Soluble Phosphorus Research Articles

Exploring the Phosphate Solubilization Potential of Rhizobia Isolated from Sesbania grandiflora

Rhizobia, are known to exhibit the ability to solubilize phosphate (P) in the soil, apart from their primary function of nitrogen fixation. Hence this study was conducted to evaluate and characterize rhizobia isolates obtained from root nodules of Sesbania grandiflora for their potential in P solubilization. Two experiments were conducted under laboratory conditions arranged in a Complete Randomized Design (CRD) with three replicates. All data were analyzed using analysis of variance (ANOVA) and means were separated using the LSD test. Four bacterial strains (a,b,c,d) were isolated from root nodules using the trap plant method. They were initially identified as Rhizobia based on morphology and authenticated through gram staining, acid-alkaline tests, Congo Red Yeast Mannitol Agar (CRYMA), and Bromothymol blue Yeast Mannitol Agar (BRYMA) tests. The most effective rhizobia for P solubilization was identified based on the Phosphorus Solubilization Index (PSI) and solubilized P in Pikovaskya (PVK) solid and liquid media. Subsequently, optimization of PVK liquid media was conducted for effective P solubilizer, varying with carbon (C), nitrogen (N), and P sources. All isolates were gram-negative and exhibited acid production, authenticated as rhizobia. The significantly (p<0.05) highest PSI was recorded with isolate “c” and it also exhibited the highest (p<0.05) solubilized P. The isolate “c” showed potassium dihydrogen phosphate (35.1±0.46 ppm), glucose (25.47±0.49 ppm), and ammonium sulfate (3.20±0.17 ppm) as the optimum sources of P, C, and N, respectively, for achieving significantly higher phosphorus solubilization in PVK medium by thriving rhizobia “c” as an effective phosphorus solubilizer. However, further field studies are required to assess performance of rhizobia “c” before introducing it as a P solubilizing inoculum.

Application of rhizobium inoculation in regulating heavy metals in legumes: A meta-analysis

Rhizobium inoculation has been widely applied to alleviate heavy metal (HM) stress in legumes grown in contaminated soils, but it has generated inconsistent results with regard to HM accumulation in plant tissues. Here, we conducted a meta-analysis to assess the performance of Rhizobium inoculation for regulating HM in legumes and reveal the general influencing factors and processes. The meta-analysis showed that Rhizobium inoculation in legumes primarily increased the total HM uptake by stimulating plant biomass growth rather than HM phytoavailability. Inoculation had no significant effect on the average shoot HM concentration (p > 0.05); however, it significantly increased root HM uptake by 61 % and root HM concentration by 7 % (p < 0.05), indicating safe agricultural production while facilitating HM phytostabilisation. Inoculation decreased shoot HM concentrations and increased root HM uptake in Vicia, Medicago and Glycine, whereas it increased shoot HM concentrations in Sulla, Cicer and Vigna. The effects of inoculation on shoot biomass were suppressed by nitrogen fertiliser and native microorganisms, and the effect on shoot HM concentration was enhanced by high soil pH, organic matter content, and phosphorous content. Inoculation-boosted shoot nutrient concentration was positively correlated with increased shoot biomass, whereas the changes in pH and organic matter content were insufficient to significantly affect accumulation outcomes. Nitrogen content changes in the soil were positively correlated with changes in root HM concentration and uptake, whereas nitrogen translocation changes in the tissues were positively correlated with changes in HM translocation. Phosphorus solubilisation could improve HM phytoavailability at the expense of slight biomass promotion. These results suggest that the diverse growth-promoting characteristics of Rhizobia influence the trade-off between biomass-HM phytoavailability and HM translocation, impacting HM accumulation outcomes. Our findings can assist in optimising the utilisation of legume-Rhizobium systems in HM-contaminated soils.

Effects of plant-soil feedbacks on the invasion and competitiveness of Aegilops tauschii

The interaction between plants and soil is an important aspect that affects the invasive ability of foreign plants and the invasiveness of ecosystems. The study on plant soil feedback of A. tauschii can provide reference for its invasion mechanism. Firstly, the effects of A. tauschii on the nutrients and enzyme activities of invaded soil were investigated; Secondly, in conjunction with soil sterilization, pot experiments were conducted using the De Wit substitution method to investigate the impact of different degree invasive soils on the development of A. tauschii and its interaction with wheat. The results showed that the invasion of A. tauschii significantly increased soil organic matter, soluble phosphorus and soluble potassium, while also causing a significant decrease in the concentration of nitrate nitrogen. And according to the changes of morphological and biomass indicators of A. tauschii, the results of two-way ANOVAs showed that the invaded soil and its microbiota have a positive feedback effect on the growth of A. tauschii. Finally, it can be seen from the value of the competition balance index, the competition ability of A. tauschii in different invasion degree soil is greater than that of wheat whether the soil invaded by A. tauschii had undergone sterilization treatment or not. In conclusion, the invasion potential of A. tauschii is not only derived from its strong competitiveness, but also may be related to the soil conditions.

Investigating the Efficacy of Dry Region Zinc Solubilizing Bacteria for Growth Promotion of Maize and Wheat under Axenic Conditions

Zinc (Zn) plays a crucial role as a micronutrient, essential for the growth, development, and proper functioning of plants. Pakistani soils are deficient of micronutrient especially zinc. Supplementation of Zn fertilizers cannot do the job because only a small fraction of Zn is available to plants and rest is fixed in soil. To enhance the Zn availability different methods are being used which are expensive. Zinc solubilizing bacteria (ZSB) can be a potential candidate for solubilization of Zn and growth promoting activities in cereals. The present study aimed to evaluate the potential of dry region bacterial strains of Bahawalpur for improving Zn uptake and growth improvement in wheat and maize. Rhizosphere samples of wheat and maize were taken from the dry regions of Bahawalpur and bacterial strains were isolated and tested for their Zn solubilizing ability and screened for urease, siderophore activity, exopolysaccharide production, phosphorus solubilization and plant growth promoting abilities. Under axenic conditions selected isolates were further screened to assessed for improving the growth of wheat and maize seedlings. The rhizobacterial isolates IUB-34, IUB-80, IUB-93 and IUB-96 performed best to improve growth, physiology, biochemical attributes and root colonization. The maximum increase in root and shoot lengths were recorded 32.2 and 35.7% in wheat under IUB-34 application and in maize 43.8 and 39.9%, respectively, under IUB-96 application as compared to uninoculated control. Furthermore, maximum root colonization was also recorded under IUB-34 in wheat and IUB-96 in maize seedlings. Moreover, the biochemical characterization of selected isolates showed IAA (Auxins) production, protease, catalase, cellulose degradation, HCN and ACC-deaminase activities by these strains. However, only IUB-34 and IUB-96 were found positive for oxidase activity. Therefore, study concluded that use of dry region ZSB can solubilize Zn and make it available for plant to improve growth of wheat and maize. So, these isolates may be utilized for coating urea as a biofertilizer to increase the biofortification in cereals.

Response characteristics of plants and pollutant removal in subsurface flow constructed wetlands under resting operation

The stable operation of subsurface flow (SSF) constructed wetlands (CWs) depends on the adopted maintenance and management strategies. To determine a suitable resting period for SSF CWs, this study investigated and compared the impacts of three resting periods on plant physiological metabolism, wetland purification effectiveness, and microbial responses. The results revealed that resting operations induced morphological adaptations in wetland plants, significantly enhanced the root-shoot ratio and specific root length. A 2-d resting period enhanced oxygen secretion from plant roots, which was beneficial for SSF CW reoxygenation, leading to significant increases in the average removal rates of chemical oxygen demand and total phosphorus. After the resting operation, the inorganic phosphorus solubilization and transporters function of rhizosphere microorganisms were enhanced, resulting in efficient phosphorus removal. The functional genes related to nitrification, nitrogen fixation, and assimilation were increased, and a 2–5 d resting period facilitated the aerobic nitrification in SSF CWs. Inversely, an excessively long resting (>5 d) significantly inhibits plant and microbial activity, resulting in a deteriorated pollutant removal performance. Plants regulate rhizosphere microorganisms by adjusting root traits, which are the key factors and important reference indicators guiding the formulation of the operation and maintenance strategies for SSF CWs during resting periods.

Effects of Waterlogging Stress on Root Growth and Soil Nutrient Loss of Winter Wheat at Seedling Stage

With global climate change, flooding events are becoming more frequent. However, the mechanism of how waterlogging stress affects crop roots needs to be studied in depth. Waterlogging stress can also lead to soil nitrogen and phosphorus loss, resulting in agricultural surface pollution. The aim of this study is to clarify the relationship between soil nitrogen and phosphorus distribution, root growth characteristics, and nitrogen and phosphorus loss in runoff water under waterlogging stress during the winter wheat seedling stage. In this paper, Zhengmai 136 was selected as the experimental material, and two water management methods (waterlogging treatment and non-waterlogging control treatment) were set up. Field experiments were conducted at the Wudaogou Hydrological Experimental Station in 2022 to assess the nitrogen and phosphorus concentrations in runoff water under waterlogging stress. The study also aimed to analyze the nitrogen and phosphorus content and the root distribution characteristics in different soil layers under waterlogging stress. The results showed as the following: 1. Waterlogging stress increased the characteristic parameters of winter wheat roots in both horizontal and vertical directions. Compared with the control treatment, the root length increased by 1.2–29.9% in the waterlogging treatment, while the root surface area and volume increased by an average of 3.1% and 41.9%, respectively. 2. Nitrogen and phosphorus contents in waterlogged soils were enriched in the 0–20 cm soil layer, but both tended to decrease in the 20–60 cm soil layer. Additionally, there was an inverse relationship between the distribution of soil nutrients and the distribution of wheat roots. 3. During the seedling stage of winter wheat, nitrogen loss was the main factor in the runoff water. In addition, nitrate nitrogen concentration averaged 55.2% of the total nitrogen concentration, while soluble phosphorus concentration averaged 79.1% of the total phosphorus concentration. 4. The results of redundancy analysis demonstrated that available phosphorus in the soil was the key environmental factor affecting the water quality of runoff water. Total phosphorus and dissolved phosphorus in the water were identified as the dominant factors influencing root growth.

Microbial detoxification of chlorpyrifos, profenofos, monocrotophos, and dimethoate by a multifaceted rhizospheric Bacillus cereus strain PM38 and its potential for the growth promotion in cotton.

Bacillus genera, especially among rhizobacteria, are known for their ability to promote plant growth and their effectiveness in alleviating several stress conditions. This study aimed to utilize indigenous Bacillus cereus PM38 to degrade four organophosphate pesticides (OPs) such as chlorpyrifos (CP), profenofos (PF), monocrotophos (MCP), and dimethoate (DMT) to mitigate the adverse effects of these pesticides on cotton crop growth. Strain PM38 exhibited distinct characteristics that set it apart from other Bacillus species. These include the production of extracellular enzymes, hydrogen cyanide, exopolysaccharides, Indol-3-acetic acid (166.8μg/mL), siderophores (47.3μg/mL), 1-aminocyclopropane-1-carboxylate deaminase activity (32.4μg/mL), and phosphorus solubilization (162.9μg/mL), all observed at higher concentrations. This strain has also shown tolerance to salinity (1200mM), drought (20% PEG-6000), and copper and cadmium (1200mg/L). The amplification of multi-stress-responsive genes, such as acdS, ituC, czcD, nifH, sfp, and pqqE, further confirmed the plant growth regulation and abiotic stress tolerance capability in strain PM38. Following the high-performance liquid chromatography (HPLC) analysis, the results showed striking compatibility with the first kinetic model. Strain PM38 efficiently degraded CP (98.4%), PF (99.7%), MCP (100%), and DMT (95.5%) at a concentration of 300ppm over 48h at 35°C under optimum pH conditions, showing high coefficients of determination (R2) of 0.974, 0.967, 0.992, and 0.972, respectively. The Fourier transform infrared spectroscopy (FTIR) analysis and the presence of opd, mpd, and opdA genes in the strain PM38 further supported the potential to degrade OPs. In addition, inoculating cotton seedlings with PM38 improved root length under stressful conditions. Inoculation of strain PM38 reduces stress by minimizing proline, thiobarbituric acid-reactive compounds, and electrolyte leakage. The strain PM38 has the potential to be a good multi-stress-tolerant option for a biological pest control agent capable of improving global food security and managing contaminated sites.

Macrogenomics reveal the effects of inter-cropping perilla on kiwifruit: impact on inter-root soil microbiota and gene expression of carbon, nitrogen, and phosphorus cycles in kiwifruit.

Intercropping systems can improve soil fertility and health, however, soil microbial communities and functional genes related to carbon, nitrogen and phosphorus cycling under the intercropping system of mesquite and perilla have not been studied. Therefore, in the present study, different planting densities and varieties of Perilla frutescens (L.) Britt and kiwifruit were used for intercropping, and changes in soil microbial communities and carbon, nitrogen, and phosphorus cycling genes in kiwifruit inter-roots under inter-cropping conditions were investigated by macro-genome sequencing technology. The results showed that intercropping with Perill caused a decrease in most soil nutrients, soil enzyme activities, and had a significant impact on the microbial (bacteria and fungi) diversity. Inter-cropping increased the relative abundance of the dominant bacterial phylum "Proteobacteria" and "Actinobacteria" by 47 and 57%, respectively, but decreased the relative abundance of the dominant fungal phylum "Chordata" and "Streptophyta" by 11 and 20%, respectively, in the inter-root soil of kiwifruit, and had a significant impact on the microbial (bacteria and fungi) diversity. In addition, inter-cropping could greatly increase the inter-root soil carbon sequestration (PccA, korA/B/C/D, fhs, and rbcl/s), carbon degradation (abfD), organic nitrogen mineralization (GDH2), denitrification (napA/B, nirB, norB), organic phosphorus mineralization (phop, phn), and inorganic phosphorus solubilization (gcd, ppk) gene abundance. The gene co-occurrence network indicated that soil korB, nirB, and gnd key functional genes for carbon, nitrogen, and phosphorus cycling in kiwifruit inter-root soils and their expression was up-regulated in the inter-cropping group. Structural equation (SEM) further showed that soil total nitrogen, organic matter, total carbon and acid phosphatase had significant effects on microbial diversity (p < 0.05) and soil carbon cycling gene korB and phosphorus cycling gene purH (p < 0.001), while korB and purH had positive effects on kiwifruit quality. In conclusion, intercropping perilla in kiwifruit orchards changed the structure of bacterial and fungal communities in the inter-root soil of kiwifruit, but I believe that intercropping perilla stimulates carbon degradation, leading to carbon emission and serious loss of soil nutrients, and that prolonged intercropping may adversely affect the quality of kiwifruit, and thus its limitations should be noted in future studies.

Impact of the tripartite interaction between rice, sheath blight and diverse crop-associated endophytes on phenotypic and biochemical responses in rice

Endophytes stimulate plant growth and inhibit phytopathogens. Most of the known endophytes are host-specific and only a few strains are effective for practical field use. Thus, this study focuses on the evaluation of endophytes viz., Bacillus pseudomycoides strain HP3d, Paenibacillus polymyxa strain PGSS1, B. velezensis strain A6 and P42 isolated from diverse crop ecosystems for their potential to promote plant growth and induce systemic resistance against sheath blight disease in rice. The endophytes were studied for plant growth promoting traits in vivo conditions and were found to exhibit ammonia (light to strong), siderophore (yellow zone on the CAS agar plate), indole-3-acetic acid (15.20–22.19 μg mL−1) production and phosphorus solubilization (1.2–1.5 cm). In the glasshouse, when applied individually and in combinations through various methods like seed treatment, seedling dip, and foliar spray these endophytes significantly reduced lesion size (2.06–2.37 fold) and ShB severity (2.60–2.58 fold), enhancing growth parameters viz., shoot (1.09–1.11 fold), root (1.02–1.20 fold), number of tillers (1.2–1.6 fold), shoot (80.58–82.64 %) and root (62.01–66.66 %) dry matter over untreated control. Consequently, enzyme activity viz., polyphenol oxidase (2.20–3.00 U−1min−1g−1), peroxidase (0.31–0.35 min−1g−1), superoxide dismutase (118.50–123.00 Ug−1 FW), and phenylalanine ammonia lyase (0.84–0.90 min⁻1g⁻1FW) was found to increase up to the fourth day after the pathogen challenge and subsequently decrease thereafter. Chlorophyll content post inoculation of ShB declined over time but endophyte treated plants exhibited lesser reductions over uninoculated control. Field trials corroborated the in vitro findings, demonstrating reduced ShB (1.71–1.88 fold decrease in PDI) and enhanced growth (1.1–1.2 fold increase in shoot length) over untreated controls. The combined application of seedling dip, seed treatment, and foliar spray proved to be the most optimum treatment. The findings highlight the potential of diverse crop-derived endophytes, emphasizing their non-host specificity and effectiveness as broad-spectrum bioagents in actual field conditions.

Isolation of the inorganic phosphorus-solubilizing bacteria Lysinibacillus sphaericus and assessing its role in promoting rice growth.

