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Keywords: Nitrogen-fixing bacteria, Purple nonsulfur bacteria, n Rhodobacter sphaeroidesn , Tran De-Soc Trang
Saltwater intrusion is a serious issue to the agriculture in Tran De district, Soc Trang province, Vietnam, by reducing soil nutrient availability and crop yield. Hence, finding a promising biofertilizer candidate to remediate salinized soil and improve crop yield is an essential strategy for sustainable agriculture. Therefore, a field trial was conducted to evaluate the efficacy of nitrogen-fixing purple non-sulfur bacteria (PNSB) on improving soil quality, N uptake, growth, and rice yield in saline soil in Tran De-Soc Trang. A field experiment was conducted using a randomized complete block design with four treatments: (i) full recommended fertilization (FRF), (ii) 75% nitrogen plus a mixed inoculant of Rhodobacter sphaeroides S01 and S06 (M-PNSB), (iii) 50% nitrogen plus M-PNSB, and (iv) farmer’s fertilization formula (FFF). Application of M-PNSB increased soil pH and ammonium content while reducing electrical conductivity and sodium concentration. Consequently, nitrogen uptake increased, sodium uptake decreased, and rice plants exhibited lower proline accumulation, indicating reduced salt stress. Plant height, panicle number, and grain filling rate improved, leading to 5.26–5.45% higher yield compared with the FRF and FFF treatments. The results demonstrate that the M-PNSB biofertilizer can mitigate salinity stress and enhance rice productivity while reducing nitrogen fertilizer demand. Further studies should explore the underlying biochemical and molecular mechanisms to optimize large-scale application in saline paddy fields.
Alloul A, Blansaer N, Segura PC, Wattiez R, Vlaeminck SE, Leroy B (2023) Dehazing redox homeostasis to foster purple bacteria biotechnology. Trends Biotechnol 41(1):106–119. https://doi.org/10.1016/j.tibtech.2022.06.010
Anh NH, Xuan LNT, Xuan DT, Quang LT, Khuong NQ (2024) Nitrogen-fixing purple nonsulfur bacteria originating from acid saline soils of a rice-shrimp farm. Indones J Agric Res 7(1):14–28. https://doi.org/10.32734/injar.v7i1.14726
Bates LS, Waldren RPA, Teare ID (1973) Rapid determination of free proline for water-stress studies. Plant Soil 39:205–207. https://doi.org/10.1007/BF00018060
Bhagat N, Raghav M, Dubey S, Bedi N (2021) Bacterial exopolysaccharides: insight into their role in plant abiotic stress tolerance. J Microbiol Biotechnol 31(8):1045. https://doi.org/10.4014/jmb.2105.05009
Chang SC, Jackson JL (1957) A fractionation of soil phosphorus. Soil Sci 84:133–144
Chowdhury NB, Alsiyabi A, Saha R (2022) Characterizing the interplay of rubisco and nitrogenase enzymes in anaerobic-photoheterotrophically grown Rhodopseudomonas palustris CGA009 through a genome-scale metabolic and expression model. Microbiol Spectr 10(4):e01463–22. https://doi.org/10.1128/spectrum.01463-22
Dan TT, Trinh TT, Minh VQ, Van HN (2016) Adaptability zoning for salty-tolerant rice varieties in Soc Trang prefecture by using GIS and remote sensing. J Geol Resour Eng 3:142–150. https://doi.org/10.17265/2328-2193/2016.03.005
Dang LT, Ishidaira H, Nguyen KP, Souma K, Magome J (2025) Short-term salinity prediction for coastal areas of the Vietnamese Mekong Delta using various machine learning algorithms: a case study in Soc Trang Province. Appl Water Sci 15(4):79. https://doi.org/10.1007/s13201-025-02419-z
Degon Z, Dixon S, Rahmatallah Y, Galloway M, Gulutzo S, Price H, Cook J, Glazko G, Mukherjee A (2023) Azospirillum brasilense improves rice growth under salt stress by regulating the expression of key genes involved in salt stress response, abscisic acid signaling, and nutrient transport, among others. Front Agron 5(4):1216503
Dinh DA, Nguyen TL, Nguyen TN, Nguyen HT (2020) Assessing existing surface water supply sources in the Vietnamese Mekong delta: case study of Can Tho, Soc Trang, and Hau Giang provinces. Vietnam J Sci Technol Eng 62(4):65–70. https://doi.org/10.31276/VJSTE.62(4).65-70
Ettadili H, Aksoy BN, Vural C (2025) Exploring the plant growth-promoting potential of a purple non-sulfur bacterium: Cereibacter sphaeroides PW15. Curr Microbiol 82(9):1–3. https://doi.org/10.1007/s00284-025-04384-x
Gangwar P, Singh R, Trivedi M, Tiwari RK (2020) Sodic soil: Management and reclamation strategies. In: Shukla V, Kumar N (eds) Environmental concerns and sustainable development. Springer, Singapore, pp 175–190. https://doi.org/10.1007/978-981-13-6358-0_8
Gonçalo Filho F, da Silva DN, Suddarth SRP, Ferreira JF, Anderson RG, dos Santos FC, de Lira RB, Neto MF, Cosme CR (2019) Reclaiming tropical saline-sodic soils with gypsum and cow manure. Water 12(1):57. https://doi.org/10.3390/w12010057
Gondek M, Weindorf DC, Thiel C, Kleinheinz G (2020) Soluble salts in compost and their effects on soil and plants: a review. Compost Sci Util 28(2):59–75. https://doi.org/10.1080/1065657X.2020.1772906
Gunasekaran Y, Thiyageshwari S, Ariyan M, Roy Choudhury A, Park JH, Selvi D, Chithra L, Anandham R (2022) Alleviation of sodic stress in rice by exploring the exopolysaccharide-producing sodic-tolerant bacteria. Agriculture 12(9):1451. https://doi.org/10.3390/agriculture12091451
Gupta SR, Dagar JC, Singh R, Sharma HR (2024) Exploring the potential of halophytes for bioremediation of salt-affected soils: a review. In: Dagar JC, Gupta SR, Kumar A (eds) Halophytes vis-à-vis Saline Agriculture. Springer, Singapore, pp 409–440. https://doi.org/10.1007/978-981-97-3157-2_16
Hafez EM, Osman HS, Gowayed SM, Okasha SA, Omara AE, Sami R, Abd El-Monem AM, Abd El-Razek UA (2021) Minimizing the adversely impacts of water deficit and soil salinity on maize growth and productivity in response to the application of plant growth-promoting rhizobacteria and silica nanoparticles. Agronomy 11(4):676. https://doi.org/10.3390/agronomy11040676
Hannachi S, Van Labeke MC (2018) Salt stress affects germination, seedling growth and physiological responses differentially in eggplant cultivars (Solanum melongena L.). Sci Hortic 228:56–65. https://doi.org/10.1016/j.scienta.2017.10.002
Harada N, Nishiyama M, Otsuka S, Matsumoto S (2005) Effects of inoculation of phototrophic purple bacteria on grain yield of rice and nitrogenase activity of paddy soil in a pot experiment. Soil Sci Plant Nutr 51(3):361–367. https://doi.org/10.1111/j.1747-0765.2005.tb00041.x
Hayashi S, Iwamoto Y, Hirakawa Y, Mori K, Yamada N, Maki T, Yamamoto S, Miyasaka H (2022) Plant-growth-promoting effect by cell components of purple non-sulfur photosynthetic bacteria. Microorganisms 10(4):771. https://doi.org/10.3390/microorganisms10040771
Hernández I, Taulé C, Pérez-Pérez R, Battistoni F, Fabiano E, Villanueva-Guerrero A, Nápoles MC, Herrera H (2023) Endophytic seed-associated bacteria as plant growth promoters of Cuban rice (Oryza sativa L.). Microorganisms 11(9):2317. https://doi.org/10.3390/microorganisms11092317
Ho TT, Shimada K (2018) The impact of climate change adaptation response on rice farmers’livelihood in Soc Tang province of Vietnam. Int J Food Agric Econom 6(3):11–31. https://doi.org/10.22004/ag.econ.283866
Horneck DA, Sullivan DM, Owen JS, Hart JM (2011) Soil test interpretation guide. Oregon State University, OR
Houba VJG, Novozamsky I, Van Der Lee JJ (1996) Quality aspects in laboratories for soil and plant analysis. Commun Soil Sci Plant Anal 27(3–4):327–348. https://doi.org/10.1080/00103629609369560
Hsu SH, Shen MW, Chen JC, Lur HS, Liu CT (2021) The photosynthetic bacterium Rhodopseudomonas palustris strain PS3 exerts plant growth-promoting effects by stimulating nitrogen uptake and elevating auxin levels in expanding leaves. Front Plant Sci 12:573634. https://doi.org/10.3389/fpls.2021.573634
Huang L, Liu X, Wang Z, Liang Z, Wang M, Liu M, Suarez DL (2017) Interactive effects of pH, EC and nitrogen on yields and nutrient absorption of rice (Oryza sativa L.). Agric Water Manag 194:48–57. https://doi.org/10.1016/j.agwat.2017.08.012
IRRI (1996) Standard evaluation system for rice, 4th edn. IRRI, Manila
Landon JR (1984) Booker soil tropical manual. Booker Agriculture International Limited, Northants
Li X, Wang A, Wan W, Luo X, Zheng L, He G, Huang D, Chen W, Huang Q (2021) High salinity inhibits soil bacterial community mediating nitrogen cycling. Appl Environ Microbiol 87(21):e01366–21. https://doi.org/10.1128/AEM.01366-21
Liang JL, Liu J, Jia P, Yang TT, Zeng QW, Zhang SC, Liao B, Shu WS, Li JT (2020) Novel phosphate-solubilizing bacteria enhance soil phosphorus cycling following ecological restoration of land degraded by mining. ISME J 14(6):1600–1613. https://doi.org/10.1038/s41396-020-0632-4
Liu S, Shen X, Daigger GT, Zhang G, Kang J, Song G, Li G, Yang G (2024) Mechanism regulation, production and potential of high value substances in the wastewater treatment by immobilized photosynthetic bacteria: a review. J Water Process Eng 58:104770. https://doi.org/10.1016/j.jwpe.2023.104770
Liu X, Chai J, Zhang Y, Zhang C, Lei Y, Li Q, Yao T (2022) Halotolerant rhizobacteria mitigate the effects of salinity stress on maize growth by secreting exopolysaccharides. Environ Exp Bot 204:105098. https://doi.org/10.1016/j.envexpbot.2022.105098
Maeda I (2021) Potential of phototrophic purple nonsulfur bacteria to fix nitrogen in rice fields. Microorganisms 10(1):28. https://doi.org/10.3390/microorganisms10010028
Meena RL, Gururaja Rao G, Jowkin V, Khandkar UR, Dagar JC (2019) Agro-interventions for sustainable management of salt-affected vertisols in India. In: Dagar J, Yadav R, Sharma P (eds) Research Developments in Saline Agriculture. Springer, Singapore, pp 653–703. https://doi.org/10.1007/978-981-13-5832-6_22
Metson AJ (1961) Methods of chemical analysis for soil survey samples, Soil bureau bulletin 12. Department of Scientific and Industrial Research, New Zealand
Moran R (1982) Formulae for determination of chlorophyllous pigments extracted with N, N-dimethylformamide. Plant Physiol 69(6):1376–1381. https://doi.org/10.1104/pp.69.6.1376
Ngoc TA, Thu VT, Van CT (2024) Characteristics of seawater intrusion in Soc Trang province, Vietnam. J Hydro-Meteorol 18:1–1. https://doi.org/10.36335/VNJHM.2024(18).1-11
Nkoh JN, Hong ZN, Xu RK (2022) Laboratory studies on the effect of adsorbed microbial extracellular polymeric substances on the acidity of selected variable-charge soils. Soil Sci Soc Am J 86(2):162–180. https://doi.org/10.1002/saj2.20299
Nookongbut P, Kantachote D, Khuong NQ, Sukhoom A, Tantirungkij M, Limtong S (2019) Selection of acid-resistant purple nonsulfur bacteria from peat swamp forests to apply as biofertilizers and biocontrol agents. J Soil Sci Plant Nutr 19:488–500. https://doi.org/10.1007/s42729-019-00044-9
Nunkaew T, Kantachote D, Nitoda T, Kanzaki H, Ritchie RJ (2015) Characterization of exopolymeric substances from selected Rhodopseudomonas palustris strains and their ability to adsorb sodium ions. Carbohydr Polym 115:334–341. https://doi.org/10.1016/j.carbpol.2014.08.099
Peng WA, ZhangG Y, Yi SH (2023) Increasing nitrogen absorption and assimilation ability under mixed NO3− and NH4+ supply is a driver to promote growth of maize seedlings. J Integr Agric 22(6):1896–1908. https://doi.org/10.1016/j.jia.2023.04.037
Poury N, Seifi E, Alizadeh M (2023) Effects of salinity and proline on growth and physiological characteristics of three olive cultivars. Gesunde Pflanz 75(4):1169–1180. https://doi.org/10.1007/s10343-022-00778-0
Praveen A, Singh S (2024) The role of potassium under salinity stress in crop plants. Cereal Res Commun 52(2):315–322. https://doi.org/10.1007/s42976-023-00393-3
Sakarika M, Spanoghe J, Sui Y, Wambacq E, Grunert O, Haesaert G, