Direct anthropogenic perturbations of the P cycle, coupled with other human-induced stresses, have impacted numerous environments. Forest ecosystems may be losing their ability to recycle P efficiently, due to excessive N input, extensive biomass removal, and climatic stress. Soils, which serve as the biogeochemical fulcrum of the terrestrial P cycle, have been greatly altered by fertilizer use in recent decades. Changes in the P cycle on land impact the magnitude and timing of P fluxes into aquatic ecosystems, influencing their trophic state. Burial in sediments returns P to the geological reservoir, eventually forming economically viable P deposits. Throughout the P cycle, redox conditions play a key role in transformations and mobility of P. Climate change and its mitigation affect and will further disrupt global P cycles. For example, the removal of CO2 from the atmosphere through an increase in global soil organic carbon stocks implies P sequestration.
This interdisciplinary session invites contributions to the study of P from all disciplines, and aims to foster collaborations links between researchers working on different aspects of the P cycle. We target a balanced session giving equal weight across the continuum of environments in the P cycle, from agriculture, forests, soils and groundwater, through lakes, rivers and estuaries, to oceans, marine sediments and geological P deposits. We welcome both empirical and modeling studies.
Phosphorus (P) and phosphate rock have been included in the list of EU’s critical raw materials, due to their importance in agricultural production and food security. However, over the latter 20th century and up to today, P use in agriculture has increased much faster than population growth (from 4.5 Tg P and 3.0 billion people in 1961 up to 18 Tg P in 2022 and 8.0 billion people in 2022)1. These growing inefficiencies in global phosphorus use are coupled with a linearized economic model of produce, use, waste, completely short circuiting the global phosphorus cycle. Indiscriminate use of P (has increased global P cropland soil stocks by over 1 Pg P over the aforementioned time period, despite cropland soils having over 100 Tg Olsen P (readily available P)2. Conversely, in many low-income nations, a volatile phosphorus market (a doubling and a halving over the past 5 years) is leading to disruptions in their phosphorus supply chain and threatening their food security. In addition, humanity’s changes to the phosphorus cycle are leading to both upstream pressures for phosphorus fertilizer production, including millions of tons of phosphogypsum waste, and downstream eutrophication pressures, as phosphorus is a limiting nutrient in many aquatic environments.
Nevertheless, increasing scientific understanding of the global phosphorus cycle, plant-nutrient interactions and mycorrhizal network, the biogeochemical interactions of P in aquatic and soil environments, phosphorus recovery and immobilitzation from wastewater and from eutrophic systems, is growing in to a strong, yet fragmented phosphorus community. Further, clear policies and regulation for phosphorus use and recovery on for closing phosphorus loops are lacking at a global level. This presentation will showcase some low-hanging fruits that can help us move toward a closing of phosphorus loops by highlighting local phosphorus balances, food and fertilizer phosphorus use and trade patterns, soil phosphorus stocks, and potential for eutrophication. Finally, it provides a call to bring together European scientists, food producers, the waste(water) sector, and policymakers together to form a coalition that can move phosphorus toward circularity, ameliorating its environmental impacts, and ultimately establishing a resilient and sustainable global food system.
1Mogollón, JM, Bouwman, AF , Beusen, AHW, Lassaletta, L, van Grinsven, HJM, Westhoek, H. (2018) More efficient phosphorus use can avoid cropland expansion
Nature Food, 2, 509-518.
2McDowell, RW, Noble, A, Pletnyakov, P, Haygarth, PM (2023) A global database of soil plant available phosphorus, Scientific Data, 10, 125.
How to cite: Navarre, N. and Mogollón, J. M.: Assessing the global phosphorus cycle and opportunities for closing the loop, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21769, https://doi.org/10.5194/egusphere-egu25-21769, 2025.
Since the second half of the 20th century, NPK (nitrogen, phosphorus, and potassium) inorganic fertilizers have been pivotal in boosting global crop yields. These fertilizers have supported the growth of the global population, facilitated dietary shifts towards protein-rich foods, and expanded industrial applications, such as biofuel production. However, the extensive use of fertilizers has disrupted natural biochemical cycles, leading to environmental impacts and raising social and economic concerns.
Four crops—maize, rice, soybean, and wheat—currently occupy over 50% of global croplands, account for more than 60% of global agricultural fertilizer inputs, and produce two-thirds of the proteins consumed by humans. Rice and wheat are primarily used for direct human consumption (food), whereas maize and soybean are also used for livestock feeding (feed) and other industrial applications. The debate over food versus feed versus other uses has typically centered on land occupation, labour, and water usage. However, the regional and temporal drivers of fertilizer use among these major crops remain poorly understood. We hypothesized that, in recent decades, larger fractions of fertilizers have been allocated to feed and other uses compared to food. Furthermore, we aim to discern whether the changes in fertilizer consumption for each use have been driven by expansions in crop areas, increased fertilizer intensification, or a greater proportion of crops being allocated to each use.
To investigate the temporal changes in total fertilizer use across the three main nutrients and four key crops, while distinguishing between their final uses (food, feed, and other uses), we adopted a comprehensive approach: First, we integrated national-level temporal data from 1961 onwards concerning crop fertilization, production, consumption, and trade, and second, we accounted for uncertainty in our estimates using Monte Carlo simulations. Finally, we performed a multiplicative factor decomposition to analyze the drivers behind the variations in total nutrient consumption for each nutrient and use category.
We found a significant increase in fertilizer use among the four main crops for the three nutrients and across all use categories over the past six decades. Globally, increases in fertilizer use for food and feed purposes are relatively balanced. However, at the national level, most countries have shifted towards a higher proportion of fertilizer use for feed compared to food. These shifts were driven by different crops: increases in fertilizer use for food were primarily linked to rice and wheat, for feed with maize and soybean, and for other uses predominantly with maize. Notably, for soybeans, the allocation of fertilizers between feed and food uses more than doubled during the studied period. Across all nutrient-use combinations, changes in total fertilizer consumption were mainly driven by increased fertilizer intensity rather than expanded cropped area or crop usage. However, for feed use, changes in total phosphorus and potassium consumption were equally influenced by increases in cropped area. The increase in fertilizer use for other uses, primarily driven by maize since 1990, appears closely linked to bioethanol production, especially in the United States, the leading producer.
