Phosphate Solubilizing Bacteria Inoculation Research Articles

Phosphate bio-solubilization and cadmium tolerance interplay in the root-microbe interface and consequences on root P absorption in wheat

Functional soil microbial communities, including phosphate solubilizing bacteria (PSB), are known for their ability to enhance P availability along with additional properties such as the immobilization of trace elements like cadmium (Cd). Bacterial P solubilization and tolerance to Cd are important biological processes that might occur simultaneously with positive influence on plant growth, thus physiological mechanisms controlling both processes need to be deciphered. This interplay was investigated in three PSB isolates (Bacillus siamensis "B. Siam", Rahnella aceris "R. Acer" and Bacillus cereus "B. Cer") and their consortium (PSBCs) with contrasting P solubilizing capacities (high-medium-low), through bacterial culture-based and plant inoculation experiments under increasing Cd concentrations and low P availability conditions (Tri-calcium P "TCP" and Rock P "RP"). Results show that PSB, particularly R. Acer and PSBCs, significantly increased P bioavailability (from TCP) under increasing Cd2+ concentrations (33 ppm “Cd33”, 67 ppm “Cd67”, 134 ppm “Cd134” and 201 ppm “Cd201”). The enhanced bioavailable P strongly correlated (B. Siam and PSBCs) with Cd bioaccumulation capacity, phosphatase enzyme activity, and organic acids (OA) production. Co-application of RP and PSB inoculation under Cd2+ stress (Cd8 and Cd16) improved wheat seedling root growth, P acquisition, and root hairs density in the piliferous zone and root cap. Moreover, inoculation with B. Cer significantly improved root inorganic P (Pi) (384 and 752%) and root acid phosphatases (176 and 131%) under Cd8 and Cd16 compared to uninoculated Cd-stressed seedlings. Such a beneficial root adaptation mechanism could be explained by the significant correlations (mainly under Cd16) between Pi content and morphological traits of wheat roots. Findings from this study demonstrate that P solubilization and Cd tolerance are likely interconnected rhizosphere processes triggered by inoculation that presumably induced the elongation of root hairs and likely the rigidity of the root cell wall to reduce Cd entrance while increasing P acquisition.

Ameriolations with VAM and PSB Inoculation of Growth and yield attributes in Pea (Pisum sativum L.) cv. Arkel

Background: Pea (Pisum sativum L.) is one of the most important legume grown all over the world with its varied uses as vegetables and other processed products. Its production and productivity in recent times have witnessed a diminishing graph due to numerous biotic and abiotic stresses. With unexploited use of synthetics in legume crops number of nodule formation have reduced to lowest levels. VAM (Vesicular Arbuscular Mycorrhiza) and PSB (Phosphate Solubilizing Bacteria) inoculation in soil have been observed in enhancing number of nodules, levels of NPK uptake and yield in pea. Methods: Considering the importance of above facts and experiment was laid in 2022 with RBD with three replications containing 7 treatments viz. T1 (Control), T2 (75% RDF + 25% PSB), T3 (50% RDF + 50% PSB), T4 (75% RDF + 25% VAM), T5 (50% RDF + 50% VAM), T6 (75% RDF + 12.5% VAM + 12.5% PSB) and T7 (50% RDF + 25% VAM + 25% PSB). Result: Investigations indicated that the treatment T7 (50% RDF + 25 % VAM + 25% PSB) showed significantly high growth, yield and quality like plant height (113.90 cm), number of leaves (87.09), number of branches (20.2), number of nodules (90.56), numbers of pod/plant (19.1), pod length (8.97 cm), number of seeds per pod (8.23), green pod yield/plot (4.80 kg), green pod yield/ha (80.12 q) compared to control. Hence, T7 (50% RDF + 25% VAM + 25% PSB) evidently exhibited a conglomeration of bio nutrient uptake enhancers resulting in maximum yield and quality.

