Cover crops (CC) mitigate nitrate leaching through nitrogen (N) uptake and carbon (C) driven microbial immobilisation. These dynamics are heavily modulated by environmental variables, which this four-year field study on a Stagnic Luvisol (Lower Rhine, Germany) quantifies to resolve the plant-soil-microbe N-nexus in intensive arable cropping systems. Annual rotations of CC species and mixtures were evaluated between winter cereals and summer crops. CC above- and below-ground biomass and their C and N content were determined in autumn and, in 2020, also at the end of winter. Further, microbial biomass (MB) C and N at 0–30 cm and inorganic N at 0–30, 30–60 and 60–90 cm depth, were quantified in autumn and end of winter. In addition, soil prokaryotic and fungal gene abundance were determined in the first two experimental years. Regardless of mixture complexity, CC reduced soil inorganic N by 54

Organic materials (OM) such as farmyard manure (FYM) and mungbean residue (MR) are used to improve soil nutrient stock and act as an alternative to fertilizers. It was hypothesized that integrating beneficial microbes (BM) with OM will enhance carbon and nitrogen mineralization, offering a novel approach for optimizing soil fertility and nutrient cycling. The experiment was conducted in a completely randomized design (CRD) having factorial combination of five OM sources (control (CON), poultry manure (PM), FYM, compost (COM), and MR at the rate of 120 kg N ha-1) and four levels of BM ( i.e. 0, 100, 200, and 300 L ton-1 of OM) in microcosm for 112 days in airtight vials incubated at 25 °C. Destructive soil samplings were analyzed for total nitrogen (TN), mineral nitrogen (MN), organic carbon (SOC), electrical conductivity (EC), pH, microbial respiration (SMR), and microbial biomass carbon (MBC), while net mineral N release and losses were calculated on a mass basis. The incubation interval had increased the soil TN, SMN, SOC, MBC and SMR by 26, 2, 28, 7 and 82

Nitrogen (N) is crucial for plant growth, but its overuse harms biodiversity. Increasing soil biodiversity might provide the means to reduce N inputs, but experimental evidence for this paradigm-shift is limited. Using microbiome predators (protists and nematodes) that shape microbiome composition and release N, we examined how interactions between their diversity and N addition affect Cannabis sativa growth. Microbiome predator addition overall boosted plant biomass by up to 53%, particularly under low N conditions, primarily by altering bacterial community composition and enriching functions related to carbon and N cycling. In turn, microbiome predator diversity had the strongest effect on biomass production, while N levels played a greater role in determining plant nutrient content. These findings suggest that increased microbiome predator diversity can reduce the plant’s dependency on added N, showing the pivotal role of soil biodiversity in enhancing plant performance and serving as tools to mitigate N inputs.

In Benin, a country in West Africa, soil degradation and erosion caused by intensive commercial crop production (conventional cotton) are affecting the livelihoods of the local population, particularly in the semi-arid climate zone. While the negative impacts of cotton cultivation on soil quality are widely acknowledged, empirical evidence on location-specific drivers and adaptive soil management responses remains limited. Furthermore, climate change is expected to have a severe impact on soil conservation in West Africa, as plant growth and soil erosion are highly dependent on rainfall. In addition, heavy rainfall is expected and will increase the risk of soil erosion. However, there is a critical knowledge gap regarding how changing rainfall regimes interact with existing agricultural practices to influence soil degradation processes under semi-arid conditions. The overall objective of this research is to assess the rate of erosion under different crops [(cash crops (conventional cotton), cereals (maize and sorghum-millet), legumes (cowpea, groundnut and soybean)] in the semi-arid climate of Benin. The methodology used is based on a combination of mapping, GIS and spatial prediction models, in particular the Revised Universal Soil Loss Equation (RUSLE), taking into account current ((Institut 2021)) and future (RCP 4.5 and RCP 8.5 for 2055 and 2085) climatic conditions. The results revealed critical cover under very low soil erosion (0–5 t ha-1yr-1) in the various crop fields. Conventional cotton fields had critical cover for high soil erosion (40–80 t ha-1yr-1) and very high soil erosion (> 80 t ha-1yr-1). Future scenarios predict a similar trend. Thus, conventional cotton production would have a significant impact on soil erosion in the study area. Sustainable land management should be developed to overcome the impact of conventional cotton production on soil erosion.

