High Phosphorus Research Articles

Responses of Soil Microbial Communities to Abandoned Paddy Fields With Different Fertilization Histories

ABSTRACTThe abandonment of cultivated fields notably affects soil characteristics. However, its impact on soil microbial community composition, particularly under different fertilization regimes, remains poorly understood. Therefore, we evaluated the effects of abandoned paddy fields with different fertilization histories (no fertilization, NK, NP, and NPK) on the abundance, composition, and their predicted function of soil bacteria and fungi. Our findings revealed that the abandonment led to a considerable decrease in soil bacterial and fungal biomass. Fertilization history and abandonment each significantly affected on the bacterial community, resulting in increased relative proportions of Acidobacteria and decreased relative proportions of Proteobacteria in the NP and NPK treatments compared to those in the CK and NK treatments. The fungal community only exhibited a notable response to abandonment, with variations in the relative abundance of Ascomycota, Mucoromycota, and Basidiomycota. Canonical correspondence analysis revealed the significant association between soil bacterial community and pH, total phosphorus, and available phosphorus, whereas the pH and NO3−–N were key drivers of fungal community variations in abandoned soils. Network analysis indicated that abandonment enhanced the complexity but decreased the stability of the bacterial community, while fungi exhibited the opposite trend. Our findings highlight that changes in bacterial functions caused by residual nutrients, particularly high residual phosphorus, may accelerate soil organic C decomposition. Overall, this study provides a novel insight into the shifts in soil bacterial and fungal communities and their ecological functions after the abandonment of cultivated fields.

Role of Arbuscular Mycorrhizal Fungi in Maintaining Sustainable Agroecosystems

Arbuscular mycorrhizal (AM) fungi play a crucial role in maintaining sustainable agroecosystems by forming mutualistic relationships with plant roots, improving soil health, facilitating nutrient uptake, and enhancing resilience to abiotic stresses. The mutualistic relationship between AM fungi and plants promotes a balanced microbial community and improves soil structure by forming stable soil aggregates. Additionally, AM fungi can lower the adverse effects of high soil phosphorus (P) while also enhancing plant tolerance to drought, salinity, and heavy metal toxicity through osmotic regulation and antioxidant production. Arbuscular mycorrhizal fungi also support beneficial microorganisms, such as potassium (K)-solubilizing microbes and nitrogen (N)-transforming bacteria, which enhance the nutrient dynamics in soil. However, intensive agricultural practices, including heavy tillage and continuous monoculture, disrupt AM fungal networks and reduce microbial diversity, impairing their effectiveness. Adopting conservation practices such as reduced tillage, crop rotation, and organic amendments supports AM fungal growth. Incorporating mycorrhizal crops and utilizing native fungal inoculants can enhance AM fungal colonization and plant growth. These strategies collectively bolster soil health, crop productivity, and resilience, offering a promising solution to the environmental and agricultural challenges posed by intensive farming. By promoting AM fungi growth and colonization, agroecosystems can achieve long-term productivity and increased sustainability.

The yield and phosphorus content of maize intercropped with faba bean are enhanced by belowground interspecies interactions at low phosphorus input and by aboveground interactions at high phosphorus input

The yield and phosphorus content of maize intercropped with faba bean are enhanced by belowground interspecies interactions at low phosphorus input and by aboveground interactions at high phosphorus input

Полевая всхожесть и густота стояния растений перед уборкой сортов льна-долгунца в зависимости от почвенно-метеорологических условий

The article presents experimental data of scientific research for 2023-2024 to identify the influence of soil and meteorological conditions of cultivation on field germination of seeds, survival during vegetation and the density of standing of flax varieties before harvesting. During the years of testing of flax varieties, a very low and average humus content, high and elevated mobile phosphorus, medium and very high mobile potassium were found in the arable soil layer of sod-medium podzolic medium loamy soil of the Middle Urals, acidic and slightly acidic reaction of the soil solution was noted. In the growing seasons of 2023 and 2024, which differ in meteorological conditions, it was revealed that the field germination of seeds, survival during the growing season and the density of long flax plants before harvesting depended on both varietal characteristics and abiotic conditions of the year of cultivation. The highest values of field germination (78%) and the number of plants to harvest (1359 pcs/m2) were provided by the standard Chance variety, the lowest (58% and 1033 pcs/m2, respectively) by the Impulse variety. It was found that the density of standing plants before harvesting depended by 71% on field germination and by 47% on the survival rate of plants during the growing season. Keywords: FIBER FLAX, VARIETY, SOIL AND METEOROLOGICAL CONDITIONS, FIELD GERMINATION, SURVIVAL RATE DURING VEGETATION, PLANTS BEFORE HARVESTING

