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Thiengo CC, Galindo FS, Bernardes JVS, da Rocha LO, da Silva CD, Burak DL, Lavres J. Nitrogen fertilization regulates crosstalk between marandu palisadegrass and Herbaspirillum seropedicae: An investigation based on 15N isotopic analysis and root morphology. ENVIRONMENTAL RESEARCH 2024; 249:118345. [PMID: 38331147 DOI: 10.1016/j.envres.2024.118345] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Revised: 01/16/2024] [Accepted: 01/27/2024] [Indexed: 02/10/2024]
Abstract
Strategies seeking to increase the use efficiency of nitrogen (N) fertilizers and that benefit plant growth through multiple mechanisms can reduce production costs and contribute to more sustainable agriculture free of polluting residues. Under controlled conditions, we investigated the compatibility between foliar inoculation with an endophytic diazotrophic bacterium (Herbaspirillum seropedicae HRC54) at control and low, medium and high N fertilization levels (0, 25, 50 and 100 mg of N kg-1 as urea, respectively) in Marandu palisadegrass. Common procedures in our research field (biometric and nutritional assessments) were combined with isotopic techniques (natural abundance - δ15N‰ and 15N isotope dilution) and root scanning to determine the contribution of fixed N and recovery of N fertilizer by the grass. Overall, the combined use of 15N isotopic techniques revealed that inoculation not only improved the recovery of applied N-urea from the soil but also provided fixed nitrogen to Marandu palisade grass, resulting in an increase in the total accumulated N. When inoculated plants grew at control and low levels of N, a positive cascade effect encompassing root growth stimulation (nodes of smaller diameter roots), better soil and fertilizer resource exploitation and increased forage production was observed. In contrast, increasing N reduced the contributions of N fixed by H. seropedicae from 21.5% at the control level to 8.6% at the high N level. Given the minimal to no observed growth promotion, this condition was deemed inhibitory to the positive effects of H. seropedicae. We discuss how to make better use of H. seropedicae inoculation in Marandu palisadegrass, albeit on a small scale, thus contributing to a more rational and efficient use of N fertilizers. Finally, we pose questions for future investigations based on 15N isotopic techniques under field conditions, which have great applicability potential.
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Affiliation(s)
- Cassio Carlette Thiengo
- Luiz de Queiroz College of Agriculture, University of São Paulo, Piracicaba, 13418-900, Brazil.
| | - Fernando Shintate Galindo
- Faculty of Agricultural and Technological Sciences, São Paulo State University, Dracena, 17900-000, Brazil.
| | | | - Leticia Oliveira da Rocha
- Nucleus for the Development of Biological Inputs for Agriculture, North Fluminense State University Darcy Ribeiro, Campos dos Goytacazes, 28013-602, Brazil.
| | - Carlos Diego da Silva
- Luiz de Queiroz College of Agriculture, University of São Paulo, Piracicaba, 13418-900, Brazil.
| | - Diego Lang Burak
- Center for Agricultural Sciences and Engineering, Federal University of Espírito Santo, Alegre, 29500-000, Brazil.
| | - José Lavres
- Center for Nuclear Energy in Agriculture, University of São Paulo, Piracicaba, 13416-000, Brazil.
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Nair GR, Kooverjee BB, de Scally S, Cowan DA, Makhalanyane TP. Changes in nutrient availability substantially alter bacteria and extracellular enzymatic activities in Antarctic soils. FEMS Microbiol Ecol 2024; 100:fiae071. [PMID: 38697936 PMCID: PMC11107947 DOI: 10.1093/femsec/fiae071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Revised: 03/07/2024] [Accepted: 05/01/2024] [Indexed: 05/05/2024] Open
Abstract
In polar regions, global warming has accelerated the melting of glacial and buried ice, resulting in meltwater run-off and the mobilization of surface nutrients. Yet, the short-term effects of altered nutrient regimes on the diversity and function of soil microbiota in polyextreme environments such as Antarctica, remains poorly understood. We studied these effects by constructing soil microcosms simulating augmented carbon, nitrogen, and moisture. Addition of nitrogen significantly decreased the diversity of Antarctic soil microbial assemblages, compared with other treatments. Other treatments led to a shift in the relative abundances of these microbial assemblages although the distributional patterns were random. Only nitrogen treatment appeared to lead to distinct community structural patterns, with increases in abundance of Proteobacteria (Gammaproteobateria) and a decrease in Verrucomicrobiota (Chlamydiae and Verrucomicrobiae).The effects of extracellular enzyme activities and soil parameters on changes in microbial taxa were also significant following nitrogen addition. Structural equation modeling revealed that nutrient source and extracellular enzyme activities were positive predictors of microbial diversity. Our study highlights the effect of nitrogen addition on Antarctic soil microorganisms, supporting evidence of microbial resilience to nutrient increases. In contrast with studies suggesting that these communities may be resistant to change, Antarctic soil microbiota responded rapidly to augmented nutrient regimes.