How to cite: Coello, F., Sardans, J., and Peñuelas, J.: Why have we fertilized the world? Global drivers of NPK fertilization in major crops since 1961, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15675, https://doi.org/10.5194/egusphere-egu25-15675, 2025.
Phosphorus (P) is an essential nutrient for plant growth, yet much of the P in agricultural soils remains inaccessible to plants, necessitating external inputs. Since the 1920s, agricultural intensification in Europe has led to significant P accumulation in soils, resulting in P surpluses (the difference between P inputs and outputs) that exceed plant needs. These surpluses contribute to environmental issues, including water quality degradation, biodiversity loss, and breaches of planetary boundaries. Despite regulatory efforts, elevated P levels persist in European water bodies, highlighting the need for long-term understanding of soil P surplus to guide future land and water management practices.
The goal of this study is to characterize the spatial and temporal pattern of the P surplus across Europe1. To achieve this goal, we constructed a long-term (1850-2019) yearly P surplus dataset across Europe at a 5 arcmin spatial resolution for agricultural and non-agricultural soils. Our gridded dataset allows for aggregating P surplus at different spatial scales of interest for soil and water management. Specifically, the dataset includes 48 P surplus estimates addressing uncertainties in key components such as fertilizers, manure, and P removal rates, acknowledging the inherent variability in nutrient budgets.
Our results show that P surplus (evaluated as one standard deviation around the mean of the 48 estimates) in the EU-27 has tripled over 170 years, increasing from 1.19±0.28 kg ha⁻¹ of physical area in 1850 to 2.48±0.97 kg ha⁻¹ of physical area in recent years. Spatially, our analysis indicates that Central European countries mainly rely on mineral fertilizers, except regions like the Netherlands, Belgium, and Denmark, where animal manure dominates due to high livestock densities. Furthermore, the long-term database allowed us to identify four distinct phases of P surplus: 1850–1920 (Pre-modern agriculture), (ii) 1921–1960 (Industrialization before the Green Revolution), (iii) 1961–1990 (Green Revolution and synthetic fertilizer expansion), and (iv) 1991–2019 (Environmental awareness and policy intervention phase). Complimenting our earlier Nitrogen (N) surplus dataset2, this work emphasizes the importance of long-term analyses to address persistent nutrient-related environmental challenges.
1Batool, M., Sarrazin, F. J., and Kumar, R.: Century Long Reconstruction of Gridded Phosphorus Surplus Across Europe (1850–2019), Earth Syst. Sci. Data Discuss. [preprint], https://doi.org/10.5194/essd-2024-294, in review, 2024.
2Batool, M., Sarrazin, F.J., Attinger, S. et al. Long-term annual soil nitrogen surplus across Europe (1850–2019). Sci Data 9, 612 (2022). https://doi.org/10.1038/s41597-022-01693-9
How to cite: Batool, M., Sarrazin, F. J., and Kumar, R.: Understanding the Long-term Spatial and Temporal Dynamics of Phosphorus Surplus Across Europe, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6465, https://doi.org/10.5194/egusphere-egu25-6465, 2025.
Phosphorus (P) is one of the key limitations to crop yields. However, the relationship between soil P and yield is far to be understood at the global scale, given some difficulties in global soil P mapping [Helfenstein et al., 2024], complexities to model soil P dynamics and spatially variable interactions between P and other sources of yield gap (nitrogen, water, pest and diseases).
To better understand the P limitation of crop yield at the global scale, we developed here a simple but mechanistic approach (called GPCROP) to simulate the interaction between plant and soil P at daily time-step for one year. The model assumes no other limitation (water, N), and thus allows quantifying the P limitation of potential yield by the current soil P. Simulations are performed for maize at half-degree latitude x longitude spatial resolution.
GPCROP combines and builds on four previously developed models that we here combined: a model of potential growth for maize (SIM, [Ringeval et al., 2021]), a model describing the soil P dynamics (GPASOIL, [Ringeval et al., 2024]), a parametrization for the P supply by root (following [Kvakic et al., 2018]), and a model describing the allocation of C and P among plant organs, inspired of [Kvakic et al., 2020]. In particular, the soil P dynamics model allows us to represent the resplenishment of the soil P solution by more stable soil P pools, the parametrization for the P supply by root allows us to represent the diffusion of P in soil and the allocation model, based on an optimization procedure, allows us to represent plant adjustments to P limitation such as change in root:shoot ratio and change in leaf P concentration.
Thanks to GPCROP, we quantified the limitation of potential yield by P at the global scale. An uncertainty related to key model parameters and model input was also provided. Simulations underlined the importance of the begin of the growing season when roots are poorly developped in the magnitude of the limitation on final yield. Plant adjustements do particularly matter at that moment of the growing season as they allow (at least partly) to alleviate the P limitation, and we estimated their contribution in the reduction of the global P limitation.
References:
Helfenstein et al., 2024 : Understanding soil phosphorus cycling for sustainable development: A review. One Earth, S2590332224003737.
Kvakic et al., 2018 : Quantifying the Limitation to World Cereal Production Due To Soil Phosphorus Status. Global Biogeochemical Cycles, https://doi.org/10.1002/2017GB005754.
Kvakic et al., 2020 : Carbon and Phosphorus Allocation in Annual Plants: An Optimal Functioning Approach. Frontiers in Plant Science, 11:149, https://doi.org/10.3389/fpls.2020.00149.