Effect of Phosphate Amendment on Cadmium Accumulation in Pepper (Capsicum annuum L.) Grown in Geogenic Cd-Rich Soil from the Karst Region

Soil in the karst region usually features high geogenic cadmium (Cd) and limited available phosphorus (P). Appropriate phosphate amendment is crucial for alleviating Cd accumulation in food crops and reducing health risks. However, the interaction of Cd and P in geogenic Cd-rich soil-plant systems is poorly understood. In this study, a pot experiment was conducted to investigate the translocation of Cd in the soil-pepper system under different amendment rates of Ca(H2PO4)2. The results showed that the biomass of pepper was not affected by the application rates of Ca(H2PO4)2, even up to 0.45 g/kg, but was affected by the application of nitrogen and potassium fertilizers. High contents of total Cd (6.19 mg/kg) and bioavailable Cd (2.72 mg/kg, 44%) in the studied soils resulted in elevated Cd content in pepper, and it decreased in the order of root (8.18 mg/kg) > stem (4.89 mg/kg) > fruit (3.88 mg/kg). This indicates that pepper planted in the studied soils may present potential health risks. Furthermore, phosphate amendment neither influences the bioavailable Cd in rhizosphere soil nor Cd uptake and transport in pepper plants. The findings of this study highlight that monocalcium phosphate is not a suitable choice for reducing the accumulation of Cd in pepper fruits in the studied soil and that other remediation strategies are needed.

Synthesis of a Bimetallic-Doped Phytate-Melamine Composite as an Efficient Additive for Epoxy Resins with High Fire Safety.

The issue of hazardous smoke and toxic gases released from epoxy resins (EP), which often causes casualties in real fires, has limited its application. Therefore, we have developed a novel flame retardant based on a bimetallic-doped phytate-melamine (BPM) structure with Zn2+ and Fe2+ ions incorporated into the polymer matrix using a straightforward solution-based synthetic method. The combustion performance of the composite was evaluated using a cone calorimeter test, which showed that the peak heat release, total heat release, and total smoke production were reduced by 50%, 31.7%, and 29.2%, respectively, compared to those of EP. Additionally, the fire growth index was noticeably reduced by 60% owing to the synergistic catalytic effect of the bimetallic ions, and the high nitrogen and phosphorus content of the additives. Overall, this study provides new insights into the application of bimetallic doping for flame retardant polymer composites.

Spatial Prediction of Soil Total Phosphorus in a Karst Area: Comparing GWR and Residual-Centered Kriging

Accurate soil total phosphorus (TP) prediction is essential to support sustainable agricultural practices and formulate ecological conservation protection policies, particularly in complex karst landscapes with high spatial variability and high phosphorus and cadmium content and interactions, complicating nutrient management. This study uses GIS and geostatistical methods to analyze the spatial distribution, influencing factors, and predictive modeling of soil TP in the karst region of northern Mashan County, Guangxi, China. Using 427 surface soil samples, we developed five predictive models: ordinary kriging (OK), regression kriging (RK) and geographically weighted regression kriging (GWRK) combined with environmental variables such as land uses, soil types, and topographic factors; residual mean-centered kriging (MM_OK), and residual median-centered kriging (MC_OK). Our results indicate that higher TP levels were observed in agricultural lands (paddy fields and dry land, at 766 and 913 mg·kg−1, respectively) may due to fertilization, while forests and shrublands showed lower TP levels (383 and 686 mg·kg−1, respectively), reflecting natural phosphorus cycling. The high-value areas of soil TP concentration are in the karst areas in the west and east of the study area, and the low-value area is in the Hongshui River valley in the north of Mashan. The spatial distribution of soil TP is affected by land use, soil type, and topography. The GWRK model exhibited superior accuracy (80.6%), with predicted concentration of TP closely aligning with observed TP values, effectively capturing fine spatial variations, and showing the lowest mean standardized error, average standard error, and mean absolute error. GWRK also achieved the highest R2 (0.67), demonstrating robust predictive capability. MM_OK and MC_OK models performed well and showed smoother spatial transitions, while the OK model displayed the lowest predictive accuracy (62%). By utilizing spatially adaptive weighting, GWRK and its residual-centered kriging method improve soil TP’s prediction accuracy and smoothness in karst areas, providing a reference for targeted soil conservation and sustainable agricultural practices in spatially complex karst environments.