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Affiliation(s)
- Girish R Nair
- Department of Microbiology, Faculty of Science, Stellenbosch University, Stellenbosch 7600, South Africa
- Centre for Epidemic Response and Innovation, School for Data Science and Computational Thinking, Stellenbosch University, Stellenbosch 7600, South Africa
| | - Bhaveni B Kooverjee
- Department of Biochemistry, Genetics and Microbiology, University of Pretoria, Hatfield, Pretoria 0028, South Africa
| | - Storme de Scally
- Department of Biochemistry, Genetics and Microbiology, University of Pretoria, Hatfield, Pretoria 0028, South Africa
| | - Don A Cowan
- Centre for Microbial Ecology and Genomics, Department of Biochemistry, Genetics and Microbiology, University of Pretoria, Hatfield, Pretoria 0028, South Africa
| | - Thulani P Makhalanyane
- Department of Microbiology, Faculty of Science, Stellenbosch University, Stellenbosch 7600, South Africa
- Centre for Epidemic Response and Innovation, School for Data Science and Computational Thinking, Stellenbosch University, Stellenbosch 7600, South Africa
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Wang Y, Long C, Yin L, Liu R, Liao Y, He G, Liu Z. Effects of simulated acid rain on hydrochemical factors and microbial community structure in red soil aquifers. RSC Adv 2024; 14:4482-4491. [PMID: 38312729 PMCID: PMC10835706 DOI: 10.1039/d3ra08820k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2023] [Accepted: 01/18/2024] [Indexed: 02/06/2024] Open
Abstract
Acid rain can lower the pH of groundwater and affect its hydrogeochemistry and microbial ecology. However, the effects of acid rain on the hydrogeochemistry and microbial ecology of red soil groundwater systems in southern China are poorly understood. Previous research had mainly investigated the sources and patterns of groundwater acidification, but not the microbial mechanisms that contribute to this process and their associations with hydrochemical factors. To address this knowledge gap, we conducted a soil column experiment to simulate the infiltration of acid rain through various filter materials (coarse, medium, and fine sand) and to examine the hydrochemical and microbial features of the infiltrate, which can reveal how simulated acid rain (pH 3.5-7.0) alters the hydrochemistry and microbial community composition in red soil aquifers. The results showed that the pH of the leachate decreased due to simulated acid rain, and that the leaching efficiency of nitrogen and metal ions was influenced by the particle size of the filter media. Illumina 16S rRNA gene sequencing revealed that the leachate was dominated by Proteobacteria, Patescibacteria, Actinobacteria, and Acidobacteria, with Proteobacteria accounting for 67.04-74.69% of the bacterial community and containing a high proportion of nitrifying and denitrifying bacteria. Additionally, several genera with heavy metal tolerance, such as Burkholderia-Caballeronia-Paraburkholderia, Delftia, Methylversatilis, Aquicella, and Ralstonia, were widely distributed in the leachate, indicating the strong adaptive capacity of the microbial population. A correlation analysis between the hydrochemical factors and the microbial community structure revealed that pH was the most influential factor, followed by NO2--N, Fe, Al, Cu, Mn, and others. These results indicate that acidification modifies the hydrochemical conditions of the aquifer, creating an environment that is unfavorable for microbial growth and survival. However, some microorganisms may acquire resistance genes to cope with environmental changes.
