Global phosphorus shortage will be aggravated by soil erosion

A unified and multi-scale Source: Pathway Priority Index for diffuse pollution management

Diffuse pollution is a global issue where management, particularly relating to phosphorus (P) transfers from agricultural land to water, needs to consider the magnitude of the source pressure and the connectivity of the hydrological pathway pressure. Combined, these pressures are considered as critical source areas (CSAs) and where mitigation resources should be focused as part of landscape targeting. However, data requirements and lack of a unified method have made this difficult to implement at national scales. To overcome this, a unique and transferrable national workflow is presented for this purpose at three scales to aid in prioritisation. First, macro- or basin-scale (100-600 km2) water quality data (soluble reactive P-SRP) were used as an initial indicator of pressures at a national river basin scale in Northern Ireland. Second, within these macro-scale catchments, meso‑scale catchments (10-100 km2) used for Water Framework Directive surveillance (n > 230) were prioritised using a validated relationship between long-term river SRP and soil test phosphorus (STP-Olsen P) as the source pressure in over 300,000 agricultural fields tested as part of a national monitoring programme. These meso‑scale catchments were also screened for persistent point source pressures using ammonium (NH4) concentration data. Within each meso‑scale catchment, micro-scale catchments (0.02 - 1.6 km2; 5th - 95th percentile) were identified (> 1.9 million) that combined summaries of STP and a runoff risk metric that was developed with a high-resolution (16 points m-2) LiDAR derived soil topographic index (STI) into an anonymised and dimensionless Source:Pressure Priority Index (SPPI). Exemplar outputs are shown in detail that weight the source and pathway pressures equally, and further emphasise source over pathway pressure, and vice versa, to ensure advisory and mitigation resources can be allocated effectively. The SPPI is a more robust diffuse pollution risk assessment and management tool as it recognises the importance of managing the magnitude of the source pressure, in combination with reducing pathway pressures, rather than focusing on the latter in isolation. This will ensure a faster route to diffuse pollution reduction and offer resilience as pathway mitigations become vulnerable to weather patterns and runoff responses in a changing climate.

Nanoscale grinding: Unlocking the nutrient potential of oxidized phosphate rocks for sustainable fertilizer innovation

The current study delves into the transformative effects of intensive grinding to nanoscale upon oxidized phosphate rocks (PRs) of various grades, high (HMP), medium (MMP) and low (LMP) micro-sizes. Hence, the consequences of these transformative changes on phosphorous dissolution rate of these fractions using acetic acid, were carefully evaluated. The produced high (HNP) and medium (MNP) grades of nano-sized fractions revealed significant changes in their chemical composition, mineralogical, morphological and geometrical properties. Whereas the low grade, LNP, was moderately changed. HNP and MNP exhibited a remarkable increase in structural disorder (slight broadening of reflections) and Loss on Ignition (LOI) contents (10.62 and 13 wt.%, orderly), surpassing their counterparts (HMP: 6.04 and MMP: 10.92 wt.%). Despite the reduction in their P2O5 contents, HNP (31.23 wt.% and MNP (24.22 wt.%), astoundingly outperformed their micro-sized equivalents (HMP: 35.70 wt.%, MMP: 27.92 wt.%) in P dissolution. Therefore, HNP and MNP emerge as promising high-reactive P fertilizers for direct agricultural use and have a great potential as a source of P/Ca liquid fertilizer after nutrients balancing. So, eco-friendly grinding offers a potential approach to maximize PRs' agronomic potential, but long-term environmental impacts should be evaluated.

Shallow groundwater table fluctuations: A driving force for accelerating the migration and transformation of phosphorus in cropland soil

The accumulation of phosphorus (P) in soil profiles of intensive cropland and the losses caused by runoff and leaching have been widely concerned. However, the loss of soil P due to shallow groundwater table (SGT) fluctuations driven by seasonal changes is often neglected, and the migration and transformation mechanisms of soil P are still unclear. On the basis of the long-term monitoring of cropland soil P accumulation and SGT fluctuations around Erhai Lake, the characteristics of soil P loss driven by SGT fluctuations and the corresponding mechanisms were investigated through a 260-day microcosm experiment. The results revealed that the fluctuations in SGT significantly changed the content and form of P in the soil profile. The soil P loss mainly occurred in dissolved form, mainly involving inorganic P, accounting for 75 %. Compared with those under continuous saturated conditions, soil total P (TP) release during SGT fluctuations significantly increased by 9.5 %, and soil TP storage was reduced by 2 %. SGT fluctuations increased the complexity of microbial networks in the soil profile, stimulated the expression of functional genes for soil P cycling, and promoted soil organic P mineralization. The SGT fluctuations caused an increase in the soil TP loss from cropland to 88.5 kg/ha, which was 70 and 25 times greater than that via leaching and runoff, respectively. These results indicated that SGT fluctuations accelerated the P loss from soil profile of cropland. Therefore, some measures should be comprehensively applied to prevent its loss, such as reducing external P input, improving surface soil P storage capacity and soil P utilization efficiency, reducing surface P leaching into deep soil, and reducing P accumulation in deep soil profiles.

Phosphorus mining and bioavailability for plant acquisition: environmental sustainability perspectives

This review aims to examine microbial mechanisms for phosphorus (P) solubilization, assess the impacts of P mining and scarcity, and advocate for sustainable recycling strategies to enhance agricultural and environmental resilience. Phosphorus is an indispensable macronutrient for plant growth and agricultural productivity, yet its bioavailability in cultivation systems is often constrained. This scarcity has led to a heavy reliance on fertilizers derived from mined phosphate rock (PR), which is a finite resource usually contaminated with hazardous elements such as uranium, radium, and thorium. Plants absorb only about 10-20% of P from applied fertilizers, leading to significant inefficiencies and negative environmental consequences. Additionally, the uneven geographic distribution of PR reserves exacerbates global socioeconomic and geopolitical vulnerabilities. Healthy soils enriched with diverse microbial communities provide a sustainable avenue to address these growing challenges. Rhizospheric organisms, including phosphorus-solubilizing and phosphorus-mineralizing bacteria and arbuscular mycorrhizal fungi, are capable and pivotal in the sustainable conversion of inorganic and organic P into bioavailable forms, reducing reliance on synthetic fertilizers. The mechanisms used by these microbes often include releasing organic acids to lower soil pH and solubilize insoluble inorganic phosphorus compounds and the production of enzymes, such as phosphatases and phytases, to break down organic phosphorus compounds, including phytates, into bioavailable inorganic phosphate. Some microbes secrete chelating agents, such as siderophores, to bind metal ions and free phosphorus from insoluble complexes and use biofilms for P exchange. This review also advocates for the recycling second-generation P from organic waste as a sustainable and socially equitable alternative to conventional phosphate mining.

Photocatalytic Hydrophosphination Using Calcium Precatalysts

Hydrophosphination using calcium compounds as catalysts under irradiation is described as a foray into s-block photocatalysis. Transition-metal compounds have been highly successful hydrophosphination catalysts under photochemical conditions, utilizing substrates previously considered inaccessible. A calcium hydrophosphination precatalyst, Ca(nacnac) (THF) (N(SiMe3)2) (1, nacnac = HC[(C(Me)N-2,6-iPr2C6H3)]2), reported by Barrett and Hill, as well as the presumed intermediate, Ca(nacnac) (THF) (PPh2) (2), and the Schlenk equilibrium product, Ca[N(SiMe3)2]2(THF)2 (3) were screened under photochemical conditions with a range of unsaturated substrates including styrenic alkenes, Michael acceptors, and dienes with modest to excellent conversions, though unactivated alkenes were inaccessible. All compounds exhibit enhanced catalysis under irradiation by light emitting diode (LED)-generated blue light. Nacnac-supported compounds generate radicals as evidenced by Electron Paramagnetic Resonance (EPR) spectroscopy and radical trapping reactions, whereas unsupported calcium compounds are EPR silent and appear to undergo hydrophosphination akin to thermal reactions with these compounds. These results buttress the notion that photoactivation of π-basic ligands is a broad phenomenon, extending beyond the d-block, but like d-block metals, consideration of ancillary ligands is essential to avoid radical reactivity.

A critical review on phosphorus recovery from source-diverted blackwater

Source-diverted blackwater refers to toilet wastewater, sometimes including kitchen wastewater, which is rich in essential nutrients such as nitrogen (N) and phosphorus (P). Blackwater, especially concentrated blackwater collected from low-flush vacuum toilet systems, represents a valuable source for P recovery, addressing future P scarcity and mitigating environmental issues like eutrophication. While there has been growing interest in technologies for P recovery from blackwater, these technologies are still in the early stages of development. This study provides a comprehensive review of the mechanisms behind phosphate salt formation, the technologies for P recovery from blackwater-particularly through struvite and calcium phosphate precipitation-and the safety concerns associated with the use of recovered products. Despite advancements, most research is limited to lab-scale experiments, leaving significant gaps in optimizing P recovery technologies for broader application. Future research will be likely to focus on integrating bioenergy recovery with P recovery in anaerobic digestion (AD) systems, aiming to create a more sustainable and zero-waste approach. Addressing current challenges and scaling up from lab research to real-world applications will be crucial for making P recovery more efficient and economically viable.