Soluble phosphorus scarcity severely limits plant growth and crop yield. In this study, a strain of inorganic phosphorus-solubilizing bacteria, Lysinibacillus sphaericus, was isolated from rice rhizosphere soil. The available phosphorus content in liquid inorganic phosphorus identification medium and in L. sphaericus-inoculated soil increased from 204.28mg/L to 1124.68mg/L and from 4.75mg/kg to 7.04mg/kg, respectively. The pH decreased significantly from 6.87 to 6.14. Incubation with L. sphaericus significantly increased malic and succinic acid content in the liquid inorganic phosphorus identification medium and increased acid phosphatase and alkaline phosphatase activity in the soil. Inoculation with L. sphaericus significantly increased rice growth, chlorophyll a/b content, and photosynthesis by increasing the soluble phosphorus content in the rice rhizosphere soil under phosphorus-deficient conditions. Further analysis revealed that L. sphaericus improved soil phosphorus release by decreasing soil pH and promoting acid phosphatase and alkaline phosphatase activity. This study supports the production of microbial fertilizers to improve rice yield in phosphorus-deficient conditions.

The Effect of Two Siderophore-Producing Bacillus Strains on the Growth Promotion of Perennial Ryegrass under Cadmium Stress.

Cadmium (Cd) is a highly toxic and cumulative environmental pollutant. Siderophores are heavy metal chelators with high affinity to heavy metals, such as Cd. Ryegrass (Lolium perenne L.) has a potential remediation capacity for soils contaminated by heavy metals. Consequently, using ryegrass alongside beneficial soil microorganisms that produce siderophores may be an effective means to remediate soils contaminated with Cd. In this study, the Bacillus strains WL1210 and CD303, which were previously isolated from the rhizospheres of Nitraria tangutorum in Wulan and Peganum harmala L. in Dachaidan, Qinghai, China, respectively, both arid and sandy environments, were evaluated for heavy metal pollution mitigation. Our quantitative analyses have discerned that the two bacterial strains possess commendable attributes of phosphorus (P) solubilization and potassium (K) dissolution, coupled with the capacity to produce phytohormones. To assess the heavy metal stress resilience of these strains, they were subjected to a cadmium concentration gradient, revealing their incremental growth despite cadmium presence, indicative of a pronounced tolerance threshold. The subsequent phylogenetic analysis, bolstered by robust genomic data from conserved housekeeping genes, including 16S rDNA, gyr B gene sequencing, as well as dnaK and recA, delineated a species-level phylogenetic tree, thereby confirming the strains as Bacillus atrophaeus. Additionally, we identified the types of iron-carrier-producing strains as catechol (WL1210) and carboxylic acid ferrophilin (CD303). A genomic analysis uncovered functional genes in strain CD303 associated with plant growth and iron carrier biosynthesis, such as fnr and iscA. Ryegrass seed germination assays, alongside morphological and physiological evaluations under diverse heavy metal stress, underscored the strains' potential to enhance ryegrass growth under high cadmium stress when treated with bacterial suspensions. This insight probes the strains' utility in leveraging alpine microbial resources and promoting ryegrass proliferation.

Screening of plant growth-promoting rhizobacteria helps alleviate the joint toxicity of PVC+Cd pollution in sorghum plants

Combined microplastic and heavy metal pollution (CM-HP) has become a popular research topic due to the ability of these pollutants to have complex interactions. Plant growth-promoting rhizobacteria (PGPR) are widely used to alleviate stress from heavy metal pollution in plants. However, the effects and mechanisms by which these bacteria interact under CM-HP have not been extensively studied. In this study, we isolated and screened PGPR from CM-HP soils and analyzed the effects of these PGPR on sorghum growth and Cd accumulation under combined PVC+Cd pollution through pot experiments. The results showed that the length and biomass of sorghum plants grown in PVC+Cd contaminated soil were significantly lower than those grown in soils contaminated with Cd alone, revealing an enhancement in toxicity when the two contaminants were mixed. Seven isolated and screened PGPR strains effectively alleviated stress due to PVC+Cd contamination, which resulted in a significant enhancement in sorghum biomass. PGPR mitigated the decrease in soil available potassium, available phosphorus and alkali-hydrolyzable nitrogen content caused by combined PVC+Cd pollution and increased the contents of these soil nutrients. Soil treatment with combined PVC+Cd pollution and PGPR inoculation can affect rhizosphere bacterial communities and change the composition of dominant populations, such as Proteobacteria, Firmicutes, and Actinobacteria. PICRUSt2 functional profile prediction revealed that combined PVC+Cd pollution and PGPR inoculation affected nitrogen fixation, nitrification, denitrification, organic phosphorus mineralization, inorganic phosphorus solubilization and the composition and abundance of genes related the N and P cycles. The Mantel test showed that functional strain abundance, the diversity index and N and P cycling-related genes were affected by test strain inoculation and were significant factors affecting sorghum growth, Cd content and accumulation. This study revealed that soil inoculation with isolated and screened PGPR can affect the soil inorganic nutrient content and bacterial community composition, thereby alleviating the stress caused by CM-HP and providing a theoretical basis and data support for the remediation of CM-HP.

