Phosphorus Solubilizing Bacteria Research Articles

Barley Growth and Phosphorus Uptake in Response to Inoculation with Arbuscular Mycorrhizal Fungi and Phosphorus Solubilizing Bacteria

ABSTRACT Biostimulants and bioinoculants offer the potential to enhance nutrient use efficiency within agricultural cropping systems and thus reduce the amount of mineral fertilizers needed to support crop growth. Considerable uncertainty, however, exists about their efficacy under different management regimes. The present field-based study investigated the effects of phosphorus (P) solubilizing bacteria (PSB) and mycorrhizal (AMF) inoculants in the presence of a range of mineral-based P fertilizers, including triple superphosphate (TSP), struvite and rock phosphate (RP), on the growth, yield, and P uptake of barley (Hordeum vulgare L.). Two consecutive field experiments performed in a low P soil (Eutric Cambisol) revealed that the bioinoculants (PSB and AMF) promoted plant P uptake and grain yield. Moreover, in comparison to P fertilizers lacking bio-inoculants, the application of external P sources combined with bio-inoculants led to significant increases in leaf P concentration, total P uptake, plant dry matter, grain P concentration, and crop yield. Grain yield significantly correlated with P uptake by roots and above-ground parts (i.e. stems, leaves, and spikes) as well as grain P concentration in both seasons. It is concluded that bioinoculants can help improve sustainable P use ultimately leading to greater sustainability of cropping systems and resilience in soil P cycling.

Screening of rhizosphere nitrogen fixing, phosphorus and potassium solubilizing bacteria of Malus sieversii (Ldb.) Roem. and the effect on apple growth

Nitrogen, phosphorus and potassium inorganic fertilizers are commonly used when growing apples, but their excessive application has resulted in a decline in soil fertility and therefore an inability to maintain sustainable cultivation systems. It is possible to compensate for this with biofertilizers. Nitrogen-fixing, phosphorus solubilizing, and potassium solubilizing bacteria are biofertilizers with a broad range of possible uses. In this study, beneficial microorganisms were screened from the rhizosphere soil of the apple tree, Malus sieversii (Ldb.) Roem., which is rich in microbial diversity in natural environments. It was essential to investigate their effects on the growth of apple seedlings. Eight populations of organic phosphorus solubilizing bacteria (56), inorganic phosphorus solubilizing bacteria (13), nitrogen-fixing bacteria (22), and potassium solubilizing bacteria (24) were isolated from eight populations of Xinjiang wild apple rhizosphere in Ili by medium culture. Their morphological characteristics were recorded and their activity was determined. The most active strains were Pseudomonas migulae, Pseudomonas poae, and Pseudomonas extremaustralis, which was determined by physiological and biochemical properties and 16S rDNA sequence analysis. The L16 (45) orthogonal experiment, which used the three strains as testing materials, was created to assess the effects of the strains on apple physiological indicators, soil nutrients, leaf nutrients, and biomass, as well as to identify the ideal combination, concentration, timing, and application method. The results indicated that the peroxidase (POD) and catalase (CAT) activities of apple seedlings increased significantly under the 10 treatment, and the (SOD) activities of the 0 (control) and 1 (inorganic fertilizer only) treatments were significantly lower than the other treatments; soluble sugar, soluble protein and chlorophyll contents increased in all treatments compared to 0 and 1, while malondialdehyde and proline contents increased or decreased compared to 0 and 1; apple seedlings in treatment 10 had the highest soil N, P, and K content, leaf N, P, and K content and biomass were also all highest in treatment 10. In summary, the strains screened for the test can be used as biofertilizers and the optimum application was determined for treatment 10, meaning that the results also provide a theoretical basis for their application in artificially grown orchards.

