Phosphate Solubilization Research Articles

From Waste to Worth: Using Fermented Orange Pomace in Sustainable Feed Production

Modern agriculture faces the dual challenge of producing environmentally friendly feed while minimizing chemical fertilizers and energy use. This study evaluates the use of orange pomace fermentation liquor (OPFL) as a bio-fertilizer to enhance the growth and nutritional content of sprouted barley for sustainable feed production. We conducted multiple assays to determine OPFL’s growth-promotion potential, including in vitro phosphate solubilization, indole-3-acetic acid (IAA) production, biofilm formation, and antimicrobial effects. Biosafety assays confirmed the absence of coliforms and hemolytic activity. Four barley varieties (Giza 2000, Giza 138, Giza 132, and Giza 126) were treated with OPFL in a hydroponic germination system, with significant improvements observed across several parameters. For example, in Giza 2000, chlorophyll content increased from 4.28 to 4.74, protein content rose from 12.15% to 22.07%, and plant height grew from 13.6 cm to 16.4 cm, representing increases of 10.7%, 81.6%, and 20.6%, respectively. Fresh biomass yield also saw a slight increase, though not statistically significant. This comprehensive evaluation suggests that OPFL is a sustainable alternative to chemical fertilizers, enhancing barley yield and quality in animal feed systems.

Enhancement of the Plant‐Accessible Phosphate Fraction in Sewage Sludge Ashes by Na+ or K+ Addition Prior to Combustion

With the aim of transforming sewage sludge into a P‐fertiliser material in a single combustion step, the chemical processes underlying sewage sludge combustion were analysed using powder X‐ray diffraction (P‐XRD), infrared spectroscopy (IR), thermogravimetric (TGA) as well as elemental analyses (EA). In addition to the combustion of sewage sludge on its own (“mono‐combustion”), additions of different additives prior to the combustion step were also carried out. Based on the very positive effects of the additives sodium and potassium carbonate on the obtained ashes concerning their phosphate solubilities in neutral ammonium citrate (NAC) solution, sewage sludge combustions after additions of Na2CO3 or K2CO3 were investigated in detail. We found that these additions altered the main phosphate‐containing product found in the ashes from whitlockite (Ca9(Mg,Fe)(PO3OH)(PO4)6), a hardly plant‐accessible species, to other phosphate containing compounds such as buchwaldite (CaNaPO4), which is known for a long time as a very good P‑source for plants. Consecutive greenhouse experiments with maize (Zea mays L.) as test plant confirmed the results of the chemical analyses and demonstrated that Na‐ or K‐ashes obtained from a “co‐combustion” of sewage sludge mixed with alkali carbonates exhibit relative P‐fertilising efficiencies of up to ~80 % in comparison to commercial superphosphate.

Isolation and characterization of non-rhizobial bacteria and arbuscular mycorrhizal fungi from legumes

This study investigates non-rhizobial endophytic bacteria in the root nodules of chickpea (Cicer arietinum L), faba bean (Vicia faba), and cowpea (Vigna unguiculata L. Walp), as well as arbuscular mycorrhizal fungi in the rhizospheric soil of chickpea and faba bean. Out of the 34 endophytic bacterial populations examined, 31 strains were identified as non-rhizobial based on nodulation tests. All strains were assessed for their plant growth-promoting (PGP) activities in vitro. The results revealed that most isolates exhibited multiple PGP activities, such as nitrogen fixation, indole-3-acetic acid (IAA) and ammonia (NH3) production, phosphate solubilization, and exopolysaccharide production. The most effective PGP bacteria were selected for 16S rRNA analysis. Additionally, a total of 36 species of native arbuscular mycorrhizal fungi (AMF) were identified. Acaulospora (100%) and Scutellospora (91.66%) were the most prevalent genera in Cicer arietinum L. and Vicia faba L. plants, respectively. Acaulospora also exhibited the highest spore density and relative abundance in both plants. Moreover, the root colonization of Cicer arietinum L. and Vicia faba L. plants by hyphae, vesicles, and arbuscules (HVA) was significant. The findings of this study provide valuable insights into non-rhizobial endophytic bacteria associated with legume root nodules and the diversity of AMF. These organisms have great potential for PGP and can be manipulated by co-inoculation with rhizobia to enhance their biofertilizer effectiveness. This manipulation is crucial for promoting sustainable agriculture, improving crop growth, and advancing biofertilizer technology.