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Affiliation(s)
- Yian Wang
- School of Life Science, Jinggangshan University Ji'an Jiangxi China
| | - Chao Long
- School of Civil and Surveying & Mapping Engineering, Jiangxi University of Science and Technology Ganzhou Jiangxi China
| | - Li Yin
- School of Life Science, Jinggangshan University Ji'an Jiangxi China
| | - Renlu Liu
- School of Life Science, Jinggangshan University Ji'an Jiangxi China
| | - Yonghui Liao
- School of Life Science, Jinggangshan University Ji'an Jiangxi China
| | - Genhe He
- School of Life Science, Jinggangshan University Ji'an Jiangxi China
| | - Zuwen Liu
- School of Life Science, Jinggangshan University Ji'an Jiangxi China
- School of Civil and Surveying & Mapping Engineering, Jiangxi University of Science and Technology Ganzhou Jiangxi China
- School of Hydraulic & Ecological Engineering, Nanchang Institute of Technology Nanchang China
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Su Y, Wang Y, Liu G, Zhang Z, Li X, Chen G, Gou Z, Gao Q. Nitrogen (N) "supplementation, slow release, and retention" strategy improves N use efficiency via the synergistic effect of biochar, nitrogen-fixing bacteria, and dicyandiamide. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 908:168518. [PMID: 37967639 DOI: 10.1016/j.scitotenv.2023.168518] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Revised: 11/10/2023] [Accepted: 11/10/2023] [Indexed: 11/17/2023]
Abstract
Irrational nitrogen (N) fertilizer management and application practices have led to a range of ecological and environmental problems that seriously threaten food security. In this study, an effective N fertilizer management strategy was established for improving N fertilizer utilization efficiency (NUE). Biochar, N2-fixing bacteria (Enterobacter cloacae), and a nitrification inhibitor (dicyandiamide, DCD) were simultaneously added to the soil during maize cultivation. The goal was to increase soil ammonium nitrogen content and NUE by regulating the relative abundance, enzyme activity, and functional gene expression of N conversion-related soil microbes. Biochar combined with E. cloacae and DCD significantly increased soil N content, and the NUE reached 46.69 %. The relative abundance of Burkholderia and Bradyrhizobium and the activity of nitrogenase increased significantly during biological N2 fixation. Further, the abundance of the nifH gene was significantly up-regulated. The relative abundance of Sphingomonas, Pseudomonas, Nitrospira, and Castellaniella and the activities of ammonia monooxygenase and nitrate reductase decreased significantly during nitrification and denitrification. Moreover, the abundance of the genes amoA and narG was significantly down-regulated. Correlation analyses showed that the increase in soil N2 fixation and the suppression of nitrification and denitrification reactions were the key contributors to the increase in soil N content and NUE. Biochar combined with E. cloacae and DCD synergistically enabled the supplementation, slow release, and retention of N, thus providing adequate N for maize growth. Thus, the combination of biochar, E. cloacae, and DCD is effective for mitigating the irrational application of N fertilizers and reducing N pollution.
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Affiliation(s)
- Yingjie Su
- Key Laboratory of Straw Comprehensive Utilization and Black Soil Conservation, Ministry of Education, Jilin Agricultural University, Changchun 130118, China
| | - Yanran Wang
- Key Laboratory of Straw Comprehensive Utilization and Black Soil Conservation, Ministry of Education, Jilin Agricultural University, Changchun 130118, China
| | - Guoqing Liu
- Key Laboratory of Straw Comprehensive Utilization and Black Soil Conservation, Ministry of Education, Jilin Agricultural University, Changchun 130118, China
| | - Zhongqing Zhang
- Key Laboratory of Straw Comprehensive Utilization and Black Soil Conservation, Ministry of Education, Jilin Agricultural University, Changchun 130118, China
| | - Xiaoyu Li
- Key Laboratory of Straw Comprehensive Utilization and Black Soil Conservation, Ministry of Education, Jilin Agricultural University, Changchun 130118, China
| | - Guang Chen
- Key Laboratory of Straw Comprehensive Utilization and Black Soil Conservation, Ministry of Education, Jilin Agricultural University, Changchun 130118, China
| | - Zechang Gou
- Key Laboratory of Straw Comprehensive Utilization and Black Soil Conservation, Ministry of Education, Jilin Agricultural University, Changchun 130118, China.
| | - Qiang Gao
- Key Laboratory of Straw Comprehensive Utilization and Black Soil Conservation, Ministry of Education, Jilin Agricultural University, Changchun 130118, China.
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Benmrid B, Ghoulam C, Zeroual Y, Kouisni L, Bargaz A. Bioinoculants as a means of increasing crop tolerance to drought and phosphorus deficiency in legume-cereal intercropping systems. Commun Biol 2023; 6:1016. [PMID: 37803170 PMCID: PMC10558546 DOI: 10.1038/s42003-023-05399-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Accepted: 09/28/2023] [Indexed: 10/08/2023] Open
Abstract
Ensuring plant resilience to drought and phosphorus (P) stresses is crucial to support global food security. The phytobiome, shaped by selective pressures, harbors stress-adapted microorganisms that confer host benefits like enhanced growth and stress tolerance. Intercropping systems also offer benefits through facilitative interactions, improving plant growth in water- and P-deficient soils. Application of microbial consortia can boost the benefits of intercropping, although questions remain about the establishment, persistence, and legacy effects within resident soil microbiomes. Understanding microbe- and plant-microbe dynamics in drought-prone soils is key. This review highlights the beneficial effects of rhizobacterial consortia-based inoculants in legume-cereal intercropping systems, discusses challenges, proposes a roadmap for development of P-solubilizing drought-adapted consortia, and identifies research gaps in crop-microbe interactions.
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Affiliation(s)
- Bouchra Benmrid
- Plant-Microbe Interactions Laboratory, AgroBiosciences Program, College for Sustainable Agriculture and Environmental Sciences, Mohammed VI Polytechnic University, Ben Guerir, 43150, Morocco.
| | - Cherki Ghoulam
- Plant-Microbe Interactions Laboratory, AgroBiosciences Program, College for Sustainable Agriculture and Environmental Sciences, Mohammed VI Polytechnic University, Ben Guerir, 43150, Morocco
- Agrobiotechnology & Bioengineering Center, Research Unit CNRST labeled, Cadi Ayyad University, Faculty of Sciences and Techniques, 40000, Marrakech, Morocco
| | - Youssef Zeroual
- Situation Innovation - OCP Group, Jorf Lasfar, 24025, Morocco
| | - Lamfeddal Kouisni
- African Sustainable Agriculture Research Institute, Mohammed VI Polytechnic University, Laayoune, Morocco
| | - Adnane Bargaz
- Plant-Microbe Interactions Laboratory, AgroBiosciences Program, College for Sustainable Agriculture and Environmental Sciences, Mohammed VI Polytechnic University, Ben Guerir, 43150, Morocco.
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Gou Z, Zheng H, He Z, Su Y, Chen S, Chen H, Chen G, Ma NL, Sun Y. The combined action of biochar and nitrogen-fixing bacteria on microbial and enzymatic activities of soil N cycling. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2023; 317:120790. [PMID: 36460190 DOI: 10.1016/j.envpol.2022.120790] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Revised: 11/04/2022] [Accepted: 11/28/2022] [Indexed: 06/17/2023]
Abstract
This study aims to investigate the positive effects of the combined use of Enterobacter cloacae and biochar on improving nitrogen (N) utilization. The greenhouse pots experimental results showed the synergy of biochar and E. cloacae increased soil total N content and plant N uptake by 33.54% and 15.1%, respectively. Soil nitrogenase (NIT) activity increased by 253.02%. Ammonia monooxygenase (AMO) and nitrate reductase (NR) activity associated with nitrification and denitrification decreased by 10.94% and 29.09%, respectively. The relative abundance of N fixing microorganisms like Burkholderia and Bradyrhizobium significantly increased. Sphingomonas and Ottowia, two bacteria involved in the nitrification and denitrification processes, were found to be in lower numbers. The E. cloacae's ability to fix N2 and promote the growth of plants allow the retention of N in soil and make more N available for plant development. Biochar served as a reservoir of N for plants by adsorbing N from the soil and providing a shelter for E. cloacae. Thus, biochar and E. cloacae form a synergy for the management of agricultural N and the mitigation of negative impacts of pollution caused by excessive use of N fertilizer.