Identification, functional annotation, and isolation of phosphorus-solubilizing bacteria in the rhizosphere soil of Swida wilsoniana (Wanger) Sojak

The Swida wilsoniana, a remarkable woody oil tree species of immense ecological and economic significance, encounters limitations in its production within southern China due to the scarcity of available phosphorus (AP) in red soil. In this study, we employed methods encompassing microbial diversity and metagenomic analysis to explore the composition as well as functional disparities among rhizosphere microbial communities associated with S. wilsoniana exhibiting varying growth potentials in red soil. In this study, microbial diversity and metagenomic analysis methods were used to investigate the composition of and functional differences among the rhizosphere microbial communities of S. wilsoniana with different growth potential in red soil. The results showed that the AP content of the rhizosphere soil of dominant trees (DTs) was higher than that of recessive trees (RTs). Three dominant phyla were identified in the rhizosphere soil of S. wilsoniana, including Proteobacteria, Actinobacteria, and Acidobacteria. Fifteen microbial communities involved in 23 metabolic activities were significantly correlated with AP content (P ≤ 0.05). A total of 55 strains of phosphorus-solubilizing bacteria were isolated from the rhizosphere soil of S. wilsoniana. Among these, SwB16 exhibited the highest efficiency in solubilizing phosphorus, with a phosphorus solubilization capacity of up to 347.23 mg·L−1. Pot experiments showed that SwB16 has the potential to promote plant growth and therefore could be used as a biofertilizer for S. wilsoniana.

Nodulation, Yield and Economics of Machine Planted Chickpea (Cicer arietinum L.) under Varied Spacing and Nutrient Management

Background: Among the agronomic practices, optimum plant population and balanced nutrient management are pivotal for enhanced pulse production besides ensuring soil health. Methods: Present study was conducted during rabi 2020-21 and 2021-22 in split plot design with four main plots viz; seed rate (52, 70, 77 and 105 kg ha-1) and seven sub-plot nutrient management practices viz., N1- absolute control , N2- 75% RDF, N3- 100% RDF (20:50:20 kg N, P2O5 and K2O ha-1), N4 -125 % RDF, S5- 75% RDF + soil application of microbial consortia (Azotobacter + Phosphorus solubilizing bacteria (PSB) + Potassium releasing bacteria (KRB)+ Zinc solubilizing bacteria (ZnSB) @ 5 kg ha-1), N6- 100 % RDF + MC and N7- 125% RDF + MC. Result: Higher nodulation, seed yield (25.8 q ha-1) and economics (net returns ₹ 88807 ha-1 and B-C ratio 2.92) were registered with seed rate of 105 kg ha-1. However, protein content of chickpea was better with seed rate of 52 kg ha-1. Among the nutrient management treatments, crop growth, nodulation, seed yield (25.8 q ha-1) and economics (net returns ₹ 84388 ha-1 and B-C ratio 2.90) were found to be better with application of 125% RDF + Microbial consortia. Significant and positive correlation was found between the parameters at p less than 0.01.

Phosphorus-solubilizing bacteria improve the growth of Nicotiana benthamiana on lunar regolith simulant by dissociating insoluble inorganic phosphorus

In-situ utilization of lunar soil resources will effectively improve the self-sufficiency of bioregenerative life support systems for future lunar bases. Therefore, we have explored the microbiological method to transform lunar soil into a substrate for plant cultivation. In this study, five species of phosphorus-solubilizing bacteria are used as test strains, and a 21-day bio-improving experiment with another 24-day Nicotiana benthamiana cultivation experiment are carried out on lunar regolith simulant. We have observed that the phosphorus-solublizing bacteria Bacillus mucilaginosus, Bacillus megaterium, and Pseudomonas fluorescens can tolerate the lunar regolith simulant conditions and dissociate the insoluble phosphorus from the regolith simulant. The phosphorus-solubilizing bacteria treatment improves the available phosphorus content of the regolith simulant, promoting the growth of Nicotiana benthamiana. Here we demonstrate that the phosphorus-solubilizing bacteria can effectively improve the fertility of lunar regolith simulant, making it a good cultivation substrate for higher plants. The results can lay a technical foundation for plant cultivation based on lunar regolith resources in future lunar bases.