Ringeval et al., 2021 : Potential yield simulated by global gridded crop models: using a process-based emulator to explain their differences. Geoscientific Model Development, 14(3):1639–1656, https://doi.org/10.5194/gmd-14-1639-2021, 2021.
Ringeval et al., 2024 : A global dataset on phosphorus in agricultural soils. Scientific Data, 11(1):17, https://doi.org/10.1038/s41597-023-02751-6.
How to cite: Ringeval, B., Demay, J., Helfenstein, J., Kvakic, M., Mollier, A., Nesme, T., Seghouani, M., and Pellerin, S.: Limitation of potential yield by phosphorus at the global scale, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8646, https://doi.org/10.5194/egusphere-egu25-8646, 2025.
Oxygen isotopes in phosphate (δ¹⁸Oₚ) have rised interest as powerful tracers for environmental studies, offering valuable insights into phosphorus cycling, biological activity, and potential phosphate source tracing in diverse environments. By January 2025, more than 180 peer-reviewed studies have explored δ¹⁸Oₚ applications in Environmental Sciences, underscoring the interest in this tool, but also its limited application. Broader adoption of δ¹⁸Oₚ analysis is hindered by challenges such as the complexity of sample preparation, uncertainties in isotopic data interpretation, and the difficulty of identifying all endmembers in field-based studies.
Recent advancements in high-resolution mass spectrometry (HRMS), allowing the isotopic measurements of oxyanions at natural abudances, have addressed key technical limitations. This innovation facilitates the analysis of smaller samples, but recent research highlights the critical need for thorough sample preparation to ensure reliable results. These advances lay the groundwork for more extensive δ¹⁸Oₚ applications, particularly since HRMS are becoming more and more widespread.
Central to δ¹⁸Oₚ studies is the process of phosphoryl transfer, a fundamental mechanism in numerous biological processes. Changes in the isotopic composition of oxygen in phosphate promoted by phosphoryl transfer is considered to reflect the metabolic status of living cells, positioning δ¹⁸Oₚ as a potential “thermometer” for assessing organism metabolic “health”. This capability is particularly evident in soil incubation experiments, where the extent of oxygen exchange during phosphoryl transfer recorded in the microbial phosphate pool correlates with respired CO₂. Such findings highlight δ¹⁸Oₚ's potential to link phosphorus cycling to carbon cycling, providing new perspectives on ecosystem functioning.
To harness this potential, future research should prioritize 18O labelling approaches in controlled incubation experiments integrating ancillary data, such as CO₂ flux measurements, to elucidate the mechanistic links between metabolic activity and changes in isotopic values. Complementary field studies, incorporating detailed assessments of δ¹⁸Oₚ alongside CO₂ and other environmental parameters, are essential for validating laboratory findings and expanding their relevance to complex natural systems.
By addressing these challenges and leveraging recent technical innovations, δ¹⁸Oₚ can emerge as a robust tool for deciphering phosphorus dynamics, their connection with metabolic processes, and their broader role in environmental systems.
How to cite: Tamburini, F., Hofstetter, T., Bernet, N., Evertz, E., Shi, C., Siegenthaler, M., von Sperber, C., and Pistocchi, C.: Oxygen Stable isotopes in phosphate: what is next?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21512, https://doi.org/10.5194/egusphere-egu25-21512, 2025.
Peatlands store about one third of the global soil organic carbon. This carbon storage is partly controlled by the availability of nitrogen (N) and phosphorus (P) in peat, which affects primary productivity, decomposition, plant community composition, and microbial community composition in these ecosystems. While extensive research has been conducted on the N cycle in peatlands, much less is known about the biogeochemistry of P. To date, little is known about how an increase of atmospheric N deposition affects the availability and biogeochemistry of P in peat. To fill this gap of knowledge, we studied the effect of increased N additions on soil P pools in an ombrotrophic bog in Canada. For this purpose, soil samples were taken from a 20 year old fertilization trial at Mer Bleue Bog in south-eastern Ontario and subjected to Hedley sequential fractionation. In unfertilized peat, P concentrations were highest in the available and highly recalcitrant pools, with little between them. This U-shaped distribution of P along the gradient of availability contrasts with established patterns in mineral soils. In plots which received PK and NPK fertilizers, concentrations of both available P and highly recalcitrant P doubled. In plots receiving N fertilization alone, available and total P concentrations decreased, which may indicate increased demand for P by plants and microorganisms when N status is high. In all plots receiving fertilizer, concentrations of highly recalcitrant P increased, which may indicate increased decomposition of peat. In addition, fertilization led to changes aboveground. Chamaedaphne calyculata leaves in plots receiving PK and NPK were enriched in P compared to Chamaedaphne calyculata leaves in unfertilized plots and plots receiving N alone. These findings indicate, that formerly N limited peatlands may become P limited due to anthropogenically enhanced atmospheric nitrogen depositions which may impact their potential to store soil organic carbon in the future.
How to cite: von Sperber, C., Jones, C., Brais, C., Moore, T., Kallenbach, C., and Wang, M.: Effects of Nitrogen addition on Soil Phosphorus Pools in an Ombrotrophic Bog in South-Eastern Ontario, Canada, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6643, https://doi.org/10.5194/egusphere-egu25-6643, 2025.
