Rock Phosphate Solubilization Research Articles

Effect of Different Phosphorus Sources on Soil Physico-Chemical Property Dynamics under Chickpea Crop

A field experiment was conducted during Rabi season of 2021-2022 to study the effect of rock phosphate (RP), poultry manure (PM) and phosphate solubilizing bacteria (PSB) on soil properties. The experiment was laid out in three replications with 9 treatments in Randomized Block design (RBD). Results revealed that the combined application of 50% P through RP + 50% P through PM + PSB (T9) significantly decrease the bulk density but, higher soil porosity was observed with application of 100% P through PM (T5) and 100% P through PM + PSB (T8) were at par. Whereas, improved in soil pH and organic carbon were reported with the application of T8. Also, the maximum available nitrogen (294.95 kg ha-1) was acquired under T8. However, the highest available phosphorus, potassium and available Fe, Mn, Cu and Zn content in soil were observed with T9. Similarly, higher PSB population and acid phosphatase activity was recorded with application of T9. Dehydrogenase activity was observed to be higher underT8 at harvest of chickpea crop. It was concluded that application of phosphate, poultry manure and phosphate solubilizing bacteria improve the soil properties.

Partial substitution of exogenously applied phosphatic fertilizers by phosphate solubilizing bacteria in maize under calcareous soil

Phosphorus (P) availability is the major constrain in obtaining optimum crop yield in calcareous soils due to its precipitation as dicalcium and octacalcium phosphate by reacting with Ca+2and Mg+2. Therefore, we explored the role of phosphate solubilizing bacteria (without and with PSB @ 2 kg ha−1) in optimizing maize yield and P availability from soluble and insoluble P sources applied @ of 100 kg P2O5into calcareous soil. PSB inoculation significantly improved maize plant height (5.6%), 1,000 grain weight (11%), dry matter (7.5%), stover (10.8%) and grain yield (6.8%), plant P concentration (10.1%) and uptake (18.6%), extractable P (3.1%), agronomic (48%) and uptake (53%) P use efficiency over uninoculated plots. Phosphorus application significantly improved maize yield, soil health and agronomic P use efficiency (4.84 times over control); however, its impact was more pronounced when applied as 50% P each from farmyard manure (FYM) and single super phosphate (SSP). On the basis of overall performance, the sources were ranked as 50% FYM + 50% SSP >50% rock phosphate (RP) + 50% SSP > 100% SSP > 75% FYM + 25% SSP > 75% RP +25% SSP > 100% FYM > 100 RP > control. Interactively, a significant and maximum increased over absolute control in most of the soil and plant tested characteristics were observed when 100 kg P2O5ha−1was supplemented 50% each as FYM and SSP along with PSB inoculation which was followed by 50% P each as FYM and SSP demonstrating that PSB were effective in enhancing RP solubilization under calcareous soil. Maximum value cost ratio of 3.1 was observed for 50% P each as FYM and SSP + PSB which was similar to 100% P as FYM + PSB and 75% FYM+ 25% SSP + PSB. Therefore, in calcareous soil P shall be amended 50% each as organic and mineral sources with PSB for its efficient utilization and obtaining optimum yield of maize.

Rock Phosphate Solubilizing Potential of Soil Microorganisms: Advances in Sustainable Crop Production

Phosphorus (P) is one of the most important elements required for crop production. The ideal soil pH for its absorption by plants is about 6.5, but in alkaline and acidic soils, most of the consumed P forms an insoluble complex with calcium, iron, and aluminum elements and its availability for absorption by the plant decreases. The supply of P needed by plants is mainly achieved through chemical fertilizers; however, in addition to the high price of these fertilizers, in the long run, their destructive effects will affect the soil and the environment. The use of cheap and abundant resources such as rock phosphate (RP) can be an alternative strategy for P chemical fertilizers, but the solubilization of P of this source has been a challenge for agricultural researchers. For this, physical and chemical treatments have been used, but the solution that has recently attracted the attention of the researchers is to use the potential of rhizobacteria to solubilize RP and supply P to plants by this method. These microorganisms, via. mechanisms such as proton secretion, organic and mineral acid production, siderophore production, etc., lead to the solubilization of RP, and by releasing its P, they improve the quantitative and qualitative performance of agricultural products. In this review, addressing the potential of rhizosphere microbes (with a focus on rhizobacteria) as an eco-friendly strategy for RP solubilization, along with physical and chemical solutions, has been attempted.

Aspergillus niger Enhances the Efficiency of Sewage Sludge Biochar as a Sustainable Phosphorus Source

Phosphorus-rich biochar derived from sewage sludge (SS) could be a sustainable alternative P source for agriculture. However, most of biochar P is not readily available to plants. We evaluated the potential of P release from SS biochar into soil solution by Aspergillus niger. Additionally, we assessed the effect of SS biochar on the solubilization of phosphate minerals by the fungus. An incubation study was performed for 7 days in shaken flasks containing culture medium supplemented, or not, with a P-fixing soil. Biochar showed a dual role in phosphate solubilization by A. niger: (i) improved solubilization of AlPO4 and rock phosphate; and (ii) acted as a P source. Aspergillus niger solubilized up to 50% of the P contained in the biochar. A combined application of SS biochar and A. niger increased P availability by 500 times in a solution containing P-fixing soil. These results suggest that P-use efficiency from SS biochar could be improved by A. niger, allowing for the use of lower doses of this soil amendment. These findings contribute to a better understanding of the role of phosphate-solubilizing microorganisms in the interaction between soil and biochar. Furthermore, the results underpin the potential P fertilizer value of the SS biochar. Finally, our results present a win–win environmental benefit as it reduces SS accumulation and improves P-use efficiency.

Rock Phosphate and Phosphorus Solubilizing Bacteria Effect on Yield and Yield Components of Chickpea

Rock Phosphate and Phosphorus Solubilizing Bacteria Effect on Yield and Yield Components of Chickpea

Improved rock phosphate dissolution from organic acids is driven by nitrate assimilation of bacteria isolated from nitrate and CaCO3-rich soil.

Until now, the solubilization capacities of insoluble mineral P by soil microorganisms have been screened in vitro with media containing NH4+ as a nitrogen source. This presence of NH4+ will lead to an acidification of the medium responsible for the solubilization of the insoluble P. However, besides proton release, the production of organic acids can play a very important role in the release of free P. This physiological mechanism can largely depend on the source of nitrogen (NH4+vs NO3-) assimilated by the bacteria but the influence of the N source on the production of organic acids has yet to be studied. Our aim was to investigate if the N source assimilated by bacteria and the soil characteristics such as the dominant N source (NH4+vs NO3-) and CaCO3 contents might influence the bacterial capacities to solubilize rock phosphate. To fill this objective, we screened the capacity of bacteria isolated from 3 soils to solubilize rock phosphate in vitro in presence of NH4+or NO3-. Then, we selected the most efficient bacterial strains to identify and quantify the release of organic anions into the medium. Among the two hundred and forty-three bacterial strains isolated from the 3 soils, nine and seven isolates were identified with the highest % rock phosphate-solubilization values with NH4+ or NO3- as the sole N-source. Only one strain was able to release free Pi with NH4+ or NO3- as the sole N-source. The most predominant organic acids released by almost all isolates were gluconic acid, lactic acid, glycolic acid, acetic acid, formic acid and pyruvic acid regardless the N-source. However, with NO3- as source of N, the highest concentrations on those acids were found together with the highest release of free Pi into the medium. Molecular analysis of 16S rRNA indicated that almost all strains belonged to Bacillus and Paenibacillus genera. The PCA analysis between soil properties and bacterial capacities to release organic acids and free Pi also revealed that soil factors such as CaCO3 and soil NO3- content positively influenced the release of organic acids by bacteria grown in vitro. Our results concluded that the bacterial rock phosphate-solubilization was intimately related to organic acids production which in turn seemed to be driven by the assimilation of NO3- by bacteria. Therefore, the N-source might be considered a key factor to take into consideration during the screening and selection of suitable strains involved in the P-solubilization.

Optimization of oxalic acid production by fungi for biotechnological solubilization of rock phosphate

This study describes a biotechnological strategy for producing and applying oxalic acid to solubilize phosphorus (P) from rock phosphate (RP). We evaluated six fungal species (Aspergillus niger FS1, Penicillium islandicum FS41, Pleurotus ostreatus PO1, Rhizoctonia solani Rhiz555, Sclerotium rolfsii Sr25, and Sclerotinia sclerotiorum Scl134) and three culture media (potato dextrose broth, Tsao and Strasser media) to maximize oxalic acid production. Among the fungal isolates tested and culture media, S. rolfsii Sr25 and Tsao medium showed efficient oxalic acid production. Tsao medium was optimized following a response surface methodology after initial screening of factors affecting RP solubilization. The optimized concentrations were 1 g L–1 NaNO3, 100 g L–1 glucose, 2 g L–1 KH2PO4, 4.5 g L–1 yeast extract, and 25 mg L–1 MgSO4·7H2O used for 20 days of incubation. Under these conditions, 71 mmol L–1 oxalic acid was obtained, representing a three-fold increase over production under non-optimized conditions (20 mmol L–1). Under optimized conditions, oxalic acid produced by S. rolfsii Sr25 reacted with low-solubility RP and solubilized 100 % of the P contained in ore. Thus, using S. rolfsii Sr25 to produce oxalic acid seems a promising biotechnological alternative for P solubilization from RP.

Enhanced phytoremediation of hexavalent chromium contamination in phosphate mining wasteland by a phosphate solubilizing bacterium

Soil chromium (Cr) contamination poses a significant threat to the environment and public health. A phosphate solubilizing bacterial strain Bacillus megaterium PMW-03 was used to enhance the phytoremediation of Cr(VI) contamination by Pteris vittata in phosphate mining wasteland in this study. The results showed that the strain PMW-03 could promote the solubilization of phosphate rock (PR) and the removal of Cr(VI) by Pteris vittata in the phosphate mining wasteland. Compared with the groups not inoculated with PMW-03, the available phosphate content in the rhizosphere soil of the inoculated groups increased by 17.6% and 24.9%, respectively (in the group with Cr(VI) added and the group with Cr(VI) and PR added), and the available Cr(VI) content decreased by 28.2%, 25.2% and 33.4%, respectively. In addition, the strain PMW-03 also promoted the growth of Pteris vittata by secreting indole acetic acid (IAA) and siderophore, promoting Pteris vittata to produce chlorophyll, increasing the concentration of soluble phosphate and reducing the concentration of Cr(VI) in root and shoot. The results of metagenomic analysis showed that changes in biological community structure, enrichment of related functional abundances, and activation of genes (FTH1, FTL, HSP90A, glgP, htpG, glnA, and GLUD1_2) located in microbes contributed to the microbial-phytoremediation of Cr(VI) contamination. These results provide a reference for future research on the microbial-phytoremediation of Cr(VI) contamination in phosphate mining wasteland.

Rock Phosphate Solubilization by Plant Growth-Promoting Bacillus velezensis and Its Impact on Wheat Growth and Yield

Application of phosphate solubilizing bacteria for improvement of existing pools of phosphate in soil is important for plant growth. From rain fed area of Mansehra, 14 microbes were isolated. Among these, three isolates Bacillus velezensis, Bacillus subtilis, and Bacillus safensis exhibited strong phosphate solubilizing potential, indole acetic acid (IAA) and organic acid production, and antibacterial and antibiotic resistances. Due to better phosphate solublization potential, plant growth-promoting rhizobacteria, B. velezensis was used as bio-inoculant on wheat var. Pir sabaq alone, with rock phosphate (RP) and with 50%, 75%, and 100% single super phosphate (SSP) and urea. Application of RP with B. velezensis increased 50% phosphate and nitrate in soil and 80% in leaves. Plants treated with 100% SSP + urea and B. velezensis showed 50% higher P in soil and 90% in leaves. Application with RP showed significant increases on growth indices of wheat and results were more pronounced in RP + B. velezensis and 100% SSP + urea + B. velezensis treatments. Soluble protein and sugar contents of leaves were 46% and 24% higher in RP + B. velezensis, while IAA and gibberellic acid (GA) were 34% and 54% higher. Highest increases in protein (56%), sugar (30%), IAA (50%), and GA (90%) were found in 100% SSP + urea + B. velezensis. Spike length, seeds per spike, and weight of 1000 seed were 19%, 32%, and 26% higher in RP + B. velezensis, while these increases were 39%, 52%, and 33%, respectively in 100% SSP + urea + B. velezensis treatment. Bio-inoculation of B. velezensis with RP and chemical fertilizer may be helpful for improving productivity of cereal crops and sustainable agriculture.

Bioconversion of Some Agro-Residues into Organic Acids by Cellulolytic Rock-Phosphate-Solubilizing Aspergillus japonicus

Biological-based conversion of agricultural residues into bioactive compounds may be considered to be the basis for various vital industries. However, finding a suitable microorganism is a challenge in the bioconversion process. Therefore, this study was conducted to find local fungal isolates able to convert a combination of plant biomass residues into organic acids (OAs). Based on their cellulase and phytase activities and rock phosphate (RP) solubilization potential, an efficient 15 fungal isolates (named F1 to F15) were selected and identified by both morphological and molecular methods using the 18S rRNA sequencing technique. The best fungal isolate (F15) was identified as Aspergillus japonicus. After 4 weeks of incubation below solid-state fermentation (SSF) with a mix of sugarcane bagasse and faba bean straw (3:7), with 7.5% (v/w) fungal inoculum to the growth medium, the biodegradation process by the fungus reached its peak, i.e., maximum cellulolytic activity and RP solubilization ability. Under such fermentation conditions, seven organic acids were detected using HPLC, in the following order: ascorbic acid > oxalic acid > formic acid > malic acid > succinic acid > lactic acid > citric acid. Based on the results, Aspergillus japonicus (F15) could produce OAs and cellulose enzymes, and could be considered a new single-step bio-converter of sugarcane bagasse and faba bean straw residues into OAs. Furthermore, this fungus could be a new source of fungal cellulose, and could present a practical approach to reducing environmental contamination. Additional work is encouraged for more optimization of fermentation conditions.

Streptomycetaceae and Promicromonosporaceae: Two Actinomycetes Families from Moroccan Oat Soils Enhancing Solubilization of Natural Phosphate.

Soil actinomycetes explorations appear to be an efficient alternative as biofertilizers to optimize the use of phosphorus (P) resources and enhance plant growth. This research aimed to explore the distribution of actinomycetes isolated from four different rhizospheric Moroccan oat soils and to investigate their potential for P solubilization. The distribution of actinomycetes was significantly more abundant in Settat (9.68%), Tangier (7.38%), and Beni Mellal (6.87%) than in the Merchouch-Rabat (4.90%) region. A total of 235 actinomycete strains were isolated from all sites and tested for their ability to grow on a synthetic minimum medium (SMM) containing insoluble natural rock phosphate (RP) or synthetic tricalcium phosphate (TCP) as the unique P source. One hundred forty-three isolates (60.8%) had the ability to grow in the SMM with RP whereas only twenty-five isolates (17%) had the most active growth using the SMM with TCP. Eight isolates with the most active growth in solid SMM were selected for their P solubilization abilities in liquid SMM cultures. The highest amount of P solubilized was 163.8 µg/mL for RP and 110.27 µg/mL for TCP after 5 days of culture. The biosolubilization process of AM2, the most efficient RP and TCP solubilizing strain, probably implied the highest excretion of siderophore substances. Eight of these strains were shown to belong to the Streptomyces genus and one to the Promicromonospora genus. These findings bolster the phosphate biosolubilization abilities of actinomycetes and may participate in increasing agricultural yields in an eco-efficient and environmentally friendly manner.

A sustainable and effective bioprocessing approach for improvement of acid phosphatase production and rock phosphate solubilization by Bacillus haynesii strain ACP1

There is indeed a tremendous increase in biotechnological production on a global scale, more and more innovative bioprocesses, therefore, require to perform ideally not only in a small lab- but also on large production scales. Efficient microbial process optimization is a significant challenge when accomplishing a variety of sustainable development and bioengineering application objectives. In Egypt's mines, several distinct types of rock phosphate (RP) are utilized as a source of phosphate fertilizers in agriculture. It is more ecologically beneficial to utilize RP bio-solubilization than acidulation. Therefore, this work aimed to strategically scale up the acid phosphatase (ACP) production and RP bio-solubilization by the newly-discovered Bacillus haynesii. The use of consecutive statistical experimental approaches of Plackett–Burman Design (PBD), and Rotatable Central Composite Design (RCCD), followed by pH-uncontrolled cultivation conditions in a 7 L bench-top bioreactor revealed an innovative medium formulation. These approaches substantially improved ACP production, reaching 207.6 U L−1 with an ACP yield coefficient Yp/x of 25.2 and a specific growth rate (µ) of 0.07 h−1. The metals Na, Li, and Mn were the most efficiently released from RP during the solubilization process by B. haynesii. The uncontrolled pH culture condition is the most suitable setting for simultaneously improving the ACP and organic acids production. The most abundant organic acid produced through the cultivation process was lactic acid, followed by glutamic acid and hydroxybenzoic acid isomer. The findings of TGA, DSC, SEM, EDS, FTIR, and XRD analysis emphasize the significant influence of organic acids and ACP activity on the solubilization of RP particles.

Solubilization of rock phosphate by phosphate solubilizing bacteria isolated from effluent treatment plant sludge of a fertilizer plant.

This study evaluates the efficiency of Phosphate solubilizing bacteria isolated from Effluent Treatment Plant sludge of Paradeep Phosphate Limited, Odisha, India, to solubilize rock phosphate (RP) and the mechanism and structural changes during solubilization investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR). Out of 13 bacterial isolates, Bacillus cereus S0B4, Solibacillus isronensis S0B8, and Bacillus amyloliquefaciens S0B17 strains were found to be the best RP solubilizers. This is the first report on S. isronensis S0B8 with the ability to solubilize RP. In particular, the potent strain B. cereus S0B4 showed maximum soluble P (338.5mg/L) on the 7th day. Negative correlations (r = -0.70; p ≤ 0.01) were observed between soluble P concentration and pH, whereas positive correlation exists with the growth of B. cereus S0B4 (r = 0.91, p ≤ 0.01), S. isronensis S0B8 (r = 0.75, p ≤ 0.01), and B. amyloliquefaciens S0B17 (r = 0.77, p ≤ 0.01) respectively. The P release kinetics followed the 1st order model well (R2 = 0.8001-0.8503). It seems that H+ ions and organic anions released from the organic acids are major factors responsible for RP solubilization. The SEM observations demonstrate that B. cereus S0B4 corroded the RP surface significantly due to the proton attack. The XRD analysis confirms that the intensity of all mineral peaks decreases after treatment with B. cereus S0B4. The FTIR analysis indicated a significant decrease of calcite and fluorapatite's vibrational bands with the disappearance of quartz.

Growth promotion and protection against root rot of sugar beet (Beta vulgaris L.) by two rock phosphate and potassium solubilizing Streptomyces spp. under greenhouse conditions

Growth promotion and protection against root rot of sugar beet (Beta vulgaris L.) by two rock phosphate and potassium solubilizing Streptomyces spp. under greenhouse conditions

Multifarious Indigenous Diazotrophic Rhizobacteria of Rice (Oryza sativa L.) Rhizosphere and Their Effect on Plant Growth Promotion.