The future potential of controlled environment agriculture

The production of high-quality food needs to increase to feed the growing global population. Controlled environment agriculture (CEA) systems in a vertical farm setting-in which several layers are stacked above each other, thus increasing the area for growth-can substantially boost productivity for crops, algae, mushrooms, fish, insects, and cultured meat. These systems are independent of climate, weather, and region, offering reduced environmental impact, although they come with high energy demands. An easy-to-understand, quantitative performance assessment of the theoretical potential for these 6 CEA systems is proposed here. It compares them against the world's main food production system: field production of maize, wheat, rice, and soybean. CEA could play a pivotal role in the global food supply if efficiencies in energy, control of growth environments, and waste stream utilization are vastly improved. Technological advancements, targeted policy support and public engagement strategies will be necessary to significantly reduce production costs and increase public acceptance.

The microbial phosphorus cycle in aquatic ecosystems

Phosphorus is an essential element for life, and phosphorus cycling is crucial to planetary habitability. In aquatic environments, microorganisms are a major component of phosphorus cycling and rapidly transform the diverse chemical forms of phosphorus through various uptake, assimilation and release pathways. Recent discoveries have revealed a more dynamic and complex aquatic microbial phosphorus cycle than previously understood. Some microorganisms have been shown to use and produce new phosphorus compounds, including those in reduced forms. New findings have also raised numerous unanswered questions that warrant further investigation. There is an expanding influence of human activity on aquatic ecosystems. Advancements in understanding the phosphorus biogeochemistry of evolving aquatic environments offer a unique opportunity to comprehend, anticipate and mitigate the effect of human activities. In this Review, I discuss the wealth of new aquatic phosphorus cycle research, spanning disciplines from omics and physiology to global biogeochemical modelling, with a focus on the current comprehension of how aquatic microorganisms sense, transport, assimilate, store, produce and release phosphorus. Of note, I delve into cellular phosphorus allocation, an underexplored topic with wide-ranging implications for energy and element flux in aquatic ecosystems.

Tolerance of Oryza sativa to low phosphate is associated with adaptive changes in root architecture and metabolic exudates

The optimum usage of fertilizers is key for the sustainable agriculture. Among nutrients, phosphorus (P) is critical for plant growth and development. Due to complete reliance on natural resources (rock phosphate) for P, the availability of P fertilizers is emerging as a global challenge for crop cultivation. Moreover, the excess application of P fertilizers in rice, mostly grown under flooded conditions, leads to water pollution called eutrophication. In this study, we employed a mutagenesis approach for developing and characterizing rice EMS (ethyl methanesulfonate) mutants with better adaptation to low soil P conditions. One such mutant of rice cultivar Nagina 22, named NH4824, was characterized comprehensively at seedling and reproductive growth stages under hydroponic and field conditions. The mutant exhibits low soil P tolerance due to combined adaptive changes in root system architecture, anatomy, organic acid exudates, plasma membrane (PM) H+-ATPase activity, induced expression of P transporter genes, and efficient mobilization and partitioning of P in different plant tissues. The activity of antioxidant enzymes and better photosynthesis suggested relatively less stress experienced by NH4824 than N22 under low soil P conditions. These insights are highly useful to develop P use efficient crop cultivars through breeding or genome editing approaches.

Systems thinking and modelling to support transformative change: key lessons from inter-disciplinary analysis of socio-ecological systems in applied land systems research

The evolving 'permacrisis' of compounding environmental and social challenges calls for transformative approaches to understanding and intervening in socio-ecological systems. Approaches to support systems thinking and understanding can be vital to achieving this goal. However, applying such systems thinking is often challenging, and we need to better reflect on the pros and cons of different approaches for building systems understanding and informing changes. In this paper, we first identify key attributes of systems thinking approaches from literature. We then use these as a framework for comparing and evaluating seven different systems thinking approaches, selected on the basis of our experience in applying them in support of the management and governance of various types of land systems. The seven approaches are: agent-based modelling, Bayesian belief networks, causal loop modelling, spatial multicriteria analysis, societal metabolic analyses, social network mapping and quantitative story telling. This framework has allowed us to appraise and reflect on our own experiences to identify the respective strengths and weaknesses of these different methodologies. We note that some of the ability to inform change depends as much on the context within which specific tools are used as the particular features of the tools themselves. Based on our appraisal, we conclude by suggesting six key recommendations that should be followed by others seeking to commission and use systems approaches, in order to enable them to support transformative change. We hope this may be useful to those working with systems approaches, since there is an urgent need for analytic efforts that can inform and enable transformative change. We also reiterate the call for sustained funding for long-term, standards-based evaluation of systems thinking approaches with respect to whether their use can demonstrate instrumental impacts leading to the kind of transformation the IPCC has called for, i.e. fundamental system change that goes beyond capacity development impacts such as network-building.

Adaptations of the Genus Bradyrhizobium to Selected Elements, Heavy Metals and Pesticides Present in the Soil Environment

Rhizobial bacteria perform a number of extremely important functions in the soil environment. In addition to fixing molecular nitrogen and transforming it into a form available to plants, they participate in the circulation of elements and the decomposition of complex compounds present in the soil, sometimes toxic to other organisms. This review article describes the molecular mechanisms occurring in the most diverse group of rhizobia, the genus Bradyrhizobium, allowing these bacteria to adapt to selected substances found in the soil. Firstly, the adaptation of bradyrhizobia to low and high concentrations of elements such as iron, phosphorus, sulfur, calcium and manganese was shown. Secondly, the processes activated in their cells in the presence of heavy metals such as lead, mercury and arsenic, as well as radionuclides, were described. Additionally, due to the potential use of Bradyrhziobium as biofertilizers, their response to pesticides commonly used in agriculture, such as glyphosate, sulfentrazone, chlorophenoxy herbicides, flumioxazine, imidazolinone, atrazine, and insecticides and fungicides, was also discussed. The paper shows the great genetic diversity of bradyrhizobia in terms of adapting to variable environmental conditions present in the soil.

Soil microbial biomass P status affecting P runoff loss from paddy fields under different agricultural practices

Phosphorus (P) runoff loss in agroecosystems is known to be soil-dependent. While the physicochemical processes of P runoff have been extensively studied, there is a lack of research on its microbial effects. This study investigated variations in P runoff loss, soil P fractions, and microbial biomass (MB) across 11 different agricultural treatments in a long-term positioning experiment of double-cropping rice cultivation. Results revealed a P-deficient state in the paddy soil, with an average total soil P content (TSP) of 0.55 g kg-1 and Olsen-P of 9.17 mg kg-1 across all treatments. Among the treatments, application of pig manure equivalent to 50 % conventional nitrogen resulted in the highest soil MB, soil P fractions, and flow-weighted dissolved-P (DP_wc) and total-P (TP_wc) concentrations in surface runoff water. Conversely, the treatment without P fertilizer application showed the lowest values. While long-term agricultural practices profoundly affected the characteristics of soil MB, soil P status, and P runoff loss, a common pattern emerged across all treatments. Specifically, all treatments exhibited wider ranges of soil microbial carbon (C):P ratio (MBC:P) (48.49-175.95) and soil microbial nitrogen (N):P ratio (MBN:P) (3.83-12.56) compared to soil microbial C:N ratio (MBC:N) (9.55-20.12). Additionally, soil P fractions decreased in the order of TSP > Citrate-P > Olsen-P > Enzyme-P, and the average DP_wc (0.12 mg L-1) accounted for approximately one-fourth of the average TP_wc (0.48 mg L-1), suggesting a critical and similar mechanism for paddy soil P runoff loss. The addition of exogenous C and P created favorable conditions for microbial growth, leading to increased MBP and subsequently elevated soil P contents, particularly Olsen-P. However, the structural equation model (SEM) analysis revealed that the mediation effect of MBP and MBN:P weakened the relationships between agronomic practices and P runoff losses, with the path coefficient decreasing from 0.34 to 0.06. Furthermore, the relative contribution of microbial biomass-induced effects to P runoff loss was about one-fifth of soil physicochemical effects in the double paddy rice ecosystem. Overall, our study quantified the effects of microbial biomass P status on P runoff loss in paddy fields under long-term agronomic measures, and these results will help us understand and manage nutrient cycling in paddy field ecosystems, thereby reducing environmental pollution, improving agricultural productivity and achieving sustainable agriculture.

UBIQUITIN-CONJUGATING ENZYME34 mediates pyrophosphatase AVP1 turnover and regulates abiotic stress responses in Arabidopsis

Understanding the molecular mechanisms of abiotic stress responses in plants is instrumental for the development of climate-resilient crops. Key factors in abiotic stress responses, such as the proton-pumping pyrophosphatase (AVP1), have been identified, but their function and regulation remain elusive. Here, we explored the post-translational regulation of AVP1 by the ubiquitin-conjugating enzyme UBC34 and its relevance in the salt stress and phosphate starvation responses of Arabidopsis (Arabidopsis thaliana). Through in vitro and in vivo assays, we established that UBC34 interacts with and ubiquitylates AVP1. Mutant lines in which UBC34 was downregulated showed higher tolerance to salt and low inorganic phosphate (Pi) stresses, while we observed the opposite for plants overexpressing UBC34. Our results showed that UBC34 co-localizes with AVP1, and AVP1 activity is enhanced in the plasma membrane fractions of ubc34 mutants, indicating that UBC34 mediates the turnover of plasma membrane-localized AVP1. We also observed that UBC34 affects the apoplastic pH but not the vacuolar pH of root cells. Based on our results, we propose a mechanistic model in which UBC34 mediates AVP1 turnover at the plasma membrane of root epidermal cells. Downregulation of UBC34 under salt and phosphate starvation conditions enhances AVP1 activity, leading to a higher proton gradient available for sodium sequestration and phosphate uptake.

