Microbial Fertilizer Research Articles

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

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

Microbially produced fertilizer provides rhizobacteria to hydroponic tomato roots by forming beneficial biofilms.

Hydroponic cultivation of Solanum lycopersicum (tomato) is important, and high tomato production depends on the use of nitrogen and phosphate fertilizers. We had developed a microbial fertilizer (MF), which is mainly composed of nitrate. To investigate the effect of MF on plant growth, hydroponic tomato was grown with MF or commercial inorganic fertilizer (IF), and the microbiomes of the rhizosphere and the liquid phase were analyzed by confocal microscopy and high-throughput sequencing. Plant biomass and biofilm formation were increased by growth in MF compared to IF. The microbial community structures of tomato roots and hydroponic water differed between the two conditions, and three operational taxonomic units (OTUs) dominated in plants grown with MF. The three OTUs were related to Rudaea spp., Chitinophaga spp., and Stenotrophobacter terrae, which are reported to be disease-suppressive epiphytic or endophytic microbes of plant roots. Because these three OTUs also predominated in the MF itself, they were likely provided to the rhizosphere or endophytic environments of tomato roots via hydroponic water. KEY POINTS: • Microbial fertilizer for hydroponic growth enhanced biofilm formation on tomato root. • Microbial fertilizer contains tomato-root epiphytic or endophytic microbes. • Microbial fertilizer provided beneficial microbes to the rhizosphere and endophytic environments of tomato roots via hydroponic water.

Effect of Chemical Fertilizer with Compound Microbial Fertilizer on Soil Physical Properties and Soybean Yield

Compound microbial fertilizer is a new type of environmentally friendly slow-release fertilizer that can effectively improve the physical and chemical properties of the soil, significantly improve the ecological environment, and promote the sustainable development of agriculture. In this study, we conducted a field experiment to evaluate the impact of different applications of chemical fertilizer combined with composite microbial fertilizer on soil physical properties and soybean yields at Heshan Farm, Heilongjiang Province, China, during 2021–2022. Soybean varieties “Jinyuan 55” and “Keshan 1” were treated with three treatments implemented as follows: T1 (conventional fertilization), T2 (50% N fertilizer + compound microbial fertilizer), and T3 (0 N fertilizer + compound microbial fertilizer). Compared to conventional fertilization (T1 treatment), the application of composite microbial fertilizers (T2 and T3) resulted in a decrease in soil bulk density and an increase in porosity. Notably, we observed that moderate application of the composite microbial fertilizer (T3) led to a decrease in the volume fraction of clay particles and an increase in the volume fraction of sand particles. Furthermore, all treatments exhibited high content of agglomerates larger than 5 mm at 0–20 cm. The application of composite microbial fertilizers (T2 and T3) promoted the formation of large soil agglomerates and reduced the presence of micro-agglomerates smaller than 0.25 mm. In 2021–2022, The soybean yield increased by 13.02% in the T2 treatment compared with the T1 treatment and decreased by 9.34% in the T3 treatment. We concluded that the appropriate application of compound microbial fertilizer can help protect black soil, enhance the self-repair capability of black soil, and improve soybean quality in abnormal precipitation years. These results provide an actionable basis for constructing and developing green fertilizer systems for the soybean industry.

Manipulating rhizosphere microorganisms to improve crop yield in saline-alkali soil: a study on soybean growth and development.

Rhizosphere microorganisms can effectively promote the stress resistance of plants, and some beneficial rhizosphere microorganisms can significantly promote the growth of crops under salt stress, which has the potential to develop special microbial fertilizers for increasing the yield of saline-alkali land and provides a low-cost and environmentally friendly new strategy for improving the crop yield of saline-alkali cultivated land by using agricultural microbial technology. In May 2022, a field study in a completely randomized block design was conducted at the Heilongjiang Academy of Agricultural Sciences to explore the correlation between plant rhizosphere microorganisms and soybean growth in saline-alkali soil. Two soybean cultivars (Hening 531, a salt-tolerant variety, and 20_1846, a salt-sensitive variety) were planted at two experimental sites [Daqing (normal condition) and Harbin (saline-alkali conditions)], aiming to investigate the performance of soybean in saline-alkali environments. Soybeans grown in saline-alkali soil showed substantial reductions in key traits: plant height (25%), pod number (26.6%), seed yield (33%), and 100 seed weight (13%). This underscores the unsuitability of this soil type for soybean cultivation. Additionally, microbial analysis revealed 43 depleted and 56 enriched operational taxonomic units (OTUs) in the saline-alkali soil compared to normal soil. Furthermore, an analysis of ion-associated microbes identified 85 mOTUs with significant correlations with various ions. A co-occurrence network analysis revealed strong relationships between specific mOTUs and ions, such as Proteobacteria with multiple ions. In addition, the study investigated the differences in rhizosphere species between salt-tolerant and salt-sensitive soybean varieties under saline-alkali soil conditions. Redundancy analysis (RDA) indicated that mOTUs in saline-alkali soil were associated with pH and ions, while mOTUs in normal soil were correlated with Ca2+ and K+. Comparative analyses identified significant differences in mOTUs between salt-tolerant and salt-sensitive varieties under both saline-alkali and normal soil conditions. Planctomycetes, Proteobacteria, and Actinobacteria were dominant in the bacterial community of saline-alkali soil, with significant enrichment compared to normal soil. The study explored the functioning of the soybean rhizosphere key microbiome by comparing metagenomic data to four databases related to the carbon, nitrogen, phosphorus, and sulfur cycles. A total of 141 KOs (KEGG orthologues) were identified, with 66 KOs related to the carbon cycle, 16 KOs related to the nitrogen cycle, 48 KOs associated with the phosphorus cycle, and 11 KOs linked to the sulfur cycle. Significant correlations were found between specific mOTUs, functional genes, and phenotypic traits, including per mu yield (PMY), grain weight, and effective pod number per plant. Overall, this study provides comprehensive insights into the structure, function, and salt-related species of soil microorganisms in saline-alkali soil and their associations with salt tolerance and soybean phenotype. The identification of key microbial species and functional categories offers valuable information for understanding the mechanisms underlying plant-microbe interactions in challenging soil conditions.

Endophytic fungus-suspension cell co-culture: A new strategy for more rapid and sustainable screening of plant beneficial microorganisms

Microbial fertilizers are increasingly used as alternatives to conventional fertilizers, while the screening process for beneficial microorganisms is inefficient and time-consuming, often taking months or years. This study aimed to evaluate whether the endophytic fungus-suspension cell co-culture strategy could be used for rapid screening of plant beneficial microorganisms. Therefore, we investigated the effects and molecular mechanisms of Fusarium oxysporum GU-7 and GU-60 on the growth and accumulation of secondary metabolites in Glycyrrhiza uralensis suspension cells and potted seedlings. GU-7 significantly promoted the growth of suspension cells and potted seedlings, which may be related to its strong phosphorus-solubilizing and indole-3-acetic acid production capacity. In contrast to GU-60, GU-7 promoted the accumulation of flavonoids and glycyrrhizin at different co-culture times and growth times. Both strains accelerated the accumulation of liquiritigenin, liquiritin, and glycyrrhizin in suspension cells after 24 h of co-culture. Meanwhile, they differentially altered the expression of critical genes. The defense response of suspension cells was enhanced at 72 h, the antioxidant enzyme activity and flavonoid aglycone content were increased and the flavonoid glycoside content was decreased. RNA-seq revealed that the two strains had five times as many glycoside hydrolases as glycosyltransferases and differed in biological processes and biosynthetic pathways involved. Conclusively, the effects of these two strains on suspension cells were consistent with those on potted seedlings, while different strains produced different effects. These results suggest that co-culture with suspension cells is a promising strategy for rapid screening of beneficial microorganisms, even for conspecific fungi. GU-7 has the potential to be further developed as a microbial fertilizer to improve the growth and secondary metabolite accumulation of cultivated licorice.

