amount of fertilizers and the preservation of biodiversity In order to achieve these objectives in the agricultural year 2021-2022, a monofactorial experiment was organized in which the impact of the crop plant on the main physical indicators of the soil, on productivity and on the biodiversity of the flora was determined. The research was carried out in the pedoclimatic conditions of the Romanian Plain on a preluvosol soil. The crops in which the determinations were made were autumn wheat and corn, both established after the harvest of the rape crop. The determinations regarding the soil physics were made after harvesting the crop plant and those regarding the biodiversity in the wheat crop after the completion of the infratit and in the corn crop 4 weeks after the emergence of the crop. the research results showed a reduction in the apparent density of the soils under the corn crop, while the permeability did not register significant differences. Regarding biodiversity, a difference can be found between the weeding spectrum of the two cultures. In the wheat culture, the dicotyledonous species that can overwinter papaver rhoeas, ephemeral (veronica hederifolia and stelaria medi, lamium sp) or with early spring germination (galium aparine, sinapis arvensis, poligonum convolvulus) predominated, and in the corn culture the monocotyledonous species Setaria sp, echinochloa cruss galli, sorghum halepense).

Authors and affiliation

ETH Zürich

• Müller, Claude         
• Hartmann, Martin           
• Feola Conz, Rafaela           
• Six, Johan, ETH Zurich
• Van de Broek, Marijn, ETH Zurich

Research Institute of Organic Agriculture FiBL

• Mäder, Paul,

Agroscope

• Mayer, Jochen

One of the aims of sustainable nutrient management in agricultural soils is to preserve soil organic matter (SOM), which influences important ecosystem services such as carbon storage and soil fertility. Maintaining high SOM stocks can reduce the need for synthetic fertilizer application. As most biogeochemical processes in soils are driven by microorganisms, understanding the impact of soil nutrient management on microbial diversity is essential to select appropriate agricultural practices that optimally use soil nutrients. While the effect of agricultural practices on the soil microbiome is very complex, previous research has identified some guiding principles. For example, the addition of organic matter does not only help to maintain SOM content but also to increase the biodiversity of soil microorganisms and favor the presence of specialized microbial taxa capable to degrade complex organic molecules. In contrast, the use of mineral fertilizers was shown to generally decrease soil microbial diversity and favor oligotrophic taxa adapted to resource-limited environments. While most of these findings are derived from surveys in topsoil (above 30 cm depth), it remains unclear to which depth layers these effects extend in arable soils.
The aim of this study is to gain insights into how agricultural nutrient management alters the structure of the soil microbiome down to 90 cm. Soil samples were collected at the DOK long-term agricultural field experiment (Therwil, Switzerland). The trial was established in 1978, and the experimental treatments include the application of different fertilizer types and crop protection regimes representing typical conventional and organic agricultural practices in Switzerland. Soil samples have been collected down to 90 cm depth in increments of 5 cm. Microbial diversity and taxonomic community composition were assessed using a DNA metabarcoding approach targeting ribosomal markers.
We hypothesize that (1) shifts in microbial community composition are mainly driven by the type of organic residues added, compared to the application of mineral nutrients and that (2) the effect of nutrient management on the microbiome decreases with depth. Also, (3) it is likely that the subsoil microbial community structure changes compared to the topsoil towards more specialist organisms that grow slow and have a higher carbon use efficiency (i.e., oligotrophs) since the abundance of readily available substrates generally decreases with depth.
Preliminary results show that the effect of agricultural practices on microbial beta diversity is significant above the plough layer (i.e, 25-30 cm depth), but not below. They also indicate that the effect of depth on microbial beta diversity can be observed all along the soil profile and that sampling in increments of 5 cm enables to account for differences that are neglected when samples are collected with a lower resolution.

Authors and affiliation

• Wasner, Daniel, ETH Zurich                
• Abramoff, Rose                                 
• Griepentrog, Marco, ETH Zurich                            
• Zagal Venegas, Erick, UDEC            
• Boeckx, Pascal, UGENT          
• Doetterl, Sebastian, ETH Zurich

The concept of distinct soil organic matter (SOM) fractions is promising to improve our understanding of soil carbon (C) dynamics. While there is widespread consensus on the general usefulness of conceptual fractions with specific functional implications, there is still a lack of information on the patterns with which they contribute to bulk soil organic carbon (SOC) at larger scales and across climatic and soil physicochemical gradients. In this study, we first assessed the quantitative importance of three key SOM fractions across a diverse range soils with global significance. In a second step, we elucidated the environmental controls that shape the contribution of these fractions to total SOC amounts.

We sampled a set of 35 grassland topsoils (0 – 10 cm) along a 2300 km north-south transect in Chile ranging from tundra to arid steppe climate. We partitioned the soils into three functional SOM fractions defined by particle size and density (free silt- and clay-sized particles, free particulate organic matter, stable microaggregates), enabling us to quantify fraction-specific total SOC amounts and their relative contribution to bulk SOC. In order to identify links between fractions and potential drivers of C accumulation, we further characterized relevant physico-chemical properties of the soils, compiled climatic data of the sites and characterized OM maturity (DRIFT spectroscopy and Rock-Eval pyrolysis) as well as pedogenic, secondary Fe-, Al- and Mn-oxide concentrations through sequential extraction.

We found that the contributions of mineral-associated SOM fractions to bulk SOC varied strongly across the soil gradient, while the contribution of free particulate organic matter was comparatively stable and low. SOM associated with free silt and clay sized particles are the most important C reservoir in soils with less than 4 % SOC, whereas in soils with higher SOC content, the majority of the SOC is associated with stable microaggregates. The amount of SOC in various fractions was sensitive to changes in temperature, pedogenic oxides, and OM input vs. decomposition. Comparison of OM maturity showed that free particulate OM and OM associated with the free silt- and clay-sized fraction can be clearly distinguished, while OM in microaggregates is likely a mixture of both.

This study demonstrates that in SOC-rich soils, microaggregates represent a major fraction of bulk SOC, and that SOC in key SOM fractions can be linked to distinct climatic and soil physicochemical factors.