Temporal shifts in the phosphate mobilising bacterial community reveal contrasting succession patterns in response to different phosphorus sources

BACKGROUND

Phosphate mobilising bacteria (PMB), such as phoD- and pqqC-harbouring bacteria, play a crucial role in mobilising insoluble phosphorus (P) in soil through the secretion of alkaline phosphatase and organic acids.

OBJECTIVES

To evaluate the succession pattern of PMB communities in response to different insoluble P sources.

METHODS

Five P source treatments, including the addition of KH2PO4 (PDP), FePO4 (FEP), Ca3(PO4)2 (TCP), lecithin (LEC), and a negative control, were established in the soil in a microcosmic system. Subsequently, phoD- and pqqC-harbouring bacterial communities were investigated by sequential sampling and high-throughput sequencing. In addition, PMB strains were isolated from these five treatments, and their phosphate mobilising activity was further analysed.

RESULTS

The effect of the insoluble organic P source (LEC) on the succession of PMB communities consistently exceeded that of insoluble inorganic P (Pi) sources (FEP and TCP). A successively enhanced succession and a successively diminishing succession were observed in PMB communities in FEP and TCP, respectively. Furthermore, the soil AP content significantly increased with incubation time in LEC and FEP. Most of the variation in phoD- and pqqC-harbouring bacterial communities was explained by all P fractions, respectively, while Fe-P and stable organic P fractions determined the PMB communities. Insoluble Pi sources, particularly FEP, tended to enrich more high-performance PMB strains for Fe-P.

CONCLUSION

This study firstly reveals the dynamic response of PMB communities to different insoluble P sources at the community level in a short time scale and identifies key PMB taxa that respond to different insoluble P sources, particularly Fe-P. It is also the first to provide community evidence and a feasible method for obtaining high-performance PMB strains for Fe-P in subtropical acidic red soils through directed enrichment culture.

Synthetic biofilm community for efficient phosphorus removal from high-salinity wastewater

Substantial amounts of phosphorus are discharged into water bodies, leading to an urgent need to develop methods for phosphorus removal. Here, 12 novel polyphosphate-accumulating organisms were identified from marine biofilms through genomic screening and incorporated into a stable community for phosphorus removal from high-salinity water. The synthetic biofilm community achieved an 82% removal efficiency in a marine broth medium. Electron microscopy showed storage of polyphosphate particles in the bacterial cells. Metatranscriptomic analysis indicated expression changes of genes for phosphate transport, as well as relevant metabolic pathways. In particular, pst genes encoding transporters with high phosphate affinity were downregulated at high-phosphorus concentration, whereas pit genes encoding transporters with low phosphate affinity were constitutively expressed. Furthermore, the synthetic biofilm community exhibited remarkable efficiency in removing over 92% of phosphorus from fish farming facility wastewater. Taken together, synthetic community using marine biofilm bacteria is a new strategy of phosphorus removal.

A dynamic optimization of soil phosphorus status approach could reduce phosphorus fertilizer use by half in China

Sustainable phosphorus (P) management is essential for ensuring crop production while avoiding environmental damage and the depletion of phosphate rock reserves. Despite local demonstration scale successes, the widespread mobilization of smallholder farmers to adopt sustainable management practices remains a challenge, primarily due to the associated high costs and complicated sampling. Here, we propose a dynamic optimization of soil P status (DOP) approach aimed at managing long-term soil P status within the range of agronomic and environmental soil P thresholds, which facilitates the precise determination of optimal P application rates without the need for frequent soil testing. We evaluate the DOP approach in 35,575 on-farm trials, and the results show that it is agronomically acceptable. Our evaluation extends to estimating future soil P status and P fertilizer inputs across all counties in China for three cereal crops (wheat, rice, and maize). The results indicate that, compared to current practices, the DOP approach can achieve a 47.4% reduction in P fertilizer use without any yield penalty. The DOP approach could become an effective tool for global P management to safeguard food security and enhance environmental sustainability.

Soil phosphorus stocks could prolong global reserves and improve water quality

Combining existing databases, we estimated global phosphorus stocks in croplands and grasslands that are not readily available to plants as 32-41% of the 2020 estimated geologic phosphorus reserves, representing 146-186 years of the 2020 mass of phosphorus fertilizer applied annually. Especially if accessed by more efficient crops, this stock could reduce the need for additional fertilizer, improve water quality and contribute to all-round phosphorus sustainability.

Optimizing soil conservation through comprehensive benefit assessment in river basins

Land degradation from water erosion poses a significant threat to water security and ecosystem stability, driving global efforts in soil conservation. Quantitative assessment of soil conservation benefits-both on-site and off-site-is crucial for guiding effective conservation strategies. However, existing methodologies often fall short in quantifying the value of these combined benefits. Here, we present a comprehensive framework for quantifying soil conservation service flows in monetary terms, evaluating the effectiveness of both on-site and off-site measures. Applying this framework to the Yellow River Basin (YRB), we employ cost-avoidance algorithms related to soil fertility maintenance, dredging cost reduction, and mitigation of nonpoint source pollution. Our results reveal that while many areas contribute to both on-site and off-site benefits, over half of the YRB relies predominantly on off-site services. By strategically enhancing key regions-which constitute 30% of the basin-we demonstrate that the overall soil conservation service supply can increase by 64.2% over the multi-year average from 2001 to 2020 compared to a consideration of on-site only. These findings underscore the essential role of off-site services in fully understanding soil conservation needs, particularly in large river basins, and the identified priority areas can offer valuable insights for optimizing soil conservation efforts.

The measurement and insight of bacterial community structure succession in cyanobacteria biochar co-composting based on basic carbon and nitrogen indices

The effects of cyanobacteria biochar (CB) amendment on microbial community succession (MCS) during pig manure co-composting was evaluated. Conventional composting (T1) and different concentrations of CB co-composting were set up here (T2: 2.5% CB, T3: 5% CB, T4: 7.5% CB, T5: 10% CB, and T6: 20% CB). Core substrate indicators and microbial information were used to gain insight into microbial community succession structure (MCSS) by CB treatments. Low concentrations of CB show higher organic degradation rates (2.4% vs 2.2%; and Y = C ∗(1- e(-k∗x))), while high concentrations increased the content of TKN (T5: 54.40%). An innovative diversity quantization method (pan-γ-diversity T5:42.275, T1: 40.642, and T2: 34.285) was proposed through linear simulation and integration. CB optimized Bacillus and Thermobacillus were key organic degradation genera during succession (collaborate with Caldicoprobacter) and increased the abundance of important nitrogen fixation genera Chelativorans (Day 42: minimun 4.8 times; and Day 72: minimum 1.3 times) and Longispora (Max 10.0%). The existence of bacteria Caldicoprobacter (2.0-9.3%) on mineralization process showed the synergy and co-assembly effects of CB on MCSS. Moreover, mantel test also shows the assembled and cooperation of Firmicutes and Actinobacteria.

Reduce the application of phosphorus fertilizer in peanut fields and improve its efficiency by using iron modified biochar to adsorb phosphorus recovery products

Introduction

To address the scarcity of agricultural phosphorus (P) fertilizers and reduce phosphorus accumulation in wastewater, this study employed iron-modified biochar (Fe-B) to adsorb phosphorus from water. The phosphorus-loaded iron-modified biochar (Fe-BP) was subsequently applied to peanut fields. Batch experiments were conducted to determine the optimal adsorption parameters and mechanism of Fe-B for phosphate ions (PO4 3-).

Methods

The field experiment utilized a randomized complete block design, comprising the following treatments: no biochar and no P fertilizer (B0P0), no biochar with conventional phosphate fertilizer (B0P1, CK, P2O5 at 144 kg ha-1), biochar with CK (B1P1), Fe-B with CK (FeB-P1), phosphorus-loaded Fe-B with CK (FeBP-P1), and phosphorus-loaded Fe-B with two-thirds CK (FeBP-P2, P2O5 at 96 kg ha-1).

Results

The results demonstrated that the biochar dosage of 0.05 g (2 g L-1) results in a phosphate removal rate exceeding 80%. Optimal adsorption efficiency occurs within a pH range of 6-9, with a sharp decline observed at pH values above 10. The presence of NO3 -, Cl-, and SO4 2- does not significantly affect the phosphate adsorption capacity of Fe-B, unlike HCO3 - and CO3 2-, which reduce it. After the fifth desorption and recycling process, the adsorption capacity of the biochar decreased to 24%. The peanut yield in the FeB-P1 treatment was 50.8% higher than that in the FeBP-P2 treatment. While the phosphorus recovery efficiency (REP) does not significantly differ between FeBP-P2 and B1P1 treatments, both are superior to B0P1. Moreover, FeBP-P2 facilitated the available phosphorus concentration in the root zone.

Discussion

Overall, phosphorus-loaded iron-modified biochar reduced the required amount of phosphorus fertilizer, maintain peanut yield, and enhanced phosphorus fertilizer utilization efficiency.