Isolation and Optimization of Phosphorus Solubilizing Bacteria from Maize Rhizosphere in Nasarawa State, Nigeria

Phosphorus solubilizing bacteria (PSB) are a type of plant growth-promoting rhizobacteria which has the ability to convert insoluble phosphate into plant available forms. They are used as biofertilizers to restore soil health and fertility. In the present investigation, isolation, characterization and optimization of phosphate solubilizing activity of these microbes at different pH, temperature and carbon source was carried out. Eight phosphorus solubilizing rhizospheric bacteria (PSRB) isolates isolates were recovered from different farms in six local government from maize rhizosphere using the spread plate method on Pikovskaya agar. Amongst these eight isolates, five were recovered from Lafia local government while three were recovered from Kokona local government with the development of a prominent halozone. All isolates were morphologically characterised, amplified, and sequenced for taxonomic identification using 16S primers. The results indicated they belong to member of the genus Acinetobacter, Ochrobactrum, Brucella, Curtobacterium, Leifsonia and Microbacterium respectively. These strains when grown at different conditions of external carbon sources, temperature and pH showed highest phosphorus solubilizations of 326.23 µg/ml ± 0.21 at 30 °C, 325.50µg/ml ± 1.13 at a pH of 7 and 320.30µg/ml ± 0.36 with glucose as carbon source. The results from these findings could indicate the use of these isolate as trial biofertilizers on the field which will help improve crop yield and enhance plant growth promotion

Deciphering the role of phosphorus management under conservation agriculture based wheat production system

Phosphorus (P) is a vital element required by all living organism (plants, animals and microbes etc.). Its application in agriculture, whether in conventional or conservation agriculture, requires careful attention due to its low use efficiency, which typically does not exceed 20%. With the increasing acceptance of conservation agriculture (CA), it is crucial to develop protocols for P management to ensure sustainable wheat production. Therefore, a field trial was conducted from 2016–2017 to 2017–2018 in the India's semiarid eco-region to study the role of P on wheat productivity, quality, and resource use efficiency under CA-based production system. We assessed the impact of tillage operations and P management practices on wheat productivity, quality, and resource use efficiency. Three tillage and residue management options such as CT-R (conventional tillage without residue); NT-R (no tillage without maize residue) and NT + R (no tillage with maize residue @ 2.5 Mg ha−1) were laid-out in main plot and five P management options subplots viz. P1 (nitrogen and potash according to recommended but not P); P2 (17.2 kg P ha−1); P3 (17.2 kg of P ha−1 + microbial fertilizer); P4 (17.2 kg P ha−1 + compost inoculant culture) and P5 (34.4 kg P ha−1) in split plot design with three replicates. The results indicates that the combination of no-tillage with residue retention (maize residue @ 2.5 Mg ha−1) (NT + R) and the application of 34.4 kg P ha−1 (P5) significantly improved grain yield by ~43.2% compared to the control treatment (conventional tillage with no residue, CT – R, and no phosphorus application). NT + R also resulted in significantly better amino acid (~22.7%) and net protein yield (~21.2%) compared to CT – R. Regarding the P management strategy, the highest amino acid (49.1%) and protein yield (12.5%) were observed under the P5 treatment compared to the no-phosphorus treatment. Conjoint use of NT – R, along with the application of 17.2 kg P ha−1 and PSB (Phosphorus Solubilizing Bacteria), resulted in a significant increase in energy use efficiency of ~58% over other treatments combination. Furthermore, the NT + R plot that received 17.2 kg P ha−1 + PSB demonstrated higher P agronomic efficiency (~43%) and recovery efficiency (~53%) over control. The study's findings underscore the significance of adopting efficient P management strategies in CA to ensure the sustainable production of wheat.

Monitoring the effect of integrated nutrient management practices on soil health in maize-based cropping system