Groundwater-derived geogenic phosphorus (P) plays a significant but often overlooked role in surface water eutrophication. Geogenic P differs from anthropogenic P in its release mechanisms, seasonal variability and magnitude of release. While many studies have addressed the spatial distribution of geogenic P, its temporal dynamics, transport and export mechanisms remain insufficiently understood. This study was conducted in a small study site (~1ha) located in a drained riparian wetland in southeastern Germany, where anthropogenic P input is minimal. The combination of a P-rich geological background, dynamic redox conditions and a drainage network provided an ideal setting to study the P mobilization and export processes. Hydrogeochemical monitoring of groundwater and drainage water over two years, complemented by vertical profile sampling of dissolved and solid phases, revealed significant P enrichment in the subsurface. About 70% of groundwater and drainage water samples exceeded the German Environment Agency’s threshold of 0.1 mg/L. Soluble reactive phosphorus (SRP) concentrations in groundwater reached up to 16 µmol/L (0.5 mg/L) in two of four wells, showing minimal seasonal variation. Drainage water SRP ranged from 6 to 15 µmol/L, with some interannual variability due to dilution during wet periods, and closely matched the chemistry of high-P groundwater wells. Both high spatial and low temporal variability were attributed to the site-specific geochemical settings. A strong correlation between P and iron (Fe) in groundwater and drainage water highlighted the critical role of Fe-P interactions in controlling P dynamics. Electrical resistivity tomography confirmed a subsurface preferential flow channel aligned with the high-P wells. These findings proposed a conceptual model: geogenic P, probably originating from the weathering of P-bearing minerals, reductive dissolution of Fe oxides, and organic matter mineralization, is stored in the subsurface. Preferential flow paths transport Fe-P-rich, anoxic groundwater to drainage systems, which further accelerate P export by creating direct groundwater-surface water connections, reducing residence time, and acting as hotspots for P accumulation and event-driven transport. This study provides novel insights into the processing of geogenic P in groundwater and its continuous contribution to surface water eutrophication. While concentrations may be lower than those from surface runoff or agriculture, geogenic P remains a long-term and persistent source of P loading. These results underscore the need for eutrophication mitigation strategies to address both geogenic and anthropogenic P sources.
How to cite: Liu, X., Winkler, M., Sass, O., and Peiffer, S.: Export of groundwater-borne geogenic phosphorus from a drained wetland into surface water, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6642, https://doi.org/10.5194/egusphere-egu25-6642, 2025.
In the global phosphorus (P) cycle, aquatic ecosystems play a crucial role, as there, long-term retention of P through sedimentation and subsequent burial of P containing minerals takes place. This study zooms into a rather overlooked section of the aquatic part of the global P cycle: The P entrapment pathways of benthic microbial biofilms. Benthic microbial biofilms are able to entrap P in its various forms, biochemically transform it, and contribute to internal loading via the release of P. The importance and the dynamics of P entrapment and P release in fluvial benthic microbial biofilms are, as of now, not completely understood.
For this field study, we performed a longitudinal sampling campaign along a 25 kilometer stretch of a third order Central European river, with the aim of investigating P entrapment patterns of benthic microbial biofilms. We distinguished between extracellular P entrapment and intracellular P entrapment and recorded metabolic characteristics of the sampled biofilm, as well as environmental variables.
We found that the ratio of intracellular P to extracellular P differed greatly between sampling sites. High values for this ratio (on average, 26.7) were related to relatively pristine sampling sites with rather recalcitrant allochthonous carbon inputs. Further downstream, at sampling sites exposed to anthropogenic disturbances, the ratio declined sharply (on average below, 1). These biofilms were subject to P-rich wastewater treatment plant effluent and labile dissolved organic matter of rather autochthonous origin. Measurements of the equilibrium P concentration, as a measure for P release potential from the sediment, showed that sites with benthic biofilms with a higher share of extracellular P have a highly increased P release potential from the sediment. We further found distinguishable carbon use metabolic profiles of the biofilms between different sampling sites, though a higher carbon use functional diversity did not necessarily contribute to a higher overall P entrapment in the biofilm.
Our results show clear patterns of benthic biofilm P entrapment along the sampled river stretch. These patterns seem to be connected to the changing environmental variables along the sampled river stretch. Furthermore, the P release potential from the sediment was highly correlated with an increased share of extracellular P in the biofilms.
How to cite: Wentritt, S., Weitere, M., Kneis, D., and Perujo, N.: Linking phosphorus entrapment and release potential in fluvial biofilms to carbon and light availability in natural environments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18632, https://doi.org/10.5194/egusphere-egu25-18632, 2025.
Baltic Sea is a geologically young semi-enclosed brackish-water body whose water exchange with the ocean has gradually declined. Approximately 85 million people live in the Baltic Sea's catchment area, resulting in significant human impact on the basin's ecosystem. Eutrophication due to anthropogenic discharge of nutrients is considered the most serious environmental problem, leading to greater growth of phytoplankton and algae, deterioration of water quality, and lack of oxygen in near-bottom water masses. As a result of recent large-scale nutrient input, phosphorus has accumulated into the seabed sediments from where it has been remobilizing and releasing into the water column under favorable conditions. Marine sediments contain phosphorus in various components, i.e. fractions, but not all of them are affected by remobilization. The release of phosphorus from sediments is affected by different oxygen conditions in the bottom water layer. Therefore, understanding the principles of phosphorus release and the distribution of phosphorus fractions in seabed sediments is extremely important.
Phosphorus fractions, porewater chemistry, and their vertical distribution were studied from the sea-bottom sediments from three locations in western Estonia in the northern Baltic Proper. The amount of mobile phosphorus fraction (mobile in hypoxic and anoxic conditions) stored in the surface sediments of the northern Baltic Proper is lower than expected, which indicates that most of the mobile phosphorus fraction has already been released back into the water column. In two out of three locations, the content of mobile phosphorus fraction in the sediment surface has decreased close to the natural background, which on average is less than 200 mg/kg (dw). Constant hypoxic conditions prevail at the sediment-water interface in all three locations. In the near future, oxygen levels can only increase in these areas due to Major Baltic Inflow (MBI) events, which introduce dense, salty, oxygen-rich water into the Baltic Sea. During sufficiently large inflow events, oxygen-rich water can reach areas previously characterized by stable hypoxic conditions, temporarily altering the deep-water oxygen levels. Under oxygen-rich conditions, organic material (including organic phosphorus) begins to decompose. The sediments in the study area contain up to 32.8% (dw) organic matter, holding substantial amounts of organic phosphorus. The released phosphorus is converted to a mobile phosphorus fraction, which becomes mobile again when oxygen conditions return to hypoxic.