A diverse group of rhizobacteria persists in the rhizospheric soil, on the surface of roots, or in association with rice plants. These bacteria colonize plant root systems, enhance plant growth and crop yield. Indigenous rhizobacteria are known to promote soil health, grain production quality and serve as sustainable bioinoculant. The present study was aimed to isolate, identify and characterize indigenous plant growth promoting (PGP) diazotrophic bacteria associated with the rhizosphere of rice fields from different areas of Jammu and Kashmir, India. A total of 15 bacteria were isolated and evaluated for various PGP traits, antagonistic activity against phytopathogens, production of hydrolytic enzymes and biofilm formation under in-vitro conditions. The majority of the isolated bacteria were Gram-negative. Out of 15 bacterial isolates, nine isolates produced IAA (12.24 ± 2.86 to 250.3 ± 1.15 μg/ml), 6 isolates exhibited phosphate solubilization activity (36.69 ± 1.63 to 312.4 ± 1.15 μg/ml), 7 isolates exhibited rock phosphate solubilization while 5 isolates solubilized zinc (10–18 mm), 7 isolates showed siderophore production, 8 isolates exhibited HCN production, 6 isolates exhibited aminocyclopropane-1-carboxylate (ACC) deaminase activity, 13 isolates exhibited cellulase activity, nine isolates exhibited amylase and lipase activity and six isolates exhibited chitinase activity. In addition, 5 isolates showed amplification with the nifH gene and showed a significant amount of nitrogenase activity in a range of 0.127–4.39 μmol C2H4/mg protein/h. Five isolates viz., IHK-1, IHK-3, IHK-13, IHK-15 and IHK-25 exhibited most PGP attributes and successfully limited the mycelial growth of Rhizoctonia solani and Fusarium oxysporum in-vitro. All the five bacterial isolates were identified based on morphological, biochemical and 16S rDNA gene sequencing study, as Stenotrophomonas maltophilia, Enterobacter sp., Bacillus sp., Ochrobactrum haematophilum and Pseudomonas aeruginosa. Rice plants developed from seeds inoculated with these PGP strains individually had considerably higher germination percentage, seed vigor index and total dry biomass when compared to control. These findings strongly imply that the PGP diazotrophic bacteria identified in this work could be employed as plant growth stimulators in rice.

Minjingu phosphate rock solubilization and potential for use of Klebsiella variicola-MdE4 and Klebsiella variicola-MdG1 as biofertilizer for maize production

Limited solubility of the Tanzania’s Minjingu phosphate rock (MPR) in non-acidic soil conditions has held back its potential for widespread use in agricultural production. This study was designed to isolate, characterize and test phosphate-solubilizing bacteria for their potential to increase solubility of MPR and enhance maize plant growth under field conditions. Ten out of 19 isolates showing greatest phosphate solubilization indices on a Pikovskaya agar medium were further characterized for other plant-growth promoting traits including production of IAA, siderophores and ammonia. Two of them, namely isolates-MdE4 and MdG1 substantially outperformed other isolates in phosphate solubilization and production of IAA, ammonia and siderophores. The two isolates molecularly identified as Klebsiella variicola-MdE4 and K. variicola-MdG1 produced up 701, 699 and 750, 680 μg/ml of soluble phosphate from tricalcium phosphate and hard Minjungu rock phosphate, respectively. Additionally, Biorock P- a biofertilizer formulation containing MdE4 and MdG1 co-cultured in a molasses-based modified broth medium retained most of the phosphate solubilizing potential and other plant-growth promoting traits of MdE4 and MdG1. Co-application of MdE1 and MdG1-containing “bio-rock P” and inorganic phosphate at 20 kg P/ha resulted in higher maize grain yield than that of positive control (40 kg P/ha) under field conditions. The two isolates- Klebsiella variicola-MdE4 and K. variicola-MdG1 have the potential for use in a biofertilizer formulation for commercial field applications.

Dynamic of Chemical and Biological Properties of Inceptisols Cilembu due to Phosphate Rock Nanoparticle Amendment and Phosphate-Solubilizing Fungi Inoculation

Cilembu's Inceptisols have great potential for agriculture. However, land management has several limiting factors: the available phosphate content, cation exchange capacity (CEC), and low population of functional soil organisms. Rock phosphate is a natural material that can increase the availability of P nutrient. Application of rock phosphate as an ameliorant in nanoparticle size and inoculation of phosphate-solubilizing fungi (PSF) is a strategy that can be implemented to address the Inceptisols constraints. However, the dynamic of chemical and biological characteristics of Cilembu Inceptisols due to amendment of phosphate rock nanoparticle (PRNp) and phosphate solubilizing fungi (PSF) inoculation is not yet understood clearly. To know the dynamics of the chemical and biological properties of the soil due to the treatment of these materials is an essential aspect for strategy and planning in its proper application to improve the properties of Inceptisols. The completely randomized design (CRD) was used in this study, with a factorial pattern, consisting of the first factor being the amendment of rock phosphate nanoparticle and the second factor being the PSF inoculation. The observation was carried out in a month interval, with a three-month incubation. The result showed there was no interaction between phosphate rock nanoparticle amendment and PSF inoculation on pH-H2O, available P, CEC, and abundance of PSF population. The independent effect showed that a characteristic pattern of pH and available P values during two months of observation was increasing by PRNp amendment. Meanwhile, inoculation of PSF did not increase soil pH and P-available. The value of CEC and the population of PSF did not increase significantly during the three-month incubation. The dose of phosphate rock nanoparticle 2% (wt/wt) increased the highest available P.