Improving Phosphate Acquisition from Soil via Higher Plants While Approaching Peak Phosphorus Worldwide: A Critical Review of Current Concepts and Misconceptions

Phosphate (P) is the plant macronutrient with, by far, the lowest solubility in soil. In soils with low P availability, the soil solution concentrations are low, often below 2 [µmol P/L]. Under these conditions, the diffusive P flux, the dominant P transport mechanism to plant roots, is severely restricted. Phosphate is sorbed into various soil solids, Fe/Al oxides, clay minerals and, sometimes overlooked, humic Fe/Al surfaces. The immobilization of P in soil is often the result of the diffusion of P into the internal surfaces of oxides or humic substances. This slow reaction between soil and P further reduces the availability of P in soil, leading to P fixation. The solubilization of soil P by root-released carboxylates is a promising way to increase the acquisition and uptake of P from P-fixing soils. Citrate and, sometimes, oxalate are effective with respect to additional P solubilization or P mobilization, which may help increase the diffusive P flux into the roots by increasing the P solution concentrations in the rhizosphere. The mobilization of humic-associated P by carboxylates may be an effective way to improve soil P solubility. Not only orthophosphate anions are mobilized by root-released carboxylates, but also higher phosphorylated inositol phosphates, as the main part of P esters in soil are mobilized by carboxylates. Because of the rather strong bonding of higher phosphorylated inositol phosphates to the soil solid phase, the mobilization step by carboxylates appears to be essential for plants to acquire inositol-P. The ecological relevance of P mobilization by carboxylates and its effect on the uptake of P by crops and grassland species are, at best, partially understood. Plant species which form cluster roots such as white lupin (Lupinus albus L.) or yellow lupin (Lupinus luteus L.) release high rates of carboxylates, mainly citrate from these root clusters. These plant species acquire fixed or low available P which is accessible to plants at rates which do not satisfy their P demand without P mobilization. And white lupin and yellow lupin make soil P available to other plants in mixed cropping systems or for subsequent plant species in crop rotations. The mobilization of P by carboxylates is probably also important for legume/grass mixtures for forage production. Species such as alfalfa, red clover or white clover release carboxylates. The extent of P mobilization and P uptake from mobilized P by legume/grass mixtures deserves further research. In particular, which plant species mostly benefit from P mobilization by legume-released carboxylates is unknown. Organic farming systems require such legume/grass mixtures for the introduction of nitrogen (N) by forage legumes into their farming system. For this agricultural system, the mobilization of soil P by carboxylates and its impact on P uptake of the mixtures are an important research task.

Phosphate solubilization and plant growth properties are promoted by a lactic acid bacterium in calcareous soil

On the basis of good phosphate solubilization ability of a lactic acid bacteria (LAB) strain Limosilactobacillus sp. LF-17, bacterial agent was prepared and applied to calcareous soil to solubilize phosphate and promote the growth of maize seedlings in this study. A pot experiment showed that the plant growth indicators, phosphorus content, and related enzyme activity of the maize rhizospheric soils in the LF treatment (treated with LAB) were the highest compared with those of the JP treatment (treated with phosphate solubilizing bacteria, PSB) and the blank control (CK). The types of organic acids in maize rhizospheric soil were determined through LC-MS, and 12 acids were detected in all the treatments. The abundant microbes belonged to the genera of Lysobacter, Massilia, Methylbacillus, Brevundimonas, and Limosilactobacillus, and they were beneficial to dissolving phosphate or secreting growth-promoting phytohormones, which were obviously higher in the LF and JP treatments than in CK as analyzed by high-throughput metagenomic sequencing methods. In addition, the abundance values of several enzymes, Kyoto Encyclopedia of Genes and Genomes (KEGG) orthology, and Carbohydrate-Active Enzymes (CAZys), which were related to substrate assimilation and metabolism, were the highest in the LF treatment. Therefore, aside from phosphate-solubilizing microorganisms, LAB can be used as environmentally friendly crop growth promoters in agriculture and provide another viable option for microbial fertilizers. KEY POINTS: • The inoculation of LAB strain effectively promoted the growth and chlorophyll synthesis of maize seedlings. • The inoculation of LAB strain significantly increased the TP content of maize seedlings and the AP concentration of the rhizosphere soil. • The inoculation of LAB strain increased the abundances of the dominant beneficial functional microbes in the rhizosphere soil.

Phosphorus dynamics and sustainable agriculture: The role of microbial solubilization and innovations in nutrient management

Phosphorus (P) is an essential element for plant growth, playing a crucial role in various metabolic processes. Despite its importance, phosphorus availability in soils is often restricted due to its tendency to form insoluble complexes, limiting plant uptake. The increasing demand for phosphorus in agriculture, combined with limited global reserves of phosphate rock, has created challenges for sustainable plant production. Additionally, the overuse of chemical phosphorus fertilizers has resulted in environmental degradation, such as eutrophication of water bodies. Increasing agronomic phosphorus (P) efficiency is crucial because of population growth and increased food demand. Hence, microorganisms involved in the P cycle are a promising biotechnological strategy that has gained global interest in recent decades. Microorganisms' solubilization of phosphate rock (PR) is an environmentally sustainable alternative to chemical processing for producing phosphate fertilizers. Phosphorus-solubilizing microorganisms (PSMs), including bacteria and fungi, and their enzymatic processes offer an eco-friendly and sustainable alternative to chemical inputs by converting insoluble phosphorus into forms readily available for plant uptake. Integrating PSMs into agricultural systems presents a promising strategy to reduce dependence on chemical fertilizers, enhance soil health, and contribute to the transition toward more sustainable and resilient agricultural practices. It can be an alternative that reduces the loss of phosphorus in the environment, especially the eutrophication of aquatic systems. This paper explores the challenges of phosphorus availability in agriculture and the potential of microbial phosphorus solubilization as a sustainable alternative to conventional practices.

Increasing phosphorus loss despite widespread concentration decline in US rivers

The loss of phosphorous (P) from the land to aquatic systems has polluted waters and threatened food production worldwide. Systematic trend analysis of P, a nonrenewable resource, has been challenging, primarily due to sparse and inconsistent historical data. Here, we leveraged intensive hydrometeorological data and the recent renaissance of deep learning approaches to fill data gaps and reconstruct temporal trends. We trained a multitask long short-term memory model for total P (TP) using data from 430 rivers across the contiguous United States (CONUS). Trend analysis of reconstructed daily records (1980-2019) shows widespread decline in concentrations, with declining, increasing, and insignificantly changing trends in 60%, 28%, and 12% of the rivers, respectively. Concentrations in urban rivers have declined the most despite rising urban population in the past decades; concentrations in agricultural rivers however have mostly increased, suggesting not-as-effective controls of nonpoint sources in agriculture lands compared to point sources in cities. TP loss, calculated as fluxes by multiplying concentration and discharge, however exhibited an overall increasing rate of 6.5% per decade at the CONUS scale over the past 40 y, largely due to increasing river discharge. Results highlight the challenge of reducing TP loss that is complicated by changing river discharge in a warming climate.

Variations in the level of available phosphorus with changes in the status of water-soluble organic matter derived from different organic materials in soil

The combined application of organic material and phosphorus fertilizer is an effective method to enhance phosphorus use efficiency for plant growth. This is partly because the presence of water-soluble organic matter (WSOM) derived from different organic materials can enhance the level of available phosphorus in the soil; however, it is poorly understood how this level varies with changes in the WSOM status (i.e., decomposed, dissolved, and retained) in the soil depending on WSOM types. This study aimed to (i) understand how changes in the WSOM status enhances the available phosphorus level in the soil, and (ii) determine the WSOM type that contributes to such enhancement. The incubation test showed that fractions of 73%-92% and 8%-27% of WSOM-derived organic carbon were retained and dissolved, respectively, at the beginning of incubation, while 31%-45% was decomposed during the incubation period. The WSOM derived from cattle manure compost (CM) and sewage sludge compost (SSC) that was initially retained was maintained until the late stage of the incubation test, whereas that derived from hydrothermal decomposed liquid fertilizer (HDLF) was rapidly desorbed during the first 14 days of the incubation period. The available phosphorus level was higher under the combined application of CM- and SSC-derived WSOM than under the single phosphorus application throughout the incubation period, while it was high only during the first 3 days of incubation under the application of HDLF-derived WSOM. The amounts of retained organic carbon at each sampling point during the incubation period compared to those at the beginning were positively and linearly correlated to the available phosphorus levels that were enhanced by the WSOM present in the soil. This study for the first time provides quantitative experimental evidence that 1) the longer the WSOM continues to be retained, the higher the amount of available phosphorus remaining in the soil, and 2) the available phosphorus level decreases with WSOM sorption or decomposition. Furthermore, it was shown that highly humified WSOM has a great potential for the maintenance of higher available phosphorus levels. This study provides the insight that a combined application of highly humified organic materials with a chemical fertilizer is necessary for not only cost effective but also sustainable fertilization design.

Integrating field surveys and remote sensing to optimize phosphorus resource management for rainfed rice production in the Central plateau of Burkina Faso

Rice production in sub-Saharan Africa (SSA) is restricted by low water availability, soil fertility, and fertilizer input, and phosphate rock (PR) application is expected to increase production. Soil water conditions and soil types affect the efficacy of phosphorus fertilization in improving productivity. However, these factors are rarely discussed together. In this study, we aimed to investigate the soil types and soil water conditions in the fields, as well as their effects on rice productivity after phosphorus fertilization, and optimize the findings using remote sensing techniques. A soil profiling survey, followed by a field experiment in seven farmer fields, was performed in the Central plateau of Burkina Faso. The following treatments were applied: nitrogen and potassium fertilization without phosphorus (NK), PR application with NK (NK+PR), and triple super phosphate (TSP) application with NK (NK+TSP). Submergence duration and cumulative water depth were recorded manually. The inundation score, estimated using a digital elevation model, explained the distribution of soil types and soil water conditions and correlated negatively with sand content and positively with silt and clay content, indicating an illuvial accumulation of fine soil particles with nutrient transportation. The field experiment showed that although grain yield was significantly restricted by phosphorus deficiency, the increase in yield after phosphorus fertilization was higher in Lixisols and Luvisols than in Cambisols because of the low Bray-2-phosphorus content of Lixisols and Luvisols. The inundation score correlated positively with grain yields after NK+PR and NK+TSP treatments. In conclusion, soils with low inundation scores (mainly Lixisols and Luvisols) showed a drastic increase in grain yield after TSP application, whereas those with high inundation scores showed comparable yields after PR and TSP application despite the low phosphorus fertilization effect. Our findings would help optimize fertilization practices to increase rice productivity in SSA.

Optimized Phosphorus Application Enhances Wheat Stem Lodging Resistance Under Spring Low-Temperature Stress

Spring low-temperature stress (LTS) has become a major limiting factor for the development of high yield, quality and efficiency in wheat production. It not only affects the function of wheat leaves and the development of spikes but also impacts stem lodging resistance, and may experience elevated risk of stem lodging. This study conducted a field pot experiment to assess the effect of phosphorus fertilizer application mode on wheat stem lodging resistance under spring LTS. Two wheat varieties, Yannong19 (YN19, cold-tolerant variety) and Xinmai26 (XM26, cold-sensitive variety) used as the experiment material. Two phosphorus fertilizer application models including traditional phosphorus application (TPA) and optimized phosphorus application (OPA) were employed. Temperature treatment was conducted at 15 °C (CK) and -4 °C (LT) in a controlled phytotron. Our results showed that spring LTS decreased the stem wall thickness and internode fullness, and altered stem anatomical structure and chemical composition, resulting in a decrease in wheat stem mechanical strength and lodging resistant index. Compared with TPA, the OPA increased the stem wall thickness and internode fullness. The thickness of the stem mechanic tissue layer and parenchymatous tissue, and the area of the large vascular bundle and small vascular bundle were increased by the OPA, which alleviated the damage to stem cell walls caused by spring LTS. At the same time, the OPA also increased the contents of lignin, cellulose, and soluble sugar, improving the C/N ratio in wheat stem. Due to the improved stem morphological characteristics, anatomical structure, and chemical compositions, the wheat stem exhibited enhanced lodging resistance, which increased the lodging resistant index of the 2nd and 3rd internodes of YN19 and XM26 by 27.27%, 11.63% and 14.15%, 15.73% at the dough stage compared with TPA under spring LTS. Meanwhile, OPA could not only alleviate the yield loss caused by spring LTS, but also increase the grain yield without spring LTS. This study indicated that OPA enhances wheat stem lodging resistance under spring LTS, and would be meaningful and practical for improving wheat resistance to low-temperature stress.

Asymmetric winter warming reduces microbial carbon use efficiency and growth more than symmetric year-round warming in alpine soils

Asymmetric seasonal warming trends are evident across terrestrial ecosystems, with winter temperatures rising more than summer ones. Yet, the impact of such asymmetric seasonal warming on soil microbial carbon metabolism and growth remains poorly understood. Using 18O isotope labeling, we examined the effects of a decade-long experimental seasonal warming on microbial carbon use efficiency (CUE) and growth in alpine grassland ecosystems. Moreover, the quantitative stable isotope probing with 18O-H2O was employed to evaluate taxon-specific bacterial growth in these ecosystems. Results show that symmetric year-round warming decreased microbial growth rate by 31% and CUE by 22%. Asymmetric winter warming resulted in a further decrease in microbial growth rate of 27% and microbial CUE of 59% compared to symmetric year-round warming. Long-term warming increased microbial carbon limitations, especially under asymmetric winter warming. Long-term warming suppressed the growth rates of most bacterial genera, with asymmetric winter warming having a stronger inhibition on the growth rates of specific genera (e.g., Gp10, Actinomarinicola, Bosea, Acidibacter, and Gemmata) compared to symmetric year-round warming. Bacterial growth was phylogenetically conserved, but this conservation diminished under warming conditions, primarily due to shifts in bacterial physiological states rather than the number of bacterial species and community composition. Overall, long-term warming escalated microbial carbon limitations, decreased microbial growth and CUE, with asymmetric winter warming having a more pronounced effect. Understanding these impacts is crucial for predicting soil carbon cycling as global warming progresses.

Reducing phosphorus losses from agricultural land to surface water

Phosphorus (P) enrichment of water impairs its quality by stimulating algal growth and eutrophication, affecting an estimated 1.7 billion people. Remediation costs are substantial, estimated at $1 billion annually in Europe and $2.4 billion in the USA. Agricultural intensification over the past 50 years has increased P use brought into the system from mined fertiliser sources. This has enriched soil P concentrations and loss to surface waters via pathways such as surface runoff and subsurface flow, which are influenced by precipitation, slope, and farming practices. Effective mitigation of losses involves managing P sources, mobilisation, and transport/delivery mechanisms. The cost-effectiveness of mitigation actions can be improved if they are targeted to critical source areas (CSAs), which are small zones that disproportionately contribute to P loss. While targeting CSAs works well in areas with variable topography, flatter landscapes require managing legacy sources, such as enriched soil P to prevent P losses.

Inorganic phosphorous availability and mobility in a manufactured soil

Manufactured soils, created by combining various organic and inorganic waste materials and byproducts, may be tailored to specific applications, providing an alternative to the extraction of natural soils. It is important for them to be capable of supporting plant growth without the need for significant management or fertiliser applications, the over-application of which can have adverse environmental effects. We examined the dynamics of phosphorus (P) transformations within a manufactured soil and the implications for nutrient cycling. A freshly prepared manufactured soil (32.5 % composted green waste, 32.5 % composted bark, 25 % horticultural grit, and 10 % lignite clay) was studied over one year in temperature and moisture controlled mesocosms. Leachate was collected to achieve high-resolution monitoring of leached phosphate concentrations. Initially, leached dissolved inorganic phosphorus (DIP) concentrations were low (0.02 ± 0.01 mg P L-1), before increasing by 160 μg P L-1 d-1 over the first 42 days to 5.57 ± 1.23 mg P L-1. After reaching a maximum concentration, DIP concentrations remained relatively consistent, varying by only 1.67 mg P L-1 until day 270. The increase in leached DIP was likely driven by soil organic matter mineralisation and the cleavage of carbon‑phosphorus bonds by the soil microbes to satisfy carbon demand with mineralogical influences, such as a decrease in apatite content, also contributing. Sorption and desorption from soil particles were the processes behind the P loss from the soil, which was followed by slow diffusion and eventual loss via leaching. The fertiliser application on phosphate dynamics resulted in increased DIP leaching. P concentrations observed in the manufactured soil were within the range considered sufficient to support plant growth. However, the mean leached phosphorus concentrations were higher than reported eutrophication thresholds suggesting that these soils may pose a risk to surface waters in their current form.

Effects of phosphorus-solubilizing bacteria and biochar application on phosphorus availability and tomato growth under phosphorus stress

BACKGROUND

Phosphorus-solubilizing bacteria (PSB) are vital in converting insoluble phosphorus into a soluble form that plants can readily absorb and utilize in soil. While previous studies have mainly focused on the extracellular secretion of microorganisms, few have explored the intricate intracellular metabolic processes involved in PSB-mediated phosphorus solubilization.

RESULTS

Here, we uncovered that Ca3(PO4)2 could serve as a source of insoluble phosphorus for the PSB, Pseudomonas sp. NK2. High-performance liquid chromatography (HPLC) results indicated higher levels of organic acids released from insoluble phosphorus compared to a soluble phosphorus source (KH2PO4), with acetic acid released exclusively under insoluble phosphorus condition. Moreover, non-target metabolomics was employed to delve into the intracellular metabolic profile. It unveiled that insoluble phosphorus significantly enhanced the tricarboxylic acid cycle, glycolysis, glyoxylic acid metabolism, and other pathways, leading to the production of acetic acid, gluconic acid, oxalic acid, and citric acid for insoluble phosphorus solubilization. In our quest to identify suitable biochar carriers, we assessed seven types of biochar through the conjoint analysis of NBRIP medium culture and application to soil for 30 days, with cotton straw-immobilized NK2 emerging as the most potent phosphorus content provider. Lastly, NK2 after cotton straw immobilization demonstrated the ability to enhance biomass, plant height, and root development of Solanum lycopersicum L. cv. Micro Tom.

CONCLUSIONS

Pseudomonas sp. NK2 with cotton straw biochar could enhance phosphorus availability and tomato growth. These findings bear significant implications for the practical application of phosphorus-solubilizing bacteria in agricultural production and the promotion of environmentally sustainable farming practices.