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Affiliation(s)
- Zechang Gou
- Key Laboratory of Straw Comprehensive Utilization and Black Soil Conservation, Ministry of Education, College of Life Sciences, Jilin Agricultural University, Changchun, 130118, China
| | - Haoyu Zheng
- Key Laboratory of Straw Comprehensive Utilization and Black Soil Conservation, Ministry of Education, College of Life Sciences, Jilin Agricultural University, Changchun, 130118, China
| | - Ziqi He
- Key Laboratory of Straw Comprehensive Utilization and Black Soil Conservation, Ministry of Education, College of Life Sciences, Jilin Agricultural University, Changchun, 130118, China
| | - Yingjie Su
- Key Laboratory of Straw Comprehensive Utilization and Black Soil Conservation, Ministry of Education, College of Life Sciences, Jilin Agricultural University, Changchun, 130118, China
| | - Siji Chen
- Key Laboratory of Straw Comprehensive Utilization and Black Soil Conservation, Ministry of Education, College of Life Sciences, Jilin Agricultural University, Changchun, 130118, China
| | - Huan Chen
- Key Laboratory of Straw Comprehensive Utilization and Black Soil Conservation, Ministry of Education, College of Life Sciences, Jilin Agricultural University, Changchun, 130118, China
| | - Guang Chen
- Key Laboratory of Straw Comprehensive Utilization and Black Soil Conservation, Ministry of Education, College of Life Sciences, Jilin Agricultural University, Changchun, 130118, China
| | - Nyuk Ling Ma
- Faculty of Science and Marine Environment, University Malaysia Terengganu, 21030 Kuala Nerus, Terengganu, Malaysia
| | - Yang Sun
- Key Laboratory of Straw Comprehensive Utilization and Black Soil Conservation, Ministry of Education, College of Life Sciences, Jilin Agricultural University, Changchun, 130118, China.
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Galindo FS, Pagliari PH, da Silva EC, Silva VM, Fernandes GC, Rodrigues WL, Céu EGO, de Lima BH, Jalal A, Muraoka T, Buzetti S, Lavres J, Teixeira Filho MCM. Co-Inoculation with Azospirillum brasilense and Bradyrhizobium sp. Enhances Nitrogen Uptake and Yield in Field-Grown Cowpea and Did Not Change N-Fertilizer Recovery. PLANTS 2022; 11:plants11141847. [PMID: 35890481 PMCID: PMC9321259 DOI: 10.3390/plants11141847] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Revised: 07/09/2022] [Accepted: 07/11/2022] [Indexed: 11/20/2022]
Abstract
This study was designed to investigate the effects of Azospirillum brasilense and Bradyrhizobium sp. co-inoculation coupled with N application on soil N levels and N in plants (total N, nitrate N-NO3− and ammonium N-NH4+), photosynthetic pigments, cowpea plant biomass and grain yield. An isotopic technique was employed to evaluate 15N fertilizer recovery and derivation. Field trials involved two inoculations—(i) single Bradyrhizobium sp. and (ii) Bradyrhizobium sp. + A. brasilense co-inoculation—and four N fertilizer rates (0, 20, 40 and 80 kg ha−1). The co-inoculation of Bradyrhizobium sp. + A. brasilense increased cowpea N uptake (an increase from 10 to 14%) and grain yield (an average increase of 8%) compared to the standard inoculation with Bradyrhizobium sp. specifically derived from soil and other sources without affecting 15N fertilizer recovery. There is no need for the supplementation of N via mineral fertilizers when A. brasilense co-inoculation is performed in a cowpea crop. However, even in the case of an NPK basal fertilization, applied N rates should remain below 20 kg N ha−1 when co-inoculation with Bradyrhizobium sp. and A. brasilense is performed.
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Affiliation(s)
- Fernando Shintate Galindo
- Center for Nuclear Energy in Agriculture, University of São Paulo, Piracicaba 13418-900, Brazil; (T.M.); (J.L.)