Effect of Different Fertilization Measures on Soil Salinity and Nutrients in Salt-Affected Soils

Saline soil from the coast is a valuable and readily available resource. It is also a valuable resource for reserving arable land. Adding organic fertilizers to salinized soils is an effective method of enhancement. However, saline soils cannot be improved using a single measure, and the effects of compound measures of organic fertilizers combined with mineral elements, such as humic acid, are significant and worthy of further examination. To explore the effects of various measures on the features of pH, electrical conductivity (EC), and nutrient changes in coastal salinized soils in Yancheng, Jiangsu Province, a ryegrass–alfalfa rotation with organic fertilizer and compound measures was designed. The findings indicated that the total nitrogen (TN) content of the soil increased and that all organic fertilizer composites decreased the electrical conductivity of the surface soil. However, the organic fertilizer with microbial fertilizer and humic acid was especially effective at regulating the pH and electrical conductivity of the surface soil when salts were prone to accumulation. In conclusion, our findings highlight new approaches to lowering salinity and boosting fertility in coastal saline soils: organic fertilizer with microbial fertilizers and humic acid, as well as organic fertilizer with attapulgite clay.

Effect of fertilization on the degradation and enantioselectivity of fipronil in soil.

Fertilizers and pesticides are commonly used simultaneously in agriculture. However, the effects of common fertilizers on the dissipation, enantioselectivity, and metabolites of the chiral insecticide fipronil in soil are yet to be reported. An enantioselective method for detecting fipronil enantiomers and their metabolites in different soil matrices was developed using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The results showed that organic and compound fertilizers significantly decreased the degradation of S- and R-fipronil, whereas phosphate and microbial fertilizers slightly reduced fipronil dissipation. The half-life values for S- and R-fipronil were 43.3 and 28.9 days, 99.0 and 63.0 days, 69.3 and 43.3 days, 46.2 and 30.1 days, and 43.3 and 31.5 days, respectively, in the control and the four fertilizer treatments, respectively. The enantioselectivity of fipronil enantiomers occurred and R-fipronil exhibited preferential degradation with an enantiomeric fraction (EF) of 0.4900-0.6238 in all treatments; but the four tested fertilizers decreased enantioselectivity with EF values changed from 0.4970 to 0.6238 in the control to 0.4900-0.6171 in fertilizer treatments. Two metabolites, fipronil sulfone and sulfide, were produced, and their amounts increased with culture time in all treatments. Fertilization reduced the content of fipronil sulfide and sulfone but hardly reduced the total amount of fipronil and its metabolites. Fertilizers affect the environmental behavior of fipronil in the soil. Fertilization alters the soil bacterial community, which may be an important factor. This influence is relatively complicated and should be comprehensively considered in the environmental risk assessment of pesticides. © 2023 Society of Chemical Industry.

Effectiveness of Phosphate and Zinc Solubilizing Paenarthrobacter nitroguajacolicus P1 as Halotolerant Rhizobacterium with Growth-Promoting Activity on Pistacia vera L.

Plant growth-promoting rhizobacteria (PGPR) are beneficial microorganisms to develop microbial fertilizers. Biofertilizers can accelerate plant growth and enhance crop yields. The current research aimed to isolate and identify rhizobacterium with plant growth-promoting activity in the rhizospheric region of pistachio trees in arid and salty region of Iran. In the present study, 26 bacterial isolates were isolated from the rhizospheric region of the pistachio trees. Plant growth-promoting characteristics of isolated bacteria, including the ability to solubilize phosphate and zinc, produce hydrolyzing enzymes, and hydrogen cyanide (HCN), as well as synthesize indole-3-acetic acid (IAA) were evaluated through in vitro assays. Based on these activities, five multifunctional bacterial strains designated P1, P10, P11, P17, and P19 were then applied and their effect was studied on the growth and physiological properties of Pistacia vera L. seedlings by pot experiments under normal conditions. Finally, the most efficient strain has been identified by analysis of the 16S rRNA gene sequence. According to the results, all the isolated bacteria exhibited considerable plant growth-promoting properties. They could produce amylase (n = 26, 2 ± 0.00-13 ± 0.42mm), lipase (n = 24, 2 ± 0.00-9 ± 0.23 mm), protease (n = 20, 1 ± 0.00-17 ± 0.0 mm), indole-3-acetic acid (n = 26, ranging from 5.05 ± 0.08 to 11.5 ± 0.11 μg/mL) and HCN (n = 24). Six isolates showed significant growth at 20% w/v NaCl. Inoculation of P1, P17, and P19 increased chlorophyll, carotenoid, and phenolic content in treated Pistacia vera L. seedlings. P1 and P11 inoculated plants showed an enhanced level of anthocyanin and proline. These most effective strains were catalase and Gram-positive bacterium and showed antibiotic sensitivity. They can consider as halotolerant PGPR, due to the growth in the presence of NaCl (20% w/v). Finally, P1 inoculated plants exhibited higher levels of sugar content. This strain showed the most similarity (99.92%-1322 bp) to Paenarthrobacter nitroguajacolicus based on 16S rRNA gene sequence. Based on the results, Paenarthrobacter nitroguajacolicus P1 with multiple PGPR can be applied as a promising candidate in the soil-Pistacia vera L. system to improve their productivity and health by increasing available nutrient content, improving photosynthetic parameters, and producing phytohormones and HCN.

A new approach on essential oil production of Origanum onites L.: Microbial fertilization and microwave extraction

In many studies plant and microbe interaction has been observed due to its stimulating effect on plant oil content. Bacillus spp. isolates used as microbial fertilizer/biostimulant have shown a higher potential for enhancing plant production and quality. However, there is still a need for investigating the essential oil content of plants, particularly for the pharmaceutical industry, to increase the targeted essential oil quantity and quality. Thyme is a crucial plant in medicinal aromatic herbal production and export, and its economic value is steadily increasing due to its high essential oil content. This study explores a novel approach to increase essential oil content through microbial fertilization (biostimulation) and microwave extraction methods. The microwave extraction method offers comparable yields to other methods, requiring less time, energy, and only a small amount of water to hydrate the dried plants. Microbial fertilizer formulations were applied to İzmir thyme (Origanum onites L.) to assess their effects on yield and quality. Three distinct microbial fertilizer formulations (N, P, NP) containing bacterial isolates of Bacillus subtilis and Bacillus megaterium, as well as a consortium of these two bacteria, were employed in this study. Among the applications on İzmir thyme, the NP formulation (a combination of two bacteria at a dosage of 6 L/ha−1) exhibited the highest efficacy in terms of yield and quality criteria. Moreover, the essential oil ratios (1–2%) obtained from the same fertilizer application, using microwave extraction to enhance quality and accelerate the extraction process, yielded higher than other methods.This study provides preliminary data and a new approach to regulate and enhance the targeted yield and essential oil content of thyme plants by utilizing microbial fertilizer applications and the microwave extraction method.

Screening and molecular identification of endophytic fungi promoting accumulation of flavonoids in callus of Scutellaria baicalensis