Authors and affiliation

University of Lausanne

• Dupla, Xavier 
• Claustre, Romane     
• Bonvin, Emma
• Grand, Stephanie

Terrestrial enhanced weathering refers to the application of crushed silicate rocks (often basalts) to agricultural soils. This practice has been labelled a negative emission technology, since it has the potential to capture some atmospheric CO2, as highly weatherable minerals react with carbonic acid. Furthermore, the addition of finely ground fresh rock has been postulated to improve soil quality, for instance by replenishing the mineral fertility of the topsoil layer; yet to our knowledge, no empirical data exists regarding the effects of silicate rock powder additions on soil processes. Using first results from an enhanced weathering field trial initiated in 2020 in vineyard soils of north-western Switzerland, we show that basalt powder application at a rate of 20 t.ha-1 significantly affects soil processes. Specifically, we found that basalt weathering was actively occurring even in soils containing calcite. Chemical weathering reactions generated alkalinity which was detectable in soil water (collected by tension lysimeters), but not in soil pH or exchangeable acidity. We observed an increase in poorly crystalline secondary inorganic phases (such as, short-range order aluminosilicates and iron oxides), which could improve the soil’s organic matter stabilization potential. Basalt powder addition also affected biological activity. We measured approximately twice as much earthworm biomass in plots treated with basalt, compared to control. Soils from basalt-amended plots also displayed increased respiration rates in an incubation trial. Altogether, these results show that soil processes are affected by the basalt powder addition. While the increase biogeochemical reactivity of basalt-amended soils could be beneficial in many cases, many unknowns remain regarding the long-term sustainability of the practice.

Authors and affiliation

• Causevic, Senka
• Sentchilo, Vladimir
• van der Meer, Jan Roelof

University of Lausanne

Currently, we are faced with extensive soil microbiome impoverishment due to soil overuse and pollution. A viable strategy to restore soil sites is bioaugmentation: introduction of new species or consortia with specific metabolic capabilities into the environment of interest. However, progress in the field is largely stagnant due to poor understanding of general principles regarding soil microbiome assembly, functioning, and response to newcomer strains.

To address these questions systematically, we have designed two soil bacterial communities of differing complexity (SynCom and NatCom) and tracked their developmental trajectories within soil microcosms. Both communities were then complemented with strains of our choice (known pollutant degraders or a plant-growth promoting bacterium), either under conditions where the resident SynComs or NatComs were themselves actively growing or when these had reached apparent steady state. In both cases, inoculant and community population densities were measured with flow cytometry and overall community compositional changes were assessed with amplicon sequencing.

In general, we observed poor establishment of inoculants within both background soil communities. Inoculants originating from soil did better than non-native strains. Population sizes of inoculants developed better under conditions of actively growing soil communities than in steady-state systems. If provided with a specific nutritional niche, inoculants proliferated 20-50-fold better and maintained during longer periods. Inoculation fates were independent of the soil community starting diversity.

In conclusion, we observe that deployment of SynComs and NatComs are useful models to test community restoration techniques, because of their high reproducibility. Successful microbiome interventions will rely both on controlling niche availability and temporal taxa succession.

Authors and affiliation

• Wright, Fergus
• Arraiano Castilho, Ricardo
• Sanders, Ian

University of Lausanne

Arbuscular mycorrhizal fungi enhance plant tolerance to biotic and abiotic stressors and their use in agricultural systems has huge potential. Once established, the fungal hyphae grow profusely through the soil to connect and distribute nutrients between plant populations as well as shape aboveground plant diversity. Belowground the interactions between arbuscular mycorrhizal fungi and the soil food web are poorly understood. It is likely these interactions greatly effect plant colonisation by the fungi, the behaviour of hyphal foraging and the success of exogenous fungal inoculum. We hypothesis that arbuscular mycorrhizal hyphae will shape belowground microbial communities and that certain functional groups of soil microorganisms support AMF nutrient uptake and hyphal proliferation. We used a metatranscriptomics approach on the rhizosphere and mycorrhizosphere of maize plants grown under greenhouse conditions to explore the interactions between two arbuscular mycorrhizal genotypes and two different soil microbial inoculums. Furthermore, a non-destructive soil core system was used to sample mid-experiment and give us two time points in our metatranscriptomics data. This allowed us to assess gene expression before and after the inoculation of the different microbial communities to understand how the soil microbiome responds to and affects arbuscular mycorrhizal fungi. We hope to identify key functional microbial groups that support the plant-fungal symbiosis and can be tested in future experiments. In general, our results will provide novel insights into the multipartite belowground interactions that shape above ground ecosystems which will inform farmers and policy makers who wish to develop practices to support soil health.

Authors and affiliation

van der Meer, Jan Roelof, University of Lausanne

Microbiomes consist of species-diverse and spatially heterogenous microbial cell assemblages within their host or environmental habitat. The collective working of the microbiota is generally assumed to lead to the emergence of specific functions and processes, which can provide crucial benefits for hosts or play important roles for biogeochemical cycles. Damaged or perturbed microbiomes, for example, under exposure to chemical or physical stresses, are at risk to become dysfunctional and prone to system collapse. One of the potential approaches to restore such microbiomes is to provide them with specific microbial strain mixtures, which may remove or resist the stressors, and lead to recovery of the original species diversity. However, it is widely unknown which mechanisms underlie development of complex microbiota, their steady-states and resilience, and which factors determine the proliferation or demise of inoculated strains. This general aspect is the broad objective of the Swiss National centre of competence in research NCCR Microbiomes.

We will give an overview of our current research that focuses on studying the developmental trajectories of soil microbial communities of different complexity and the roles played by interspecific interactions. We will further highlight studies aimed at introducing bacterial strains capable of degrading polluting compounds as a means to restore contaminated sites, and our approaches to understand the successes and limitations of inoculation intervention methods.