How to cite: Ausmeel, M., Liira, M., and Suuroja, S.: Mobile phosphorus in the seabed sediments of the northern Baltic Proper, Baltic Sea: hypoxic conditions limit large-scale phosphorus release, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12722, https://doi.org/10.5194/egusphere-egu25-12722, 2025.
Estimates of phosphorus (P) fluxes at the global scale were already available in the early 2010s and led to the establishment of planetary boundaries for P. In the meantime, estimates of P stocks and fluxes have been revised and updated for natural biomes, agriculture, fishery, and global biogeochemical models. However, improvements toward attaining P-related sustainable development goals requires policies informed by the situation at the corresponding scales, ranging from plot to national to global scale. Here, we bridge this gap by synthesizing the relative sizes of P stocks and fluxes in natural and agricultural terrestrial environments from existing literature, focusing on the plot scale. Though the P cycle is context specific, our analysis of roughly 790 empirical flux measurements from 27 studies supports drawing several general conclusions about relative magnitudes of P stocks and fluxes. For example, in both natural and agricultural systems, empirical data on P stocks tend to follow the pattern soil >> microbial biomass > plant biomass. Similarly, we summarize empirical measurements of P fluxes and show that in natural ecosystems, fluxes between P pools within soil >> fluxes between soils-plants > system inputs (weathering, atmospheric deposition) and losses (erosion, leaching). We also discuss specific contexts where these general patterns do not hold, and what that means for management. Finally, we will discuss how a better understanding of P stocks and fluxes is relevant for science-informed management of P resources, for example through improved representation of P in vegetation or crop models.
How to cite: Helfenstein, J., Ringeval, B., Tamburini, F., Mulder, V., Goll, D., He, X., Alblas, E., Wang, Y., Mollier, A., and Frossard, E.: A synthesis of phosphorus stocks and fluxes in natural and agricultural environments, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2511, https://doi.org/10.5194/egusphere-egu25-2511, 2025.
Atmospheric particles originating from combustion byproducts (burned biomass or wildfire ash) are highly enriched in nutrients such as P, K, Ca, Mg, Fe, Mn, Zn and others. Over long time scales, deposited wildfire ash particles contributes to soil fertility by replenishing soil nutrient reservoirs. However, the immediate nutritional effects of freshly deposited fire ash on plants are mostly unknown. Here we study the influence of fire ash on plant nutrition by applying particles directly on plant leaves or onto the roots of chickpea, which was used as our model plant. The experiment was conducted under ambient and elevated CO2 levels, (412 and 850 ppm) that reflect both current and future climate scenarios. We found that plants can uptake fire ash P only from their leaves, through direct nutrient uptake from particles captured on their foliage, but not via their roots. In a future climate scenario, foliar nutrient uptake pathway may be even more pronounced for plants, due to the partial inhibition of key root uptake mechanism. Our findings highlight the effectiveness of the foliar nutrient uptake mechanism under both ambient and elevated CO2 levels, with fire ash P being the sole nutrient absorbed by the foliage. These findings demonstrate the substantial contribution of fire ash to the nutrition of plants. The role of fire ash is expected to increase in a future world, thus giving a competitive advantage to plants that can utilize fire ash P from the foliar pathway.
How to cite: gross, A., palchan, D., and lokshin, A.: Direct foliar phosphorus uptake from wildfire ash , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5234, https://doi.org/10.5194/egusphere-egu25-5234, 2025.
Long-term applications of organic fertilizers significantly influence soil organic matter (SOM) and phosphorus (P). However, the interactions between SOM and P remain poorly understood. A better understanding of these interactions is important for efficient fertilization strategies. Methods of size and density fractionation of SOM have been used to study the fate of carbon from organic inputs and have been instrumental in understanding the mechanisms of SOM processing, storage, and interaction with soil minerals.
The Danish long-term field experiment CRUCIAL (Closing the Rural-Urban Nutrient Cycle – Investigations through Agronomic Long-term Experiments) was established to explore the soil impacts of excessive organic material applications (e.g., sewage sludge, compost, cattle manure) over more than two decades. These amendments have provided annual P inputs of up to 621 kg·ha-1, greatly exceeding crop P requirements (~25 kg·ha-1), significantly increasing soil carbon stocks, total and organic P stocks, microbial biomass, and reducing soil bulk density.
To investigate the associations of SOM and P in fractions that serve as proxies for SOM with different degradation levels and interactions with specific soil minerals, we are employing size and density fractionation techniques. However, optimized protocols for fractionating SOM with a focus on P are lacking. We are currently optimizing such a method. Soils fertilized with compost, sewage sludge, cattle manure, or unfertilized controls were fractionated as follows:
20g air-dried soils were dispersed in water using glass beads. Thereafter, soils were wet-sieved into two size fractions: (A) 2 mm - 100 µm and (B) <100 µm. Density fractionation was conducted by suspending fractions A and B in a sodium polytungstate solution (density 1.8 or 2.4 g·ml-1), separating the lighter fraction (a) and progressively denser fractions (b and c). Fraction Bb was further sonicated and centrifuged.
Preliminary results highlight the influence of organic fertilizers on SOM fraction size and P distribution. In compost-fertilized soils, fraction Aa contained visible plant fragments, roots, and coarse composted material (P concentration: 0.7 g·kg-1), while fraction Ab, comprising darker and finer plant material, had a higher P concentration (4.6 g·kg-1). Fraction Ac, likely consisting of sand, contained no detectable P. Fraction Ba, finely particulate organic matter of gray color, had 2.8 g·kg-1 P, while fraction Bb, dark black in color, contained 4.1 g·kg-1 P.