Pengaruh Campuraan Bakteri Pelarut Fosfat dan Bakteri Penambat Nitrogen terhadap Pertumbuhan Tanaman Jagung pada Lahan Kelapa Sawit (Elaeis guineensis Jacq.) Menghasilkan

Intercropped farming utilizez used open spaces as an alternative to making empty land more productive. In certain periods, oil palm plantations have open spaces that can be used for planting intercropped plants. The problem is, in general, that oil palm plantations are planted on marginal land, such as inceptisol that is weak in phosphate, so if they are planted with palm oil, it is necessary to provide fertilizer with the main macro element content for palms to grow optimally, such as phosphorus (P) and nitrogen (N). Efforts can be made to meet the P and N requirements by applying combinations of microorganisms such as phosphate solubilizing bacteria (PSB) and nitrogen-fixing bacteria (NFB). The study aims to find out the effect of various dosages of PSB and NFB combinations on the growth and yield of corn crops, as well as the effect of corn crops on the growth and physiology of palm oil crops. The experiment was conducted at the Ciparanje Experimental Farm, Faculty of Agriculture, Padjadjaran University, January to April 2024. The study used a randomized block design (RBD) with six treatments repeated four times. The treatments included the application of a combination of Pseudomonas sp. and Azotobacter sp., which included: 10 kg/ha of PSB and NFB per plant, 20 kg/ha of PSB and NFB per plant, 30 kg/ha of PSB and NFB per plant, 40 kg/ha of PSB and NFB per plant, and 50 kg/ha of PSB and NFB per plant. Experimental results showed that the PSB and NFB mixture increased crop height 5.28%, stem diameter 3.19%, cob length 9.2%, cob diameter 9.8%, dried weight by 100 seeds 14.5%, and dried weight by corn plant 33.46%. The 40 kg/ha and 50 kg/ha dose of PSB and NFB per plant is the most efficient dose for the growth and of palm oil crops producing 2.

Management of soil phosphorous using phosphate solubilizing microorganisms: A sustainable approach

Phosphorus is crucial for plant growth and productivity, and its scarcity in soil negatively affects crop yields. A major portion of chemical phosphate fertilizer precipitates with soil minerals, making it unavailable for plant growth. Phosphate-solubilizing microorganisms play a pivotal role in enhancing phosphorus availability, facilitating better nutrient absorption, and ultimately boosting plant growth. This article presents a brief overview of the phosphorus status in Indian soil, discusses the various forms of phosphorus and its dynamics across different soil types, and analyses the factors involved, highlighting the importance of phosphorus management for sustainable agriculture. Physiological and molecular mechanisms of microbial phosphate solubilization provide deep insights into exploring PSMs for managing phosphorous in different soil types. It also provides a path for the necessity to explore the multifarious plant growth-promoting traits of PSMs underscoring its applicability for sustainable agricultural practices with viable economy. The mechanism of solubilization of phosphorus has been discussed to understand the role of microorganisms in different soils. The study highlights the role of significant microorganisms in developing tailored consortia of PSMs and other plant growth-promoting rhizobacteria (PGPR) based on the chemical composition of the soil, along with an integrated nutrient approach incorporating PSMs. This review offers valuable insights into harnessing PSMs and their practical applications, facilitating their broader adoption in agricultural systems to maintain soil health.