- Correspondence:
| | - Paulo Humberto Pagliari
- Southwest Research and Outreach Center, Department of Soil, Water, and Climate, University of Minnesota, Lamberton, MN 56152, USA;
| | | | - Vinicius Martins Silva
- Department of Biology Applied to Agriculture, São Paulo State University, Jaboticabal 14884-900, Brazil;
| | - Guilherme Carlos Fernandes
- Department of Plant Health, Rural Engineering, and Soils, São Paulo State University, Ilha Solteira 1585-000, Brazil; (G.C.F.); (W.L.R.); (E.G.O.C.); (B.H.d.L.); (A.J.); (S.B.); (M.C.M.T.F.)
| | - Willian Lima Rodrigues
- Department of Plant Health, Rural Engineering, and Soils, São Paulo State University, Ilha Solteira 1585-000, Brazil; (G.C.F.); (W.L.R.); (E.G.O.C.); (B.H.d.L.); (A.J.); (S.B.); (M.C.M.T.F.)
| | - Elaine Garcia Oliveira Céu
- Department of Plant Health, Rural Engineering, and Soils, São Paulo State University, Ilha Solteira 1585-000, Brazil; (G.C.F.); (W.L.R.); (E.G.O.C.); (B.H.d.L.); (A.J.); (S.B.); (M.C.M.T.F.)
| | - Bruno Horschut de Lima
- Department of Plant Health, Rural Engineering, and Soils, São Paulo State University, Ilha Solteira 1585-000, Brazil; (G.C.F.); (W.L.R.); (E.G.O.C.); (B.H.d.L.); (A.J.); (S.B.); (M.C.M.T.F.)
| | - Arshad Jalal
- Department of Plant Health, Rural Engineering, and Soils, São Paulo State University, Ilha Solteira 1585-000, Brazil; (G.C.F.); (W.L.R.); (E.G.O.C.); (B.H.d.L.); (A.J.); (S.B.); (M.C.M.T.F.)
| | - Takashi Muraoka
- Center for Nuclear Energy in Agriculture, University of São Paulo, Piracicaba 13418-900, Brazil; (T.M.); (J.L.)
| | - Salatiér Buzetti
- Department of Plant Health, Rural Engineering, and Soils, São Paulo State University, Ilha Solteira 1585-000, Brazil; (G.C.F.); (W.L.R.); (E.G.O.C.); (B.H.d.L.); (A.J.); (S.B.); (M.C.M.T.F.)
| | - José Lavres
- Center for Nuclear Energy in Agriculture, University of São Paulo, Piracicaba 13418-900, Brazil; (T.M.); (J.L.)
| | - Marcelo Carvalho Minhoto Teixeira Filho
- Department of Plant Health, Rural Engineering, and Soils, São Paulo State University, Ilha Solteira 1585-000, Brazil; (G.C.F.); (W.L.R.); (E.G.O.C.); (B.H.d.L.); (A.J.); (S.B.); (M.C.M.T.F.)
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Garcia MVC, Nogueira MA, Hungria M. Combining microorganisms in inoculants is agronomically important but industrially challenging: case study of a composite inoculant containing Bradyrhizobium and Azospirillum for the soybean crop. AMB Express 2021; 11:71. [PMID: 34021824 PMCID: PMC8141083 DOI: 10.1186/s13568-021-01230-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2020] [Accepted: 05/11/2021] [Indexed: 12/29/2022] Open
Abstract
The increasing global perception of the importance of microbial inoculants to promote productivity and sustainability in agriculture prompts the adoption of bio-inputs by the farmers. The utilization of selected elite strains of nitrogen-fixing and other plant-growth promoting microorganisms in single inoculants creates a promising market for composite inoculants. However, combining microorganisms with different physiological and nutritional needs requires biotechnological development. We report the development of a composite inoculant containing Bradyrhizobium diazoefficiens and Azospirillum brasilense for the soybean crop. Evaluation of use of carbon sources indicates differences between the microbial species, with Bradyrhizobium growing better with mannitol and glycerol, and Azospirillum with malic acid and maleic acid, allowing the design of a formulation for co-culture. Species also differ in their growth rates, and the best performance of both microorganisms occurred when Azospirillum was inoculated on the third day of growth of Bradyrhizobium. The composite inoculant developed was evaluated in five field trials performed in Brazil, including areas without and with naturalized populations of Bradyrhizobium. The composite inoculant resulted in symbiotic performance comparable to the application of the two microorganisms separately. In comparison to the single inoculation with Bradyrhizobium, co-inoculation resulted in average increases of 14.7% in grain yield and 16.4% in total N accumulated in the grains. The performance of the composite inoculant was similar or greater than that of the non-inoculated control receiving a high dose of N-fertilizer, indicating the importance of the development and validation of inoculants carrying multiple beneficial microorganisms.
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