Characterization of Lipid Production in Chlorella sp. Cultivated in Different Plant Fertilizers

Microalgae have gained attention due to their higher reproduction rate and lipid productivity. In particular, various stress conditions lead to an overproduction of lipids in microalgae cells. The study investigated the influence of additional CO2 introduced with air into the reactor during biomass growth of Chlorella sp. Additionally, increased phosphorus concentration in the medium under stress cultivation (low nitrogen concentration) was examined. The partial pressure of CO2 and its increased availability to Chlorella sp. in the cultivation medium increased biomass growth (1.4 times) and chlorophyll content (2.5 times) in microalgae cells. A high phosphorus fertilizer significantly increased lipid production under stress conditions with CO2 supply to 85.2 mg/g (2.6 times) and without CO2 to 73.8 mg/g (2.2 times). A high concentration of phosphorus in the culture medium stimulated the synthesis of C16:0 (about 38–45%) and C18:1 CIS9 (about 24–30%). The results confirm that the fertilizers can be used as a culture medium to induce stress and stimulate lipid production. Adjusting the composition of the fertilizers and controlling the additional CO2 supply could prove beneficial to increase the content of the desired fatty acids.

Effect of Lime Solution Soaking on Physicochemical Characteristics of Catfish Bone Powder (Arius thalassinus)

Fish bone powder is one of the fisheries by product processing that has a high nutritional content, especially calcium and phosphorus content. In the processing of fish bone powder, the fishy odor is still detected due to organic compound such as protein and lipid which produce volatile compounds yielded unpleasant odor. The use of lime can eliminate fishy odors, improve color, shape, taste, texture, and extend shelf life. This study aimed to determine the difference of lime solution concentration on the physicochemical characteristics of catfish bone powder and to determine the best lime concentration used on the volatile compound content of catfish bone powder. The method carried out in this study was a laboratory experimental method and used a Complete Random Design (CRD) with 4 treatments (0%, 15%, 20%, 25%) and carried out in triplicate. Data analysis from physical and chemical tests were analyzed using ANOVA, while hedonic tests were performed using the Kruskal-Wallis test followed by the Mann-Whitney test. The results showed that soaking lime solution had a significant effect (P<5%) on moisture content, protein content, fat content, ash content, calcium content and color. Catfish bone powder with the best treatment of soaking in lime solution of 20% contained a calcium of 25.17%.The results of the hedonic test showed that the best treatment (20%) had a confidence interval of 3.95 < μ < 4.19 from 5 scale. The volatile compound of 4-[4-(dimethylamine) Benzaldehyde associated with fishy odor was detected in fish bone powder without lime solution, but it could not be detected in sample soaked in 20% lime solution showing the capability of lime solution to reduce fishy odor in fishbone powder.

The use of a benign fast-growing cyanobacterial species to control microcystin synthesis from Microcystis aeruginosa.

Microcystis aeruginosa (M. aeruginosa), one of the most prevalent blue-green algae in aquatic environments, produces microcystin by causing harmful algal blooms (HAB). This study investigated the combined effects of nutrients and cyanobacterial subpopulation competition on synthesizing microcystin-LR. In varied nitrogen and phosphorus concentrations, cyanobacterial coculture, and algicidal DCMU presence, the growth was monitored by optical density analysis or microscopic counting, and the microcystin production was analyzed using high-performance liquid chromatography-UV. Furthermore, growth and toxin production were predicted using MATLAB. First, coculturing with a fast-growing cyanobacterium Synechococcus elongatus UTEX 2973 (S. elongatus) reduced M. aeruginosa biomass and microcystin production at 30oC. Under high nitrogen and low phosphorus conditions, S. elongatus is mostly effective, with up to 94.7% and 92.4% limitation of M. aeruginosa growth and toxin synthesis, respectively. Second, this biological strategy became less effective at 23oC, where S. elongatus grew slower. Third, photosynthesis inhibitor DCMU (3-(3,4-dichlorophenyl)-1,1-dimethylurea) hindered M. aeruginosa growth (at 0.1 mg/L) and microcystin production (at 0.02 mg/L). DCMU was also effective for controlling microcystin production in S. elongatus-M. aeruginosa cocultures. Based on experimental results, a multi-substrate, multi-species kinetic model was built to describe coculture growth and population interactions. Future research should examine more complex models to further develop and refine to facilitate the derivation of more effective recommendations for health prevention programs, particularly for mothers and girls.