IntroductionSoil organic matter (SOM) plays a vital role in enhancing soil characteristics and promoting sustainable crop production. The active and passive components of SOM tend to be more effective indicators of soil changes than total SOM content.MethodsThis study aimed to examine the impact of integrated nutrient management (INM) on the active and passive segments of SOM in maize during the kharif seasons of 2019 and 2020 at the Instructional Farm of Rajasthan College of Agriculture, Udaipur. A total of 11 treatments comprising of control (no application of manures/fertilizers/biofertilizers), different INM combinations, and application of inorganic fertilizers were laid in a randomized block design (RBD) with three replications tested in this study.ResultsThe use of INM through enriched phosphorus compost (EPC), biofertilizers, and chemical fertilizers significantly boosted both the active and passive constituents of the organic matter of the soil. In this study, a combination of 75% NPK fertilizers via soil test response (STR), EPC @ 5 t ha−1, an Azotobacter consortium, phosphorus solubilizing bacteria (PSB), and a foliar spray of 0.5% Zn considerably increased the active fraction of SOM than other treatments as indicated by microbial biomass carbon (251 mg kg−1), microbial biomass nitrogen (36.8 mg kg−1), microbial biomass phosphorus (6.82 mg kg−1), water-soluble organic carbon (73.9 mg kg−1), water-soluble carbohydrates (43.8 mg kg−1), presence of dehydrogenase in soil (6.82 μg TPF g−1 soil 24 h−1), and carbon mineralization (43.8 mg CO2C kg−1 soil 24 h−1). This treatment was also found to increase the passive fraction as shown by the presence of humic acid (0.332%), fulvic acid (0.210%), hymatomelanic acid (0.052%), brown humic acid (0.252%), and humin (0.604%).DiscussionFrom this study, it can be concluded that the application of 75% NPK fertilizers as per STR + EPC + Azotobacter + PSB + 0.5% foliar Zn spray can improve soil health in maize-based cropping systems.

Effect of Phosphorus Solubilizing Bacteria in Combination with Poultry Manure on Soil Health and Sugarbeet Productivity under Arid Climate

Sustainable agricultural productivity is under threat due to lack of interest in the use of bio-organic fertilizers to alleviate drawbacks of conventional agricultural practices. Phosphorus solubilizing bacteria plays vital role in improving phosphorus availability to plants through slowly release from inorganic and organic soil phosphorus budgets by solubilization and mineralization. Furthermore, phosphorus solubilizing bacteria in combination with poultry manure has great potential to improve phosphorus uptake, growth and development of the plants. Firstly, a pot experiment consisted of seven strains of phosphorus solubilizing bacteria (PSB) with one control (un-inoculated) were used using completely randomized design (CRD) for 55 days screening trial to screen out the efficient phosphorus solubilizing bacterial strains. Secondly, a field experiment was performed in a randomized complete block design (RCBD) at Research Farm of College of Agriculture, Bahauddin Zakariya University, Bahadur Sub Campus Layyah, South Punjab-Pakistan during 2019-2020 to explore the effect of screened efficient phosphorus solubilizing bacterial strains; PSB0=No inoculation; PSB2=Bacillus spp. PSB2, PSB3=Bacillus spp. PSB3, PSB5=Bacillus spp. PSB5, PSB6=Bacillus spp. PSB6 in combination with poultry manure; PM0= without poultry manure and PM1= with poultry manure (20 t ha-1) on growth and yield traits of sugarbeet, and rhizosphere soil health indicators. Results regarding pot experiment showed that phosphorus solubilizing bacterial strains PSB2, PSB3, PSB5 and PSB6 had great potential to improve growth traits of sugarbeet crop and screened as efficient phosphorus solubilizing bacterial strains. Results of field experiment revealed that the combined application of efficient phosphorus solubilizing bacterial strains (PSB2 and PSB5) with poultry manure (20 t ha-1) produced the highest growth, and yield traits of sugarbeet crop, and rhizosphere soil health indicators.Our findings suggest that the combined application of efficient phosphorus solubilizing bacterial strains (PSB2 and PSB5) with poultry manure (20 t ha-1) is a promising and viable option to achieve the maximum sugarbeet productivity under changing environmental scenarios.

Phosphorus accumulation aggravates potato common scab and to be controlled by phosphorus-solubilizing bacteria

Phosphorus accumulation aggravates potato common scab and to be controlled by phosphorus-solubilizing bacteria

Effects of phosphate-solubilizing bacteria on phosphorus components, humus and bacterial community metabolism during spent mushroom substrate composting

To address the low conversion of effective phosphorus during previous studies on spent mushroom substrate (SMS) composting, phosphorus-solubilizing bacteria (PSB) were utilized to increase the effective phosphorus content in this study. The results demonstrated that PSB treatments exhibited higher temperature levels up to 66 °C. The TN, NH4+-N, and NO3−-N contents were higher than those of the control treatment (CK) by 9.01%, 50.01%, and 4.61%, respectively. Inoculation with PSB increased effective phosphorus, total phosphorus, and humus content in the SMS compost by 6.84%, 11.05%, and 9.10%. In addition, based on PICRUSt analysis, inoculation with PSB significantly promoted metabolic pathways associated with phosphorus conversion or the production of substances that can facilitate phosphorus conversion or phosphorus leaching, thus improving phosphorus utilization in compost. In conclusion, the addition of PSB can improve the bioavailability of P and the humus content in SMS compost to realize the green and sustainable development of the edible mushroom industry.

