Soluble Phosphorus Research Articles

Revealing of Potential Plant Growth-Enhancing Traits Through In Silico Genomic Analysis of Bacillus Rhizoplanae CIP111899

The objective of this study was to examine the whole genome of the bacterial strain CIP111899, isolated from the root surface of maize (Zea mays), in order to reveal the presence of genes implicated in enhancing plant growth. The genome-based taxonomy revealed that strain CIP111899 belongs to a new species called Bacillus rhizoplanae. In the second step, the genome of CIP111899 was analyzed on multiple levels using various information tools. This involved examining functional categories associated with genes using analytical techniques, namely, annotation using the RAST server, then identifying growth-promoting genes with the Prokka program, and finally detecting groups of genes responsible for secondary metabolism through antiSMASH analysis. The results of the genomic analysis of strain CIP111899 showed the presence of multiple genes that enhance stress tolerance, such as those encoding enzymes and antioxidants (superoxide dismutase, peroxidases, and catalase). Additionally, various plant growth-promoting genes were identified, including those involved in the solubility of inorganic phosphorus, phytohormone production, and iron uptake. In conclusion, strain CIP111899 has shown promise as a potential agent for promoting plant growth and thereby improving food security due to its genetic composition.

Microflow synthesis of a formulation of phosphorus fertiliser to enhance the P content in soil and P uptake in wheat

Highly soluble phosphorus (P) fertilisers have been commonly used in agriculture for decades, but their efficiency can be low due to forming precipitation with cations in the soil or leaching into nearby water sources, thus causing eutrophication.

Screening of phosphorus solubilizing microorganisms in cold environment and their effects on the growth of Brassica napus.

To screen out phosphorus solubilizing strains that can adapt to cold climate in Qinghai Province, Bacillus mucilaginosus, B. megaterium, B. cereus, Streptomyces violovariabilis, S. cinnamofuscus, and S. flavoagglomeratus were screened with solid plate medium as the primary and liquid medium as the secondary screening, with calcium phosphate, lecithin, and phytic acid as the single source of phosphorus. By comprehensively comparing the size of phosphate solubilizing circle in the solid plate medium and the soluble phosphorus content in the liquid medium, three strains of phosphate solubilizing bacteria with good phosphate solubilizing effects were screened, S. violovariabilis, S. cinnamofuscus, and B. mucilaginosus. The three phosphate solubilizing bacteria were made into liquid ino-culants, and the small rapeseed pot experiment was carried out with two soils with different fertilities in a cold climate in September. Compared with the control, plant height, fresh weight, root length, and root weight of rapes in high-fertility cultivated soil increased by 35.5%, 191.0%, 26.2%, and 282.7%, while plant phosphorus absorption, total phosphorus and available phosphorus contents in the rhizosphere soil increased by 968.9%, 5.1%, and 2.1%, respectively. In low-fertility soil, plant height and fresh weight was increased by 45.8% and 61.3%, root length and weight was decreased by 2.6% and 4.4%, while plant phosphorus absorption and the contents of total P and available P in rhizosphere soil were increased by 91.5 %, 29.1%, and 213.7%, respectively. The effect of the other two inoculants treatments was less significant than S. violovariabilis. Therefore, S. violovariabilis was the phosphate solubilizing strain suitable for the cold climate in Qinghai.

Assessment of Nutrient Leaching Losses and Crop Uptake with Organic Fertilization, Water Saving Practices and Reduced Inorganic Fertilizer