The Importance of Considering Levels of P and N Fertilization to Promote Beneficial Interaction between Rapeseed and Phosphate-Solubilizing Bacteria

Biointrants constitute a promising opportunity to lower mineral input on rapeseed, characterized by high nutrient requirements. As bio-inoculants, phosphate-solubilizing bacteria (PSB) could increase the amount of available P in a soil solution. However, the deployment of these bio-inoculants in fields is not always successful. Disentangling the factors conditioning their reliability is necessary. Because the activities of microorganisms are particularly subject to nutrient availability, the N fertilization level could represent a key factor for the success of PSB inoculation in the early stages of plant growth. In this study, Pfaba (Pseudomonas sp.), a promising plant growth-promoting rhizobacteria (PGPR) strain isolated from soil, was inoculated on rapeseed grown in rhizotrons under two N fertilization levels (N160 or N80) in P labile or P complexed conditions. Pfaba confirmed its PSB potential to solubilize recalcitrant P complexed forms for the benefit of plant growth, but only when the N supply is adequate (N80). In a P complexed environment, Pfaba tended to increase root and shoot biomass (respectively, from 2.17 ± 0.47 g for control modality to 2.88 ± 0.85 g, and from 6.06 ± 1.67 g for control modality to 8.33 ± 1.70 g), increase the P and N contents in roots (respectively, from 0.15 ± 0.09 mg for control modality to 0.70 ± 0.51 mg, and from 37.90 ± 11.09 mg for control modality to 41.34 ± 14.16 mg), and restore root length at a comparable level than plants supplemented with labile P. Conversely, these positive effects were inhibited with lower levels of N fertilization. Our results highlight the importance of nutrient availability to promote beneficial interaction between plants and microorganisms. These findings could also contribute to ensuring the successful deployment of microbial biointrants.

Azolla pinnata ammendment and P-solubilizing bacteria inoculation for improving Inceptisols fertility and rice (Oryza sativa L.) yield production

Continuous and long-term use of chemical fertilizers in lowland rice fields can have negative impacts on the environment, causing harm to aquatic life and a decrease in soil health. Applying Azolla pinnata and inoculating phosphate solubilizing bacteria (PSB) in organic farming is an appropriate strategy to increase soil nutrients and lowland rice production. Azolla pinnata plays a role in increasing N nutrients, while phosphate solubilizing bacteria (PSB) increase available phosphate in the soil. This study aims to assess the effectiveness of varying doses of Azolla pinnata and PSB inoculant in increasing soil available P, plant-P concentration, plant hegh, productive tiller, and rice yield. The experimental design used a Factorial Randomized Block Design of two factors in three replications. The first factor was Azolla pinnata application (0 ton ha-1; 10 ton ha-1; 20 ton ha-1; 30 ton ha-1), and the second factor was PSB inoculation (0 kg ha-1; 12.5 kg ha -1; 25 kg ha-1). The experimental results showed that the Azolla pinnata application at a dose of 10 t ha-1 with inoculation of 12.5 kg ha-1 PSB significantly increased the highest soil available P by 48.3 ppm. The application of Azolla pinnata 30 t ha-1 significantly increased the P content of plants—0.26 mg g-1. Azolla pinnata 30 t ha-1 application and PSB inoculation produced significantly the highest productive tillers of rice plants, 38 plants pot-1. Azolla pinnata 10 tons ha-1 application with BPF inoculant 12.5 kg ha-1 significantly increased the highest grain yield, namely 81.47 g pot.-1

English

Global warming stimulates soil salinization and calcification, resulting in phosphorus (P) deficiency in arid and semiarid regions worldwide. Phosphate-solubilizing bacteria (PSB) can enhance phosphorus availability, but their role has been less explored under arid and semiarid climatic conditions. A two-year consecutive field experiment was conducted to assess the effectiveness of PSB loading onto seeds, organic, and mineral fertilizers. The trial followed a randomized complete block design (RCBD) with three replications for each treatment. There were five treatments: T1 was the uninoculated control with no fertilizer (Control), T2 was uninoculated with recommended NPK (NPK), T3 was PSB-inoculated wheat seeds (PSB-Seed), T4 was PSB-inoculated organic fertilizer (PSB-OF), and T5 was PSB-inoculated mineral fertilizer (PSB-MF). Results revealed that inoculation with PSB onto seeds, organic, or mineral fertilizer had a more pronounced impact not only on the vegetative development and yield of wheat but also on P contents in grains. It was observed that the PSB-inoculated mineral fertilizer treatment responded well, showing noticeable wheat biomass accumulation, grain yield, and improved P uptake in grain and straw. Interestingly, the highest uptake of nitrogen (N) in wheat grain was observed with both PSB-inoculated organic fertilizer treatment and PSB-inoculated mineral fertilizer treatment, highlighting the efficacy of slow-release nitrogen from organic fertilizer in addition to the impact of PSB. In conclusion, PSB inoculation on organic or mineral fertilizer has substantial potential in enhancing crop productivity and combating P deficiency in arid and semi-arid regions.