Impact of Combining Bio-Inoculants along with Inorganic Fertilizers on Soil Biological Characteristics in Transplanted Rice (Oryza sativa L.) Crop

A field experiment was carried out during the Kharif season in the year 2022 to assess the impact of inorganic fertilizers along with Bio-inoculants on soil biological properties in rice (Oryza sativa L.). The experiment consists of seven treatments viz., T1 Control, T2 100% RDF (150, 60, 40 N2, P2O5, K2O kg ha-1), T3 80% RDF + 10 kg BGA ha-1 Soil application + PSB (Phosphate solubilizing bacteria) 3kg/ha, T4 60% RDF + 10kg BGA ha-1 Soil application + PSB, T5 80% RDF + 500kg Azolla ha-1 Soil application +PSB, T6 60% RDF + 500kg Azolla ha-1 Soil application +PSB and T7 10kg BGA ha-1 Soil application + 500kg Azolla ha-1 Soil application + PSB were comprised in Randomized Block Design with three replication. The incorporation of inorganics, Azolla PSB, and BGA (bio-inoculants) actively activated microbial activities, resulting in a greater increase in the populations of total bacteria, actinomycetes, and fungi was observed throughout all growth stages, regardless of the treatments applied, when compared to their initial densities. This phenomenon supports the notion of a stronger rhizosphere effect. This trend aligns with the rise in organic carbon content. Moreover, soil dehydrogenase, alkaline phosphatase activities, along with microbial biomass carbon, displayed an upward trend in tandem with the progressive growth phases of the rice plant.

Two Novel Bacterial Species, Rhodanobacter lycopersici sp. nov. and Rhodanobacter geophilus sp. nov., Isolated from the Rhizosphere of Solanum lycopersicum with Plant Growth-Promoting Traits

Two novel bacterial species were isolated from the rhizosphere of Solanum lycopersicum (tomato plant), both exhibiting plant growth-promoting properties. Two isolated strains, Rhodanobacter lycopersici sp. nov. Si-cT and Rhodanobacter geophilus sp. nov. S2-gT, were classified through a polyphasic approach, confirming their novel status within the Rhodanobacter genus. The strains demonstrated a remarkable tolerance to extreme pH conditions, with R. lycopersici Si-cT surviving in pH 3.0–13.0 and R. geophilus S2-gT tolerating pH 2.0–13.0. Additionally, both strains exhibited multiple plant growth-promoting traits, including indole-3-acetic acid and ammonia production, phosphate solubilization, and siderophore formation. These characteristics suggest that the two strains may play an important role in promoting plant growth, especially in soils with variable pH levels. However, since the direct impact on plant growth was not experimentally tested, the potential of these bacteria for agricultural applications remains to be confirmed through further research. This study expands our understanding of the diversity within the Rhodanobacter genus and provides insights into the potential use of these novel species in sustainable agriculture.

Phosphate-solubilizing fungus (PSF) - mediated phosphorous solubilization and validation through Artificial intelligence computation.

Phosphate-solubilizing fungus (PSF) strain alaromyces funiculosus was investigated for phosphorus solubilization, utilizing a range of pH levels and phosphate sources, followed by data confirmation through artificial intelligence modeling. T. funiculosus strain was exposed to five different phosphate sources [Ca3(PO4)2, FePO4, CaHPO4, AlPO4, and phytin] at different pH levels (4.5, 5.5, 6.5, 7.0, and 7.5). ANOVA, Pareto charts, and normal plots were used for analyzing the data. Artificial intelligence-based multilayer perceptron (MLP), random forest (RF) and extreme gradient boosting (XGBoost) models were used for data validation and prediction. Five-fold more phosphate (P) solubility by T. funiculosus was registered as compared to the control. The maximum soluble P was found at pH 4.5 (318324 ppb) and CaHPO4 (444045 ppb). Combination of phytin × 4.5 pH yielded the highest dissolved phosphorus (1537988 ppb), followed by 127458 ppb from the control × 4.5 pH. Pareto chart and normal plot analysis showedthe negative impact of pH (B), pH × F/C (fungus/control) × P-Source (ABC), and F/C (A) factor. Whereas pH × P-Source (AC) and P-Source (C) has positive impact on P solubility. The maximum R2 scores showed the order of RF (0.944) > MLP (0.938) > XGBoost (0.899). T. funiculosus strain has a grain potential for sustainable use for different types of phosphate sources. Application AI/ML models based on different performance metrics predicted the validated the attained results. In future research, it is recommended to check the efficacy of developed strategy under field conditions and to check the impact on soil and plant.