The increasing world population has forced excessive chemical fertilizer and irrigation to complete the global food demand, deteriorating the water quality and nutrient losses. Short-term studies do not compile the evidences; therefore, the study aimed to identify the effectiveness of reduced doses of inorganic fertilizer and water-saving practices, hence, a six-year experiment (2015–2020) was conducted in China to address the knowledge gap. The experimental treatments were: farmer accustomed fertilization used as control (525:180:30 kg NPK ha−1), fertilizer decrement (450:150:15 kg NPK ha−1), fertilizer decrement + water-saving irrigation (450:150:15 kg NPK ha−1), application of organic and inorganic fertilizer + water-saving irrigation (375:120:0 kg NPK ha−1 + 4.5 tones organic fertilizer ha−1), and application of controlled-release fertilizer (80:120:15 kg NPK ha−1). Each treatment was replicated thrice following a randomized complete block design. The results achieved herein showed that control has the highest losses in the six-year study for total nitrogen (225.97 mg L−1), total soluble nitrogen (121.58 mg L−1), nitrate nitrogen (0.93 mg L−1), total phosphorus (0.57 mg L−1), and total soluble phosphorus (0.57 mg L−1) respectively. Reduced fertilizer and water application improved crop nutrient uptake, nitrogen concentration was significantly enhanced with organic and inorganic fertilizer + water-saving irrigation, P concentration was increased with fertilizer decrement + water-saving irrigation, and K concentration was improved with fertilizer decrement + water-saving irrigation. Hence, this study concludes that reduced inorganic fertilizer dose combined with water-saving practices is significantly helpful in reducing nutrient leaching losses and improving nutrient uptake and water pollution. Further studies are needed to explore the impacts of reduced fertilization and water-saving irrigation on leaching losses. The benefits at different climatic conditions, soil types, and fertilizer types with application methods are also a research gap.

Effect of Integrated Nutrient Management on Physical and Physico-chemical Properties of Soil

Increasing food production while reducing environmental impact and resource use is the main challenge in agriculture. The usage of inorganic fertilizers in agriculture for increasing food production does not guarantee a sustainable future. In Integrated Nutrient Management (INM) we make conjunctive use of organic manures and inorganic fertilizers for improving soil productivity while also protecting soil properties from being destructed. In this research, the effect of INM on various soil properties is been investigated. The field experiment was carried out in India, during the rabi season of 2020 in a sandy loam soil of ustic Inceptisols under maize (Zea mays L.) variety Pioneer - 3396 as the Test crop. Application of Farm Yard Manure (FYM) @ 10 t/ha, biofertilizers namely Azospirillum and Phosphorus Solubilizing Bacteria (Pseudomonas sp.) @ 5 kg/ha each, was followed. The inorganic fertilizers @ 200:60:50 N-P2O5-K2O kg ha-1 were followed as recommended dose and applied in three splits. The experiment is conducted in Randomised Complete Block Design (RCBD) comprising eight treatments and three replications viz., T1: Control, T2: 100% RDN, T3: 125% RDN, T4: 75% RDN+ 25% N through FYM, T5: 75% RDN + 25% N through FYM + Biofertilizers, T6: 100% RDN+ 25% N through FYM, T7: 100% RDN+ Biofertilizers and T8: 100% RDN+ 25% N through FYM + Biofertilizers. Statistical significance was tested by applying F-test at a 0.05 level of probability. There was observed a non-significant effect on the Bulk Density (BD), Porosity, Water Holding Capacity (WHC), Cation Exchange Capacity (CEC), Soil reaction (pH), and Electrical Conductivity (EC), Organic Carbon (OC) of the experimental soil, which might be due to the short duration of the study.

Characterization of Paenibacillus spp. CBRM17 as antagonist of phytopathogenic fungi and growth promoter of Capsicum chinense Jacq.

Studies of the plant-microorganism relationship have made it posible to explore the potential of rhizospheric bacteria to improve the health and quality of plants. In the present study, Paenibacillus sp. CBRM17 was characterized in vitro for its ability to inhibit the growth of phytopathogenic fungi that cause diseases in horticultural crops in the tropics, finding a reduction in the mycelial growth of Alternaria, Fusarium and Helmintosphorium strains in the range of 50 to 70 %, additionally its biochemical properties related to the promotion of plant growth were characterized, registering the production of 0.36 µg/mL of indole acetic acid (IAA), the solubilization of tricalcium phosphate with solubilization index (SI) of 2.41 mm and solubilization efficiency (SE) of 140.6 %, producing in the supernatant 63.5 mg/L of soluble phosphorus, in addition to being positive for ACC deaminase activity. Inoculations trials of habanero chili (Capsicum chinense Jacq.) seeds with Paenibacillus sp. CBRM17 showed its potential to be used as an inoculant in the growth promotion of this crop, since it increased all growth variables; increasing the total fresh and dry biomass by 93.3 and 96.4 %, respectively.