Fire enhances changes in phosphorus (P) dynamics determining potential post-fire soil recovery in Mediterranean woodlands

Soil phosphorus (P), which is essential for ecosystem functioning, undergoes notable changes after fire. However, the extent to which fire characteristics affect P dynamics remains largely unknown. This study investigated the impact of type of fire (prescribed burning and natural wildfires) of different levels of severity on P dynamics in Mediterranean soils. Soil P concentrations in the organic layers were strongly affected by fire severity but not fire type. Low severity fire did not have any observable effect, while moderate fire increased soil P levels by 62% and high severity decreased soil P concentration by 19%. After one year, the soil P concentration remained unchanged in the low severity fires, while rather complex recovery was observed after moderate and high severity fires. In the mineral layers, P concentration was reduced (by 25%) immediately after the fires and maintained for one year (at 42%). 31P-NMR spectroscopy revealed almost complete post-fire mineralization of organic P forms (mono- and diesters), large increases in inorganic orthophosphate and a decrease in the organic:inorganic P ratio (Po:Pi). After one year, di-esters and orthophosphate recovered to pre-fire levels at all sites, except those where parent material composition (high pH and Fe concentration) had an enduring effect on orthophosphate retention, and thus, on the total soil P. We showed that fire severity and soil pH (and hence, soil mineralogy) played an essential role in soil P dynamics. These findings are important for reliable assessment of the effects of fire on soil P conservation and for improving the understanding the impact of prescribed burning.

Spatio-temporal evolution mechanism and dynamic simulation of nitrogen and phosphorus pollution of the Yangtze River economic Belt in China

Excess nitrogen and phosphorus inputs are the main causes of aquatic environmental deterioration. Accurately quantifying and dynamically assessing the regional nitrogen and phosphorus pollution emission (NPPE) loads and influencing factors is crucial for local authorities to implement and formulate refined pollution reduction management strategies. In this study, we constructed a methodological framework for evaluating the spatio-temporal evolution mechanism and dynamic simulation of NPPE. We investigated the spatio-temporal evolution mechanism and influencing factors of NPPE in the Yangtze River Economic Belt (YREB) of China through the pollution load accounting model, spatial correlation analysis model, geographical detector model, back propagation neural network model, and trend analysis model. The results show that the NPPE inputs in the YREB exhibit a general trend of first rising and then falling, with uneven development among various cities in each province. Nonpoint sources are the largest source of land-based NPPE. Overall, positive spatial clustering of NPPE is observed in the cities of the YREB, and there is a certain enhancement in clustering. The GDP of the primary industry and cultivated area are important human activity factors affecting the spatial distribution of NPPE, with economic factors exerting the greatest influence on the NPPE. In the future, the change in NPPE in the YREB at the provincial level is slight, while the nitrogen pollution emissions at the municipal level will develop towards a polarization trend. Most cities in the middle and lower reaches of the YREB in 2035 will exhibit medium to high emissions. This study provides a scientific basis for the control of regional NPPE, and it is necessary to strengthen cooperation and coordination among cities in the future, jointly improve the nitrogen and phosphorus pollution tracing and control management system, and achieve regional sustainable development.

Early exposure to phosphorus starvation induces genetically determined responses in Sorghum bicolor roots

KEY MESSAGE

We identified novel physiological and genetic responses to phosphorus starvation in sorghum diversity lines that augment current knowledge of breeding for climate-smart crops in Europe. Phosphorus (P) deficiency and finite P reserves for fertilizer production pose a threat to future global crop production. Understanding root system architecture (RSA) plasticity is central to breeding for P-efficient crops. Sorghum is regarded as a P-efficient and climate-smart crop with strong adaptability to different climatic regions of the world. Here we investigated early genetic responses of sorghum RSA to P deficiency in order to identified genotypes with interesting root phenotypes and responses under low P. A diverse set of sorghum lines (n = 285) was genotyped using DarTSeq generating 12,472 quality genome wide single-nucleotide polymorphisms. Root phenotyping was conducted in a paper-based hydroponic rhizotron system under controlled greenhouse conditions with low and optimal P nutrition, using 16 RSA traits to describe genetic and phenotypic variability at two time points. Genotypic and phenotypic P-response variations were observed for multiple root traits at 21 and 42 days after germination with high broad sense heritability (0.38-0.76). The classification of traits revealed four distinct sorghum RSA types, with genotypes clustering separately under both low and optimal P conditions, suggesting genetic control of root responses to P availability. Association studies identified quantitative trait loci in chromosomes Sb02, Sb03, Sb04, Sb06 and Sb09 linked with genes potentially involved in P transport and stress responses. The genetic dissection of key factors underlying RSA responses to P deficiency could enable early identification of P-efficient sorghum genotypes. Genotypes with interesting RSA traits for low P environments will be incorporated into current sorghum breeding programs for later growth stages and field-based evaluations.

Climate change exacerbates the environmental impacts of agriculture

Agriculture's global environmental impacts are widely expected to continue expanding, driven by population and economic growth and dietary changes. This Review highlights climate change as an additional amplifier of agriculture's environmental impacts, by reducing agricultural productivity, reducing the efficacy of agrochemicals, increasing soil erosion, accelerating the growth and expanding the range of crop diseases and pests, and increasing land clearing. We identify multiple pathways through which climate change intensifies agricultural greenhouse gas emissions, creating a potentially powerful climate change-reinforcing feedback loop. The challenges raised by climate change underscore the urgent need to transition to sustainable, climate-resilient agricultural systems. This requires investments that both accelerate adoption of proven solutions that provide multiple benefits, and that discover and scale new beneficial processes and food products.

Organophosphorus mineralizing-Streptomyces species underpins uranate immobilization and phosphorus availability in uranium tailings

Phosphate-solubilizing bacteria (PSB) are important but often overlooked regulators of uranium (U) cycling in soil. However, the impact of PSB on uranate fixation coupled with the decomposition of recalcitrant phosphorus (P) in mining land remains poorly understood. Here, we combined gene amplicon sequencing, metagenome and metatranscriptome sequencing analysis and strain isolation to explore the effects of PSB on the stabilization of uranate and P availability in U mining areas. We found that the content of available phosphorus (AP), carbonate-U and Fe-Mn-U oxides in tailings was significantly (P < 0.05) higher than their adjacent soils. Also, organic phosphate mineralizing (PhoD) bacteria (e.g., Streptomyces) and inorganic phosphate solubilizing (gcd) bacteria (e.g., Rhodococcus) were enriched in tailings and soils, but only organic phosphate mineralizing-bacteria substantially contributed to the AP. Notably, most genes involved in organophosphorus mineralization and uranate resistance were widely present in tailings rather than soil. Comparative genomics analyses supported that organophosphorus mineralizing-Streptomyces species could increase soil AP content and immobilize U(VI) through organophosphorus mineralization (e.g., PhoD, ugpBAEC) and U resistance related genes (e.g., petA). We further demonstrated that the isolated Streptomyces sp. PSBY1 could enhance the U(VI) immobilization mediated by the NADH-dependent ubiquinol-cytochrome c reductase (petA) through decomposing organophosphorous compounds. This study advances our understanding of the roles of PSB in regulating the fixation of uranate and P availability in U tailings.

Phosphorus recovery via struvite crystallization in batch and fluidized-bed reactors: Roles of microplastics and dissolved organic matter

Struvite crystallization, a promising technology for nutrient recovery from wastewater, is facing considerable challenges due to the presence of emerging contaminants such as microplastics (MPs) ubiquitously found in wastewater. Here, we investigate the roles of MPs and humic acid (HA) in struvite crystallization in batch and fluidized-bed reactors (FBRs) using synthetic and real wastewater with a Mg:N:P molar ratio of 1:3:(1-1.3) at an initial pH of 11. Batch reactor (BR) experiment results show that MPs expedited the nucleation and growth rates of struvite (e.g., the rate of crystal growth in the presence of 30 mg L-1 of polyethylene terephthalate (PET) was 1.43 times higher than that in the blank system), while HA hindered the formation of struvite. X-ray diffraction and the Rietveld refinement analysis revealed that the presence of MPs and HA can result in significant changes in phase compositions of the reclaimed precipitates, with over 80 % purity of struvite found in the precipitates from suspensions in the presence of 30 mg L-1 of MPs. Further characterizations demonstrated that MPs act as seeds of struvite nucleation, spurring the formation of well-defined struvite, while HA favors the formation of newberyite rather than struvite in both reactors. These findings highlight the need for a more comprehensive understanding of the interactions between emerging contaminants and struvite crystallization processes to optimize nutrient recovery strategies for mitigating their adverse impact on the quality and yield of struvite-based fertilizers. ENVIRONMENTAL IMPLICATION: The presence of microplastics in wastewater poses a significant challenge to struvite crystallization for nutrient recovery, as it accelerates nucleation and growth rates of struvite crystals. This can lead to changes in the phase compositions of the reclaimed precipitates, with implications for the quality and yield of struvite-based fertilizers. Additionally, the presence of humic acid hinders the formation of struvite, favoring the formation of other minerals like newberyite. Understanding the interactions between emerging contaminants and struvite crystallization processes is crucial for optimizing nutrient recovery strategies and mitigating the environmental impact of these contaminants on water quality and struvite-based fertilizers.