Implication of phosphate solubilizing microbial formulations on biomass and yield of chickpea (Cicer arietinum)

Implication of phosphate solubilizing microbial formulations on biomass and yield of chickpea (Cicer arietinum)

Outside-in enhancement of phosphate solubilizing bacteria by sludge biochar for phenol remediation in soil: Pollution stress reduction, electron transfer gain and secretion regulation

The high toxicity of phenol poses a significant barrier to bacterial bio-removal capacity. This study innovatively proposes the utilization of sludge biochar (SB) to embed phosphate-solubilizing bacteria (CZB1), creating a composite system (SB-CZB1) that enhances the bio-removal efficiency of phenol. The research findings indicate that after being embedded with biochar, Phosphorus solubilizing bacteria (PSB) achieved a significant enhancement (49.7 %-67.0 %) in phenol removal efficiency across different concentration gradients (1500, 2000, 2500 mg/L). SB component in the SB-CZB1 composite system provides a stable and favorable growth environment for CZB1, significantly enhancing microbial metabolic activity. Notably, it stimulates CZB1 to secrete succinic acid and malic acid (with increases of 3.8 % and 23.9 %, respectively), effectively mitigating the detrimental effects of phenol toxicity on microorganisms. Three-dimensional fluorescence and electrochemical analysis demonstrate that SB not only exhibits exceptional electrochemical performance but also stimulates CZB1 to generate redox-active substances (quinone components in humic acid). The electron transfer rates between microorganisms and phenol in the SB-CZB1 system are 9.75–21.71 times and 23.94–63.95 times higher than those in SB and CZB1 alone, respectively. Meanwhile, the abundant oxygen-containing functional groups (COH/COC, COOH, CO) on the surface of SB-CZB1 play a pivotal role in the adsorption and removal of phenol. Furthermore, pot experiments further reveal that the SB-CZB1 composite system significantly enhances the removal efficiency of phenol in soil (98.1 %). Additionally, the application of SB-CZB1 effectively modulated soil properties, notably increasing available potassium and available phosphorus content by 40.86 % and 136.69 %. This application not only enriched soil microbial diversity but also promoted the proliferation of native organic pollutant remediation bacteria in the soil. Notably, the proliferation of Bacillus species affiliated with CZB1 was the most significant, increasing by 82.1 %. This result confirms that biochar embedding technology effectively enhanced the colonization of CZB1 in the soil, thereby significantly accelerating the bio-removal process of phenol.

Prospects of iron solubilizing Bacillus species for improving growth and iron in maize (Zea mays L.) under axenic conditions