Integrated Effect of Heavy Metal-Tolerant Rhizobacteria and Phosphorus on Maize Growth and Phosphorus Bioavailability in Contaminated Soil

Toxic metals significantly influence agricultural crop yields and adversely affect animals and humans. Hence, in the current study impact of different strains of phosphorus-solubilizing bacteria (PSB) and levels of phosphorus on the solubility of phosphorus and the stabilization of heavy metals in contaminated soil were studied in a greenhouse pot experiment in 2022. The PSB strains included Bacillus CUM6, Bacillus DUM7, and Bacillus PIS7. Phosphorus was applied at rates of 40, 60, and 80 kg P2O5 ha-1 using single superphosphate, with a basal dose of 120 kg N and 60 kg K2O ha-1. The experiment followed a randomized, two-factorial design. Maize plants (variety "Azam") were inoculated with the PSB strains. Consequently, combining Bacillus PIS7 with 80 kg P2O5 ha-1 significantly increased both fresh and dry maize biomass (35.33 and 24.56 g pot-1) compared to the control (unspiked soil). Phosphorus bioavailability (7.07 and 5.14 mg kg-1) significantly improved with 80 kg ha-1 phosphorus and Bacillus PIS7. Heavy metal concentrations in soil (Cd, Pb, Cr, and Ni) decreased significantly at 80 kg ha-1 phosphorus and Bacillus PIS7, and Cd concentrations in plants decreased to 3.31 mg kg-1 with Bacillus DUM7 and to 2.96, 0.42, and 1.33 mg kg-1 with Bacillus PIS7. The application of PSB strains and phosphorus fertilizer reduced heavy metal concentrations. Notably, 80 kg P2O5 ha-1 with Bacillus PIS7 showed the best performance. Phosphorus uptake increased significantly (0.106 mg pot-1), while heavy metal uptake (Cd, Pb, and Cr) decreased linearly with increasing phosphorus levels and PSB strains. Bacillus PIS7 with 80 kg P2O5 ha-1 had the lowest heavy metal translocation, doing better than the control and other PSB strains (Bacillus CUM6 and Bacillus DUM7). Soil characteristics indicated increased organic matter content (0.73%) and decreased pH (7.61) and electrical conductivity (0.17 dSm-1) with applied phosphorus and PSB strains, suggesting enhanced phosphorus bioavailability and reduced heavy metal concentrations. In conclusion, adding 80 kg P2O5 ha-1 with Bacillus PIS7 helps plants grow better when they are stressed by heavy metals and keeps Cd, Pb, Cr, and Ni stabilized in the soil.

Effect of Photosynthetic Bacteria, Vermiwash and Phosphorus Solubilizing Bacteria on Growth, Yield and Quality of French Bean (Phaseolus vulgaris L.)

The present investigation was carried out with title ‘Effect of Photosynthetic bacteria, Vermiwash and Phosphorus Solubilizing Bacteria on growth, Yield and Quality of French bean (Phaseolus vulgaris L.)’ at the Central Research Farm, Department of Horticulture, Naini Agricultural Institute, Sam Higginbottom University of Agriculture Technology and Sciences, Prayagraj, Uttar Pradesh during the 2021-22 with a view to identify the effects of different combinations of biofertilizers and organic nutrition and its role in growth, yield and quality of French bean variety Lakshmi. The experiment was laid in Randomized block design with 7 treatments and 3 replications with different combination in Biofertilizers and application of organic nutrition. Under this experiment, overall, 7 treatment was taken T1 (Photosynthetic Bacteria @ 30 ml/ m2 (PSB-1)), T2 (Vermiwash @ 40 ml/ m2 (VW)), T3 (Phosphate Solubilizing Bacteria (30 ml/ m2) (PSB-2)), T4 (PSB-1 + VW (40 each ml/ m2)), T5 (PSB-1 + PSB-2 (30 ml/ m2)), T6 (PSB-2 + VW (40 ml/ m2)) and T0 (Control). From the above experimental finding it was concluded that the treatment T5 (PSB-1 + PSB-2 (30 ml/ m2) was found to be best in the terms of growth parameters like plant (240.51 cm), plant spread (1984.64 cm2), earliness parameters like days to first flowering (54.33 days), days to 50% flowering (64.67 days), days to first pod setting (59.78 days) and days to first pod picking (67.47 days). T5 (PSB-1 + PSB-2 (30 ml/ m2) was also found best in terms of yield parameters like number of pods per plant (132.33 pods), pod length (13.73 cm), pod width (10.11 mm), individual pod weight (7.99 g), yield per plant (1.04 kg/plant) and yield per hectare (12.53 t/ha) of French bean. Therefore, Treatment combination of biofertilizers T5 (PSB-1 + PSB-2 (30 ml/ m2) can be suggested for better yield achievement in French bean.