Application of Bacillus spp. Phosphate-Solubilizing Bacteria Improves Common Bean Production Compared to Conventional Fertilization.

The use of phosphate-solubilizing bacteria (PSB) can be a sustainable strategy to increase phosphorus availability and promote satisfactory crop yields. The objective of this study was to evaluate whether inoculation with PSB in common bean increases (i) growth, (ii) nutrition, (iii) yield, and (iv) grain quality, and (v) reduces the chemical phosphorus application dose to obtain maximum yields. The experiment was conducted in an Oxisol using a randomized block design in a 4 × 4 factorial scheme, with four replicates, using the cultivar IAC 2051. The first factor was four doses of P2O5 (0, 20, 40 and 60 kg ha-1), and the second factor was four doses of PSB (0, 100, 200 and 300 mL ha-1). For leaf area and leaf chlorophyll content, the association of PSB inoculation with a P2O5 dose of 40 kg ha-1 promoted the best conditions for the common bean. P2O5 application increased yield by 79 kg ha-1 for each 10 kg ha-1 added. PSB inoculation at a dose of 192 mL ha-1 promoted P export of 15.3 kg ha-1, and the PSB dose of 159 mL ha-1 increased yield by 389 kg ha-1 (12%) compared to the control. Grain quality remained within the standards required by the consumer market, being little affected by the treatments. Improvements in common bean growth and nutritional and physiological status promoted by P2O5 application and PSB were essential in increasing yield, so these are sustainable production strategies.

Enhancing Nutrient Content and Uptake in Chickpea through Phosphorus and PSB Inoculation in Custard Apple Based Agri-horti System

The field experiment was conducted during the Rabi season of 2018-19 at the Agricultural Research Farm of Rajiv Gandhi South Campus, Banaras Hindu University, Barkachha, Mirzapur, Uttar Pradesh, India. This study aimed to investigate the effects of varying levels of phosphorus and inoculation with Phosphate Solubilizing Bacteria (PSB) on nutrient content and uptake in chickpea (Cicer arietinum L.) in a custard apple-based agri-horticultural system. The experimental design employed a Factorial Randomized Block Design with three replications and twelve treatments, resulting in a total of 36 plots. The treatments ranged from different levels of phosphorus and PSB inoculation, denoted as T1 to T12. The study assessed the impact of these treatments on nitrogen (N), phosphorus (P) and potassium (K) content in grain and straw, as well as their uptake by chickpea. Findings reveal that higher PSB levels and phosphorus applications led to increased nitrogen and phosphorus content and uptake in both grain and straw, demonstrating a significant synergistic effect. Conversely, potassium content and uptake exhibited limited response to PSB inoculation. Moreover, protein content and yield in grain and straw significantly improved with these treatments.

Influence of Nitrogen Levels and Microbial Inoculants on Yield and Economics of French Bean (Phaseolus vulgaris L.)