Unraveling spatial heterogeneity of soil legacy phosphorus in subtropical grasslands

Humans have profoundly altered phosphorus (P) cycling across scales. Agriculturally driven changes (e.g., excessive P-fertilization and manure addition), in particular, have resulted in pronounced P accumulations in soils, often known as "soil legacy P." These legacy P reserves serve as persistent and long-term nonpoint sources, inducing downstream eutrophication and ecosystem services degradation. While there is considerable scientific and policy interest in legacy P, its fine-scale spatial heterogeneity, underlying drivers, and scales of variance remain unclear. Here we present an extensive field sampling (150-m interval grid) and analysis of 1438 surface soils (0-15 cm) in 2020 for two typical subtropical grassland types managed for livestock production: Intensively managed (IM) and Semi-natural (SN) pastures. We ask the following questions: (1) What is the spatial variability, and are there hotspots of soil legacy P? (2) Does soil legacy P vary primarily within pastures, among pastures, or between pasture types? (3) How does soil legacy P relate to pasture management intensity, soil and geographic characteristics? and (4) What is the relationship between soil legacy P and aboveground plant tissue P concentration? Our results showed that three measurements of soil legacy P (total P, Mehlich-1, and Mehlich-3 extractable P representing labile P pools) varied substantially across the landscape. Spatial autoregressive models revealed that soil organic matter, pH, available Fe and Al, elevation, and pasture management intensity were crucial predictors for spatial patterns of soil P, although models were more reliable for predicting total P (68.9%) than labile P. Our analysis further demonstrated that total variance in soil legacy P was greater in IM than SN pastures, and intensified pasture management rescaled spatial patterns of soil legacy P. In particular, after controlling for sample size, soil P was extremely variable at small scales, with variance diminished as spatial scale increased. Our results suggest that broad pasture- or farm-level best management practices may be limited and less efficient, especially for more IM pastures. Rather, management to curtail soil legacy P and mitigate P loading and losses should be implemented at fine scales designed to target spatially distinct P hotspots across the landscape.

Reutilization of post-adsorption lanthanum-loaded straw alleviates phosphorus pollution in rice-wheat system: Subsequent performance and underlying mechanisms

Adsorption technology for phosphorus (P) removal is considered promising and reutilization of post-adsorbent can contribute to promoting sustainable agricultural production. However, the long-lasting impact of the post-adsorbent on crop growth and P remains unclear. This study assessed the effects of P-adsorbed lanthanum-modified straw (La@straw-P) on the rice yield, P fractionation and associated water quality parameters. The findings indicated that, compared with traditional fertilizer regimes, La@straw-P expedited the P reduction in the flooding water achieving a rate of decline to the tertiary standard for surface water (0.20 mg/L) 3.8 times faster and enhanced increased the P harvest index by 17.00 %. Economic estimation proved the positive benefits of La@straw-P in planting-breeding combination system. Redundancy analysis (RDA) and co-occurrence network analysis (CONA) revealed that electrical conductivity (EC) and dissolved Fe played primary roles in regulating total P. Fourier transform infrared spectra (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), and soil P fractions collectively demonstrated that the abundant adsorption sites on La@straw-P could facilitate the transformation of active P into moderately Ca-bound P. This study proposes a strategy for recycling P-adsorbed materials to mitigate agricultural non-point P pollution.

Multi-locus genome-wide association study for phosphorus use efficiency in a tropical maize germplasm

Phosphorus (P) is an essential macronutrient for maize (Zea mays L.) growth and development. Therefore, generating cultivars with upgraded P use efficiency (PUE) represents one of the main strategies to reduce the global agriculture dependence on phosphate fertilizers. In this work, genome-wide association studies (GWAS) were performed to detect quantitative trait nucleotide (QTN) and potential PUE-related candidate genes and associated traits in greenhouse and field trials under contrasting P conditions. The PUE and other agronomy traits of 132 maize inbred lines were assessed in low and normal P supply through the greenhouse and field experiments and Multi-locus GWAS was used to map the associated QTNs. Wide genetic variability was observed among the maize inbred lines under low and normal P supply. In addition, we confirm the complex and quantitative nature of PUE. A total of 306 QTNs were associated with the 24 traits evaluated using different multi-locus GWAS methods. A total of 186 potential candidate genes were identified, mainly involved with transcription regulator, transporter, and transference activity. Further studies are still needed to elucidate the functions and relevance of these genes regarding PUE. Nevertheless, pyramiding the favorable alleles pinpointed in the present study can be considered an efficient strategy for molecular improvement to increase maize PUE.

Shallow groundwater table fluctuations promote the accumulation and loss of phosphorus from surface soil to deeper soil in croplands around plateau lakes in Southwest China

The continuous excessive application of phosphorus (P) fertilizers in intensive agricultural production leads to a large accumulation of P in surface soils, increasing the risk of soil P loss by runoff and leaching. However, there are few studies on the accumulation and loss of P from surface soil to deep soil profiles driven by shallow groundwater table (SGT) fluctuations. This study used the intensive cropland around 7 plateau lakes in Yunnan Province as an example and conducted in situ monitoring of P storage in the soil profile and SGT during the rainy season (RS) and dry season (DS) as well as simulation experiments on soil P loss. The aim was to study the spatiotemporal variation in P accumulation in the soil profile of cropland driven by SGT fluctuations in the RS and DS and estimate the P loss in the soil profile driven by SGT fluctuations. The results showed that fluctuations in the SGT promoted P accumulation from the surface soil to deeper soil. The proportions of P stored in various forms in the 30-60 cm and 60-100 cm soil layers in the RS were greater than those in the DS, while the average proportion in the 0-30 cm soil layer in the DS was as high as 48%. Compared with those in the DS, the maximum decreases in the proportion of P stored as TP and Olsen-P in the 0-100 cm soil layer in the RS were 16% and 58%, respectively, due to the rise in the SGT (SGT <30 cm), while the soil TP storage decreased by only 1% when the SGT was maintained at 60-100 cm. The critical thresholds for soil Olsen-P and TP gradually decreased with increasing soil depth, and the risk of P loss in deeper soil increased. The loss of soil P was increased by fluctuations in the SGT. Based on the cropland area around the 7 plateau lakes, P storage, and SGT fluctuations, the average loss intensity and loss amount of TP in the 0-100 cm soil layer around the 7 plateau lakes were estimated to be 25 kg/ha and 56 t, respectively. Therefore, reducing exogenous P inputs, improving soil endogenous P utilization efficiency and maintaining deep soil P retention are the basic strategies for preventing and controlling P accumulation and loss in deep soil caused by SGT fluctuations.

Mining for QTL controlling maize low-phosphorus response genes combined with deep resequencing of RIL parental genomes and in silico GWAS analysis

KEY MESSAGE

Extensive and comprehensive phenotypic data from a maize RIL population under both low- and normal-Pi treatments were used to conduct QTL mapping. Additionally, we integrated parental resequencing data from the RIL population, GWAS results, and transcriptome data to identify candidate genes associated with low-Pi stress in maize. Phosphorus (Pi) is one of the essential nutrients that greatly affect the maize yield. However, the genes underlying the QTL controlling maize low-Pi response remain largely unknown. In this study, a total of 38 traits at both seedling and maturity stages were evaluated under low- and normal-Pi conditions using a RIL population constructed from X178 (tolerant) and 9782 (sensitive), and most traits varied significantly between low- and normal-Pi treatments. Twenty-nine QTLs specific to low-Pi conditions were identified after excluding those with common intervals under both low- and normal-Pi conditions. Furthermore, 45 additional QTLs were identified based on the index value ((Trait_under_LowPi-Trait_under_NormalPi)/Trait_under_NormalPi) of each trait. These 74 QTLs collectively were classified as Pi-dependent QTLs. Additionally, 39 Pi-dependent QTLs were clustered in nine HotspotQTLs. The Pi-dependent QTL interval contained 19,613 unique genes, 6,999 of which exhibited sequence differences with non-synonymous mutation sites between X178 and 9782. Combined with in silico GWAS results, 277 consistent candidate genes were identified, with 124 genes located within the HotspotQTL intervals. The transcriptome analysis revealed that 21 genes, including the Pi transporter ZmPT7 and the strigolactones pathway-related gene ZmPDR1, exhibited consistent low-Pi stress response patterns across various maize inbred lines or tissues. It is noteworthy that ZmPDR1 in maize roots can be sharply up-regulated by low-Pi stress, suggesting its potential importance as a candidate gene for responding to low-Pi stress through the strigolactones pathway.

GEMAS: Phosphorus in European agricultural soil - sources versus sinks at the continental-scale - the geological perspective

Phosphorus (P) is one of the essential elements for life on Earth. As a major nutrient it is needed for healthy growth both in plants and living organisms. Although the abundance of P in the Earth's upper continental crust is relatively high (655 mg/kg), many soil types are poor in available phosphorus. The main natural factors controlling the availability of P in soil are pH, mineralogy, and formation of insoluble complexes with Al and Fe under acidic, and with Ca and Mg under alkaline soil conditions. Superimposed weathering processes and climate contribute strongly to P mobility and availability. Additionally, a large fraction of total soil P is in organic forms, which are not directly available to plants. Phosphorus is a major component in fertilisers and thus a significant source of anthropogenic P in soil and water. In the agricultural soil samples that were collected during the Geochemical Mapping of Agricultural and grazing land Soil (GEMAS) project, the total P concentrations (XRF, median 786 m/kg) are only slightly higher than those extracted by hot aqua regia (AR, median 653 mg/kg), while the median concentration in the weak MMI® cold extraction is as low as 4.1 mg/kg. The AR results show very low P concentrations over the coarse-grained sandy sediments of the last glaciation in central and northern Europe and in calcareous soil. The southern limit of the last glaciation is visible as a concentration break on the geochemical maps. In general, north-eastern and north-western Europe are marked by high P values, probably related to cold and humid climate and enrichment in humus-rich coastal soil. The spatial distribution of P at the continental-scale is dominated by geogenic and climatic factors, and the anthropogenic influence is difficult to assess and quantify.