Authors and affiliation

Farkas, Éva¹, Bárcena, Teresa G.²; Rittl, Tatiana F. ³; Henriksen, Trond M. ⁴; Dörsch, Peter⁵; Kjær, Sigrid T.⁵, Rasse, Daniel P.¹ and Frøseth, Randi B.⁴

• ¹ Norwegian Institute of Bioeconomy Research (NIBIO), Department of Biogeochemistry and Soil Quality, NO-1431 Ås, Norway
• ² Norwegian Institute of Bioeconomy Research (NIBIO), Department of Agricultural Soil Survey, NO-1431 Ås, Norway
• ³ Norwegian Centre for Organic Agriculture (NORSØK), NO-6630 Tingvoll, Norway
• ⁴ Norwegian Institute of Bioeconomy Research (NIBIO), Division of food production and society, NO-1431 Ås, Norway
• ⁵ Norwegian University of Life Sciences, Faculty of Environmental Sciences and Natural Resource Management, NO-1434 Ås, Norway

Cover crops have emerged as valuable tools in modern agricultural practices, serving multiple purposes such as restoring soil organic matter and improving soil health. In Norway, cover crops have been specifically introduced to mitigate the loss of nitrogen and phosphorous from fields to waterways, addressing environmental concerns and promoting sustainable farming practices.
While cover crops offer carbon sequestration benefits, their overall climate impact may be offset by nitrous oxide (N2O) emissions during the decomposition of plant residues in the soil . In this study, we investigate the role of different cover crops in agriculture on carbon sequestration and climate change mitigation through N2O emissions. Supported by funding from the Agriculture and Food Industry Research Funds, the CAPTURE project seeks to evaluate the climate effects of different cover crop varieties within the main cereal production regions of South- and Mid-Norway.
To determine the soil carbon sequestration potential of different cover crops, a 3-year field experiment was carried out in the South of Norway, where four cover crop species (Italian ryegrass, phacelia, oilseed radish, and summer vetch) were planted in monoculture (with 4 replicates) during the spring of 2021 and were pulse-labelled with 13CO2 throughout the growing season. The plants received 5-6 pulses within 1 m3 transparent chambers. Following the final pulse, biomass (above- and belowground) and soil samples were collected and analyzed in the laboratory using IRMS. Additionally, the fate and persistence of this carbon input are being assessed by monitoring the retention of 13C in particulate organic matter (POM) and mineral-associated organic matter (MAOM) throughout the experiment. By the end of the first growing season, 3-5% of cover crop C was found in the soil particulate organic matter (POM) fraction and 2-4% in the soil mineral organic matter fraction (MAOM).
To explore the contribution of shoot and root biomass to carbon sequestration, the aboveground biomass of cover crops was reciprocally exchanged and incorporated, resulting in plots featuring labelled shoots and unlabelled roots, and plots with unlabelled shoots and labelled roots of the same cover crop specie. Within these plots, the distribution of 13C in the soil organic matter fractions will be monitored, and by sampling the plots in consecutive years, we will be able to determine the input of cover crop-derived carbon (13C) to the soil. The IRMS analyses of soil samples collected in September 2022 (a year after pulse-labelling) are currently underway and the results will be presented at the Conference. Based on the preliminary results, one more sampling is planned for September 2023.
In the neighboring plots, we scaled the soil carbon sequestration potential of different cover crops to barley plots by undersowing them during the spring or summer. Here, the N2O emissions were measured weekly throughout the growing period and even more frequently during autumn and winter. The results of the carbon capture experiment and the N2O emissions should allow us to estimate the greenhouse gas trade-offs of cover crops in Norwegian cereal production. These findings also contribute to the enhancement of the national greenhouse gas inventory and provide valuable insights into the role of cover crops in influencing greenhouse gas dynamics.

Authors and affiliation

University of Málaga

• Gavira, Óscar
• Santos-Barea, Estefania
• Real, Raimundo

Andrena Iniciativas y Estudios Medioambientales

• Aguado, Óscar, 

Syngenta

• Miranda-Barroso, Luis
• Gayan, Ana Lia
• Gugger, Rudolf
• Javier Peris-Felipo, Francisco
• Oyserman, Ben
• Schade, Michael
• Swart, Gina

Soil health, comprising soil life as a substantial component, is indispensable to feeding a growing human world population. Soil arthropods play a crucial role in maintaining soil fertility. They are involved in various processes that contribute to the overall health of the soil ecosystem. Some of the roles of soil arthropods in soil fertility are nutrient cycling through processes such as the decomposition of organic matter and releasing nutrients into the soil. They transform dead plant and animal material, and their excreta and secretions, enriching the soil with essential nutrients. By burrowing through the soil, arthropods create channels that improve soil aeration, allowing air and water to penetrate deeper into the soil, helping for better soil structure, improved porosity, and ultimately enhanced nutrient availability.

In the context of LivinGro™, an international scientific project to fostering agroecosystem biodiversity, we investigated the effects of inter-row flowering corridors in olive and fruit tree orchards on subterranean arthropod biodiversity. The study focused on 8 fields throughout Spain. Each field was divided into 4 sampling zones: 1) tree line as control #1; 2) tree line with treatment; 3) corridor as control #2; 4) corridor with treatment. Sampling frequency was six times per year in six out of the eight fields, and three times per year in the remnant two. Two kinds of traps were used: surface pitfall traps and subterranean sampling devices (SSDs). The pitfalls remained in the fields for 2-3 days, while the SSDs were kept for 15 days. The taxonomic identification was mainly done at the family level, although for certain groups it ended at the order or suborder level. During the sampling time, of the organisms examined, more than 25,000 organisms came from pitfall traps and more than 30,000 from SSDs.

Preliminary results show a greater quantity of organisms in treatment zones than in control zones, for both pitfalls and SSDs and for both tree lines and corridors. The organisms most frequently found in the pitfalls were, in order of frequency: springtails (Entomobryomorpha), mites (Trombidiformes: Prostigmata), and ants (Hymenoptera: Formicidae). In the SSDs we mainly found, in descending order: springtails (Entomobryomorpha), ants (Hymenoptera: Formicidae), and mites (Sarcoptiformes: Cryptostigmata). This study supports the hypothesis that inter-row flowering corridors improve soil fertility through enhanced arthropod activity.