Integrated Nutrient Management to increase Productivity and Profitability in Dual Purpose Oat (Avena sativa L.)

Field experiments were carried out to Study the Integrated Nutrient Management to increase Productivity and Profitability in Dual Purpose Oat (Avena sativa L.) at Genetics and Plant Breeding Research Farm, Acharya Narendra Deva University of Agriculture and Technology, Kumarganj, Ayodhya, Uttar Pradesh (UP), during Rabi season 2018-19. The experiment was laid out in Randomized block design (RBD) with three replications and nine treatments viz., T1: Control, T2: RDF (100 kg N : 40 kg P2O5 : 40 kg K2O ha-1), T3: 75 % RDN + Vermicompost @ 2t ha-1, T4: T3 + PSB (soil application @ 1.5 kg ha-1), T5: T4 + Azotobacter (seed treatment @10g kg-1 seed), T6: T5 + ZnSO4 @ 20 kg ha-1 (soil application as basal ), T7: T5+ ZnSO4 @ 15 kg ha-1 (soil application as basal), T8: T6 + Foliar spray of ZnSO4 (0.5%) at just before flowering, T9: T7 + Foliar spray of ZnSO4 (0.5%) at just before flowering. Results revealed that higher yield attributes viz. panicle length (37.40cm), panicle weight (9.80g), number of grain panicle-1 (56.33), test weight (48.70g), green forage yield (90.60 q ha-1), dry matter yield (17.51 q ha-1), yield parameters viz. grain yield (16.51 q ha-1), straw yield (72.97 q ha-1) and profitability viz. gross income (INR 82069.5 ha-1), net income (INR 51605.5 ha-1) and B:C ratio (1.69) of oat for T8: 75% RDN + Vermicompost @ 2t ha-1 + PSB (soil) @ 1.5 kg ha-1 + Azotobacter (seed treatment) @ 10 g kg-1 of seed + ZnSO4 @ 20 kg ha-1 (basal) + foliar spray of ZnSO4 (0.5%) at just before flowering of oat as compared to the control. Whereas, application of organic and inorganic fertilizers in combinations viz., Nitrogen, Phosphorus, Potassium, Vermicompost, Phosphorus Solubilizing Bacteria (PSB), Azotobacter and Zinc had a significant effect on total biomass production, yield attributes, yield and profitability of oat.

Effect of pH and Carbon Source on Phosphate Solubilization by Bacterial Strains in Pikovskaya Medium.

Phosphate-solubilizing bacteria (PSB) transform precipitated inorganic phosphorus into soluble orthophosphates. This study evaluated the efficiency of tricalcium and iron phosphate solubilization in Pikovskaya medium using five bacterial strains (A1, A2, A3, A5, and A6) cultured in acidic and alkaline pH levels. The bacterial strain that proved to be more efficient for P solubilization and was tolerant to pH variations was selected for assessing bacterial growth and P solubilization with glucose and sucrose in the culture medium. The bacterial strains were identified through 16S rRNA gene sequencing as Pseudomonas libanensis A1, Pseudomonas libanensis (A2), Bacillus pumilus (A3), Pseudomonas libanensis (A5), and Bacillus siamensis (A6). These five bacterial strains grew, tolerated pH changes, and solubilized inorganic phosphorus. The bacterial strain A3 solubilized FePO4 (4 mg L-1) and Ca3(PO4)2 (50 mg L-1). P solubilization was assayed with glucose and sucrose as carbon sources for A3 (Bacillus pumilus MN100586). After four culture days, Ca3(PO4)2 was solubilized, reaching 246 mg L-1 with sucrose in culture media. Using glucose as a carbon source, FePO4 was solubilized and reached 282 mg L-1 in six culture days. Our findings were: Pseudomonas libanensis, and Bacillus siamensis, as new bacteria, can be reported as P solubilizers with tolerance to acidic or alkaline pH levels. The bacterial strain B. pumilus grew using two sources of inorganic phosphorus and carbon, and it tolerated pH changes. For that reason, it is an ideal candidate for inorganic phosphorus solubilization and future production as a biofertilizer.

Simple and efficient method for purification and recovery of gypsum from phosphogypsum: Reverse-direct flotation and mechanism

A simple and efficient approach of high-speed stirring scrubbing, reverse flotation and direct flotation was adopted to the purification of phosphogypsum (PG), and KH and dodecylamine hydrochloride (DH) were first used as the collectors of reverse and direct flotation, respectively. X-ray diffractometer (XRD), thermal gravimetric analyser (TGA), X-ray photoelectron spectrometry (XPS), and Fourier transform infrared spectroscopy (FT-IR) were used to characterise the samples and analyse the mechanism. KH selectively reactes with organic matter, slime, quartz and pyrite via hydrogen bond and dehydration condensation between the –OH in silanol hydrolyzed by KH and –OH on the surface of quartz and pyrite, and –COOH in the organic matter. Furthermore, the direct flotation collector of DH exhibited superior selectivity of gypsum via electrostatic attraction, and increased the whiteness and purity of the gypsum concentrate to 69.2% and 97.24%, respectively, and the soluble phosphorus and fluorine contents decreased to 0.046% and 0.024%, respectively. The gypsum concentrate reached the first-grade national standard of PG in China (GB/T 23456-2018). Therefore, this study provided a new approach for the purification of PG, which has an important guiding significance for the resource utilisation of PG.

Plant microbiomes harbor potential to promote nutrient turnover in impoverished substrates of a Brazilian biodiversity hotspot

The substrates of the Brazilian campos rupestres, a grassland ecosystem, have extremely low concentrations of phosphorus and nitrogen, imposing restrictions to plant growth. Despite that, this ecosystem harbors almost 15% of the Brazilian plant diversity, raising the question of how plants acquire nutrients in such a harsh environment. Here, we set out to uncover the taxonomic profile, the compositional and functional differences and similarities, and the nutrient turnover potential of microbial communities associated with two plant species of the campos rupestres-dominant family Velloziaceae that grow over distinct substrates (soil and rock). Using amplicon sequencing data, we show that, despite the pronounced composition differentiation, the plant-associated soil and rock communities share a core of highly efficient colonizers that tend to be highly abundant and is enriched in 21 bacterial families. Functional investigation of metagenomes and 522 metagenome-assembled genomes revealed that the microorganisms found associated to plant roots are enriched in genes involved in organic compound intake, and phosphorus and nitrogen turnover. We show that potential for phosphorus transport, mineralization, and solubilization are mostly found within bacterial families of the shared microbiome, such as Xanthobacteraceae and Bryobacteraceae. We also detected the full repertoire of nitrogen cycle-related genes and discovered a lineage of Isosphaeraceae that acquired nitrogen-fixing potential via horizontal gene transfer and might be also involved in nitrification via a metabolic handoff association with Binataceae. We highlight that plant-associated microbial populations in the campos rupestres harbor a genetic repertoire with potential to increase nutrient availability and that the microbiomes of biodiversity hotspots can reveal novel mechanisms of nutrient turnover.

The salutary impacts of AMF species, rock phosphates (RP), and organic matter (FYM) fertilizers on the development and chemical behavior of Mentha arvensis L.

Phosphorus availability from rock phosphate (RP) can be improved through composting with organic manure and phosphate-solubilizing microorganisms in the soil to improve phosphorus status and plant growth in alkaline and calcareous soils of Pakistan. As a result, an experiment was carried out to determine the impact of arbuscular mycorrhizal fungi (AMF) species as biofertilizers on Mentha arvensis when rock phosphate and organic manure (FYM) levels were varied (0%, 50%, and 100%). In M. arvensis, plant growth performance, mycorrhizal dependence values, oil output, mineral, and nutritional analysis, infection, and spore density were evaluated. The experiment was designed with eight RCBD treatments and five replications. Compared to non-inoculated plants, the growth responses of M. arvensis to AM inoculation with rock phosphate and organic manure were pronounced. Mycorrhizal dependencies increased with increasing levels of rock phosphate and organic manure, which were 40.82% and 46.92%, respectively. The results showed that M. arvensis produced a higher percentage of essential oil for AMF inoculation at higher and lower levels of rock phosphate and organic manure. In terms of nutrient uptake by mycorrhizal plants, there were a significant improvement in macro (P, N, K, Mg) and micronutrients (Fe, Cu, and Zn) in all tested mycorrhizal plants compared to non-treated plants. The nutritional value of M. arvensis rises with the amount of fertilizer added. Results proved that as fertility levels rise, the number of spores (150 to 190/100 g of soil) and the percentage of association (70.51 to 95.23%) increase in Mentha arvensis. The findings imply that inoculating plants with AMF might increase phosphorus solubility from rock phosphate and organic manure. Local rock phosphate and organic manure may be used to reduce reliance on expensive commercial synthetic fertilizers while also increasing crop yields.

Screening of potential phosphate solubilizing bacteria inoculants should consider the contrast in phosphorus bio-solubilization rate along with plant growth promotion and phosphorus use efficiency.

Although phosphate solubilizing bacteria (PSB) have been globally reported to improve soil phosphorus (P) availability and plant growth, technical gaps such as the lack of an ideal screening approach, is yet to be addressed. The potential of non-halo-forming PSB remains underestimated because of the currently adopted screening protocols that exclusively consider halo-forming and PSB with high phosphorus solubilization (PS) capacities. Yet, caution should be taken to properly assess PSB with contrasting PS rates regardless of the presence or absence of the solubilization halo. This study sought to examine the PS rate and plant growth promotion ability of 12 PSB categorized as high PSB (H-PSB), medium PSB (M-PSB), and low PSB (L-PSB) based on their PS rates of rock phosphate (RP). The non-halo-forming PSB Arthrobacter pascens was categorized as H-PSB, which might have been eliminated during the classical screening process. In addition, induction of organic acids and phosphatase activity in rhizosphere soils by H-, M-, and L-PSB was proportional to increased wheat P content by 143.22, 154.21, and 77.76 mg P g-1 compared to uninoculated plants (18.1 mg P g-1). Isolates considered as M- and L-PSB could positively influence wheat above-ground physiology and root traits as high as H-PSB. In addition, non-halo-forming PSB revealed significant PS rates along with positive effects on plant growth as high as halo-forming PSB.

Consolidation of phosphorus tailings and soluble fluorine & phosphorus with calcium carbide residue-mirabilite waste as a green alkali activator

Two alkalis of industrial solid wastes, calcium carbide residue-mirabilite (CCRM), were used as a green combined activator to consolidate phosphorus tailings and soluble phosphorus as well as fluorine through the alkaline activation process. The results based on XRD, FTIR, 29Si NMR and SEM indicated that most of the blast furnace slag (BFS) forms gels to consolidate phosphorus tailings, and the calcium silicate hydrate (C-S-H) gel dominated mechanical properties and immobilization of soluble phosphorus and fluorine. Comparing with the classical alkaline activators Na2SiO3 and NaOH, the CCRM activated materials displayed great competitiveness in mechanical properties with the order of NaOH < CCRM < Na2SiO3. Its maximum compressive strength reached to 10.9 MPa, and the compressive strength increased greatly with certain increasing content of BFS. In addition, the toxicity characteristic leaching procedure (TCLP) tests found the consolidation of risky soluble fluorine and phosphorus ions in the alkaline activation materials (AAMs) presented in the trend of CCRM > NaSiO3 > NaOH, and the tendency enlarges with increasing BFS addition, over 93.1 % and 98.9 % of soluble fluorine and phosphorus ions could be well fixed. Considering on the environmental and economic efficiency, mechanical properties, soluble phosphorus and fluorine immobilization, the CCRM is found a quite potential solid waste alkali activator for phosphorus tailings and soluble fluorine & phosphorus solidification.

Effect of Rock Phosphate, Single Super Phosphate and Phosphorus Solubilizing Bacteria on Phosphorus Concentration and Dry Matter Yield of Paddy

The majority of tropical and subtropical soils are acidic which are mostly deficient in phosphorus and have strong phosphorus sorption capacity. Exploring different phosphorus inputs is essential not only to increase crop production but also to improve soil phosphorus status to avoid further soil degradation. Acidic nature of the soils of these regions help to solubilize the rock phosphate and increases the amount of phosphorus that is made available to the plants. A pot experiment was conducted in Department of Soil Science and Agricultural Chemistry of College of Agriculture, Central Agricultural University, Imphal (Manipur) during kharif season of 2021 to study the effect of rock phosphate, single super phosphate and phosphorus solubilizing bacteria on phosphorus concentration and dry matter yield of paddy. To each experimental pot, recommended dose of 60 kg of N ha-1 in the form of urea and 30 kg K2O ha-1 in the form of muriate of potash were applied as basal and thoroughly mixed with the soil. Rock phosphate and single super phosphate were administered to the pots as phosphorus sources according to different sets of treatment based on the recommended amount of 40 kg P2O5 ha-1 for paddy. Seeds were treated with Bacillus megatherium. Result revealed that the changes in soil phosphorus concentration and dry matter yield of paddy were significantly affected by rock phosphate applied either singly or in combination with single super phosphate and phosphorus solubilizing bacteria. All the parameters showed different trend of changes during the whole crop growth stages till harvest. Among the treatments higher values were recorded in soil treated with T10 (50% recommended dose of P2O5 from single super phosphate + 50% recommended dose of P2O5 from rock phosphate + phosphorus solubilizing bacteria). Addition of phosphorus solubilizing bacteria enhances release of less soluble and fixed forms into easily available form as well as reduces phosphorus fixation. Efficiency of rock phosphate as phosphorus source for crop production is improved by the solubility effect of phosphorus solubilizing bacteria.

Combined Application of Calcium-Magnesium Phosphate Fertilizer with Soluble Phosphorus Improves Maize Growth in a Calcareous Soil

Combined Application of Calcium-Magnesium Phosphate Fertilizer with Soluble Phosphorus Improves Maize Growth in a Calcareous Soil

Isolation, identification, and biocontrol mechanisms of endophytic Burkholderia vietnamiensis C12 from Ficus tikoua Bur against Rhizoctonia solani

Rice sheath blight is a devastating fungal disease caused by Rhizoctonia solani. Biocontrol utilizing endogenous microorganisms has been considered a safe and sustainable strategy. To obtain a new type of antagonistic bacteria with a high biocontrol effect on rice sheath blight, over 50 endophytic bacteria were isolated from the root of the medicinal plant Ficus tikoua Bur and screened for their antifungal activity by dual culture assay. Among them, strain C12 showed the strongest inhibitory activity against R. solani (inhibition rate 94.78%), and exhibited a broad-spectrum antifungal activity. According to the phylogenetic tree based on 16S rDNA and recA genes, C12 was identified as Burkholderia vietnamiensis, belonging to the Burkholderia cepacia complex, and safe for plants and humans. Through the study on B. vietnamiensis C12, the strain could secrete cell wall degrading enzymes (protease and chitinase), produce IAA, and siderophores, fix nitrogen, and solubilize phosphorus. The bacterial culture filtrate (although treated at 121 °C) of strain C12 and its ethyl acetate extract significantly inhibited the growth of R solani and resulted in distorted hyphae. Moreover, when the extract was 50 μg/mL, 100 μg/mL, 200 μg/mL, and 500 μg/mL, the diameter of mycelium was decreased by 50.44%, 56.43%, 67.27%, and 74.80% respectively, the number of sclerotia was decreased by 85.45%, 90.42%, 96.83%, and 99.22% respectively. Multiple antifungal substances in extracts of C12 were detected through LC-MS. Strain C12 gave a 70.98% reduction in lesion length in a detached inoculated leaf assay. In greenhouse and field tests, strain C12 significantly reduced the disease index of rice sheath blight, and the control efficiency reached 68.75% and 66.52%, respectively. Furthermore, C12 enhanced the resistance of rice to R. solani by increasing the activities of defense enzymes SOD, PAL, POD, CAT, and PPO. The strain also exhibited plant-promoting abilities on rice. The results indicated that B. vietnamiensis C12 had great biocontrol potential and could be used as a candidate strain for green control of rice sheath blight.