The field experiment entitled “Influence of Nitrogen levels and Microbial inoculants on Yield and Economics of French bean" was conducted during rabi season, 2022 at Crop Research Farm in the Department of Agronomy, Naini Agriculture Institute, Sam Higginbottom University of Agriculture, Technology and Sciences, Prayagraj Uttar Pradesh. The soil in the experimental area was sandy loam with pH (8.0), Organic Carbon (0.42%), Available N (180.58 kg/ha), Available P (15.54 kg/ha), and Available K (198.67 kg/ha). The treatment consisted of two factors, Factor-1 levels of Nitrogen (75,100,125 kg/ha) and factor-2 Microbial inoculants (Rhizobium, PSB & Rhizobium +PSB). The experiment was layout in Randomized Block Design (RBD) with 10 treatments and replicated thrice. It was noticed that application of Nitrogen levels and Microbial inoculants had a significant effect on growth, yield, and yield parameters. The results indicated that the higher seed yield (22.47 q/ha), stover yield (50.08 q/ha), harvest index (30.95%), gross return (133601.00 INR/ha), net return (91333.00 INR/ha) and benefit-cost ratio (2.16) were observed in treatment 6, which involved the seed inoculation of Rhizobium and PSB along with the soil application of Nitrogen 100 kg/ha. So, in order to get higher productivity and returns from French bean, application of 100kg N/ha along with seed inoculation with phosphate solubilizing bacteria (PSB) and Rhizobium should be followed in sub-humid condition of Prayagraj, UP.

Nutrient-cycling functional gene diversity mirrors phosphorus transformation during chicken manure composting

Elucidating ecological mechanism underlying phosphorus transformation mediated by phosphate-solubilizing bacteria (PSB) during manure composting is an important but rarely investigated subject. The research objective is to disentangle ecological functions of the inoculation of PSB Pseudomonas sp. WWJ-22 during chicken manure composting based on gene quantification and amplicon sequencing. There are large dynamic changes in phosphorus fractions, gene abundances, and bacterial community structure. The PSB addition notably increased available phosphorus from 0.29–0.89 g kg−1 to 0.49–1.39 g kg−1 and significantly affected phosphorus fractionation. The PSB inoculation significantly affected composition of nutrient-cycling functional genes (NCFGs), and notably influenced bacterial community composition and function. Compost bacteria showed significant phylogenetic signals in response to phosphorus fractions, and stochastic processes dominated bacterial community assembly. Results emphasized that PSB addition increased functional redundancy, phylogenetic conservatism, and stochasticity-dominated assembly of bacterial community. Overall, findings highlight NCFG diversity can be a bio-indicator to mirror phosphorus transformation.

Phosphate-Solubilizing Bacteria with Low-Solubility Fertilizer Improve Soil P Availability and Yield of Kikuyu Grass.

Inoculation with phosphate-solubilizing bacteria (PSB) and the application of phosphorus (P) sources can improve soil P availability, enhancing the sustainability and efficiency of agricultural systems. The implementation of this technology in perennial grasses, such as Kikuyu grass, for cattle feed in soils with high P retention, such as Andisols, has been little explored. The objective of this study was to evaluate the productive response of Kikuyu grass and soil P dynamics to BSF inoculation with different P sources. The experiment was conducted on a Kikuyu pasture, which was evaluated for 18 months (September 2020 to March 2022). Three P fertilizers with different solubility levels were applied: diammonium phosphate (DAP) (high-solubility), rock phosphate (RP), and compost (OM) (low-solubility). Moreover, the inoculation of a PSB consortium (Azospirillum brasilense D7, Rhizobium leguminosarum T88 and Herbaspirillum sp. AP21) was tested. Inoculation with PSB and fertilization with rock phosphate (RP) increased soil labile P and acid phosphomonoesterase activity. Increased grass yield and quality were related with higher soil inorganic P (Pi) availability. This study validated, under field conditions, the benefits of PSB inoculation for soil P availability and Kikuyu grass productivity.

Influence of phosphorus and biofertilizers on symbiotic parameters, productivity and profitability of soybean (Glycine max)

A field study was carried out during the rainy (kharif) season of 2019 at the Regional Research Station, Punjab Agricultural University, Ludhiana and Faridkot, Punjab, to study the effect of phosphorus levels and biofertilizers on the symbiotic parameters, productivity, and profitability of soybean [Glycine max (L.) Merr.]. The experiment comprised 4 phosphorus levels (0, 17, 26 and 35 kg P/ha) and 4 biofertilizer treatments [uninoculated control, Bradyrhizobium, Phosphate-solubilizing bacteria (PSB) and Bradyrhizobium + PSB]. Total 16 treatment combinations were laid out in a factorial randomized complete-block design, replicated 3 times. Application of 35 kg P/ha recorded the highest symbiotic parameters, growth and yield attributes and seed yield of 2 and 1.84 t/ha at Ludhiana and Faridkot, respectively, which were significantly higher than the control and 17 kg P/ha but statistically at par with 26 kg P/ha at both the locations. However, the highest production efficiency (14.62 and 13.50 kg/ ha/day at Ludhiana and Faridkot, respectively) was recorded with application of 35 kg P/ha, being statistically at par with 26 kg P/ha. The highest monetary efficiency (302 and 277 `/ha/day at Ludhiana and Faridkot, respectively) was obtained with the application of 35 kg P/ha which were at par with 26 and 17 kg P/ha at Ludhiana, while with 26 kg P/ha at Faridkot. Inoculation with Bradyrhizobium + PSB and sole inoculation of PSB were at par with each other and both proved superior to uninoculated control for growth and yield attributes, seed yield and monetary efficiency.

Inoculation of phosphate-solubilizing bacteria improves soil phosphorus mobilization and maize productivity

Phosphate-solubilizing bacteria represent a bioalternative in making soil-immobilized phosphorus (P) available to plants, and consequently improve agriculture sustainability and reduce nutrient pollution. In this study, we examined whether Rhizobium sp. B02 inoculation can affect the soil P fractions. Moreover, we investigated how inoculation influences the growth, physiological traits, and productivity of the maize crop. Field tests were carried out to evaluate the combined application of strain B02 and reduced doses of P fertilizer. Soil P fractionation was performed after crop harvesting, assessing the P dynamics. To study the plant response, samplings were carried out in three phenological stages—the vegetative stage of the 7 fully emerged leaves with leaf collars (V7), the vegetative stage of the tassel (VT), and the reproductive stage of physiological maturity (R6). Using 50% of P fertilizer recommended, the strain inoculation increased the labile inorganic P fraction by 14% compared to the control treatment at the same dose, indicating that it favored the Pi mobility. Under these same conditions in the V7 and VT phenological stages, the inoculation significantly improved shoot length (28 and 3%) and shoot dry weight (9.8 and 12%). B02 inoculation increased grain yield by 696 kg ha−1 using 50% of the recommended rate of P fertilizer, phenocopying the complete P fertilization treatment without inoculation. Therefore, Rhizobium sp. B02 inoculation replaced 50% of P fertilizer in maize and increased the soil P availability.

Phosphorus transformation behavior and phosphorus cycling genes expression in food waste composting with hydroxyapatite enhanced by phosphate-solubilizing bacteria

This study aimed to explore the effect of phosphate-solubilizing bacteria (PSB) Bacillus inoculation in the cooling stage on hydroxyapatite dissolution, phosphorus (P) forms transformation, and bacterial P cycling genes in food waste composting with hydroxyapatite. Results indicated that PSB inoculation promoted the dissolution of hydroxyapatite, increased P availability of compost by 8.1% and decreased the ratio of organic P to inorganic P by 10.2% based on sequential fractionation and 31P nuclear magnetic resonance spectroscopy. Illumina sequencing indicated Bacillus relative abundance after inoculation increased up to one time higher than control after the cooling stage. Network analysis and metabolic function of bacterial community analysis suggested inorganic P solubilizing genes of Bacillus and organic P mineralization genes of other genera were improved after inoculation in the core module. Therefore, bioaugmentation of PSB in the cooling stage may be a potential way to improve P bioavailability of bone and food waste in composting.

Cold-tolerant phosphate-solubilizing Pseudomonas strains promote wheat growth and yield by improving soil phosphorous (P) nutrition status.