Authors and affiliation

dos Santos, Salomé and Franca, Lucas, Syngenta

Soil is the foundation of all life on land. Soil biodiversity drives many processes that sustain food production and purify soil and water. Fertile, healthy soils are essential for food security.
The rapid population increase means that by 2050 farmers will need to grow 50 % more crops to make sure everyone has enough safe, healthy, and affordable food. At the same time, it is critical that we ensure agriculture is part of the solution for healthier soils. To meet this goal, we must continue to work together with experts to develop, implement, and equip growers with the right tools to enable a more sustainable and profitable farming.
Both plant protection products (formulations) and application approaches must be revised and designed to mitigate their impact on soil health. Syngenta takes actions on that direction very seriously and commits to listen to and welcome the views from the experts on soil fertility. The use of sustainable inerts in product formulations, the focus on biologicals, and implementation of precision application enabling tools such as optical spot spray services, prescription maps through Interra®Scan and Cropwise® platforms and Closed-Loop Knapsack Systems (CLKS) for smallholder farmers in APAC are just a few examples of Syngenta’s activities. Taking part in forums, technical seminars, and conferences is important to promote open discussions between experts and potentially drive initiatives which have soil health as main focus.

Authors and affiliation

Agroscope:

• Malinowski, Marco
• Rog, Ido
• van der Heijden, Marcel

Integrating the benefits provided by microorganisms into agricultural management systems can reduce the overwhelming requirement for external resources supplements. However, incorporating microorganisms such as Arbuscular mycorrhiza fungi (AMF) into current agricultural practices has been hampered by the need for more yield consistency, despite the improvement in plant nutrition and water availability. While specific AMF variants are identified to show positive effects on different crops, less is known about the impact of the plant’s genetic background on the AMF interaction properties. This study investigates the potential effect of the genetic background of maize plants on AMF inoculation successes and mycorrhiza growth response (MGR). We tested 15 maize varieties from more than eight breeding backgrounds on the Swiss list of recommended varieties for farmers in an experimental greenhouse setup with Rhizoglomus irregulare AMF inoculation. Most of the cultivars showed no to positive MGR, the largest MGR was 10%, and three varieties showed negative MGR. In all varieties, we measured 0-12% lower chlorophyll content in plants inoculated with AMF, while varieties with high MGR show a relatively small reduction in chlorophyll content. Interestingly, seeds from the same breeding company, potentially with closely related genetic backgrounds, clustered together in the MGR and chlorophyll content response range. We propose that even after many years of breeding, plants with different genetic backgrounds may have different interaction properties with AMF. More analysis, such as AMF inoculation success, nutrient content, and field inoculation experiments, is required for further conclusions. Adding the interaction characteristics of plant genetic background with mycorrhizal response to the selection of recommended varieties for farmers can lead to higher yields and more sustainable agriculture.

Authors and affiliation

University of Malaga

• Tienda, Sandra
• González, Javier
• López, Marina
• Antonio Gutierrez-Barranquero, Jose
• Carrión, Victor
• Damián Ruiz, José
• Cazorla, Francisco

Syngenta

• Oyserman, Ben
• Peris, Javier
• Gayán, Ana Lia

This research has been carried out within the international project LIVINGRO,® promoted by Syngenta, and is based on the application of the best ecological management practices in different cultivation systems and in various modern crop protection technologies. The study was carried out on selected plots of stone fruit trees and olive trees in different locations in Spain. Soil samples were collected over three years and the beneficial impact that ecological practices can have on soil health and microbial biodiversity was studied by assessing soil characteristics such as organic matter, basal respiration, nitrates and porosity. In addition, microbial biodiversity was also obtained from the same soil samples. Alpha and beta diversity was obtained by the relative abundance of prokaryotic and eukaryotic microorganisms. More specifically, microbial groups were proposed that increase in relative abundance with ecological soil management and that could have a possible beneficial role for soil or plant health. The results indicate that the implementation of the ecological management measures of the LIVINGRO® project could have an effect on soil characteristics, with an increase in total nitrogen, nitrate and basal respiration. In addition, we have also observed that this management could have an effect by increasing the relative abundance of specific microbial genera that could have a beneficial role for soil and plants. Finally, the results reflect spatial differences due to geographical location, with different climatic conditions, relief and lithology, which can affect soil quality and the composition of microbial populations.

Authors and affiliation

Syngenta

• Beyer, Corinna
• Coll, Claudia
• Screpanti, Claudio

Agroscope

• Bucheli, Thomas
• Schönsee, Carina D.

In December 2022 the EU released the assessment framework for “safe and sustainable by design chemicals” which indicates that the hazard assessment of chemicals (including mobility assessment) should take place as early as possible in the innovation stage. Early stage KOC measurements enable chemists to consider the mobility of a new PPP to limit their potential for leaching and subsequent contamination of water bodies and thus reducing the likelihood of environmental contamination. The standard batch equilibrium method for KOC determination is very time-consuming and labor intensive, as well it has high chemical and consumable costs. That is the reason these tests are usually done only for a selected range of PPP candidates at a later R&D stage.

Flow-through column experiments have been used for several years to develop a less time-consuming and more cost-effective alternative method to the batch equilibrium method, with a potential for full automatization and the possibility to process 150 compounds per month. The KOC is determined by assessing the retention of the compound of interest on a chromatographic column packed with the sorbent of interest. In the OECD Guideline 121 it is advised to use a cyanopropyl solid phase containing lipophilic and polar moieties. This stationary phase is though very synthetic and artificial. In the alternative method we present, the columns are manually packed with a mixture of Silicon and Pahokee Peat. Solutions of the compounds of interest are then injected on the columns using an HPLC-DAD using a low flow (quasi-equilibrium condition) of CaCl2 solution as a mobile phase. One injection therefore has a run-time of 20 minutes (very mobile sorbates) up to two hours (for less mobile sorbates). With this method the sorption coefficient can be derived from the net retention times of the sorbates. A comparison of the sorption coefficients found in literature of 18 commercial PPPs (ranging from KOC’s of 2 to 1080) to the sorption coefficients determined with this flow-through columns method resulted in a correlation of 95.7%. By flexibly changing the pH of the mobile phase, or the mobile phase itself, we can unveil molecular interactions between chemical and soil (in example pH dependencies).