Background and aimsEastern Denmark’s agricultural landscapes feature numerous topographic depressions that are frequently flooded during late winter and spring. These poorly drained, carbon- and nitrogen-rich depression soils receive eroded material from adjacent slopes. Fertilization and water saturation create N2O emission hotspots. However, the potential legacy effects of these topographic locations on microbial communities involved in N2O production and reduction remain unclear. One approach to mitigating high denitrification rates (as a source of N2O) is to alter microbial pathways by adding nonhazardous levels of copper.MethodsWe conducted an incubation study using upland and depression soils from the same site, incorporating varying Cu levels (0, 130, and 260 mM) and water levels (60% and 90% water holding capacity).ResultsDepression soils emitted eight times more N2O than upland soils at 90% WHC. Cu addition did not reduce cumulative N2O emissions but delayed or lowered the flux peak. Depression soils exhibited 3,000- and 4,000-fold higher 16S rRNA and nosZ clade I abundances, respectively, compared to upland soils. Cu addition significantly decreased 16S rRNA abundance, eliminated AOB amoA in upland soils, and slightly reduced the tested gene abundances in depression soils. The nosZ gene community structure differed significantly between the two soils.ConclusionsOverall, our study suggests that erosional differentiation of soil properties, together with frequent waterlogging conditions, can result in distinct microbial communities, fostering legacy effects that lead to differences in N2O emissions between upland and depression soils. Adding Cu to these intensively managed soils is unlikely to be an effective strategy for mitigating N2O emission hotspots in arable fields.

There is an increasing interest in using plant growth-promoting rhizobacteria as alternatives for fertilisers and pesticides in sustainable agriculture. In this study, rhizosphere soil samples from 15 crop species in Sudan and Saudi Arabia were extracted, and 113 rhizobacterial isolates were obtained. Out of eight Bacillus isolates, seven were identified as members of the Bacillus cereus group, which is mainly differentiated by their plasmid-driven phenotypes. The eight strains were tested for their plant growth stimulatory effects on maize (Zea mays L.) and wheat (Triticum aestivum L.) using a model biotest under controlled environmental conditions in a growth chamber. Depending on application form, i.e. viable cells or their culture supernatant, and applied concentrations, six isolates stimulated maize plant growth. Similarly, six isolates enhanced wheat growth, but the influence of the single isolates differed between and within plant species, indicating plant-specific responses. Furthermore, diversity of rhizospheric members of the B. cereus group is highlighted, as all seven isolates differed in terms of colony traits, capacity to produce indole-3-acetic acid, and response by the maize and wheat plants. Overall, this study indicates the potential of plant growth-promoting Bacillus strains for commercial application promoting further investigation in soil and under field applications.

Microbial necromass carbon (MNC) can contribute 50 % or more to soil organic C (SOC) and may thus be crucial for C sequestration in soil. However, it is not known how persistent MNC is and whether the turnover of fungal and bacterial necromass C differs from that of SOC in this respect. The current study therefore investigates the turnover times of fungal glucosamine (GlcN) and bacterial muramic acid (MurN) in two soils from the long-term Darmstadt fertilization trial with distinct fungal communities. The soil with inorganic fertilization and straw return (MIN) contains significantly more saprotrophic fungi than the organically managed soil with cattle farmyard manure fertilization (FYM). The soil organic carbon (SOC) turnover time was 10.0 years in the FYM soil, 16 % longer than the 8.6 years in the MIN soil. In contrast, the microbial biomass C (MBC) turnover time of 147 days in the FYM soil was more than twice the 67 days found in the MIN soil. The turnover time of fungal GlcN and MurN varied around 6.3 years in the FYM soil and around 4.9 years in the MIN soil. In contrast to plant residues, fungal GlcN and MurN are constantly recycled in the microbial biomass during growth, which results in shorter turnover times compared to SOC. The different conversion factors from amino sugars to necromass currently used have only minor effects on the estimates of turnover times. The main drivers for the turnover of MBC and MNC in soil are microbial C use efficiency (CUE) and C input. There is particularly a serious lack in knowledge on the CUE values of partly decomposed organic fertilizers such as FYM. Future studies also need to more accurately estimate quantity and quality of the C input by straw, harvest residues, roots, rhizodeposits, and organic fertilizers.

Enhanced rock weathering aims at capturing atmospheric carbon dioxide as inorganic carbon, while potentially stabilizing soil organic carbon. However, the role of soil biota in this process remains underexplored. Earthworms, being key soil engineers, may impact carbon dynamics both when alive, through mineral ingestion and casting activities, and when dead, through microbial processes. Using stable isotope tracing, we investigate how live and dead earthworms affect carbon dynamics during rock weathering. We demonstrate that both living and dead earthworms contributed to carbon capture, albeit through distinct pathways. Live earthworms enhanced the formation of organo-mineral associations via their dejections over time, promoting organic carbon persistence. Dead earthworms boosted microbial abundance and activity, enhancing organo-mineral associations and atmospheric-derived inorganic carbon capture between 60 and 120 days. We show that earthworms influence carbon cycling beyond their lifespan, with contrasting physico-chemical and biological pathways driving carbon capture through rock weathering throughout their life cycle.

Land and soil degradation caused by arable farming affects the livelihoods of the local population in semiarid climate regions, such as in West Africa. In particular, cotton (Gossypium hirsitum L.) production is a crucial driver of soil degradation. However, the extent of soil degradation under cotton compared to other crops and the natural vegetation as a possible benchmark for non-degraded soil needs to be better understood. Topsoil at 0–10 cm depth from fields of cotton (G. hirsitum), three cereal species (maize [Zea mays L.], millet [Eleusine corocana L.] and sorghum [Sorghum bicolor (L.) Moench]), three legume species (cowpea [Vigna unguiculata L.], peanut [Arachis hypogaea L.] and soybean [Glycine max L.]) and woodland as natural vegetation were analyzed for soil porosity, water stable aggregates, water holding capacity, pH, electrical conductivity, soil organic carbon, total nitrogen and total sulfur. A simple soil degradation index was derived from the measurements. Findings revealed that the topsoil of cereal crop fields was more compacted, with less porosity, than the topsoil of cotton and legume crop fields. However, the soil degradation index was higher in the cotton fields than in the legume and cereal fields. The soil fertility was reduced on cropland compared with natural vegetation, following the order of woodland > legumes > cereals > cotton. Integration of tree components in agricultural production systems through agroforestry may provide an option to improve soil fertility in semiarid regions.

The current study quantified the carbon (C) and nitrogen (N) transfer from peas to oats under field conditions to assess the effects of intercropping. The data obtained were compared with previously published pot and field experiments. Pea (Pisum sativum L. cv. Santana) and oat (Avena sativa L. cv Dominik) plants were grown as intercrops for 105 days. Pea plants were labelled with a solution of 2

BackgroundThe by-product of insect larval production, frass, can be applied to soil as an organic fertiliser. Its three main organic N fractions are assumed to be ureic, protein and chitin. The significance of the latter is unknown, and it is not known if lignaceous sources have been overlooked.AimsThis study sought to gauge the activities of the (respectively, lignolytic and chitinolytic) enzymes peroxidase and N-acetyl-ss-D-glucosaminidase following frass application to soil. Their activities were monitored under conditions of urease inhibition, with a particular focus on the fungal domain.MethodsMealworm or buffalo worm frass was applied, with or without inhibitors, to a sand/soil substrate at 3% (w/w). After 16 weeks, concentrations of the fungal biomarker ergosterol and enzyme activities were determined.ResultsSoil amendment with frass had no significant effect on peroxidase activity. Fungal biomass was stimulated in particular by application of mealworm frass, which was further improved by urease inhibition. Chitinase activity was positively correlated with fungal biomass, and was increased under urease inhibition when applied with mealworm frass.ConclusionsThere were no appreciable quantities of lignaceous compounds in the frass used in this study. Importantly, the use of urease inhibitors co-applied with frass has demonstrated that when its ureic N breakdown is prevented, chitin becomes a significant organic N source to soil fungi. The superior fungal response to mealworm frass indicates a larger chitin content than in buffalo worm frass.

This paper aims to find socially acceptable solutions of circularity as measure to reduce nitrogen (N) losses and prevent environmental damage by combining participatory modelling and scenario Substance Flow Analyses (SFA). A local perspective was taken on the agro-food-waste system in the animal production-dominated German district Cleves. Three scenarios were programmed as Monte Carlo simulation of SFA with stakeholder input regarding crop allocation, livestock composition, livestock reduction, and manure allocation following the elimination of feed imports. The three scenarios either utilized the unaltered stakeholder input (PS), altered crop allocation to satisfy the demand for feed (CBS), or adjusted the livestock numbers to match the locally available feed (LBS). In the reference year (2020) agricultural losses amounted to 68 kg N year-1 ha-1 agricultural land and 116 kg N in feed was imported year-1 ha-1 agricultural land. In the PS feed import elimination led to deficits in feed availability. The LBS showed the biggest reduction of agricultural N losses and improved N use efficiency (+6 %), however agricultural losses were still high (50 kg N year-1 ha-1 agricultural land). The results show a limited effect of feed import elimination on N losses if no further measures are taken, such as reduced consumption of animal-based products. Further, the study shows that it is important to improve stakeholders' knowledge about approaches to circular agro-food-waste systems. The discrepancy between stakeholder visions and N circularity provide policy makers with the recommendation to improve stakeholders' visions of a circular agro-food-waste system.

It is crucial to promote soil carbon sequestration while reducing CO2 emissions to mitigate climate change. However, the extent of increasing actual soil carbon storage depends on the amount and composition of organic matter input, including its fate during decomposition and soil organic matter (SOM) formation via microbial transformation. With respect to the need to increase carbon sequestration in soil and sustain soil fertility, it is of great interest to better understand how soils with different organic matter content react to amendment with fresh organic matter. Here, we incubated three agricultural soils representing a gradient in C content, adding two different 13C labeled plant residues varying in carbon-to-nitrogen ratio. Carbon mineralization was monitored together with the analysis of the 13CO2 signatures. After the incubation, 13C compound-specific PLFAs, microbial necromass, and enzyme activities were analyzed. This study demonstrates that the carbon return on investment, thus the amount of retained fresh carbon in relation to the amount of added organic matter, clearly depends on the amount of native soil carbon. Notably, the addition of fresh organic matter to carbon-deficient soils leads to a higher specific CO2 release compared to soils with high carbon loading, which can be attributed to the differences in the soil microorganisms' response. The CO2 release of the soil with the lowest C-content was 2.1 and 2.0 mg g−1 soil for treatment with oat and pea litter addition, respectively, whereas for the soil with the highest C-content, CO2 release was 1.7 mg g−1 soil for oat treatment and 1.6 mg g−1 soil for pea treatment. Thus, higher SOC contents sustain a higher ‘return on investment’ for the fresh carbon that is amended to soils. With plant litter amendments the microbial community shifted towards a higher fungi-to-bacteria ratio (F/B). This shift in the microbial community was more pronounced (F/B ranging from 0.04 to 0.11) with the addition of oat litter (low quality) compared to pea litter (high quality). Hence, it is important to consider the fate of organic amendments with different N availability when aiming to rebuild soil carbon stocks in degraded soils. Soil management should focus on sustaining soil carbon in balance with current carbon stocks to avoid the vicious circle of soils losing carbon in conjunction with increased greenhouse gas release.

Climate change causes altered precipitation patterns and temperature increases, which may affect food quantity and quality. In Kyrgyzstan anticipated temperature changes are expected to influence the physiology of walnuts (Juglans regia L.) and soil properties relevant to plant nutrition, thereby impacting walnut fruit quality. This study explores the relationship between plant available nutrients in soil and walnut fruit nutrient content as affected by future temperature changes. The soil samples were collected in the walnut forests of Southern Kyrgyzstan from top- and subsoils at three elevation levels (1000, 1300, and 1600 m above sea level). The walnut samples were collected from the same sampling sites and both soil Mehlich-3 extracts and acid digests of walnut fruits analyzed by ICP-OES. The results revealed no consistent relationship between Mehlich-3 extractable elements and walnut extractable elements, except for a weak negative correlation with zinc (Zn). Stronger relationships were observed among soil elements, but no clear associations with elevation levels were found. The walnut kernel ionome exhibited differences, particularly in calcium (Ca) and potassium (K) concentrations, with the low elevation site showing higher Ca and lower K concentrations compared to the high elevation site. Differences in average temperature as caused by elevation did not affect available plant nutrients in the soil but altered the walnut kernel ionome and thus affected the walnut quality in the investigated forest systems. Future investigations should focus on climate change effects, such as altered precipitation patterns and drought, which may impact walnut fruit development and kernel properties.