Estuarine mangrove niches select cultivable heterotrophic diazotrophs with diverse metabolic potentials-a prospective cross-dialog for functional diazotrophy.

Biological nitrogen fixation (BNF), an unparalleled metabolic novelty among living microorganisms on earth, globally contributes ~88-101 Tg N year-1 to natural ecosystems, ~56% sourced from symbiotic BNF while ~22-45% derived from free-living nitrogen fixers (FLNF). The success of symbiotic BNF is largely dependent on its interaction with host-plant, however ubiquitous environmental heterotrophic FLNFs face many limitations in their immediate ecological niches to sustain unhindered BNF. The autotrophic FLNFs like cyanobacteria and oceanic heterotrophic diazotrophs have been well studied about their contrivances acclimated/adapted by these organisms to outwit the environmental constraints for functional diazotrophy. However, FLNF heterotrophs face more adversity in executing BNF under stressful estuarine/marine/aquatic habitats. In this study a large-scale cultivation-dependent investigation was accomplished with 190 NCBI accessioned and 45 non-accessioned heterotrophic FLNF cultivable bacterial isolates (total 235) from halophilic estuarine intertidal mangrove niches of Indian Sundarbans, a Ramsar site and UNESCO proclaimed World Heritage Site. Assuming ~1% culturability of the microbial community, the respective niches were also studied for representing actual bacterial diversity via cultivation-independent next-generation sequencing of V3-V4 rRNA regions. Both the studies revealed a higher abundance of culturable Gammaproteobacteria followed by Firmicutes, the majority of 235 FLNFs studied belonging to these two classes. The FLNFs displayed comparable selection potential in media for free nitrogen fixers and iron-oxidizing bacteria, linking diazotrophy with iron oxidation, siderophore production, phosphorus solubilization, phosphorus uptake and accumulation as well as denitrification. This observation validated the hypothesis that under extreme estuarine mangrove niches, diazotrophs are naturally selected as a specialized multidimensional entity, to expedite BNF and survive. Earlier metagenome data from mangrove niches demonstrated a microbial metabolic coupling among C, N, P, S, and Fe cycling in mangrove sediments, as an adaptive trait, evident with the co-abundant respective functional genes, which corroborates our findings in cultivation mode for multiple interrelated metabolic potential facilitating BNF in a challenging intertidal mangrove environment.

Evaluation of Water Quality of Lakhanvaram Lake : A Comparative Study of Three Locations of Lake

The present study evaluated on the quality of Lakhanvaram Lake for two years during 202-23(April to March) and 2023-24(April to March) along with seasonal changes during the period of study. The research focuses on detecting, monitoring, and predicting water quality of lake at three different sites/locations using nineteen parameters viz., pH, Carbonates (CO3),Bicarbonates(HCO3), Chlorides (Cl), Dissolved Oxygen (DO), Biological Oxygen Dissolved (BOD), Organic Matter (OM), Chemical Oxygen Dissolved (COD), (TH), Calcium(Ca), Magnesium(Mg), Total Solids (TS), Total Dissolved Solids (TDS), Total Soluble Salts(TSS), Sulphur (SO4), Phosphorus(PO4), Nitrates (NO3) and Nitrites(NO2). The results demonstrated that Dissolved Oxygen (DO), Biological Oxygen Dissolved (BOD), Organic Matter (OM), Chemical Oxygen Dissolved (COD), (TH), Calcium(Ca), Magnesium(Mg), Total Solids (TS) and Total Dissolved Solids (TDS) increased during rainy season and pH, Dissolved Oxygen (DO), Biological Oxygen Dissolved (BOD) Chemical Oxygen Dissolved (COD) decreased during summer months in both the years of study. It indicated that the overall water quality will improve more if the period is sustained for another 2 to 3 years. The outcomes of the study will help the stakeholders develop effective regulations and strategies for the timely restoration of lake water quality.