This cost-effective, less time- and labor-intensive method proved to be an effective tool for early stage KOC determination which allows chemists to make evidence-based decisions on the design of safe and sustainable chemicals.

Authors and affiliation

Syngenta

• Coll, Claudia
• Screpanti, Claudio

University of Zürich

• Fenner, Kathrin

The persistence of plant protection products (PPPs), or in other words, the lack of degradation of PPP in the environment, is one of the hazard criteria that increases the potential environmental and human-health risks of a chemical because it increases the probability and length of exposure. Increased exposure to PPPs applied directly to crops or soil can thus cause adverse effects on non-target organisms and directly impact soil health.
The EU recently published in December 2022 the recommendations for safe and sustainable chemicals and the challenge is clear: the hazard assessment of chemicals (including persistence assessment) should take place as early as possible in the innovation stage. The assessment of persistence of a PPP in soil is done through laborious standard laboratory tests that can last several months. These standard tests in soil are not suitable for early assessment of persistence during the research and development of new active ingredients for crop protection. New approach methodologies, with high(er) throughput are initially recommended for screening of less hazardous and biodegradable chemical candidates.
We propose a 72h- assay in activated sludge as a medium throughput method to screen for non-persistence of chemicals during the research and development of new active ingredients for PPPs. In experiments performed between 2018 and 2021, a mix of 20 benchmark PPPs was tested in the activated sludge assay. After obtaining the PPP’s half-life in sludge and their partition coefficient Koc, a K-nearest neighbors’ algorithm was used to train classification models. These classification models were able to segregate test compounds (a mix of 22 commercial PPPs) into persistent and non-persistent (according to a half-life threshold of 70 d).
Using liquid chromatography and high-resolution mass spectrometry, we screened for suspect transformation products of the benchmarks in activated sludge and confirmed many similarities to the degradation pathways in soil obtained in regulatory dossiers. Important aerobic transformation pathways such as oxidation reactions, as well as hydroxylation and hydrolysis reactions seem to be represented in both activated sludge and soil.
The read-across of biotransformation potential between activated sludge and soil illustrates a new way to obtain reliable predictions of non-persistence of PPPs. Innovative high-throughput methods are needed to align the safe and sustainable by design principles to the R&D of new chemical ingredients and prevent future soil health damage.

Authors and affiliation

Research Institute of Organic Agriculture FiBL

• Wiget, Andrea
• Kundel, Dominika

The release of tire wear particles (TWP) into the environment is becoming an increasingly important issue that needs to be addressed. Based on modelling data from various studies, the Swiss Federal Office for the Environment (FOEN) estimates that around 14’000 tonnes of macro- and microplastics end up in Swiss soil, surface water and sediments every year. With about 64% of the total microplastic loads, TWPs are the main source of microplastic pollution entering Swiss soils, sediments and surface water. However, data about the amount of TWP released into the environment are usually based on model calculation whilst there are only few actual measurements of TWP loads in soils. This lack of monitoring data is partly due to the limited availability of accessible and cost-effective extraction and analysis methods and the absence of a broadly accepted standard method. The two common approaches used in microplastic monitoring studies are either quantification by gas chromatography combined with mass spectrometry (GC-MS) or Fourier-transform infrared (FTIR) microscopy. Neither instrument is part of a standard lab infrastructure. Adrian Grunder and Alexandra Foetisch from the University of Bern adapted and developed a procedure described by Scheurer and Bigalke in 2018 and Olsen et al. in 2020 into a cost-effective and accessible method to extract and quantify TWP in soil. I tested their method in the frame of the FOAG microplastics project at the Research Institute of Organic Agriculture. In this study, 60 soil samples were collected from permanent grassland at 15 different road sites and defined distances from the road (1, 2, 5, 10 m) in the canton Solothurn.
The TWP were extracted from the soil by density fractionation using a sodium bromide solution. The particles of the supernatant were first soaked in a solution containing urea, thiourea and sodium hydroxide, followed by the Fenton reaction to destroy the organic material. After another density fractionation, the particles were collected on a cellulose filter. A stereomicroscope equipped with a camera was used to capture about 140 pictures per filter at 40-fold magnification. The individual images were then combined to form a panorama. Quantification of the extracted TWP was done with a colour-based approach using a machine learning pixel segmentation algorithm trained to identify background and black particles, the latter being considered TWP.
In the context of my thesis in MAS Environmental Technique and -management at the FHNW, TWP of 20 soil samples from 4 of the 15 sampling areas have been extracted and analysed using the method described above. Roughly, an average of 200’000 TWP numbers per kg dried soil was obtained per site. Numbers of TWP were comparable between sites and particle numbers decreased with increasing distance from the road. The results will be presented in the flash poster session.

Authors and affiliation

Agricultural Research and Testing Institute (LUFA) Speyer

• Schneeweis, Fabian
• Prigge, Max
• Armbruster, Martin

The Agricultural Research and Testing Institute (LUFA) Speyer is offering six standard soils (2.1, 2.2, 2.3, 2.4, 5M, 6S) for scientific purposes with contrasting characteristics according to OECD guidelines. The standard soils are natural grown soils of commonly occurring soil types from selected sites in the South of Rhineland- Palatinate, which are sampled, processed and analyzed under controlled conditions, according to GLP. The sampling sites are under extensive agricultural use or fellow without application of plant protection agents, biocidal fertilizers or organic manure at minimum for the least 4 years. Mineral fertilizers or lime is applied if required no more than three month before sampling. The soils are sampled from about 0-20 cm depth, gently dried and sieved with a 2 mm screen as fresh as possible.
The conditions of sampling (date, weather, temperature, amount) and procession (date of sieving, temperatures, water content) are given for each soil-batch. Twice per year, physical (weight per volume, particle size distribution, maximum water holding capacity) and chemical (pH in CaCl2, CECpot) soil characteristics are analyzed under GLP conditions in the laboratories of the LUFA Speyer. Based on the last five GLP reports, a data sheet of analysis documents the mean values and standard deviation for the named soil characteristics. For internal quality assurance, the organic carbon content and the pH-value are measured for every soil batch. If wanted, physical and chemical characteristics as named above or further parameters (e.g. water retention characteristics, microbial biomass, CECeff) can be analyzed under GLP conditions for the specific soil batch.
The soils are mainly required for laboratory permission studies according to GLP and OECD: Leaching, degradation and metabolism, adsorption and desorption characteristics of plant protections agents in soils can be analyzed as well as influence on soil microflora and fauna. Moreover, Standard soils are used in different scientific applications for example incubation experiments to analyze nutrient release of fertilizers.
Using Standard soils from LUFA Speyer has several advantages: Long time availability and therefore comparability of tests from different years and/or with different pesticides. No difficulty in searching, procuring, preparing and care of suitable soils. Short dated delivery with all needed data concerning location, history, treatment, and sampling. The soils are offered field fresh (sampled no longer than 3 weeks before shipment, stored (air-dried) or steamed.