Information on microbial biomass carbon (MBC) is crucial to assess their stocks and role for plant nutrient release in soil. Next to fumigation-extraction, molecular methods are routinely used to estimate the contribution of fungi, bacteria, and archaea to the soil microbial community. However, more information on the links between these different indices would deepen the understanding of microbial processes. The current study is based on 11 datasets, which contain MBC and MBN data obtained by fumigation-extraction and information on bacterial, archaeal, and fungal gene abundance, totalling 765 data points from agricultural, forest, and rangeland soils. Some of these datasets additionally provide information on double-stranded deoxyribonucleic acid (dsDNA) and fungal ergosterol. MBC varied around the median of 206 µg g −1 soil. MBN followed with a median MB-C/N ratio of 4.1. Median microbial gene abundance declined from bacteria (96 × 10 8 ) to archaea (4.4 × 10 8 ) to fungi (1.8 × 10 8 ). The median ratio of MBC/dsDNA was 15.8 and that of bacteria/dsDNA was 5.8 × 10 8 µg −1 . The relationships between MBC and dsDNA as well as between bacterial gene abundance and dsDNA were both negatively affected by soil pH and positively by clay content. The median ergosterol/MBC and fungi/ergosterol ratios were 0.20% and 4.7 (n × 10 8 µg −1 ), respectively. The relationship between fungal gene abundance and ergosterol was negatively affected by soil pH and clay content. Our study suggests that combining fumigation-extraction with molecular tools allows more precise insights on the physiological interactions of soil microorganisms with their surrounding environment.

Climate change causes temperature increase and alteration of precipitation patterns with frequent droughts. These are known to influence soil microorganisms leading to community shifts and physiological adaptations, with consequences for biogeochemical cycles. However, whether soil microbial communities evolved at different average temperature differ in their response to drought is not well understood. Therefore, we collected ten soil samples per site (0-30 cm soil depth) from a walnut-fruit forest at 1000, 1300 and 1600 m above sea level with similar vegetation which represent average temperature differences of 1.3 degrees C between sites, mimicking potential climate change. We incubated these for 70 days at 22 degrees C either at (i) constant moisture of 50 % soil water holding capacity, or subjected them to (ii) two or (iii) three drying-rewetting (DRW) cycles. Respiration was measured during the incubation; microbial and chemical properties were determined at the end. No elevation specific or interactive effects with DRW were detected, except for fungal gene abundance, where values were highest at the intermediate elevation level. This reveals that soil microbial communities evolved at different average temperature regimes do not differ in their response to drought. Therefore, data were pooled across all sites and analyzed for the main effects of DRW. Microbial activity increased with DRW as reflected by enhanced net-nitrogen mineralization and basal respiration. However, microbial biomass carbon and ergosterol were reduced by 20 and 25 % and bacterial gene abundance between 20 and 40 %. This reflects the strong osmotic pressure of DRW causing death of microbial cells. The higher maintenance requirements for cell adjustment to osmotic pressure of surviving microorganisms was revealed by an increase of the metabolic quotient qCO2 by 60 % and accumulation of potassium in the microbial biomass. Fungi cope better with DRW as shown by higher fungal gene abundance as well as their ratio to ergosterol after DRW, reflecting shifts in cell volume due to community shifts or morphological adaptations. Our findings highlight that soil microbial communities evolved under different average temperature regimes respond similarly to DRW, but overall shift towards fungi as this taxon can potentially physiologically better adapt to osmotic pressure. Consequently, DRW may cause higher organic matter turnover and nutrient release due to higher microbial maintenance costs for osmotic cell adjustments.

Understanding the temperature sensitivity (Q(10)) of soil organic matter (SOM) decomposition is crucial to predict CO2 emissions and carbon (C) stocks under global warming. This study describes the decomposition and Q(10) of four soil C pools: (1) very labile (glucose addition (GLU), representing root exudates), (2) labile (microbial turnover, MT), (3) potentially labile (primed C pool, PE), and (4) resistant (inherent soil C, RES). The soil (loamy Luvisol) was incubated for 4 and 144 days at five temperatures (0, 10, 20, 30, and 40 degrees C) with or without C-14-labeled glucose. The dynamics of CO2 fluxes were measured during short (0-4 days) and long (5-144 days) term incubations. Glucose was mineralized following a two-pool exponential function. The half-life of the decomposition of the GLU pool decreased by 3 times as temperature increased from 10 to 40 degrees C. The flux of unlabeled CO2 over 4 days reflects a strong contribution to the apparent priming especially at high temperature, which was due to the accelerated microbial biomass turnover. Accordingly, the CO2 flux increased during short-term incubation and was dominated by the decomposition of labile SOM and microbial biomass turnover, whereas during the long-term incubation, the CO2 was mainly released from the temperature-stimulated decomposition of RES pool. The short-term Q(10) of the soil C pools decreased in the order: GLU (2.1) > MT (1.8) > PE (1.3) approximate to RES (1.6) over a few days (0-4 days), but the Q(10) measured over the long-term period (144 days) was in the range of 1.2 (PE) to 1.8 (RES) and decreased in the order RES > MT > PE > GLU. In conclusion, CO2 emissions linearly increased with temperature in all pools over short- and long-term incubation, except for the GLU pool during long-term incubation. The Q(10) strongly depends on the availability of C pools for microorganisms and decreases over time with the exhaustion of available substances in soil. This needs to be considered when estimating temperature effects on CO2 emissions and C turnover in soil.

Crop-specific cultivation practices including crop rotation, cover cropping, and fertilisation are key measures for sustainable farming, for which soil microorganisms are important components. This study aims at identifying links between agronomic practices, potato yield and quality as well as soil microorganisms. We analysed the roles of cover crops and of the soil prokaryotic, fungal, and protistan communities in a long-term trial, differing in crop rotation, i.e. winter wheat or silage maize as pre-crop, presence and positioning of oil radish within the rotation, and fertilisation, i.e. mineral fertiliser, straw, manure, or slurry. Up to 16

Given the increasingly recognised importance of microbial biomass (MB) in soil organic carbon (SOC) sequestration, knowledge of the microbial ionome beyond carbon (C), nitrogen (N) and phosphorus (P) becomes crucial. The microbial ionome could indicate nutritional restrictions related to MB growth and microbial necromass C (MN-C) accumulation. In this study, soils receiving different combinations of mineral N, P and potassium (K) were sampled in the Askov long-term field experiment, Denmark, and analysed for MB elemental composition including N, P, K, magnesium (Mg), manganese (Mn) and zinc (Zn) using fumigation-extraction and ICP-OES. Furthermore, bacterial, archaeal and fungal gene abundance was determined by qPCR as microbial community shifts may relate to microbial ionome shifts. MN-C was determined by amino sugar analysis. MB-C was unaffected by fertiliser treatments and not correlated with MN-C. N fertilisation increased MN-C. N and K additions increased plant-derived SOC, indicating the importance of N for microbial and plant-derived SOC accumulation. Availability of P and K increased MB-P and MB-K, respectively, and reduced the MB-C:P ratio but not MB-C:K. N fertilisation reduced the pH and increased Mn availability which increased MB-Mn and reduced MB-C:Mn. ITS1 gene copies responded positively to P availability. A reduced MB-C:Mn ratio was associated with a relative increase in fungal gene copy abundance. This was linked to an increase in SOC, indicating a positive link between Mn availability, fungal abundance and SOC level, yet this was not reflected in MN-C accumulation, but by the accumulation of plant-derived SOC, possibly due to reduced plant C turnover.

The intensification and specialization of global agriculture has led to a nutrient surplus resulting in regional environmental issues such as eutrophication and loss of biodiversity due to nutrient accumulation. Addressing these challenges requires a shift towards regional nutrient circularity, inspired by the principles of a circular economy, to create a more resource-efficient agricultural system. Circular agriculture, particularly in Europe, provides a model for sustainable nutrient management at various scales—local, regional, national and international. Existing technologies enable the production of fertilizers from secondary or waste streams and can improve nutrient use efficiency. The development of a market with transparency of supply and demand dynamics, standardized products, and reliable traceability is essential for the effective implementation of nutrient circularity. However, practical nutrient management takes place on a local level, with significant variability in environmental, economic, and social conditions at the farm and field levels due to differences in nutrient demand by crops or farm management, e.g. organic farming with often lower total nutrient intensity. Therefore, the successful development of a regional circular nutrient economy necessitates a stronger stakeholder perspective, emphasizing the importance of participatory research approaches. In addition to circularity, the efficiency of nutrient use from secondary fertilizers must be enhanced, and the broader food system must evolve towards more nutrient-efficient practices. This transformation will likely require adopting a planetary health diet that promotes both sufficiency and sustainability in nutrient use. Therefore, policy measures need to provide a clear regulatory framework at supranational (e.g. European Union) or national level, targeting environmental and societal goals, while at the same time supporting locally adaptable interventions through economic incentives and innovation support.