Compost applications increased the size of all SOM fractions compared to unfertilized soils, whereas sewage sludge treatment resulted in significantly smaller Aa, Ab, and Ba fractions compared to soils treated with compost. Preliminary findings suggest that soil P and SOM fractions are influenced by organic amendments. Currently, we are optimizing the fractionation method to enhance P recovery in each fraction and avoid chemical interference. Future work will study isotopes and concentrations of carbon and nitrogen in the SOM fractions, along with microscopy techniques to identify organic macromolecules and porous structures.
How to cite: Álvarez Salas, M. and Magid, J.: Understanding Phosphorus Association with Soil Organic Matter: Size and Density Fraction Analysis in Intensively Fertilized Soils with Organic Materials, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8490, https://doi.org/10.5194/egusphere-egu25-8490, 2025.
Phosphorus (P) is a bio-critical and non-substitutable element, essential for life, forming the backbone of DNA, RNA, and ATP, playing a vital role in agricultural productivity. Unlike nitrogen, P lacks an atmospheric cycle, relying solely on slow rock weathering or finite geological reserves for replenishment. The challenges surrounding phosphorus are less about its geological availability and more about socio-economic factors, such as limited access to fertilizers, and environmental concerns, including water pollution. These challenges emphasize the importance of adopting sustainable agricultural practices to optimize phosphorus use and reduce environmental impact. The instability of the phosphorus market, as demonstrated during the 2007-2008 global food crisis and the recent 2020-2022 and ongoing price surges, further underscores the need for effective phosphorus management, particularly in countries like India, which relies heavily on imports to sustain agricultural productivity [1][2].
We examined two contrasting soil types, ultisols and vertisols, collected from the Western Ghats, India. These soils were characterized physiochemically, geochemically and mineralogically. Ultisols, with slightly acidic pH, are enriched in iron and aluminium oxides, oxyhydroxides, and 1:1 type clay minerals. In contrast, vertisols, which are alkaline, are dominated by primary basaltic minerals, 2:1 and 1:1 type clay, with minor amounts of iron oxides and hydroxides. We performed sorption isotherm, bioavailability, and fractionation experiments on representative samples of each soil type. Sorption experiments were fitted using Langmuir and Freundlich isotherm models, revealing significantly higher adsorption maxima for phosphorus in ultisols than vertisols. Bioavailability tests reveal greater phosphorus availability in vertisols compared to ultisols, both pre-and post-fertilizer application. Hedley fractionation revealed that phosphorus in ultisols is mainly partitioned in moderately available fractions, while in vertisols, it is predominantly in readily available fractions, explaining the higher phosphorus bioavailability in vertisols than in ultisols. This difference is linked to the mineralogical composition of the soils; ultisols, enriched with iron and aluminium oxides, oxyhydroxides, bind phosphorus to high-energy sites associated with Fe and Al, thereby restricting its availability. In contrast, the near absence of these minerals in vertisols allows for greater phosphorus bioavailability. These findings underscore the importance of considering soil mineralogy in developing efficient and sustainable fertilizer application strategies. Currently, we are investigating the interactions between individual minerals prevalent in these soils and bacteria isolated from the same soils to understand the role of microbes in phosphorus dynamics.
References:
[1] Cordell, D., Drangert, J. O., & White, S. (2009). The story of phosphorus: global food security and food for thought. Global environmental change, 19(2), 292-305.
[2] Brownlie WJ, Sutton MA, Cordell D, Reay DS, Heal KV, Withers PJA, Vanderbeck I and Spears BM (2023) Phosphorus price spikes: A wake-up call for phosphorus resilience. Front. Sustain. Food Syst. 7:1088776. doi: 10.3389/fsufs.2023.1088776
How to cite: Mehta, S. and Mathew, G.: Influence of Soil Mineralogy on Phosphorus Sorption, Partitioning, and Bioavailability in Contrasting Tropical Soils of India, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14701, https://doi.org/10.5194/egusphere-egu25-14701, 2025.
The competitive adsorption of glyphosate and phosphate (PO43-) on mineral surfaces mutually affects their mobility in the environment. Iron hydroxides, such as goethite and ferrihydrite, are abundant in soils and serve as important sinks for both glyphosate and phosphate. The adsorption of these compounds is modulated by pH which affects their surface complexation and mineral surface charge. Moreover, the release of ferrous ions (Fe2+) from the natural iron cycle may further impact glyphosate adsorption by altering surface complexation equilibria. Understanding these interactions is crucial for developing predictive models of glyphosate transport and retention in the environment.
In this study, we employed a surface complexation model (SCM) to evaluate adsorption data of glyphosate and PO43- in aqueous suspensions of goethite and ferrihydrite, focusing on their pH-dependent processes, competitive interactions, and binding modes. Additionally, the influence of Fe2+ on glyphosate adsorption at pH 7 and the adsorption mechanism of Fe2+ on iron hydroxides were examined. Surface complexation constants (log K) for glyphosate, PO43-, and Fe2+ were estimated, providing a robust thermodynamic basis for modeling interactions with the two iron minerals. The surface complexation of glyphosate and PO43- varied with pH, concentration and competitive interactions. Despite the strong competition by PO43-, complete desorption of glyphosate by PO43- was only observed under alkaline conditions, indicating partial retention of glyphosate on iron hydroxides in most natural environments. Notably, Fe2+ and glyphosate mutually promote their adsorption on ferrihydrite at pH 7, indicating synergistic interactions or co-complexation, whereas on goethite Fe2+ has minimal influence on glyphosate adsorption. Structural modeling revealed that Fe2+ adsorption is dominated by monodentate complexes, highlighting the uniformity of adsorption mechanisms across these iron hydroxides.
Our findings underscore the significance of PO43- in attenuating glyphosate retention in soils, while Fe2+ appears to play a dual role, enhancing glyphosate adsorption under specific conditions. This study contributes to a more comprehensive understanding of glyphosate dynamics in iron hydroxide-rich soils and provides directions for environmental management strategies aimed at mitigating glyphosate leaching and optimizing soil remediation practices.