Effects of Rhizophagus intraradices and Acinetobacter calcoaceticus on Soybean Growth and Carbendazim Residue

In agricultural production, carbendazim and other pesticides are used to prevent soybean root rot. However, carbendazim degrades slowly and affects a series of biochemical processes such as soil biological nitrogen fixation and soil nutrient activation in the natural environment. This study mainly investigated the effects of Rhizophagus intraradices, Acinetobacter calcoaceticus, and carbendazim on soybean biomass, the incidence of root rot, the total number of bacterial colonies and phosphorus-solubilizing bacteria in rhizosphere soil, and carbendazim residue in soybean grains and rhizosphere soil. The results showed that the arbuscular mycorrhizal fungi (AMF) spore density, AMF infection rate, soybean biomass, nodule number, total bacterial colonies, and phosphorus-solubilizing bacteria colonies in the soybean rhizosphere soil were the highest in the R. intraradices and A. calcoaceticus treatment groups under natural soil conditions. Moreover, the incidence of root rot and carbendazim residue in soybean grains and rhizosphere soil were the lowest in the R. intraradices and A. calcoaceticus treatment group under natural soil conditions. This result indicated that R. intraradices and A. calcoaceticus can effectively reduce carbendazim residue in soybean grains and rhizosphere soil. This study provided theoretical support for the development of microbial fertilizer and microbial degradation of pesticide residues and improved the practical basis for ensuring food safety.

Inference of Rock Phosphate, Phosphorus Solubilizing Bacteria and Lime on Phosphorus Content and Economic Yield of Green Gram

Aim: To study the effect of Rock Phosphate, Phosphorus Solubilizing Bacteria, and Lime on phosphorus content in the soil, Phosphorus Uptake, and Economic yield of green gram (var. DGGS-4).
 Study Design: This experiment was conducted through a completely randomized design with 10 treatments and 3 replications.
 Place and Duration of Study: The research was conducted at the Department of Soil Science and Agricultural Chemistry, Central Agricultural University, Imphal between February 2019- November 2019.
 Methodology: Available phosphorus content in soil was estimated spectrophotometrically by Bray and Kurtz No. 1 method, the Active Phosphorus was determined by the addition of Saloid-bound phosphate, Aluminum phosphate, iron phosphate, and calcium phosphate, and total Inorganic P is the summation of all the inorganic forms of P. Total Phosphorus (Total P) in Soil was estimated by using Murphy-Riley solution and 5M NaOH and the intensity of yellow color was read at 730 nm in a spectrophotometer, organic P was calculated from the difference between total phosphorus and total mineral P, and the uptake of phosphorus was computed from the data on P concentration and dry matter yield.
 Results: The release and fixation pattern of different forms of phosphorus, its uptake, and the economic yield of green gram were significantly affected by the application of rock phosphate singly or combination with PSB and lime. Comparing among the different treatments, significantly higher accumulation of available Phosphorus, Phosphorus uptake, and economic yield were recorded in soil treated with Rock phosphate in combination with Phosphocare, Bacillus megatherium, and lime which is at par with treatment with Rock phosphate in combination with Bacillus megatherium and lime.
 Conclusion: The investigation revealed that the release and fixation pattern of different forms of phosphorus, its uptake, and the yield of green gram are significantly affected by the application of RP singly or combination with PSB and lime.