To screen and identify the endophytic fungal strains that could promote the accumulation of flavonoids in the callus of Scutellaria baicalensis. Seventeen endophytic fungal strains from S. baicalensis were used to prepare mycelium elicitors and fermentation broth elicitors. Their effects on flavonoid accumulation in S. baicalensis callus were then determined. The results showed that the fermentation broth elicitors of two strains(CL79, CL105) promoted the accumulation of flavonoids. The fermentation broth elicitor of CL79 significantly promoted accumulation of baicalin, wogonoside, baicalein, and wogonin, with the maximum levels increased by 37.8%, 40.4%, 44.7%, and 42.2%(vs. blank), respectively. Similarly, the fermentation broth elicitor of CL105 significantly promoted the accumulation of baicalin, wogonoside, baicalein, and wogonin, with the maximum levels increased by 78.1%, 140.9%, 275.6%, and 208.5%(vs. blank), respectively. CL79 was identified as Alternaria alternata, and CL105 as Fusarium solani. The fermentation broth elicitors of A. alternata CL79 and F. solani CL105 were able to promote the flavonoid accumulation in the callus of S. baicalensis, which enriched the resources of endophytic fungi and provided candidate strains for the development of microbial fertili-zers for improving the quality of S. baicalensis.

Combination of artificial zeolite and microbial fertilizer to improve mining soils in an arid area of Inner Mongolia, China

Combination of artificial zeolite and microbial fertilizer to improve mining soils in an arid area of Inner Mongolia, China

ECONOMIC ANALYSIS AND EFFECT OF TRIPLE BACTERIAL AND MINERAL FERTILIZERS ON THE GROWTH AND YIELD TRAITS OF WHEAT

The conduct of a field trial in the 2021–2022 cropping season assessed the economic feasibility and effect of using locally produced microbial biofertilizers on the growth and yield traits of wheat (Triticum aestivum L.). The manures of Providencia vermicola, Alcaligenes faecalis, and Raoultella planticola served as sample treatments in the study. The research was in a randomized complete block design at the Agricultural Experiment and Research Station (31°20′19″N 45°17′20″E), College of Agriculture, Al-Muthanna University, Iraq. Microbial fertilizers were the first factor, with the second factor comprising two levels of mineral fertilizers, i.e., a) no chemical fertilizer and b) using half of the recommended chemical fertilizer, addressing the interactions between biofertilizers and chemical fertilizers, having a two-factor experiment. Field results showed that triple biofertilization consisting of A. faecalis, R. planticola, and P. vermicola proved superior based on grain yield and biomass using half of the recommended fertilizer (P7) (8.038 t ha-1 and 24.938 t ha-1 ). In turn, the economic analysis results were consistent with the technical outcomes, as treatment P7 recorded the highest profit amounting to USD 483.625 ha-1 . In addition to recording the highest revenue per ha at the rate of 6.2477, treatment P7 for the level of fertilization F1 recorded the maximum level, amounting to about USD 144.284, 165,298.65, and 48,362.5 ha-1 for the criteria of the invested USD return, productive profitability, and added value, respectively.

The effects of Bacillus amyloliquefaciens on Mentha piperita grown under salt stress

Climate change threatens agricultural areas and food supply security not only in our country but also worldwide. As a result, plants are exposed to many abiotic stresses such as salt stress, drought stress, etc. Various methods are being tried to cope with abiotic stress, but sustainable alternative methods are needed in agriculture and one of them is biological fertilizers. Microbial fertilizers such as plant growth promoting bacteria (PGPB) reduce the use of chemical fertilizers and support environmentally friendly, soil-friendly, and more economical production in agriculture. In this study, the effects of Bacillus amyloliquefaciens, defined as a salt tolerant species, on the morphological parameters of Mentha piperita, which has significant commercial value and was grown under salty conditions, were investigated. Surprisingly, Bacillus amyloliquefaciens did not significantly alleviate the effects of salt stress on M. piperita grown under saline conditions (0, 50, 75, and 100 mM NaCl) in almost all parameters except for water content.

Phytoremediation of arsenic contaminated soils by Arundo donax L. enhanced with Earth Total Support (ETS)

Applying microbial fertilizer to assist phytoremediation using high production energy crops is a promising method to improve the removal efficiency of metals contaminated soils. The study was conducted to evaluate the effects of Earth Total Support (ETS, a complex microbial agent) in enhancing the phytoremediation of Arsenic (As) in soils using Arundo donax L, which were grown in mesocosms with As at 20 mg kg-1. The results showed that the addition of ETS significantly increase the biomass of A. donax L by 27.27 %–37.04 %. Additionally, ETS was found to mitigate the adverse effects of As stress on A. donax L by enhancing net photosynthetic rate and transpiration, increasing the activities of superoxide dismutases and peroxidases, and decreased malondialdehyde content. Moreover, the addition of ETS led to a 99.25 % increase in As content in roots and a 7.10 % increase in stems. These findings suggest that ETS agents hold promise in improving the remediation efficiency of low concentration As contaminated soil by significantly increasing the biomass of A. donax and facilitating As extraction.

Nutrient runoff loss from saline-alkali paddy fields in Songnen Plain of Northeast China via different runoff pathways: effects of nitrogen fertilizer types.

The application of nitrogen (N) fertilizer aggravates the nutrient runoff loss from paddy, causing serious agricultural non-point source pollution, and leading to a serious decline in water quality. The global area of saline-alkali paddy has expanded, but the response of nutrient loss via runoff to N-fertilizer applications in saline-alkali paddy is still unclear. This study conducted a 147-day field experiment to evaluate the nutrient runoff loss from saline-alkali paddy with different N-fertilizer application strategies in Songnen Plain of Northeast China. Regardless of N-fertilizer types, the nutrient loss via rainfall runoff in the entire rice-growing season was significantly (p < 0.05) higher than that via artificial drainage. The N and phosphorus (P) concentrations in runoff water were correlated with salinity and alkalinity. Especially, pH had a significant positive correlation with total-P (TP) (r = 0.658, p < 0.01). In the entire rice-growing season, the TN runoff losses in urea (U), microbial fertilizer (MF), and inorganic compound fertilizer (ICF) treatments were significantly (p < 0.05) lower compared with carbon-based slow-release fertilizer (CSF) and organic-inorganic compound fertilizer (OCF), respectively. Meanwhile, the TP runoff losses in OCF and ICF treatments were significantly (p < 0.05) lower than U and MF, respectively. Overall, the application of ICF is a better choice to avoid N and P losses via runoff from saline-alkali paddy fields.

Effects of Microbial Fertilizer on Physicochemical Properties and Bacterial Communities of Saline Soil Under Brackish Water Irrigation

The improvement of saline soil with microbial fertilizer has numerous advantages including high efficiency, green environmental protection, etc. At the same time, applying microbial fertilizer is an effective way to safely use brackish water. Based on the moderately saline soil in the Hetao irrigation area, four treatments of F1 (4500 kg·km-2), F2 (7500 kg·km-2), F3 (10500 kg·km-2), and CK without microbial fertilizer were applied under brackish water irrigation using Lycium barbarum as the indicator plants. The aim was to study the effects of different microbial fertilizer application rates on soil ions, soil moisture content, pH value, nutrients, and bacterial community in four key growth stages of L. barbarum (flowering stage, fruit expansion stage, full fruit stage, and deciduous stage). The results showed that, compared with that in CK, F1 only significantly decreased Na+ content in the first two growth stages (P<0.05), whereas F2 and F3 significantly decreased Na+ content in the whole growth period (P<0.05), with an average reduction of 33.66% and 57.98%, respectively, and F3 significantly increased soil moisture content (MC), organic matter (OM), alkaline hydrolysis nitrogen (AN), and available phosphorus (AP) contents (P<0.05) during the whole growth period. In the flourishing period of L. barbarum, the Shannon index of F3 increased by 4.41% compared with that of CK. The dominant bacterial phyla in the soil were Proteobacteria, Bacteroidetes, and Actinobacteria, and the dominant bacterial genera were Sphingomonas and Pseudomonas. The most abundant functions of bacterial communities in the study area were chemoheterotrophy and aerobic chemoheterotrophy, with an average relative abundance of 15.07% and 13.16%, respectively. The application of microbial fertilizer increased the chitinolysis function and chloroplast functions of soil bacteria, which F2 increased to the highest degree. Canonical correlation analysis (CCA) showed that MC, Na+, and OM were important factors affecting the composition of the bacterial community. The correlation heat map showed that MC was positively correlated with Planctomycetes (P<0.01), and Gp6 was positively correlated with AN (P<0.01). Compared with that in CK, the F3 treatment increased the relative abundance of Gp6 and optimized the community structure during the growth period. In conclusion, the application of 10500 kg·km-2 microbial fertilizer (F3 treatment) under brackish water irrigation could significantly reduce soil salinity, increase nutrients, and improve the diversity of the soil bacterial community structure, which is conducive to the safe utilization of brackish water and the maintenance of soil ecological health.