Soil chemical fumigation alters soil phosphorus cycling: effects and potential mechanisms

Soil chemical fumigation is an effective and popular method to increase agricultural productivity. However, the broad-spectrum bioactivity of fumigants causes harm to soil beneficial microorganisms involved in the soil phosphorous cycle, such as soil phosphorus solubilizing microorganisms (PSMs). We review the effects of soil chemical fumigation on soil phosphorus cycling, and the potential underlying mechanisms that ultimately lead to altered phosphorus availability for crops. These complex processes involve the highly diverse PSM community and a plethora of soil phosphorus forms. We discuss phosphatizing amendments aimed at counteracting the possible negative effects of fumigation on phosphorus availability, phosphorus use efficiency, and crop yields. We also emphasize distinguishing between the effects on soil phosphorus cycling caused by the chemical fumigants, and those caused by the fumigation process (e.g. plastic mulching). These are typically conflated in the literature; distinguishing them is critical for identifying appropriate amendments to remediate possible post-fumigation soil phosphorus deficiencies.

A unifying modelling of multiple land degradation pathways in Europe

Land degradation is a complex socio-environmental threat, which generally occurs as multiple concurrent pathways that remain largely unexplored in Europe. Here we present an unprecedented analysis of land multi-degradation in 40 continental countries, using twelve dataset-based processes that were modelled as land degradation convergence and combination pathways in Europe's agricultural (and arable) environments. Using a Land Multi-degradation Index, we find that up to 27%, 35% and 22% of continental agricultural (~2 million km2) and arable (~1.1 million km2) lands are currently threatened by one, two, and three drivers of degradation, while 10-11% of pan-European agricultural/arable landscapes are cumulatively affected by four and at least five concurrent processes. We also explore the complex pattern of spatially interacting processes, emphasizing the major combinations of land degradation pathways across continental and national boundaries. Our results will enable policymakers to develop knowledge-based strategies for land degradation mitigation and other critical European sustainable development goals.

Large reductions in nutrient losses needed to avoid future coastal eutrophication across Europe

Rapid technological development in agriculture and fast urbanization have increased nutrient losses in Europe. High nutrient export to seas causes coastal eutrophication and harmful algal blooms. This study aims to assess the river exports of nitrogen (N) and phosphorus (P), and identify required reductions to avoid coastal eutrophication in Europe under global change. We modelled nutrient export by 594 rivers in 2050 for a baseline scenario using the new MARINA-Nutrients model for Europe. Nutrient export to European seas is expected to increase by 13-28% under global change. Manure and fertilizers together contribute to river export of N by 35% in 2050. Sewage systems are responsible for 70% of future P export by rivers. By 2050, the top ten polluted rivers for N and P host 42% of the European population. Avoiding future coastal eutrophication requires over 47% less N and up to 77% less P exports by these polluted rivers.

Rare microbial taxa as the major drivers of nutrient acquisition under moss biocrusts in karst area

Karst rocky desertification refers to the process of land degradation caused by various factors such as climate change and human activities including deforestation and agriculture on a fragile karst substrate. Nutrient limitation is common in karst areas. Moss crust grows widely in karst areas. The microorganisms associated with bryophytes are vital to maintaining ecological functions, including climate regulation and nutrient circulation. The synergistic effect of moss crusts and microorganisms may hold great potential for restoring degraded karst ecosystems. However, our understanding of the responses of microbial communities, especially abundant and rare taxa, to nutrient limitations and acquisition in the presence of moss crusts is limited. Different moss habitats exhibit varying patterns of nutrient availability, which also affect microbial diversity and composition. Therefore, in this study, we investigated three habitats of mosses: autochthonal bryophytes under forest, lithophytic bryophytes under forest and on cliff rock. We measured soil physicochemical properties and enzymatic activities. We conducted high-throughput sequencing and analysis of soil microorganisms. Our finding revealed that autochthonal moss crusts under forest had higher nutrient availability and a higher proportion of copiotrophic microbial communities compared to lithophytic moss crusts under forest or on cliff rock. However, enzyme activities were lower in autochthonal moss crusts under forest. Additionally, rare taxa exhibited distinct structures in all three habitats. Analysis of co-occurrence network showed that rare taxa had a relatively high proportion in the main modules. Furthermore, we found that both abundant and rare taxa were primarily assembled by stochastic processes. Soil properties significantly affected the community assembly of the rare taxa, indirectly affecting microbial diversity and complexity and finally nutrient acquisition. These findings highlight the importance of rare taxa under moss crusts for nutrient acquisition. Addressing this knowledge gap is essential for guiding ongoing ecological restoration projects in karst rocky desertification regions.

Phosphorus recovery from phosphate tailings through a two-stage leaching-precipitation process: Toward the harmless and reduction treatment of P-bearing wastes

To achieve highly efficient extraction of phosphorus (P) and comprehensive utilization of phosphate tailings, a two-stage leaching-precipitation method was proposed. Phosphate tailings primarily consisted of dolomite, fluorapatite, and quartz. During the first-stage leaching, the large majority of dolomite was selectively dissolved and the leaching efficiency of Mg reached 93.1 % at pH 2.0 and 60 °C. The subsequent second-stage leaching of fluorapatite was performed and the P leaching efficiency was 98.8 % at pH 1.5 and 20 °C, while the quartz remained in the residue. Through two-stage leaching, a stepwise leaching of dolomite and fluorapatite was achieved. After chemical precipitation, calcium phosphate with a high purity of 97.9 % was obtained; and the total recovery efficiency of P exceeded 98 %. The obtained calcium phosphate can be a raw material in the phosphorus chemical industry, while the Mg-rich leachate and the final quartz-rich residue have the potential for Mg extraction and the production of mortars or geopolymers, respectively. The two-stage leaching-precipitation process could significantly reduce the leaching costs, and enhance the reaction rates. It is expected to realize a volume reduction and efficient resource utilization of the phosphate tailings by using this sustainable and promising solution.

Bacillus subtilis promotes plant phosphorus (P) acquisition through P solubilization and stimulation of root and root hair growth

Bacteria can be applied as biofertilizers to improve crop growth in phosphorus (P)-limited conditions. However, their mode of action in a soil environment is still elusive. We used the strain ALC_02 as a case study to elucidate how Bacillus subtilis affects dwarf tomato cultivated in soil-filled rhizoboxes over time. ALC_02 improved plant P acquisition by increasing the size and P content of P-limited plants. We assessed three possible mechanisms, namely root growth stimulation, root hair elongation, and solubilization of soil P. ALC_02 produced auxin, and inoculation with ALC_02 promoted root growth. ALC_02 promoted root hair elongation as the earliest observed response and colonized root hairs specifically. Root and root hair growth stimulation was associated with a subsequent increase in plant P content, indicating that a better soil exploration by the root system improved plant P acquisition. Furthermore, ALC_02 affected the plant-available P content in sterilized soil differently over time and released P from native P pools in the soil. Collectively, ALC_02 exhibited all three mechanisms in a soil environment. To our knowledge, bacterial P biofertilizers have not been reported to colonize and elongate root hairs in the soil so far, and we propose that these traits contribute to the overall effect of ALC_02. The knowledge gained in this research can be applied in the future quest for bacterial P biofertilizers, where we recommend assessing all three parameters, not only root growth and P solubilization, but also root hair elongation. This will ultimately support the development of sustainable agricultural practices.

Smoothing the Phosphorus Resource Stress under the Socioeconomic Development in China

Phosphorus (P) is the key in maintaining food security and ecosystem functions. Population growth and economic development have increased the demand for phosphate rocks. China has gradually developed from zero phosphate mining to the world's leading P miner, fertilizer, and agricultural producer since 1949. China released policies, such as designating phosphate rock as a strategic resource, promoting eco-agricultural policies, and encouraging the use of solid wastes produced in mining and the phosphorus chemical industry as construction materials. However, methodological and data gaps remain in the mapping of the long-term effects of policies on P resource efficiency. Here, P resource efficiency can be represented by the potential of the P cycle to concentrate or dilute P as assessed by substance flow analysis (SFA) complemented by statistical entropy analysis (SEA). P-flow quantification over the past 70 years in China revealed that both resource utilization and waste generation peaked around 2015, with 20 and 11 Mt of mined and wasted P, respectively. Additionally, rapidly increasing aquaculture wastewater has exacerbated pollution. The resource efficiency of the Chinese P cycle showed a U-shaped change with an overall improvement of 22.7%, except for a temporary trough in 1975. The driving force behind the efficiency decline was the roaring phosphate fertilizer industry, as confirmed by the sharp increase in P flows for both resource utilization and waste generation from the mid-1960s to 1975. The positive driving forces behind the 30.7% efficiency increase from 1975 to 2018 were the implementation of the resource conservation policy, downstream pollution control, and, especially, the circular agro-food system strategy. However, not all current management practices improve the P resource efficiency. Mixing P industry waste with construction materials and the development of aquaculture to complement offshore fisheries erode P resource efficiency by 2.12% and 9.19%, respectively. With the promotion of a zero-waste society in China, effective P-cycle management is expected.