Metal oxide modified biochars for fertile soil management: Effects on soil phosphorus transformation, enzyme activity, microbe community, and plant growth

Metal oxide modified biochars are increasingly being used for intensive agricultural soil remediation, but there has been limited research on their effects on soil phosphorus transformation, soil enzyme activity, microbe community and plant growth. Two highly-performance metal oxides biochars (FeAl-biochar and MgAl-biochar) were investigated for their effects on soil phosphorus availability, fractions, enzyme activity, microbe community and plant growth in two typical intensive fertile agricultural soils. Adding raw biochar to acidic soil increased NH4Cl–P content, while metal oxide biochar reduced NH4Cl–P content by binding to phosphorus. Original biochar slightly reduced Al–P content in lateritic red soil, while metal oxide biochar increased it. LBC and FBC significantly reduced Ca2–P and Ca8–P properties while improving Al–P and Fe–P, respectively. Inorganic phosphorus-solubilizing bacteria increased in abundance with biochar amendment in both soil types, and biochar addition affected soil pH and phosphorus fractions, leading to changes in bacterial growth and community structure. Biochar's microporous structure allowed it to adsorb phosphorus and aluminum ions, making them more available for plants and reducing leaching. In calcareous soils, biochar additions may dominantly increase the Ca (hydro)oxides bounded P or soluble P instead of Fe–P or Al–P through biotic pathways, favoring plant growth. The recommendations for using metal oxides biochar for fertile soil management include using LBC biochar for optimal performance in both P leaching reduction and plant growth promotion, with the mechanisms differing depending on soil type. This research highlights the potential of metal oxide modified biochars for improving soil fertility and reducing phosphorus leaching, with specific recommendations for their use in different soil types.

First Report on Novel Psychrotrophic Phosphorus-Solubilizing Ochrobactrum thiophenivorans EU-KL94 from Keylong Region in Great Himalayas and Their Role in Plant Growth Promotion of Oats (Avena sativa L.).

Cold stress leads to the disruption of the cellular homeostasis in plants and generation of reactive oxygen species (ROS) and productivity losses. In the present study, 94 psychrotrophic phosphorus-solubilizing bacteria with multiple plant growth-promoting (PGP) capabilities were isolatedfrom rhizosphere of wheat. The most efficient strain EU-KL94 showing highest amount of solubilized phosphorus and maximum number of PGP attributes was identified using 16S rRNA sequencing as Ochrobactrum thiophenivorans. Ochrobactrum thiophenivorans EU-KL94 along with recommended doses of the chemical fertilizers as controls were used for alleviation of cold stress in oats. The strain improved the root and shoot length, dry and fresh weight, proline, glycine betaine, chlorophyll content as well as the superoxide dismutase (SOD) and glutathione reductase (GR) activities of oats under cold stress conditions. Ochrobactrum thiophenivorans with all promising plant growth activities under cold stress could be used as an environmental friendly strategy for mitigation of low temperature stress. To the best of our knowledge, Ochrobactrum thiophenivorans has been reported for the first time as P-solubilizer and as bioinoculants in oats for cold stress mitigation.

Isolation of Inorganic Phosphorus-Solubilizing Bacteria from the Rhizosphere of Festuca arundinacea Schreb.

Inorganic phosphorus-solubilizing bacteria promote plant growth. However, different strains have different effects. The objective of this study was to screen efficient inorganic phosphorus-solubilizing bacteria (iPSB) from the rhizosphere of Festuca arundinacea Schreb. using Pikovskaya (PVK) medium. The results showed that 43 iPSB isolates were screened by clear halo zone production on PVK medium. Among them, the phosphate solubilization index (PSI) on the PVK medium of 31 iPSBs was calculated to be more than 1.5 at 28 °C in 7 days and ranged from 1.52 to 2.63. The best 31 iPSB isolates were selected for further study, including molecular identification using the 16S rRNA gene, testing of their P solubilization capacity in PVK broth medium, and the detection of catalase activity and organic acid and siderophore production. Among the 31 isolates, the phosphate solubilization of 8 isolates ranged from 203.96 to 412.22 µg/mL, and the value was significantly larger than that of the PVK broth medium without any bacterial isolates. These isolates were identified and belonged to Acinetobacter calcoaceticus, Buttiauxella sp., and Erwinia piriflorinigrans by sequence analysis of the 16S rRNA gene. These iPSB bacterial isolates enrich plant growth-promoting rhizobacteria and can promote the development of sustainable agriculture as phosphate fertilizer synergists.