Effect of Phosphorus Levels and Phosphorus-Solubilization Rock Phosphate by Spent Wash on Growth and Productivity of Wheat

Field experiment was conducted at Agriculture Research Farm, Institute of Agricultural Science during 2014-15 and 2015-16. The experiments comprising five levels of phosphorus (control, 100% Recommended dose of N & K +50% P through SSP, 100% Recommended dose of N & K +75% P through SSP, 100% Recommended dose of N & K +50% P through rock phosphate and 100% Recommended dose of N & K +75% P through rock phosphate) in main plots and four levels of solubilization of rock phosphate treatments (control, RP:SW@1:10, RP:SW@1:40 and RP:SW@1:80) in sub-plots combinations of twenty treatment were tested in split plot design with three replications. Wheat HUW-468(variety) was sown seed of 100 kg ha-1 in rows spaced at 22.5 cm. Results revealed indicate that solubilization of rock phosphate remained at par with RP:SW@1:80 but recorded significantly higher plant height (cm), Total number of tillers/m row length, Chlorophyll content (SPAD), Test weight (gram), Grain yield, Straw yield and Biological yield (kg/ha) as compared to remaining levels of rock phosphate and control and Results further indicate that solubilization of rock phosphate remained at par with RP:SW@1:80. Results revealed that application of 100% N&K + 75% P through SSP found significantly superior over the other level.

Phosphorus excess changes rock phosphate solubilization level and bacterial community mediating phosphorus fractions mobilization during composting

This study investigated the changes of phosphorus (P) fractions, bacterial community and their response to available P or carbon (C):P during composting with different rock phosphate (RP) addition levels. Results showed that adding RP at 10% or 15% promoted the rise of temperature, maturity and Olsen P accumulation in composting, which had a higher amount of RP solubilization than other groups. Available P changed bacterial composition and decreased diversity in composts. RP solubilization efficiency was negatively correlated to C:P ratio and the highest (22.7%) when 10% RP was added, in which bacterial community changed from “function redundancy” to “intensive P-solubilization”. Low C:P ratio (〈300) increased the RP solubilization ratio especially within 135–160. Therefore, this study proposed that adding P-rich substrates to decrease C:P ratio could regulate P-solubilizers’ activity for increasing RP solubilization efficiency during composting.

Isolation and Characterization of Phosphate Solubilizing Streptomyces sp. Endemic from Sugar Beet Fields of the Beni-Mellal Region in Morocco.

In the course of our research, aimed at improving sugar beets phosphorus nutrition, we isolated and characterized Streptomyces sp. strains, endemic from sugar beet fields of the Beni-Mellal region, which are able to use natural rock phosphate (RP) and tricalcium phosphate (TCP) as sole phosphate sources. Ten Streptomyces sp. isolates yielded a comparable biomass in the presence of these two insoluble phosphate sources, indicating that they were able to extract similar amount of phosphorus (P) from the latter for their own growth. Interestingly, five strains released soluble P in large excess from TCP in their culture broth whereas only two strains, BP, related to Streptomyces bellus and BYC, related to Streptomyces enissocaesilis, released a higher or similar amount of soluble P from RP than from TCP, respectively. This indicated that the rate of P released from these insoluble phosphate sources exceeded its consumption rate for bacterial growth and that most strains solubilized TCP more efficiently than RP. Preliminary results suggested that the solubilization process of BYC, the most efficient RP and TCP solubilizing strain, involves both acidification of the medium and excretion of siderophores. Actinomycete strains possessing such interesting RP solubilizing abilities may constitute a novel kind of fertilizers beneficial for plant nutrition and more environmentally friendly than chemical fertilizers in current use.