"Higher renal net acid, but not higher phosphate excretion during growth associates with lower adult circulating uromodulin".

Uromodulin is the most abundant urinary protein in healthy subjects which under physiological conditions protects against kidney stone formation. Acid-base imbalances, especially states with acidic urine, increase the risk for uric acid and oxalate stones, but lower it for phosphate-containing stones. Whether habitual high acid loads and high dietary phosphorus intake (P-In) themselves may influence plasma uromodulin concentrations in the long-term is not known. we prospectively examined biomarker-based the associations of P-In and endogenous acid loads of 3-17 years old healthy participants (n=358) of the DONALD study (Dortmund, Germany) with their circulating uromodulin levels later in adulthood. Urinary phosphate excretion (PO4-Ex), net acid excretion (NAE), potential renal acid load (uPRAL), and pH were analyzed in 24-hour urine samples repeatedly collected during growth. Circulating uromodulin was analyzed in adult fasting blood samples. Individual means of age- and sex-stratified standard-deviation-scores of growth- and nutritional biomarker-related parameters were calculated. Multi-linear regression models adjusted for anthropometric, renal, and blood parameters were conducted to examine the prospective relationships of pre-adulthood urinary biomarkers with adult circulating uromodulin. Uromodulin associated inversely with NAE (Pfor-trend<0.03) and positively with urinary pH (Pfor-trend=0.05; lowest pH-quintile vs. highest quintile: P=0.03), but not significantly with uPRAL and PO4-Ex during growth. the known increased urolithiasis risk associated with high endogenous acid production may be further augmented by a high NAE-related reduction of the stone-formation inhibitor uromodulin. Despite not observing a significant association with uPRAL, the potential of habitual low-PRAL diets to raise uromodulin needs to be further studied.

Soil Organic Carbon Increases With Decreasing Microbial Carbon Use Efficiency During Vegetation Restoration.

Microbial carbon (C) use efficiency (CUE) describes the proportion of organic C used by microorganisms for anabolic processes, which increases with soil organic C (SOC) content on a global scale. However, it is unclear whether a similar relationship exists during natural vegetation restoration in terrestrial ecosystems. Here, we investigated the patterns of CUE along a 160-year vegetation restoration chronosequence (from farmland to climax forest) estimated by stoichiometric modeling; additionally, we examined the relationship between CUE and SOC content and combined these results with a meta-analysis. The combination indicated that vegetation restoration decreased CUE from 0.35 to 0.28. Surprisingly, SOC content increased with decreasing CUE during vegetation restoration because forest soils have low pH values and high microbial phosphorus limitations compared to early ecosystems, implying that climax forests may not sequester as much soil C as expected. The shift in soil pH was the most important predictor of CUE compared to climate, plant, and microbial factors. CUE changes were directly induced by soil pH and not by the pH-induced microbial community. Alkaline soil acidification tended to decrease CUE. This first large-scale estimate of the relationship between CUE and SOC during natural restoration highlights the need to strengthen C sink management in mature forests to sustain their C sequestration potential.

Development of dephosphorization technology for iron ores with high phosphorus content

Development of dephosphorization technology for iron ores with high phosphorus content

Evaluating Black Soldier FLY (Hermetia illucens) Frass and Larval Sheddings in the Production of a Quality Compost

Black Soldier Fly (Hermetia illucens) is well-known for having a high protein and lipid content during its larval stage and is cultivated for animal feed. Rearing Black Soldier Fly larvae (BSFL) produces byproducts known as frass and larval sheddings in large volumes with limited applications. Therefore, there is a need to identify viable sustainable management strategies to prevent potential environmental issues associated with their accumulation. Accordingly, the purpose of this study was to evaluate BSFL frass and larval sheddings as viable ingredients in composts that utilize additional nitrogen feedstocks. Four experimental compost piles (22.7 m3) with different ratios of BSFL frass and sheddings were developed based on previous research; two piles included 25% frass, whereas the other two included 30% frass. Across these piles, the inclusion of wood chips, food waste, and livestock manure varied to determine the best proportions for compost. The compost piles were maintained for five months, including a curing phase. After curing, samples from each pile were collected to analyze their pH, macro- and micro-nutrients, particle size, stability, and maturity. The findings indicated that the pH levels (7.1–8.1) and carbon-to-nitrogen ratios (10.40–13.20) were within the optimal ranges for all piles. The phosphorus levels (0.75–1.30%) of each pile exceeded typical ranges, likely due to the high phosphorus content of the frass itself. The moisture content varied widely (24.5–51.7%), with some piles falling below optimal levels. Stability and maturity tests yielded mixed results, with some piles demonstrating continued decomposition activity. Overall, the findings indicated that inclusion rates of 25–30% of BSFL frass and sheddings produced compost with generally favorable characteristics when high nitrogen feedstocks were also incorporated into the compost piles. These findings align with those from previous research and highlight both the potential and challenges of incorporating BSFL frass into compost production.