Screening of phosphate-solubilizing bacteria and their abilities of phosphorus solubilization and wheat growth promotion.

Phosphate-solubilizing bacteria (PSB) can enhance plant growth and phosphorus (P) solubilization, it also has been reported to reduce the negative effects of overused agricultural fertilizer in farmland and protect the soil environment. However, the mechanism behind this interaction has not been fully elucidated. In this study, we screened out Pseudomonas moraviensis, Bacillus safensis, and Falsibacillus pallidus which can both solubilize P efficiently and produce indole-3-acetic acid (IAA) from sandy fluvo-aquic soils. The yield of wheat (Triticum aestivum) under PSB inoculation significantly increased up to 14.42% (P < 0.05) compared with the control treatment in phosphate fertilizer-used farmland. Besides promoting wheat growth, we found the labile P fraction in soil was significantly increased by over 122.04% (P < 0.05) under PSB inoculation compared with it in soils without, in parallel, the stable P fraction was significantly reduced by over 46.89% (P < 0.05). Furthermore, PSB inoculation increased the soil microbial biomass and activity, indicating that PSB screened out in this work performed a remarkable ability to colonize the soils in the wheat field. PSB from sandy fluvo-aquic soil improve wheat growth and crop productivity by increasing the labile P fraction and IAA content in the greenhouse and wheat field. Our work provides an environment and economy-friendly bacterial resource that potentially promotes sustainable agricultural development in the long term.

Two novel phosphorus/potassium-degradation bacteria: Bacillus aerophilus SD-1/Bacillus altitudinis SD-3 and their application in two-stage composting of corncob residue

For effective utilization of corncob residue to realize green circular production, using composting to obtain a high-quality and low-cost biomass fertilizer has become a very important transformation avenue. In this paper, two novel phosphorus/potassium-degradation bacterial strains were isolated from tobacco straw and identified as Bacillus aerophilus SD-1/Bacillus altitudinis SD-3 (abbreviated as SD-1/SD-3). These identified two novel bacteria SD-1/SD-3 show that the soluble phosphorus content of SD-1/SD-3 reached 360.89mgL-1/403.56mgL-1 in the shake flask test, and the mass concentration of soluble potassium is 136.56mgL-1/139.89mgL-1. In addition, the Laccase (Lac), Lignin peroxidase (LiP), and Manganese peroxidase (MnP) activities of SD-1 and SD-3 are 54.45UL-1/394.84UL-1/222.79UL-1 and 46.27UL-1/395.26UL-1/203.98UL-1 respectively, with the carboxy-methyl cellulase (CMCase) of 72.07UmL-1 and 52.69UmL-1. Meanwhile, the effects of three different combinations of cultures, i.e., no inoculation (K1), inoculation of SD-1/SD-3 on day 21 (K2) and on day 0 (G) are investigated to understand the influence on the degradation degree of corncob residue compost. The results of K2 compost treatment showed that the effective P/K content increased nearly 3.1/2.4 times, the degradation of cellulose/lignin was 49.1/68.0%, and the germination rate was 110.23%, which were higher than other experiment groups K1/G. In conclusion, knowledge of this paper will be very useful for the industrial sector for the treatment of complex corncob residue.

Identification of Halophilic and Halotolerant Bacteria from the Root Soil of the Halophyte Sesuvium verrucosum Raf.

Soil salinity is a condition that limits crop growth and productivity, and soil-dwelling bacteria from halophytic plant roots may be a viable strategy to cope with low productivity due to salt stress. Halophilic and halotolerant bacteria of the root soil of Sesuvium verrucosum were analyzed in this study as there is little evidence regarding its associated microbiology. Soil was sampled from the roots of Sesuvium verrucosum to obtain the cultivable bacteria. Their morphological characteristics were identified and they were molecularly identified by the 16S sequence. The growth capacity of the bacteria was determined at different levels of pH and salinity, and several growth promotion characteristics were identified, such as phosphorus solubilization, indole acetic acid production by the tryptophan-dependent (AIAt) and tryptophan-independent (IAA) pathways, ammonium production from organic sources, solubilization of carbonates, and zinc and sodium capture capacity. In addition, the bacteria that presented the best characteristics for germination variables of Solanum lycopersicum were evaluated. A total of 20 bacteria from root soil of Sesuvium verrucosum Raf. belonging to the phyla Proteobacteria (50%), Firmicutes (45%) and Actinobacteria (5%) were identified, with each one having different morphological characteristics. Among the bacterial isolates, 45% had the ability to resist different levels of salinity and pH, ranging from 0 to 20% of NaCl, and pH between 5 and 11. Moreover, these bacteria had the capacity to solubilize carbonates, phosphorus and zinc, capture sodium, produce ammonium from organic substrates and IAA (indole acetic acid), and promote enzymatic activity of amylases, proteases, lipases and cellulases. The bacteria evaluated on the germination of Solanum lycopersicum had an influence on germination at different salinity levels, with greater influence at 100 mM NaCl. This demonstrated that halophilic bacteria belonging to the rhizosphere of Sesuvium verrucosum have the ability to promote growth in extreme salinity conditions, making them candidates for the recovery of productivity in saline soils.

Exploring the Plant Growth-Promotion of Four Streptomyces Strains from Rhizosphere Soil to Enhance Cucumber Growth and Yield

The genus Streptomyces is the most abundant and essential microbes in the soil microbial community. Streptomyces are familiar and have great potential to produce a large variety of bioactive compounds. This genus considers an efficient biofertilizer based on its plant growth-promoting activities. Based on their ability to produce a wide varieties of bioactive molecules, the present study aimed to explore the potential plant growth promotion of four Streptomyces strains and their role in enhancing cucumber growth and yield under greenhouse conditions. Streptomyces sp. strain HM2, Streptomyces thinghirensis strain HM3, Streptomyces sp. strain HM8, and Streptomyces tricolor strain HM10 were chosen for the current study. Plant growth-promoting (PGP) features, i.e., indole acetic acid (IAA) production, siderophore excretion, and solubilizing phosphate, were evaluated in vitro. All four strains produced IAA, siderophore, and immobilized inorganic phosphate. Following 4 days of incubation at 30 °C, strains HM2, HM3, HM8, and HM10 produced copious amounts of IAA (18, 22, 62, and 146 µg/mL, respectively) and siderophores (42.59, 40.01, 16.84, 64.14% SU, respectively). At the same time, P solubilization efficacy scored 64.3%, 84.4%, 57.2%, and 81.6% with the same frequency. During in planta evaluation, selected Streptomyces strains combined with rock phosphate were assessed as biofertilizers on the growth and yield of cucumber plants. Under all treatments, positive and significant differences in studied traits were manifested except dry stem matter (SDM), net assimilation rate (NAR), relative growth rate (RGR), and fruit firmness (FF). Treatment T4 (rock phosphate + strain HM3) followed by T5 (rock phosphate + strain HM8) revealed the best results for plant height (PH), number of leaves per plant (NLPP), root length (RL), number of fruits per plant (NFPP), fruit length (FL), fruit diameter (FD), fruit fresh weight per plant (FFWPP), soil P (SP) after 21 DAT, and soil P at the end of the experiment. Notably, T6 (rock phosphate + strain HM10) caused a considerable increase in leaf area (LA). Plant growth-promoting bacteria enhance plant growth and yield through phosphorus solubilizing, improve nutrient availability, produce phytohormones, and support plant growth under abiotic stress. These features are important for sustainable agriculture and reducing environmental pollution with chemical fertilizers and pesticides.