It is well-known that phosphate-solubilizing bacteria (PSB) promote crop growth and yield. The information regarding characterization of PSB isolated from agroforestry systems and their impact on wheat crops under field conditions is rarely known. In the present study, we aim to develop psychrotroph-based P biofertilizers, and for that, four PSB strains (Pseudomonas sp. L3, Pseudomonas sp. P2, Streptomyces sp. T3, and Streptococcus sp. T4) previously isolated from three different agroforestry zones and already screened for wheat growth under pot trial conditions were evaluated on wheat crop under field conditions. Two field experiments were employed; set 1 includes PSB + recommended dose of fertilizers (RDF) and set 2 includes PSB - RDF. In both field experiments, the response of the PSB-treated wheat crop was significantly higher compared to the uninoculated control. In field set 1, an increase of 22% in grain yield (GY), 16% in biological yield (BY), and 10% in grain per spike (GPS) was observed in consortia (CNS, L3 + P2) treatment, followed by L3 and P2 treatments. Inoculation of PSB mitigates soil P deficiency as it positively influences soil alkaline phosphatase (AP) and soil acid phosphatase (AcP) activity which positively correlated with grain NPK %. The highest grain NPK % was reported in CNS-treated wheat with RDF (N-0.26%, P-0.18%, and K-1.66%) and without RDF (N-0.27, P-0.26, and K-1.46%), respectively. All parameters, including soil enzyme activities, plant agronomic data, and yield data were analyzed by principal component analysis (PCA), resulting in the selection of two PSB strains. The conditions for optimal P solubilization, in L3 (temperature-18.46, pH-5.2, and glucose concentration-0.8%) and P2 (temperature-17°C, pH-5.0, and glucose concentration-0.89%), were obtained through response surface methodology (RSM) modeling. The P solubilizing potential of selected strains at <20°C makes them a suitable candidate for the development of psychrotroph-based P biofertilizers. Low-temperature P solubilization of the PSB strains from agroforestry systems makes them potential biofertilizers for winter crops.

Integrated nutrient management in barley (Hordeum vulgare) under central plateau and hills agroecological region

A field experiment was conducted during the winter (rabi) seasons of 2017–18 and 2018–19 at the Rajasthan College of Agriculture, Maharana Pratap University of Agriculture and Technology, Udaipur, Rajasthan, to find out best integrated nutrient management strategy in barley (Hordeum vulgare L.). The correlation and regression were studied between yield attributes and yield as influenced by these treatments. The experiment was laid out in a randomized block design (factorial), comprising combinations of 6 fertility levels [75% recommended dose of fertilizers (RDF), (45 kg N and 22.5 kg P2 O5 ) 100% RDF (60 kg N and 30 kg P2 O5 ); 125% RDF (75 kg N and 37.5 P2 O5 ); 75% RDF + farmyard manure (FYM) 5 t/ha; 100% RDF + FYM 5 t/ha; and 125% RDF + FYM 5 t/ha, and 4 liquid bioinoculants, viz. Azotobacter, phosphate solubilizing bacteria (PSB), Azotobactor + PSB and Azotobactor + Azospirillum + phosphates solubilizer + PGPR (plant-growth promoting rhizobacteria) at the rate 5 ml/kg seed. The results indicated that, application of 125% RDF in conjunction with FYM 5 t/ha had significant effect on yield attributes, viz. effective tillers (45.36), ear length (9.37 cm), ear weight (3.22g), grains/ear (54.49), grain weight/ear (2.70 g), straw weight/ear (0.52 g), filled spikelet/ear (54.47), least number of unfilled spikelet/ear (3.24) and test weight (49.92 g), and grain (5.20 t/ha), straw (7.79 t/ha) and biological yield (12.99 t/ha) which was at par with 100% RDF + FYM 5 t/ha. However, both these fertility levels significantly increased the grain weight/ear over application of 75% RDF + FYM 5 t/ha, 125% RDF, 100% RDF and 75% RDF during both the years. The barley crop under the influence of conjoint inoculation with liquid bio-fertilizers, consisting combination of Azotobacter + Azospirillum + phosphates solubilizer + plant growth-promoting rhizobacteria (PGPR) recorded significantly higher yield attributes, grain (5.12 t/ha), straw (7.57 t/ha) and biological yields (12.69 t/ha) and was found at par with inoculation of Azotobacter + PSB inoculation. The results showed positive interrelationship between grain yield and yield components, viz. effective tillers, ear length, test weight, grain/ear and grain weight/ear, clearly indicate that grain yield is dependent on several component which are interrelated with each other.