Iron (Fe) deficiency in calcareous soils is a significant agricultural challenge, affecting crop productivity and nutritional quality. This study aimed to isolate, characterize, and evaluate Fe solubilizing rhizobacterial isolates from maize rhizosphere in calcareous soils as potential biofertilizers. Forty bacterial isolates coded as SG1, SG2, …, SG40 were isolated and screened for siderophore production, with ten showing significant Fe solubilizing capabilities. These isolates were further assessed for phosphate solubilization and exopolysaccharides production. The selected bacterial isolates were also screened under axenic conditions for their ability to improve maize growth. The isolates SG8, SG13, SG24, SG30 and SG33 significantly enhanced growth parameters of maize. Notably, SG30 showed highest increment in shoot length (58%), root length (54%), root fresh and dry biomass (67% and 76%), SPAD value (67%), relative water contents (69%), root surface area (61%), and Fe concentration in shoots (79%) as compared to control. The biochemical characterization of these strains showed that all these strains have capability to solubilize insoluble phosphorus, produce indole-3-acetic acid (IAA), and ammonia with catalase, urease and protease activity. Molecular identification through 16s rRNA gene sequencing confirmed high similarity (99.7–100%) of the selected isolates to various Bacillus species, including B. pyramidoids, B. firmicutes, and B. cereus. The study provides a strong base for developing eco-friendly, cost-effective biofertilizers to address Fe deficiency in crops and promote sustainable agriculture.

Plant growth promoting Rhizobacteria for sustainable tomato production

Numerous phosphate solubilizing bacteria (PSB) are found in the rhizosphere, benefiting the host plant in different mechanisms and promoting sustainable agriculture. They improve soil fertility with minimum cost requirements using an eco-friendly approach, which is an essential attribute for small-scale farm production. Thus, isolation, characterization, and evaluation of symbiotic effectiveness are hierarchical procedures to develop bioinoculants. Using a dual (plate and liquid medium) screening technique and a greenhouse trial, four potential PSB strains (Mk-1–25, Mk-13–16, Mk-20–7, and Mk-20–20) were selected from tomato rhizosphere soil. All isolates exhibited the following traits: produced colony clear-zone, lowered liquid medium pH, gram-positive, produced urease and IAA, dissolved substantial P from various substrates, symbiotically effective, and improved tomato growth and yield. Taxonomically, they belong to Bacillus and Priestia species (i.e., Mk-1–25 Bacillus halotolerance, Mk-13–16 Bacillus amyloliquefaciens, Mk-20–7 Bacillus megaterium, and Mk-20–20 Priestia megaterium). Among the current strains, Bacillus halotolerance recorded higher SI (3.11), was able to grow in extreme conditions (10% salt, up to 45 °C), produced HCN and siderophore, and improved tomatoes’ shoot length and weight, in contrast, Mk-20–20 produced HCN, siderophore, was able to fix nitrogen, improved tomato germination, shoot dry weight, and fruit weight. Various P-supplements (Ca3(PO4)2, bonemeal, FePO4, AlPO4, compost, and DAP fertilizer) were added to induce tomato-strain symbiotic interaction; hence, compost substantially promoted the interaction and resulted in higher symbiotic effectiveness. Ca3(PO4)2 was a good media composite preferred by most PSB strains; consequently, a higher concentration (219 µg/ml) of dissolved P was recorded from the liquid medium after 10 days of incubation than other substrates. Based on the data obtained from laboratory and greenhouse trials, the current strains were found to be potential candidate. Future work should confirm their efficacy at the field level using model host crops at different sites to recommend them as farm inputs and biofertilizer.

Interaction with IP6K1 supports pyrophosphorylation of substrate proteins by the inositol pyrophosphate 5-InsP7.

Inositol pyrophosphates (PP-InsPs) are a sub-family of water soluble inositol phosphates that possess one or more diphosphate groups. PP-InsPs can transfer their β-phosphate group to a phosphorylated Ser residue to generate pyrophosphorylated Ser. This unique post-translational modification occurs on Ser residues that lie in acidic stretches within an intrinsically disordered protein sequence. Serine pyrophosphorylation is dependent on the presence of Mg2+ ions, but does not require an enzyme for catalysis. The mechanisms by which cells regulate PP-InsP-mediated pyrophosphorylation are still unknown. We performed mass spectrometry to identify interactors of IP6K1, an enzyme responsible for the synthesis of the PP-InsP 5-InsP7. Interestingly, IP6K1 interacted with several proteins that are known to undergo 5-InsP7-mediated pyrophosphorylation, including the nucleolar proteins NOLC1, TCOF and UBF1, and AP3B1, the β subunit of the AP3 adaptor protein complex. The IP6K1 interactome also included CK2, a protein kinase that phosphorylates Ser residues prior to pyrophosphorylation. We observe the formation of a protein complex between IP6K1, AP3B1, and the catalytic α-subunit of CK2, and show that disrupting IP6K1 binding to AP3B1 lowers its in vivo pyrophosphorylation. We propose that assembly of a substrate-CK2-IP6K complex would allow for coordinated pre-phosphorylation and pyrophosphorylation of the target serine residue, and provide a mechanism to regulate this enzyme-independent modification.