Plant Growth Promoting Rhizobacteria (PGPR) Increases Yield and Mineral Contents of Rice by Mobilizing Nutrients in the Rhizosphere

Plant growth-promoting rhizobacteria (PGPR) are multipurpose entities in case of crop quality and yield improvement. This study evaluated the impact of PGPR inoculation in root zone nutrient release, rice yield, and grain nutrient (P, Fe, Mn, and Zn) content in two popular rice varieties of Bangladesh (viz., BRRI dhan49 and Binadhan7). It was a single factor (bacterial treatment) experiment where B0, B1, B2, and B3 treatments represented the inoculated control, indole acetic acid (IAA) producing bacteria consortium, phosphorus solubilizing bacteria (PSB) consortium, and combination of B1 and B2 treatments, respectively. Nutrients released in pore water was higher at 5 days after transplanting (DAT), compared to 25 DAT. Mostly B2 and B3 treatments performed significantly in the number of tillers/pots, straw yield, grain yield, grain P, Mn, Fe content, and all four nutrients uptake. The highest grain yield observed in B3 treatment is in both Binadhan7 (42.10±1.76 g/pot) and BRRI dhan49 (36.20±1.57 g/pot). PSB containing B2 treatment bio-fortified the largest amount of P in both rice varieties. On the other hand, the B3 treatment stored the highest amount of Mn (46.70±1.30 and 44.30±1.37 mg/kg) and Fe (45.30±2.90 and 25.70±2.37 mg/kg) in Binadhan7 and BRRI dhan49, respectively. The B3 treatment resulted in maximum nutrient content (P, Mn, and Fe) and uptake (P, Mn, Fe, and Zn) in both rice varieties. These bacterial isolates seemed promising for rice yield and quality improvement in an eco-friendly and sustainable way. Res. Agric. Livest. Fish. 10(1): 73-81

Occurrence forms and environmental characteristics of phosphorus in water column and sediment of urban waterbodies replenished by reclaimed water

To illustrate the evolution process, environmental feature and phytoremediation effect of phosphorus (P) in waterbodies with long-term replenishment by reclaimed water (RW), an urban waterbody using RW as the sole supply was selected as a case study. The concentration and distribution of soluble reactive phosphate (SRP), dissolved organic P (DOP) and particulate P (PP) in water column, as well as organic P (OP), inorganic P (IP), exchangeable P (Ex-P), BD-P (redox-sensitive P), NaOH-P (P bound to Fe and Al oxyhydroxides) and HCl-P (P bound to Ca) in sediment were investigated. Results showed that the seasonal average concentrations of total phosphorus (TPw) in water column ranged from 0.048 to 0.130 mg∙L−1, with the highest in summer and the lowest in winter. P in water column was predominantly present in dissolved state, with the similar proportions of SRP and DOP. SRP decreased apparently in midstream, where the phytoremediation was applied extensively. PP content obviously increased in non-phytoremediation area in downstream, due to visitor activity and sediment resuspension. Total phosphorus (TPs) in sediments was between 352.9 and 1331.3 mg∙kg−1, with average 365.7 mg∙kg−1 of IP and 382.8 mg∙kg−1 of OP. Among IP, HCl-P had the highest proportion, followed by BD-P, NaOH-P and Ex-P. OP was significantly higher in phytoremediation areas than that in non-phytoremediation areas. Coverage of aquatic plants was positively correlated with TP, OP, BAP, while it was negatively correlated with BD-P. Hydrophyte stabilized and conserved active P in sediment and prevented release of active P. Moreover, hydrophyte increased NaOH-P and OP contents in sediment through regulating the abundance of phosphorus-solubilizing bacteria (PSB), such as Lentzea and Rhizobium. Four sources were identified through two multivariate statistical models. RW and runoff were the dominant sources of P accounting for 52.09 %, which mainly contributed to P in sediment especially IP.