Authors and affiliation

Bern University of Applied Science, School for Agricultural, Forest and Food Science

• Schmücker, Niklas
• Nussbaum, Madlene

ETH Zürich USYS

• Duddek, Patrick
• Kirchgessner, Norbert
• Carminati, Andrea
• Lehmann, Peter

1. Background
Human activities and climate change limits the capacity of the soil to maintain essential functions for ecosystems and society. To combat further degradation and support remediation, general knowledge on current soil conditions is crucial to recommend site-specific action to improve soil health. Identifying realistic and scalable proxies for soil health, capable of reflecting soil ecosystem function changes, becomes indispensable for envisaged EU wide soil health policy.
Soil structural attributes, inextricably linked to processes such as nutrient dynamics, carbon cycle, root penetration, biological activity, rainfall partitioning, play a significant role in determining susceptibility to erosion, hence offer great potential as soil health indicators.
A direct expression of these attributes is observed in the soil hydraulic properties, particularly in the water infiltration capacity during sustained rainfall. Limitations in water infiltration can potentially result in surface runoff, thus leading to soil erosion and nutrient loss. Forming of ponds or early surface runoff can serve as measurable indicator of unhealthy soils. After infiltration, soils may reach near-saturation water content levels, leading to anaerobic conditions, that are detrimental to ecosystem functions. Efficient gravitational drainage, which replenishes air within the large pores, thus serves as additional indicator of healthy soil.
High infiltration and drainage fluxes are both linked to the presence of well-connected macropores. In this study, we aim to elucidate the relationships between pore size distribution and connectivity (as structural attributes) and the hydraulic properties controlling infiltration and drainage, namely water retention and hydraulic conductivity. Our objective is to examine the influence of different land use types on structural attributes and their effect on soil hydraulic properties. Therefore, we address the following questions:

l How do pore size distribution and connectivity impact the hydraulic properties controlling water infiltration and gravity drainage?

ll How does land use influence structural attributes determining soil hydraulic properties?

2. Experimental Setup
Soil samples will be collected in topsoil at 50-100 mm depth at locations within the soil survey pilot study area Wohlen-Meikirch, in the canton of Bern (Switzerland). Sites were chosen to represent different land use (forest, arable and grassland or pasture, respectively) with a similar texture range across all sites. For all sites, a visual assessment of the soil structure was carried out. Volume samples were taken with PVC plastic cylinders with dimensions of 80 mm in diameter and 50 mm in height. Pore size distribution and connectivity within soil samples was examined using Computed Tomography (CT) scans with a spatial resolution of 0.1 mm. After scanning, the saturated hydraulic conductivity of the same sample was measured, before it was further investigated in the laboratory by HYPROP 2 (water retention and unsaturated hydraulic conductivity) and WP4C instruments (water content in the dry range).

3. Impact
Quantifying the relationships between soil structure and water dynamics enabled to assess the soil’s ability to retain water and resist erosion, two important aspects for maintaining healthy and productive soils. Next steps include the upscaling of local in-depth characterization of land use dependent structural water dynamics to the full extent of Wohlen-Meikirch pilot area using pedo-transfer functions. Outcomes of this study will not only contribute to fundamental understanding of soil processes but will also influence practical applications in soil management and conservation, and ultimately supporting the development of soil health indicators and future soil health policy.

4. Acknowledgements
This research is part of the project Artificial Intelligence for Soil Health. Funded by the European Union. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or of the Research Executive Agency (REA). Neither the European Union nor the granting authority can be held responsible for them.

Authors and affiliation

Kerstan, Andreas, Agilent Technologies

Over the last 3.5 years, QCL technology has become increasingly important in IR microscopy. The advantages over FTIR are that large areas of a few square centimeters can be measured in minutes and that the light intensive QCL makes it possible to obtain spectra with excellent S/N even with just one scan. A meanwhile firmly established solution of the LDIR 8700 is the analysis of microplastics. The presence of microplastics in the environment, drinking water, and food chains is gaining significant public interest. To study their presence, rapid and reliable characterization of microplastic particles is essential. Significant technical hurdles in microplastics analysis stem from the sheer number of particles to be analyzed in each sample. Total particle counts of several thousand are not uncommon in environmental samples, while well treated bottled drinking water may contain relatively few.
While visual microscopy has been used extensively, it is prone to operator error and bias and is limited to particles larger than 300 µm. As a result, vibrational spectroscopic techniques such as Raman and FTIR microscopy have become more popular, however they are time-consuming. There is a demand for rapid and highly automated techniques to measure particle count, size, and provide high-quality polymer identification. Analysis directly on the filter that often forms the last stage in sample preparation is highly desirable as, by removing a sample preparation step, it can both improve laboratory efficiency and decease opportunities for error.
Recent advances in infrared micro-spectroscopy combining a Quantum Cascade Laser (QCL) with scanning optics has created a new paradigm, laser direct infrared imaging (LDIR). It offers improved speed of analysis as well as high levels of automation. Its mode of operation however requires an infrared (IR) reflective background, and this has, to date, limited the ability to perform direct “on-filter” analysis. This study explores the potential to combine the filter with an infrared reflective surface filter.
By combining an IR reflective material or coating on a filter membrane, with advanced image analysis and detection algorithms, it is demonstrated that such filters can indeed be used in this way. Vibrational spectroscopic techniques play a vital role in the investigation and understanding of microplastics in the environment and food chain. While vibrational spectroscopy is widely deployed, improvements and novel innovations in these techniques that can increase the speed of analysis and ease of use can provide pathways to higher testing rates and hence improved understanding of the impacts of microplastics in the environment.
Due to its capability to measure large areas in minutes, its speed; degree of automation and excellent S/N the LDIR could also implemented for various other samples like food adulteration, coatings, laminates, fabrics, textiles and tissues. This presentation will highlight a few a few of them and focus on the benefits of the LDIR vs classical techniques.