Effects of long-term nitrogen and phosphorus fertilization on soil phosphorus forms and dynamics under continuous wheat production in Saskatchewan, Canada

Many agricultural crops require both nitrogen (N) and phosphorus (P) fertilizers to sustain crop yields. However, long-term application of NH4–N fertilizers can cause soil acidification, which alters soil abiotic and biotic processes, including soil P dynamics. Long-term continuous wheat plots in Saskatchewan, Canada, were used to assess effects of N and P fertilization from 1967 and P fertilizer cessation in subplots from 1995. General soil chemical properties and soil P pools and forms were determined and then correlated with soil pH, total N (TN), and total P (TP) concentrations to show the relative importance on soil P dynamics of (a) crop nutrition (TN and TP); (b) soil acidification (pH); or (c) P fertilization/cessation. Fertilization with NH4–N decreased soil pH and altered exchangeable cation concentrations; however, long-term crop growth was poor in no-N plots and was best with both N and P fertilizers, in turn increasing soil carbon and organic matter. Applying P fertilizers without N increased soluble phosphates and the risk of P losses in runoff. Soil organic P (TPo) concentrations were correlated negatively to pH and positively to TN, but the concentrations of P compounds were not correlated to pH. This suggests that TPo accumulation may be from increased long-term crop residue inputs from crops with N and P fertilizers, rather than increased sorption from reduced pH. However, soil pH will continue to decrease with continued NH4–N fertilization, affecting soil chemistry and future P cycling; monitoring with a suite of wet chemistry and spectroscopic techniques is recommended.

Isolation and Identification of Multi-Traits PGPR for Sustainable Crop Productivity Under Salinity Stress

High salinity poses a significant threat to arable land globally and contributes to desertification. Growth-promoting rhizobacteria assist plants in mitigating abiotic stresses and enhancing crop productivity through the production of siderophores, exopolysaccharides (EPS), solubilisation of phosphate, indole-3-acetic acid (IAA), and other secondary metabolites. This study aimed to isolate, identify, and characterise bacteria that exhibit robust growth-promoting properties. A total of 64 bacterial isolates from the rhizosphere of Miscanthus sinensis were evaluated for plant growth-promoting (PGP) traits, including IAA, EPS, siderophores, and solubilisation of phosphate. Among them, five isolates were selected as plant growth-promoting rhizobacteria (PGPR) based on their PGP features and identified via 16S rRNA sequencing: Enterococcus mundtii strain INJ1 (OR122486), Lysinibacillus fusiformis strain INJ2 (OR122488), Lysinibacillus sphaericus strain MIIA20 (OR122490), Pseudomonas qingdaonensis strain BD1 (OR122487), and Pseudomonas qingdaonensis strain MIA20 (OR122489), all documented in NCBI GenBank. BD1 demonstrated a higher production of superoxide dismutase (SOD) (17.93 U/mg mL), catalase (CAT) (91.17 U/mg mL), and glutathione (GSH) (0.18 U/mg mL), along with higher concentrations of IAA (31.69 µg/mL) and salicylic acid (SA) (14.08 ng/mL). These isolates also produced significant quantities of amino and organic acids. BD1 exhibited superior PGP traits compared to other isolates. Furthermore, the NaCl tolerance of these bacterial isolates was assessed by measuring their growth at concentrations ranging from 0 to 200 mM at 8-h intervals. Optical density (OD) measurements indicated that BD1 and INJ2 displayed significant tolerance to salt stress. The utilisation of these isolates, which enhances plant growth and PGP traits under salt stress, may improve plant development under saline conditions.