How to cite: Wang, M. and Haderlein, S.: Modeling pH-dependent Adsorption of Glyphosate on Iron Hydroxides: Competition with Phosphate and Influence of Fe2+, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8402, https://doi.org/10.5194/egusphere-egu25-8402, 2025.
Legacy anthropogenic phosphorus (P) accumulated in sediments influences nutrient cycling in eutrophic lakes through so-called internal loading. However, due to the complexity of processes influencing P mobility in the sediment column, the temporal response of internal loading to reduction of external P inputs is difficut to predict. In this study, we use a comprehensive set of porewater and sediment geochemical data to constrain a reaction-transport model simulating long-term anthropogenic inputs and processing of P in Lake Hiidenvesi, a eutrophic lake in southern Finland. The 180 cm sediment core used to train the model encompasses over 800 years of accumulation, including the transitions into and out of the Little Ice Age when land use in the region changed considerably. By defining top 6 cm of sedimentary P as "freshly-deposited" (within the past 10 years) and deeper layers as "legacy P", we find that at any given point in time, the freshly deposited material contributes the majority of regenerated P in porewaters, with an additional contribution from legacy P. A set of linear regressions between P deposition and diffusion rates indicate that internal P loading is primarily controlled by particulate P deposition of organic-P and Fe-P, which may be directly derived from catchment exports or autochthonously produced through in-lake biogeochemical processes. The Little Ice Age is shown by the model to be a period of relatively lower external P inputs an consequently also lower internal loading rates. However, the overall retention of P in sediments is sufficient to suggest that sediment P content can be used as an indicator for historical anthropogenic impacts in catchment areas of lakes in the boreal region.
How to cite: Jilbert, T., Zhao, S., Sun, X., and Niemistö, J.: Reaction-transport modeling of centennial-scale phosphorus accumulation and internal loading in a human-impacted boreal lake, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21599, https://doi.org/10.5194/egusphere-egu25-21599, 2025.
To address the environmental challenges posed by eutrophication, removal of excess phosphorus from aquatic ecosystems is imperative. This study presents a cationic adsorbent synthesized by modifying nanofibrillated cellulose (NFC), derived from agrowaste, using surfactant cetyltrimethylammonium bromide (CTAB). Comprehensive characterization techniques, including XRD, FTIR, HR-SEM, SEM-EDX, BET, and XPS, confirmed successful introduction of quaternary ammonium groups, significantly enhancing the surface chemistry of NFC. This modification imparted a positive ζ potential over a wide pH range, ensuring a strong affinity for negatively charged phosphate ions. Increased surface roughness and improved active site availability resulted in a nearly threefold improvement in phosphate removal efficiency compared to pristine NFC. The adsorption followed a pseudo-second-order kinetic model and Sips isotherm, achieving a maximum capacity of 21.78 mg P/g within 120 minutes. The adsorbent displayed pH-dependent behavior, retaining stability and optimal performance under weakly acidic to neutral conditions, with minimal desorption (12.61%) after three cycles. Mechanistic insights from XPS and FTIR revealed that electrostatic interactions and hydrogen bonding were the primary drivers of phosphate adsorption.
How to cite: Pandey, A., Sharma, Y. C., and Kalamdhad, A. S.: Optimized CTAB-Modified Nanofibrillated Cellulose for Phosphate Recovery: Adsorption Mechanisms and Performance Insights, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-626, https://doi.org/10.5194/egusphere-egu25-626, 2025.
Phosphate contamination in water bodies is a global environmental issue that can result in eutrophication, affecting sectors like agriculture and fishing and thereby jeopardizing the long-term viability of water resources. Phosphate, a non-renewable resource, is a crucial mineral for crop production and a key component of NPK (Nitrogen, Phosphorus, and Potassium) fertilizer. Only 16% of the applied phosphate as fertilizer is utilized by crops; the rest is lost through soil erosion and aquatic runoff, increasing the risk of eutrophication. Therefore, environmental concerns and phosphate depletion have increased the need for phosphate recovery and recycling. This study explored the potential of engineered sewage sludge biochar for the sorption of aqueous phosphate. Biochar was obtained after pyrolyzing sewage sludge at 500°C, which was modified using coprecipitation of FeCl3.6H2O and ZnCl2. At pH 6, the engineered biochar exhibited around 92% phosphate sorption compared to 20% by pristine sewage sludge biochar. The highest sorption capacity (using Langmuir isotherm) was 129 mg/g at 15°C. Phosphate-laden biochar can further be utilized in agricultural fields, where it will act as a slow-release fertilizer to improve soil fertility or restore contaminated soil, thereby providing a sustainable solution for waste management and enhancing soil fertility. This will help achieve SDG 2 (Zero hunger) and SDG 6 (Clean water and sanitation).
Keywords: Eutrophication, Sorption, Engineered biochar, Sewage sludge, Sustainable Development Goals
How to cite: Kapoor, S. and Mohan, D.: Enhancing sustainability by utilizing engineered sewage sludge biochar for aqueous phosphate sorption, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16738, https://doi.org/10.5194/egusphere-egu25-16738, 2025.
Multifunctional enzymes can significantly impact biotechnological applications by performing activities beyond their primary functions. This presentation explores the role of the multifunctionality of alkaline phosphatase, a key enzyme in the phosphorus cycle, focusing on the molecular mechanisms influencing its activity, and its biotechnological potential. Based on these findings we argue that understanding these aspects can enhance the utility of alkaline phosphatase in research and industry, fostering innovations in enzyme engineering, environmental biotechnology, and metabolic engineering. Furthermore, by exploring enzyme promiscuity, we highlight alkaline phosphatase’s versatility, paving the way for advancements in sustainable agriculture, environmental remediation, clinical diagnostics in particular, and in ecological and biotechnological progress in general.
How to cite: Baltar, F. and Saavedra, D. E. M.: Multifunctionality of Alkaline Phosphatase in Ecology and Biotechnology, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2226, https://doi.org/10.5194/egusphere-egu25-2226, 2025.