Insight into application of phosphate-solubilizing bacteria promoting phosphorus availability during chicken manure composting

Understanding ecological roles of phosphate-solubilizing bacteria (PSB) is important to optimize composting systems. Illumina MiSeq sequencing, gene quantitation, and statistical analyses were employed to explore ecological mechanisms underlying available phosphorus (AP) facilitation during composting with the inoculation of PSB Pseudomonas sp. WWJ-22. Results displayed that the inoculation of PSB significantly increased AP from 0.83 to 1.23 g kg−1, and notably increased abundances of phosphorus-cycling genes as well as numbers of PSB mineralizing phytate and lecithin. The PSB addition significantly affected compost bacterial community composition, and phosphorus factions and phosphorus-cycling genes independently explained 25.4 % and 25.0 % bacterial compositional dissimilarity. Stochastic and homogenizing processes affected more on bacterial community assembly, and rare bacteria potentially mediated organic phosphorus mineralization. These results emphasized that phosphorus fractions, PSB number, phosphorus-cycling gene abundance, and bacterial community composition contributed differently to phosphorus availability. Findings highlight ecological roles of exogenous PSB during chicken manure composting.

Effects of Phosphate-solubilizing Bacteria on Soil Phosphorus Fractions and Supply to Maize Seedlings Grown in Lateritic Red Earths and Cinnamon Soils.

Phosphorus (P) is often the limiting factor for plant growth because of its low mobility and availability in soils. Phosphate-solubilizing bacteria (PSB) have been shown to increase the availability of soil P fractions, thereby promoting plant growth. We herein investigated the effects of PSB on P availability in two important Chinese soil types: Lateritic red earths (La) and Cinnamon soils (Ci). We initially isolated 5 PSB strains and assessed their effects on soil P fractions. PSB mainly increased moderately labile P in La and labile P in Ci. We then selected the most promising PSB isolate (99% similarity with Enterobacter chuandaensis) and examined its effects on P accumulation in maize seedlings. The results obtained showed that plant P accumulation increased in response to a PSB inoculation in both soil types and the combination of the PSB inoculation and tricalcium phosphate fertilization in La significantly enhanced P accumulation in plant shoots. The present study demonstrated that the PSB isolates tested differed in their ability to mobilize P from distinct P fertilizers and that PSB isolates have potential as a valuable means of sustainably enhancing seedling growth in Chinese agricultural soils.

Integration of phosphate solubilizing bacteria and ponska fertilizer as a soybean fertilization method that is adaptive to climate change

Climate change, such as altering rainfall patterns and increasing the risk of extreme droughts cause degradation of soil chemical properties, deficiency of soil nutrients and reduction of plant growths and productions. Therefore, an alternative strategy is necessary to overcome those issues. A method of appropriate fertilization was likely to be applied to conserve soil fertility and maintain sustainable plant growth which might benefit facing the issues. This study examined the integration fertilization between phosphate solubilizing bacteria (PSB) and PONSKA fertilizer on changes in soil chemical properties and plant growth under greenhouse conditions. The trial pot were applied using a completely factorial randomized design of two factors with three replication for each combined treatment. The first factor was PSB inoculation with three levels (B0=0. B1= 5 and B2 = 10 ml. plant-1) and the second one was PONSKA fertilizer application with three doses ( P1=100. P2=150. P3= 200 kg. ha-1). The results showed that neither the interaction treatments nor each factor significantly affect the soil pH-H2O and the total content of N and organic C. Each factor of PSB and PONSKA fertilizer, respectively, significantly affected available P content. A PSB level of 10 ml. plant-1 indicated the highest P content (15.5 ppm), while the PONSKA doses of 150 and 200 kg. ha-1 insignificantly affected but the availability of P content was higher that of P1 parameter. Even though, the single factor of PSB and PONSKA fertilizer significantly affected the shoot of dry weight, the level of roots, and the number of active root nodules, they were insignificantly affected the shoot/root ratio. Treatment of B1 and B2 showed an insignificant difference in the dry weight of roots (1.61 g plant-1) and active root nodules (55.23-62.31) but desired effects of those treatments were higher than that of B0 parameter. The treatment B2 yielded the highest dry weight of shoots. Moreover, the composite of PONSKA fertilizer and PONSKA dose of 150 (P1) and 200 kg ha-1 (P2) yielded the shoot dry weight, root dry weight and number of active root nodules higher than the P1 parameter. A combination of P2 and B1 results in 22.97 g. plant-1 of seed bean. Therefore, a PONSKA dose of 150 kg. ha-1 added by a PSB of 5 ml.plant-1 was likely to be an alternative fertilization method to cope the issues of climate change.