The Ability of Endophytic Bacteria in Phosphate Solubilization and IAA Production on Chili Plant Growth

Biofertilizer is considered an alternative to chemical fertilizers for enhancing plant productivity while minimizing ecological damage. Endophytic bacteria have the ability to solubilize phosphate and produce IAA (indole acetic acid). The aim of this research is to assess the phosphate solubilization and IAA production abilities of bacterial isolates applied to chili plants. Seven bacterial isolates collection from the Microbiology Laboratory, Universitas Sumatera Utara, were tested. In quantitative tests conducted in vitro, isolates MB10 and MB11 demonstrated the highest phosphate solubilization capabilities, yielding solubilization indices of 16.2 mm and 9.5 mm, respectively. Additionally, the ability of bacterial isolates to produce IAA in vitro was evaluated using calorimetry, revealing that isolates MB8 and MB2 produced the highest concentrations of IAA, measuring 58.58 ppm and 54.64 ppm, respectively. Furthermore, in vivo application involved the inoculation of isolates MB10 and MB11 on chili plants for 30 days. Seed treatment with suspensions of isolates MB10 and MB11 resulted in decreased plant performance compared to the control. These findings indicate that some endophytic bacteria originating from the mangrove root Avicennia marina have potential for producing relatively high levels of secondary metabolites. However, direct application did not significantly enhance plant growth performance.

Hydroponic Lettuce Cultivation with Organic Liquid Fertilizer: Examining Bacterial Inhibition and Phosphate Solubilization

This study explores organic hydroponic cultivation as a sustainable alternative to chemical fertilizers amid global supply challenges. With rising costs and the depletion of conventional nitrogen sources, organic liquid fertilizers are gaining attention for their microbial enrichment processes (MEP) that convert organic matter into plant-accessible nutrients. This experiment focuses on lettuce cultivation using two organic liquid fertilizers, Power Fish and POF vol. 2, in controlled environments. The results show that there are significant differences in plant growth parameters such as leaf number, fresh weight, chlorophyll content, and root length across different fertilizer treatments. Key findings include that effective management practices, including pH control and regular nutrient application, are crucial for maintaining microbial activity and optimizing nutrient uptake efficiency. Additionally, Bacillus sp. and Xanthomonas sp. were isolated from these fertilizers and dual-cultured with rot fungi, Pythium sp. and Fusarium sp. This dual cultivation demonstrated inhibitory activity against these pathogens, showcasing the potential of these microorganisms in promoting biofilm-mediated disease resistance in organic hydroponic systems. The study also emphasizes the phosphate solubilization capabilities of isolated bacteria, essential for sustainable nutrient cycling. Overall, organic hydroponic systems present a promising strategy for sustainable agriculture, reducing dependency on chemical inputs while enhancing crop productivity and resilience to environmental stressors.

Co-applied biochar and drought tolerant PGPRs induced more improvement in soil quality and wheat production than their individual applications under drought conditions.