Influences of pretreatment methods on the mechanical and environmental behaviors of PG-GGBS-LM ternary stabilizer.

Phosphogypsum is a kind of acidic industrial byproducts with high content of soluble phosphorus and fluorine pollutants, which requires to be pretreated when used as cementitious material to (partial) replace traditional Portland cement. In this study, five different pretreatment methods were proposed for comparative analysis to examine the pretreatment effect on the mechanical and environmental behaviors of ternary phosphogypsum (PG), ground granulated blast-furnace slag (GGBS), and lime (LM) mixed stabilizer. Series laboratory tests, including unconfined compressive strength (UCS), pH, phosphorus (P)/fluorine (F) leaching, scanning electron microscopy (SEM), and X-ray diffraction (XRD) tests, were conducted to comprehend the macro- and microscopic mechanism. The results show that it is essential to grind raw PG to finer powdered state, so that it reacts more easily and quickly with LM and water. In addition, it was noticed that the UCS and P/F leaching concentration are not only affected by the mixing proportion of the PG-GGBS-LM ternary stabilizer, but also by the curing duration. The UCS increases rapidly from initial curing period and then grows slowly after 28days of curing. From the perspective of strength evolution, mixing proportion of PG: GGBS: LM = 15:80:5 is optimal, but considering the economy and environmental related issues, PG: GGBS: LM = 30:65:5 was regarded as a more attractive choice. The findings can provide a reference for the selection of pretreatment methods and design of PG-based cementitious materials suited for stabilized soils.

Effect of Phosphate Rock Powder, Active Minerals, and Phosphorus Solubilizing Microorganisms on the Phosphorus Release Characteristics of Soils in Coal Mining Subsidence Areas

Effect of Phosphate Rock Powder, Active Minerals, and Phosphorus Solubilizing Microorganisms on the Phosphorus Release Characteristics of Soils in Coal Mining Subsidence Areas

Fulvic acid and fermentation agent optimize in situ composting by reducing antibiotic resistance genes abundances and altering succession of bacterial communities

The use of biostimulants to enhance microbial activity has been extensively reported. However, their regulatory properties on the ecological security of in situ composting have not yet been fully elucidated. Here, the effects of two biostimulants (fermentation agent [FM] and fulvic acid [FA]) on in situ composting were investigated under field conditions. The abundances of antibiotic resistance genes (ARGs), as well as those of the microbial communities and the activities of enzymes, were comprehensively investigated. The addition of biostimulants significantly reduced the abundances of streptomycin and sulfonamide resistance genes by 79%–97% and decreased the abundance of Gammaproteobacteria. This was particularly true for species that are members of the Enterobacteriaceae and contain many ARGs. The addition of biostimulants promoted the succession of bacterial communities toward enhancing the solubility of phosphorus, promoting the degradation of aromatic compounds, and reducing the emissions of NOx gas. The application of FA and FM resulted in distinct bacterial network structures, and many negative correlations were associated with ARGs in the temperature subnetwork in the FM treatment. This study provides an effective strategy for the in situ treatment of agricultural waste and underscores the significance of biostimulants in improving the biological safety of medium-temperature in-situ composting.

Drought stress tolerance and metabolomics of Medicago sativa induced by Bacillus amyloliquefaciens DGL1.

This study used Bacillus amyloliquefaciens DGL1 isolated from the arid sandy land of the Qinghai-Tibetan Plateau as the research strain and investigated the effects of DGL1 on the biomass, physiology, and metabolites of Medicago sativa under different intensities of drought stress to provide a high-quality bacterial source and a theoretical basis for the research and development of biological fertilizer suitable for arid areas. The exopolysaccharides (EPS), 1-Aminocyclopropane-1-carboxylate deaminase (ACC), and phosphorus solubilizing capacity of DGL1 were determined. The effects of a DGL1 suspension on alfalfa biomass, physiological indexes, degree of peroxidation of cell membranes, and activity of antioxidant enzymes were determined after irrigating roots under drought stress. The effects on soil physicochemical properties were also evaluated, and metabolomics analysis was performed to explore the effect of DGL1 on the metabolites of alfalfa under drought stress. Strain DGL1 produced extracellular polysaccharide EPS and ACC deaminase and was capable of phosphorus solubilization. Treatment with DGL1 increased the biomass of alfalfa under different degrees of drought stress, significantly increased the activities of alfalfa antioxidant enzymes Super Oxide Dismutase (SOD), Peroxidase (POD), and catalase (CAT), reduced the content of MDA and H2O2, and increased the content of quick-acting phosphorus, quick-acting potassium, ammonium nitrogen, and nitrate nitrogen in the soil, thus improving soil fertility. Through metabolomics analysis, DGL1 was shown to affect amino acid metabolic pathways, such as arginine, leucine, glutamate, and tyrosine, as well as the levels of energy-providing polysaccharides and lipids, in alfalfa under 15% PEG-6000 drought stress, enhancing alfalfa's capacity to resist drought stress. Strain DGL1 enhances the drought suitability of alfalfa and has the potential for dryland development as a biological agent.