Effect of Nitrogen Application and Microbial Fertilizer on Nitrogen Conversion Processes in Saline Farmland

The nutrient utilization rate of salinized farmland soils is low, the nitrogen loss is high, and soil salinity inhibits the hydrolysis of urea and the release of nutrients. In this work, the effect of microbial fertilizer on the nitrogen transformation characteristics and nitrogen morphology of salinized soils was studied using indoor constant temperature incubation tests with different nitrogen application rates—without (A0) and with microbial fertilizer application (A1 (15 t/ha)) or nitrogen application (N) of 0 kg/ha (N0), 97.5 kg/ha (N1), or 195 kg/ha (N2). The results show the following: (i) When no microbial fertilizer was applied, an increased nitrogen application promoted nitrogen fertilizer’s ammonification and nitrification reactions. Furthermore, the maximum net nitrification rate with the high nitrogen fertilizer application decreased; the apparent ammonification rate and net ammonification rate A0N2 increased by 26.1% and 24.6%, respectively, compared with A0N1 on the first day of incubation; the maximum net nitrification rate of A0N1 was more than that of A0N2; and A0N1 &gt; A0N2 on day 3, while A0N2 &gt; A0N1 on days 3 to 15. At 3 d, the nitrogen conversion process of A0N1 was dominated by the nitrification reaction, while the ammonification reaction dominated in A0N2. (ii) Microbial fertilizers significantly increased the ammonification and nitrification rates under the low N fertilizer application. The intensity of ammonification and nitrification under the low N fertilizer application was greater than that under the high N fertilizer application. The apparent ammonification rate and net ammonification rate of A1N1 increased by 60.9% and 52.6% compared with A0N1 and 21.9% and 21.7% compared with A1N2 on the first day of incubation, and the peak net nitrification rates of A1N1 and A1N2 (28.19 mg/kg d and 11.02 mg/kg d, respectively) and net nitrification rates of A1N1 and A1N2 were 113.7% higher than those of A0N1. The net nitrification rates of A1N1 and A1N2 were 82.3% and 58.6% lower than the maximum net nitrification rates on the 15th day of incubation, respectively. (iii) In saline soils, low-nitrogen microbial fertilizers led to more ammonium nitrogen in the soil, and the high-nitrogen fertilizer application resulted in higher nitrate nitrogen in the soil, leading to nitrogen leaching. Therefore, when applying microbial fertilizer, choosing the most suitable period for reduced chasing is important for the efficient use of fertilizers, the alternative role of biofertilizers, and the study of environmental pollution.

Cadmium alters the rhizosphere bacterial community structure in blueberry roots and increases the content of lipids in the soil

Vaccinium spp. Is a small berry that grows in acidic environments. Relying on the exchange of nutrients and defense against adverse environments through the root system microbiota, bacteria play an important role. As a widely distributed pollutant, the mobility and bioavailability of Cd are enhanced in acidic environments, which can affect the community composition of blueberry root microbiota and alter the composition of soil metabolites. Therefore, studying the changes in the bacterial microbiota of blueberry roots and soil metabolomics under Cd stress can provide a foundation for the development of blueberry microbial fertilizers and the management of soil Cd pollution. In this study, 16 S rDNA sequencing and untargeted metabolomics were used to analyze the rhizosphere, root surface and root endophytic bacterial diversity as well as soil metabolites of Vaccinium spp. Under cadmium (Cd) contamination. The results indicate that the addition of cadmium (Cd) significantly reduces the α-diversity of the rhizosphere, rhizoplane, and endophytic bacteria in blueberries and has a significant impact on the dominant bacterial species. With the application of Cd, the relative abundance of the dominant taxa such as Diplorickettsiaceae_unclassified, Legionella, Streptomyces and Rhodanobacter decreased significantly at the genus level and turned into general or rare bacterial taxa. Meanwhile, the relative abundance of LWQ8_unclassified, WPS-2_unclassified, Acetobacteraceae_unclassified, Acidibacter, Acidiphilium and Granulicella with extreme tolerances increased significantly and gradually became the dominant taxa. Of the 364 metabolites in the soil, 31 varied significantly as the structure of the rhizosphere bacterial community changed. Among them, the lipids and lipid-like molecules clade showed the greatest variation in species and a significant increase in content. It was also associated with changes in bacterial taxa such as Tundrisphaera, Spirochaetaceae_unclassified, Dyella and CHAB_XI_27_unclassified.

Research progress on iron absorption, transport, and molecular regulation strategy in plants.

Iron is a trace element essential for normal plant life activities and is involved in various metabolic pathways such as chlorophyll synthesis, photosynthesis, and respiration. Although iron is highly abundant in the earth's crust, the amount that can be absorbed and utilized by plants is very low. Therefore, plants have developed a series of systems for absorption, transport, and utilization in the course of long-term evolution. This review focuses on the findings of current studies of the Fe2+ absorption mechanism I, Fe3+ chelate absorption mechanism II and plant-microbial interaction iron absorption mechanism, particularly effective measures for artificially regulating plant iron absorption and transportation to promote plant growth and development. According to the available literature, the beneficial effects of using microbial fertilizers as iron fertilizers are promising but further evidence of the interaction mechanism between microorganisms and plants is required.

Coupling amendment of microbial and compound fertilizers increases fungal necromass carbon and soil organic carbon by regulating microbial activity in flue-cured tobacco-planted field

Microbial necromass carbon (MNC) is an essential component of soil organic carbon (SOC). The contribution of MNC to SOC has been acknowledged in previous studies; however, there is a gap in understanding the effect of fertilization treatment on MNC, especially in rhizosphere soil. In the current study, four types of treatments were selected to examine the impact of fertilization on MNC and its contribution to SOC, particulate organic carbon (POC) and mineral-associated organic carbon (MAOC). These treatments included conventional compound fertilizer (Control), conventional compound fertilizer combined with microbial fertilizer (T1), a mixture of 75% conventional compound fertilizer with microbial fertilizer (T2), and microbial fertilizer (T3). The results indicated that the type of fertilization treatments and sampling time affected the MNC accumulation, especially fungal necromass carbon (FNC), and its contribution to SOC. Combined application of microbial and compound fertilizers increased the amino sugar (TAS) and MNC contents, especially during the harvest period (3.47–27.35%). The accumulation of MNC (5.13–9.42 g kg−1) and its contribution to SOC (38.03–50.49%) increased with the growth period, and the ratios of FNC to SOC, POC, and MAOC were about three times than that of the bacterial necromass carbon (BNC). Further, the regression analysis revealed a higher POC accumulation than MAOC. In addition, POC was positively correlated with MNC and FNC (p < 0.05). RDA analysis exhibited that microbial biomass phosphorus, phosphorus acquiring enzyme activity, POC, and the ratio of fungal to bacterial biomass had significant effects on amino sugar and MNC accumulation and contribution (p < 0.05). Further, T2 was found to be beneficial for FNC accumulation, promoting POC formation and increasing SOC content in tobacco planting soil. Taken together, our findings suggest that fertilization treatments affected microbial activity by regulating the N or P demand, leading to modulations in MNC accumulation and SOC storage.