Plant growth and development can be greatly impacted by drought stress. Suitable plant growth promoting rhizobacteria (PGPR) or biochar (BC) application has been shown to alleviate drought stress for plants. However, their co-application has not been extensively explored in this regard. We isolated bacterial strains from rhizospheric soils of plants from arid soils and characterized them for plant growth promoting characteristics like IAA production and phosphate solubilization as well as for drought tolerance. Three bacterial strains or so called PGPRs, identified as Bacillus thuringiensis, Bacillus tropicus, and Bacillus paramycoides based on their 16S rRNA, were screened for further experiments. Wheat was grown on normal, where soil moisture was maintained at 75% of water holding capacity (WHC), and induced-drought (25% WHC) stressed soil in pots. PGPRs were applied alone or in combination with a biochar derived from pyrolysis of tree wood. Drought stress substantially inhibited wheat growth. However, biochar addition under stressed conditions significantly improved the wheat growth and productivity. Briefly, it increased straw yield by 25%, 100-grain weight by 15% and grain yield by 10% compared to the control. Moreover, co-application of biochar with PGPRs B. thuringiensis, B. tropicus and B. paramycoides further enhanced straw yield by 37-41%, 100-grain weight by 30-36%, and grain yield by 22-22.57%, respectively. The co-application also enhanced soil quality by increasing plant-available phosphorus by 4-31%, microbial biomass by 33-45%, and soil K+/Na+ ratio by 41-44%. Co-application of PGPRs and biochar alleviated plant drought stress by improving nutrient availability and absorption. Acting as a nutrient reservoir, biochar worked alongside PGPRs, who solubilized nutrients from the former and promoted wheat growth. We recommend that the co-application of suitable PGPRs and biochar is a better technology to produce wheat under drought conditions than using these enhancers separately.

Isolation and Characterization of Arsenic-Tolerable Bacteria from Groundwater and Their Implementation on Rice Seedling's Shoot and Root Enhancement.

Arsenic exerts detrimental impacts on primary metabolism in plants, leading to reduced crop yield. Some arsenic-resistant plant growth-promoting bacteria (PGPB) help plants by providing some plant hormones to sustain their growth and development under arsenic stress. Here, seven different species of Bacillus were isolated from arsenic-contaminated groundwater of West Bengal, India. Those species were capable of growing in the presence of > 3.12g/L arsenate (AsV) and > 0.65g/L arsenite (AsIII) salts and also resist different heavy metals like Cu2+, Fe2+, Co2+, Zn2+, Pb2+, etc. They were susceptible to multiple groups of antibiotics like beta-lactam, aminoglycosides, etc. All species were capable of detoxifying arsenite and influenced rice seedlings' growth in the presence of arsenic salts by their capabilities likenitrogen-fixing ability, phosphate solubilization, indole 3-acetic acid (IAA), gibberellic acid (GA), proline production, etc. Most species helped enhance root and shoot lengths under arsenic stress. These primary findings suggest that those Bacillus spp. could be used as potential bio-fertilizers in arsenic-contaminated agricultural fields.

Biofertilizers: A sustainable strategy for enhancing physical, chemical, and biological properties of soil

A biofertilizer is a biologically derived substance that can enhance soil fertility. It is beneficial for enhancing soil fertility by introducing microorganisms that produce organic nutrients and perhaps decreasing plant illnesses. An extensive review was done to examine the efficacy of several biofertilizers in improving soil properties, including their physical, chemical, and biological characteristics. The secondary data and material for the article were gathered from a variety of sources, including government reports, published research papers, reports from various organizations, and pertinent websites that were examined and their conclusions presented. Although biofertilizers have proven to be a very sustainable method for improving soil quality and increasing crop output, there is a lack of extensive research on their effects on soil’s physical, chemical, and biological aspects. This study aims to offer a comprehensive understanding of various biofertilizers and their effects. This investigation indicated that biofertilizers such as Nitrogen-fixing bacteria, phosphate solubilizers, and potassium solubilizers help to increase NPK content in the soil leading to an increase in the productivity of soil. Moreover, biofertilizers help to enhance soil physical properties (soil bulk density, soil moisture, soil temperature, and soil color), chemical properties (soil pH, soil nitrogen content, soil phosphorus content, soil potassium content, and soil organic carbon content), and chemical properties (population of bacteria, fungi, and actinomycetes). Overall, by overcoming the challenges with biofertilizers in agriculture, we can attain agricultural sustainability.