Effects and mechanisms of phosphate solubilizing bacteria on enhancing phytoextraction of lead from contaminated soil by Celosia cristata L.

Phosphate solubilizing bacteria (PSB)-assisted phytoextraction can enhance the removal of toxic metals by plants from contaminated soil. Here, we investigated the promotion effects of a Pb-tolerant PSB strain, Leclercia adecarboxylata L1-5, on assisting Pb phytoextraction by Celosia cristata L.. The results showed that PSB inoculation could increase the plant shoot and root biomass by 34.90% and 55.56% when the Pb concentration was 800 mg kg−1. Pb contents in the root and shoot were enhanced 3.06 and 0.72-fold by PSB inoculation, resulting in a bioaccumulation factor (BCFaboveground) of 0.2, a translocation factor (TF) of 1.92, and a maximum total Pb extraction amount of 222.94 μg kg−1. The positive effects of PSB on Pb bioaccumulation by C. cristata L. could be attributed to its abilities of increasing soil available phosphorus. PSB inoculation benefited osmotic potential balance and membrane stability in the plant leaves, as evidenced by 2.39-fold increase of the soluble protein, 71.39% decrease of malondialdehyde and 74.31% decrease of hydrogen peroxide. The main mechanism of the enhancement of Pb phytoextraction efficiency induced by PSB inoculation could be summarized as helping Pb absorption by root elongation, and increasing endurable Pb concentration by osmotic regulation and detoxification ability optimization. This work demonstrated that PSB combined with C. cristata L. was an excellent candidate for lead extraction and could be considered as an effective way for soil lead remediation in the future.

Phosphate Solubilizing Bacteria (PSB) Improve Phosphorus Availability from Various Sources in Alkaline Soils

Phosphorus (P) is one of the major essential macronutrients for plants, applied to soil in the form of phosphatic fertilizers and organic manures. The application of PSB to soils can replace or partially reduce use of inorganic P fertilizers and could be one of the cost effective, highly efficient, and sustainable approaches to conserve P resources. The aim of the study was to evaluate the role of PSB in phosphorus (P) availability from organic, mineral and natural sources. For this purpose, a laboratory incubation experiment was conducted at the University of Agriculture Peshawar. The experiment was consisting of four sources of P [poultry manure (PM), farm yard manure (FYM), rock phosphate (RP) and single supper phosphate (SSP)] for obtaining 45 mg P2O5 kg-1 and two types of inoculation (control and PSB) arranged in two factorial complete randomized design with three replications. Resultantly, PSB inoculation significantly improved. P availability at all incubation interval except day zero. A 3.4%, 5.4%, 12% and 16 % increased were observed in P as compared to control, at day 7, 14, 28 and 56 respectively. Similarly, significant differences were observed in P release for P sources at all incubation intervals. Initially higher P release was observed for SSP but at day 14 onward PM and FYM proved to be the best P releasable sources as compared to mineral P sources. RP released the lowest P at all incubation intervals however it performed statistically at par to SSP at 56 days. The significant interactive effect of P sources and PSB at day 28 and 56 demonstrated that soil receiving P from organic sources inoculated with PSB released higher P than other treatments combination. Thus, it is suggested that P must be applied from organic P sources (PM and FYM) along with PSB inoculation for better P nutrition and crop yield.