Worldwide rapid industrial growth is leading to heavy urbanization in the coastal areas. Therefore coastal areas are becoming critically contaminated with heavy metal and nutrients, which is serious environmental concern as they are bio-accumulative in nature. Due to its non-biodegradable in nature trace metal is toxic to biotic communities and environment (Gong et al., 2020, Parul and Rina, 2021). The present study has been carried out in India’s second largest mangrove cover in the world. The study area is witnessing rapid urbanization as the area is inhabiting the Asia’s largest fertilizer refinery IFCO along with multiple seaports, with large number of chemical and petroleum industries, and the region is the prime gateway of trade and commerce. Besides this extensive salt producing units with extensive agricultural and aquaculture activities are present which are posing severe threat to the mangroves. The gulf is also inhabiting the complex geomorphological setup such as alluvial plains, tidal mudflats, lagoons creek and stabilized dune area (Deshraj et al. 2012). Construction of saltpan/aquaculture is deteriorating the mangroves health, impairing productivity (Jigar et al, 2022). Phosphorus (P), is one of the important macronutrients that governs the primary productivity and it affects both the terrestrial and marine biogeochemical cycling. P is released in dissolved or suspended forms, holding both inorganic and organic forms, which undergo a continuous transformation. Knowledge of P speciation in sedimentary environments is crucial to understand the P cycling, bioavailability, and the mechanism of their release, which will help to assess the ecological risk associated with P enrichment. Along with Phosphorous, metal fractionation study is also important to determination of bioavailability and mobility of trace metals in geochemical fractions and ecological risk to the ecosystem. Results suggested that Total sedimentary P was found beyond the global limit and consists of inorganic-P fraction predominantly. PEI values suggest higher P loading in sediment which leads to higher eutrophication risk.
Metal fraction study suggested, a considerable variation in the speciation pattern of trace metals. In the study area, highest proportion of trace elements was associated with the residual phase (F4), which manifested that metals bounded with the alumino-silicate mineral and detritus matter in sediments was highest. Therefore, Present study would be helpful to the policymakers in the view of the current Land use-land cover change and contamination level in Gulf of Kachchh, mangroves for implementation of protection strategies for this precious natural resources.
Keywords:
Phosphorus Fractionation, Metal Fractionation, Sequential extraction, Mangroves Sediment, Ecological risk, Gulf of Kachchh, India
How to cite: Kumari, R. and Maurya, P.: Assessing the Geochemical Fractionation of Phosphorous and Heavy metal in Surface Sediments of Mangroves and assertaining its Ecological Risk, Gulf of Kachchh, Second largest mangrove cover of India., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16447, https://doi.org/10.5194/egusphere-egu25-16447, 2025.
Posters virtual: Wed, 30 Apr, 14:00–15:45 | vPoster spot A
EGU25-8511 | Posters virtual | VPS4
Microbial phosphorus processing in a gradient of agricultural soil development following mining activityWed, 30 Apr, 14:00–15:45 (CEST) | vPA.5
Open-cast lignite mining significantly disrupts cultivated soils. Restoration and re-cultivation processes enable the conversion of these disturbed areas back into productive land. These processes involve mixing original topsoil (~20%) with parent material loess (~80%), diluting the organic carbon (C) and nitrogen (N) pools, as well as the soil's biological parameters. To restore soil fertility and physical structure, Phase I includes the cultivation of alfalfa to replenish C and N, re-establish biological functions, and the addition of mineral fertiliser (N:P:K, 15:15:15 kg ha-1). Following two to three years of Phase I, the restoration transitions to Phase II for three to five years, with an initial application of green waste compost (30 t ha-1) and annual basal mineral fertiliser (N:P:K, 200:80:60 kg ha-1). Phase III then involves returning the land to farmers with a typical rotation including sugar beet-winter wheat and a mix of organic and mineral fertilisation.
Previous studies have shown that soil C recovery and several key biological functions have only partially recovered, even after more than 50 years since re-cultivation. However, the evolution of P cycling, especially microbial-mediated P cycling, along this gradient remains unknown. This study aims to investigate interactions between soil P, soil microorganisms, and soil properties that affect microbial P cycling and P availability to plants following mining activity.
Hedley fractionation was employed to estimate various P pool sizes, while ion-exchange kinetics (IEK) assessed P exchangeability and reactivity in eight soils (soils restored from 2022 – year 0 – Phase I, 2020 – year 2 – Phase I, 2018 – year 5 – Phase II, 2014 – year 9 – Phase III, 2006– year 17 – Phase III, 1979 – year 44 – Phase III and 1964 – year 59 – Phase III and an original soil undisturbed). In three key soils (year 0 - Phase I; year 59 - Phase III; original undisturbed soil), 18O-labeled water was used in incubation to determine the degree of 18O integration within microbial biomass and in various P fractions.
In Phase I, a decrease in the relative size of the most labile-P pool was observed. In Phases II and III, this proportion increased, notably with a larger NaOH-extractable-P increase. P exchangeability decreased during Phase I, then significantly increased in older soils, surpassing that of the original undisturbed soil. Preliminary results indicate microbial P processing is highly correlated with total soil organic C. For instance, microbial P processing was nearly non-existent in newly formed soil (organic C: 0.54 g kg-1) and was found to be twice as low in 59-year-old soil (organic C: 1.24 g kg-1) compared to the original soil (organic C: 1.62 g kg-1).
The current findings demonstrate that despite measured P levels surpassing those of the original soil in the oldest soils, biologically-driven P cycling has not fully recovered more than 50 years after soil re-cultivation.
How to cite: Raymond, N. S., Tamburini, F., Oberson, A., Reichel, R., and Mueller, C. W.: Microbial phosphorus processing in a gradient of agricultural soil development following mining activity, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8511, https://doi.org/10.5194/egusphere-egu25-8511, 2025.