Authors and affiliations

Agroscope

• Walder, Florian
• Hirte, Juliane
• Mayer, Jochen
• Keller, Thomas
• van der Heijden, Marcel

University of Greenwich

• Büchi, Lucie

Government of Canada

• Wagg, Cameron

Swedish University of Agricultural Sciences

• Colombi, Tino

Not stated

• Banerjee, Samiran

ETH Zürich USYS

• Six, Johan

FiBL

• Charles, Raphaël

One of the critical challenges in agriculture is enhancing yield without compromising its foundation, a healthy environment, and, particularly, soils. Hence, there is an urgent need to identify management practices that simultaneously support soil health and production and help achieve environmentally sound production systems. To investigate how management influences production and soil health under realistic agronomic conditions, we conducted an on-farm study involving 60 wheat fields managed conventionally, under no-till or organically. We assessed 68 variables defining management, production and soil health properties. We examined how management systems and individual practices describing crop diversification, fertiliser inputs, agrochemical use, and soil disturbance influenced production – quantity and quality – and soil health focusing on aspects ranging from soil organic matter over soil structure to microbial abundance and diversity. Our on-farm comparison showed marked differences between soil health and production in the current system: organic management resulted in the best overall soil health (+ 47%) but the most significant yield gap (- 34%) compared to conventional management. No-till systems were generally intermediate, exhibiting a smaller yield gap (- 17%) and only a marginally improved level of soil health (+ 5%) compared to conventional management. Yet, the overlap between management systems in production and soil health properties was considerably large. Our results further highlight the importance of soil health for productivity by revealing positive associations between crop yield and soil health properties, particularly under conventional management, whereas factors such as weed pressure were more dominant in organic systems. None of the three systems showed advantages in supporting production-soil health-based multifunctionality. In contrast, a cross-system analysis suggests that multifunctional agroecosystems could be achieved through a combination of crop diversification and organic amendments with effective crop protection. Our on-farm study implies that current trade-offs in managing production and soil health could be overcome through more balanced systems incorporating conventional and alternative approaches. Such multifunctionality supporting systems could unlock synergies between vital ecosystem services and help achieve productive yet environmentally sound agriculture supported by healthy soils.

Authors and affiliation

• Johannes, Alice, Agroscope
• Boivin, Pascal, HEPIA

Reference values of soil physical properties assessing soil structure quality (SSQ) are necessary both for the purpose of soil physical protection regulation and for farmers to take soil management decisions. Such reference values are however scarce due to inherent difficulties in soil physics, including large variance and cost. The purpose of this study (STRUDEL project) supported by the Swiss Federal Office for the Environment was to develop an inexpensive, simple, and highly discriminant method with threshold values allowing to score the soil physical quality as a regulation basis for quantitative soil protection against compaction. The Swiss Ordinance of impact on Soils (OIS) provides target, warning, and remediation values for the management of pollution hazard. We, therefore, aimed at determining similar thresholds for structure degradation levels. Issues such as soil swelling with moisture content, spatial variability, differences in soil types and soil composition were considered.

For this purpose, we used soil shrinkage analysis well known to provide an accurate diagnosis of SSQ and compaction on the full water content range and simplified desorption methods on unconfined samples for soil physical caracterisation. We used CoreVESS and SubCoreVESS which are semi-quantitative visual soil structure assessment methods, dedicated to topsoil and subsoil respectively to classify soil structure quality classes. The methods yield scores from 1 (very good SSQ) to 5 (very poor SSQ), respectively, 3 being the limit between fair and degraded structure. For topsoil, the scores of 2, 3 and 4 were used to determine the following reference values for “target value”, “warning value” and “remediation value” limits, respectively. For subsoil, only the score of Ssq3 was used to propose a “guide value”.

All properties were determined on the same sample, together with the analysis of the main constituents known to determine the physical properties, and, therefore, their spatial variability, namely soil organic carbon content (SOC) and clay content. The sample moisture content was standardized by equilibrating the soil samples without constraint at standardized matric potentials before physical measurements. A total of 286 topsoil and of 167 subsoil samples were collected in Cambi-Luvisol from the Swiss cropland, the most represented soil groups in Switzerland and Europe, in spring, summer and autumn from 2013 to 2019. The sample fields were selected to cover the largest range of SSQ from very good to highly degraded.

By analysing the relationships between the soil physical properties, their visual scoring, and the soil SOC and clay contents, we found that the SSQ scores were explained by structural porosity parameters and SOC, with a good determination. We then tested the capacity of simpler and easy to determine properties to reflect the observed SSQ behaviour. We found a that the two covariables could be replaced by the gravimetric air content -100 hPa (replacing structural porosity) and water content at -100 hPa (replacing SOC content), providing excellent separation between the SSQ scores. These properties are obtained by measuring only the soil bulk volume and water content at -100 hPa. Gravimetric air content indeed had the best reliability statistics but bulk density (at dry state and -100 hPa) and volumetric air content at -100 hPa were also promising parameters. A table with the three levels of reference values for different soil physical properties (including volumetric air content or bulk density) for two different depths are presented together with their reliability statistics. As an example, the gravimetric air content “warning value” is 0.072 cm3 g-1 for the topsoil and its subsoil “guide value” is 0.048 cm3 g-1.