High-efficiency anaerobic digestion of soybean curb residue with simultaneous phosphorus recovery by Mg[sbnd]Fe layered double hydroxides addition

Anaerobic digestion of food waste faces several technical problems, such as process failure caused by over-acidification, low heating value of biogas, and high treatment cost of liquid digestate. Layered double hydroxides (LDH) are expected to simultaneously enhance biogas production and quality and immobilize soluble phosphorus in AD due to their excellent anion exchange capability. This study first verified the above hypothesis, indicated by a dramatically enhanced methane yield of 17 folds under a high substrate load and a high quality of generated biogas with 89 % methane content and 90 % lowered hydrogen sulfide. Meanwhile, the soluble phosphorus was efficiently reduced to 3 mg/L after AD. Moreover, the calcined product of LDH showed comparable performance, indicating the possibility of reusing LDH in the AD process. The above results implied the great potential of LDH as a multifunctional material for enhancing the efficiency of waste treatment and energy/resource conversion in the AD process.

Effect of Exogenous Organic Matter on Phosphorus Forms in Middle-High Fertility Cinnamon Soil.

To slow down the chemical fixation of phosphate fertilizer, reduce the risk of active phosphorus leaching, stimulate the inherent phosphorus resource activity of soil, and improve phosphorus supply capacity. This study utilized a combination of field experiments and indoor chemical analysis. Six types of exogenous organic matter (fulvic acid, biochar, compound microbial fertilizer, high-energy microbial inoculum, pig manure-vermicompost, cow manure-vermicompost) were added based on conventional fertilization. The experiment was conducted under the wheat-maize rotation system in the Huang-Huai-Hai region. Compared with control (CK) without exogenous organic matter (EOM), all the other treatments with EOM had an enhancing effect on the available phosphorus of the cultivated soil. During the maize harvest, the combined application of biochar, pig manure-vermicompost and cow manure-vermicompost treatment significantly increased the content of available phosphorus in 0-20 cm soil by 45.87-56.59% compared with CK. The combined application of fulvic acid, biochar, pig manure-vermicompost and cow manure-vermicompost treatment significantly increased the content of Ca2-P in 0-20 cm soil by 34.04-65.14%. The content of Ca10-P in each treatment with EOM exhibited a lower level compared to CK. EOM could slow down the fixation of phosphorus to some degree. Correlation analysis revealed significant associations between Ca2-P, Ca8-P, Al-P, Fe-P, neutral phosphatase activity, acid phosphatase activity, and the available phosphorus content in the soil. The combined application of fulvic acid, biochar, and cow manure-vermicompost could enhance the activity of neutral and acid phosphatase in topsoil to a certain extent, thereby facilitating the conversion of phosphorus into highly available Ca2-P. EOM could enhance the soil phosphorus availability and decelerate the conversion of soil phosphorus into O-P and Ca10-P forms with low availability. Among all treatments, biochar exhibited the most pronounced efficiency in mitigating phosphorus leaching downward. All the EOMs had the potential to enhance the conversion of phosphorus into soluble phosphorus (Ca2-P), thereby mitigating the chemical fixation of soil phosphorus and ameliorating non-point source pollution caused by phosphorus. EOM enhanced the activity of neutral and acid phosphatase, which was beneficial to the conversion of organic phosphorus to inorganic phosphorus and increasing the content of available phosphorus. All EOMs had good effects on the retention of soil effective phosphorus, among which biochar had the best effect on retaining effective phosphorus in the tillage layer and blocking phosphorus leaching downward.