Toxicological Effects of Sewage Sludge on Biochemical Biomarkers of Earthworms (Eisenia andrei)

ABSTRACTSewage sludge, or biosolids, produced in wastewater treatment plants (WWTP) can be used as an alternative to organic fertilizer in the agricultural field. However, it holds a large amount of anthropogenic chemicals, such as drugs and metals. The aim of the present study is to evaluate biochemical biomarker responses in earthworms (Eisenia andrei) exposed to soil presenting different sludge concentrations deriving from the largest WWTP in Southern Brazil. Treatments comprised 3%, 6%, 12%, 24%, 50%, and 75% of sludge incorporated to native forest soil, 100% of sludge and the control group (0%). Concentrations of different drugs, mainly of antibiotics, as well as high sulfur, magnesium, potassium, zinc, and phosphorus were identified in analyzed sewage sludge. Exposed earthworms were collected on the 7th, 14th, and 28th day of the experiment and subjected to analysis of lipid peroxidation levels (TBARS), acetylcholinesterase (AChE), catalase (CAT), and glutathione S‐transferase (GST) activity. Treatments with 50%, 75%, and 100% of sludge were lethal to earthworms after 7 days. Based on biochemical tests performed in treatments with 3%, 6%, 12%, and 24% of sludge, the highest sludge concentrations (12% and 24%) and the longest exposure time (28 days) led to significant changes in biomarkers. Therefore, sewage sludge must be incorporated into the soil at concentrations lower than 3%, mainly due to changes in CAT, AChE, GST, and the resulting lipid damage observed at concentrations of 6%, 12%, and 24%.

Red mud as a green dephosphorization agent: Co-reduction with high phosphorus oolitic hematite for iron extraction and dephosphorization

The large utilization of red mud (RM) presents many challenges due to its high alkalinity, which is attributed to the presence of CaO and Na2O. High phosphorus oolitic hematite (HPOH) is a typical refractory ore for Fe and P separation. During the direct reduction of HPOH to produce direct reduced iron (DRI) and achieve simultaneous dephosphorization, sodium or calcium salts are typically added as dephosphorization agents. This study investigated the feasibility of using RM as a green dephosphorization agent. Co-reduction of RM with HPOH was conducted to prepare DRI. By adding 60 % RM and using a reductant dosage of 17 %, a DRI with 90.89 % Fe and 0.095 % P was obtained. The corresponding total iron recovery was 87.79 %. This indicated that the addition of RM facilitated effective simultaneous iron extraction and dephosphorization. The co-reduction mechanisms were analyzed using X-ray diffraction (XRD), thermodynamic analysis, and scanning electron microscopy combined with energy dispersive spectroscopy (SEM–EDS). In the absence of RM, the reduction of fluoroapatite occured, leading to the incorporation of P into metallic iron. However, with adding RM, albite and anorthite were generated, hindering the reduction behavior of fluoroapatite and reducing P content in DRI. Thus, RM effectively served as a green dephosphorization agent in the co-reduction process.

Study of temperature dynamics and influencing factors during composting process

Abstract This study investigated the most influential composting parameters (temperature, pH, humidity, C/N ratio, and CO2 emissions) on final compost quality. Composting bags (turned daily) containing prunings, lignocellulose material, cattle manure, and household organic waste were monitored for eight weeks across three batches. All the temperature data registered daily were statistically analyzed with one-way ANOVA to verify the consistency between batches. This study employs a first-order kinetic model to quantify the decomposition of organic matter in composting, revealing the influence of temperature on the decomposition rate. Principal component analysis was conducted for these factors and their interactions with respect to the final compost quality. Finished compost showed a significantly high nitrogen, phosphorus, and potassium content compared with that in the feedstock of the initial compost mixture, while there was constant organic carbon content. In addition to the control of key parameters, a linear regression analysis allowed us to identify the factors that most influenced temperature. We identified two key models: one including pH, humidity, C/N ratio, and CO2 emissions, and another focusing only on CO2. This study emphasized the importance of monitoring and controlling the crucial parameters of the composting process in order to obtain quality compost suitable for application in soil use. Moreover, high temperatures possibly attained in the process of aerobic decomposition destroy the pathogens, making the end products safer for uses in agriculture.

Effect of Dehydrogenation and Heat Treatments on the Microstructure and Tribological Behavior of Electroless Ni-P Nanocomposite Coatings.

High phosphorus Ni-P coatings, both unreinforced and modified by the addition of alumina (Al2O3) and zirconia (ZrO2) nanoparticles, were manufactured by electroless deposition technique and heat-treated with different temperature and duration schedules. The effect of dehydrogenation (200 °C for 2 h) and its combination with crystallization heat treatment was studied in terms of microstructural changes and wear resistance. The amorphous structure of the coatings was not altered by the introduction of both Al2O3 and ZrO2 nanoparticles, and the addition of 1.5 g/L of ZrO2 yielded the highest microhardness due to better particles dispersion. Dehydrogenation improved hardness because of the early stages of grain growth; however, the greatest improvement in hardness (+120% compared to unreinforced Ni-P) was obtained after annealing at 400 °C for 1 h, because of the microprecipitation of the Ni3P crystalline phase induced by thermal treatment. No detectable differences in hardness and microstructure were detected when annealing at 400 °C for 1 h with or without prior dehydrogenation; however, the dehydrogenated coatings exhibited a lower Young's modulus. ZrO2-reinforced coatings demonstrated improved wear resistance, and wear tests revealed that dehydrogenation is fundamental for lowering the coefficient of friction (-14%) and wear rate (-97%) when performed before annealing at 400 °C for 1 h. The analysis of the wear tracks showed that the non-dehydrogenated samples failed by complete coating delamination from the substrate, with abrasion identified as the predominant wear mechanism. Conversely, the dehydrogenated samples demonstrated better resistance due to the formation of a protective oxide layer, leading to an overall increase in the coating wear resistance.

Organic Farming Enhances Diversity and Recruits Beneficial Soil Fungal Groups in Traditional Banana Plantations.

This study investigates the impact of organic (OF) and conventional farming (CF) on soil fungal communities in banana monoculture plantations on Madeira Island. We hypothesized that OF promotes beneficial fungal groups over harmful ones, sustaining soil health. Soil samples were collected from six plantations (three OF and three CF) for ITS amplicon sequencing to assess fungal diversity. Results showed that OF significantly enhanced fungal alpha-diversity (Shannon-Wiener index) and Evenness. The phylum Ascomycota dominated OF systems, while Basidiomycota prevailed in CF. Mortierella, a beneficial genus, was abundant in OF and is observed in CF but was less evident, being the genus Trechispora the most well represented in CF agrosystems. Additionally, OF was associated with higher soil pH and Mg levels, which correlated positively with beneficial fungal groups. Functional analysis revealed that OF promoted saprotrophic fungi, crucial for the decomposition of organic matter and nutrient cycling. However, both systems exhibited low levels of arbuscular mycorrhizal fungi, likely due to high phosphorus levels. These findings suggest that organic practices can enhance soil fungal diversity and health, although attention to nutrient management is critical to further improving soil-plant-fungi interactions.

Key Process Control for Synthesizing High-Performance Inherently Flame-Retardant Long-Chain Bio-Based Polyamide.

Long-chain bio-based polyamide has shown promising development prospects due to its excellent properties and green renewable characteristics; however, synthesizing inherently flame-retardant long-chain bio-based polyamide remains a big challenge due to the lack of effective knowledge of the key polymerization process. Herein, intrinsicly flame-retardant long-chain bio-based polyamide 512 (PA512) was synthesized in the presence of a reactive flame retardant with high thermal stability and good water solubility. The reaction conditions and existing problems in each stage of the copolymerization system have been clarified and optimized. By utilizing a two-step pre-polymerization approach, a series of intrinsicly flame-retardant PA512 (FRPA512) with large molecular weight, high phosphorus element content and good mechanical properties were obtained. More importantly, the prepared FRPA512 with 5 wt % flame retardant loading exhibited good flame retardancy, showing a limiting oxygen index (LOI) of 28.1 % and a vertical burning rating of V-0. This study provides a feasible solution to the common problem in the synthesis of flame-retardant polyamides, while also offering new insights for future modification of polyamide copolymerization.