Reference values are a necessary step for an effective soil protection implementation. Until now, soil physical protection did not have reliable reference values because the large variability usually associated with measuring physical properties have made it difficult to define a limit. Additionally, it is difficult to decide on what this limit must be based. The reference values proposed by the STRUDEL project offer a unique opportunity to have relatable values. Firstly because of their representativity of Swiss soil, i.e. they are based on large-scale on-farm data and reflect real conditions. Secondly because they have a clearly defined basis, namely visual evaluations of soil structure quality. These advancements in defining reference values should help implement soil protection strategies in Switzerland in future.

Authors and affiliation

University College Dublin School of Agriculture and Food Science

• Khalil, Mohammad Ibrahim
• Osborne, Bruce

Maintained grasslands play a significant role in the exchange of greenhouse gases (GHGs) between the biosphere and the atmosphere. This exchange is influenced by various management practices, including the type of fertilizer used, soil type and composition, and prevailing climatic conditions. Considering organic farming as a means of GHG mitigation and sustainable production, it’s important to note that both inorganic and organic fertilizers can contribute significantly to the emission of nitrogen (N) into the atmosphere. These emissions primarily take the form of ammonia (NH3), nitrous oxide (N2O), nitric oxide (NO), and di-nitrogen (N2). The loss of nitrogen from fertilizers not only reduces nitrogen use efficiency but also leads to environmental impacts and compromises sustainable production goals. Despite numerous measurements, these often have significant limitations, so that accurate and verifiable accounting of nitrogen emissions, particularly NH3 and N2O, using advanced methodologies with minimal spatial and temporal variations has become a global concern. In Ireland, country specific NH3 and N2O emission factors (IPCC Tier 2) are primarily derived from short-term measurements and limited coverage of different land uses. To address these challenges, a simulation was conducted using the updated biogeochemical model DeNitrification-DeComposition (DNDC v9.5). The study focused on nitrogen emissions from a 3-cut moist temperate grass silage system managed for over 45 years. Different fertilizers, including inorganic (urea) and organic (cattle and pig slurry) fertilizers were applied at varying rates (low, medium, and high). The primary objective was to offer a detailed assessment of annual nitrogen emission factors (EFs), comparing them with existing research and IPCC defaults. Based on the national average, the model exhibited reasonable but less NH3 volatilization from urea (11%) and largely underpredicted the values for animal slurry (< 0.1%). Conversely, the model overestimated NO3 leaching losses, particularly for the medium to high rates of animal slurry, despite moderate soil drainage conditions, leading to limitations in the calculation of indirect N2O emissions from both NH3 and NO3. Regardless of fertilizer type, the model accurately predicted N2O and N2 emissions. The resulting N2O EFs were estimated on average at 0.35±0.02, 1.80±0.28, and 1.53±0.41% of applied-N for urea, cattle, and pig slurry, respectively. These estimates are close to national and IPCC estimates. The study revealed that the production and release of the denitrification end product, N2, representing complete denitrification, remained at low rates, ranging from 0.02 to 0.25%. This increased with higher amounts of applied N, particularly from cattle slurry compared to pig slurry. Variation in the N2O/(N2O+N2) ratio among fertilizer treatments was minimal, ranging from 0.89 to 0.96. This implies the dominance of denitrification in N2O production and release within many Irish grasslands. The study’s findings were within the upper limit of national measurements for grasslands encompassing various soil types. The findings imply that the updated DNDC v9.5 model can proficiently depict the primary factors influencing nitrogen emissions, thus enhancing our understanding of nitrogen dynamics in grassland systems. Nonetheless, it might not be as precise in capturing NH3 volatilization and NO3 leaching, necessitating further adjustments to precisely model their behaviour in scenarios related to temperate grass silage.
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This research was conducted under a project financed by the Department of Agriculture, Food and the Marine within the European Joint Programme (EJP) Soil “TrueSoil”. Thanks to Dr. Dario Fornara, a former Scientist in AFBI, Northern Ireland, UK for supplying the input and activity data. Attendance at the conference was partly supported by ISCRAES 2024 (www.iscraes/org).

Authors and affiliation

Wagner, Magnus, Universität Hohenheim

Studying the Influence of Soil BIOdiversity and FArming Innovations on the Mineral Nutrition and Stress Tolerance of Wheat Plants for Improved Resilience to Climate Change Impacts
The Green Deal and Farm-to-Fork policies of the European Union (EU) set ambitious targets for the ecological transformation and sustainable adaptation of agriculture, including the challenges of the advancing climate change. Wheat, as a major staple food worldwide, is given a particularly high focus in this context.
In the current EU project BIOFAIR, innovative cultivation strategies for improved resilience in European wheat cultivation are being researched in cooperation with international project partners. In addition to field trials, ECOTRON experiments are with current and future climate scenarios conducted at the TERRA Teaching and Research Center in 2023. In this facility at the Gembloux site of the University of Liège (Belgium), research can be used to simulate climate scenarios for complex ecosystems such as plants, soil organisms and soils at the latest state of the art. BIOFAIR holistically determines soil biodiversity under different farming practices and environmental stressors to anticipate negative impacts of climate change on belowground processes and provide adaptation strategies. Regarding the wheat crop, traits of grain quality such as vitamin and mineral nutrient contents are investigated. By studying the physiological performance of wheat plants together with the activity of the associated rhizosphere micro- and mesofauna populations in multiple climate scenarios, biodiversity ecosystem functioning relationships are assessed to gain a better understanding of the influence of biogeochemical cycles on the yield and quality of wheat crop. Here particular emphasis is put on the interaction between alterations in soil and root microbiology, mineral nutritional status of the wheat plants, and their impact on phytopathological diseases like take-all (caused by the root fungus Gaeumannomyces graminis). This takes place under three differently modeled climate scenarios in order to develop adapted crop management strategies for an improved resilient wheat production.
References:

BIOdiversity of soils and FArming Innovations for improved Resilience in European wheat agrosystems (BIOFAIR) project website (2021) via www.biofair.uliege.be
Weinmann M. and Neumann G. (2022). BIOFAIR – innovative Anbaustrategien zur besseren Resilienz im europäischen Weizenanbau. FONA, availale from: https://www.fona.de/de/aktuelles/nachrichten/2022/220912_Biofair.php [date of access: 27. July 2023]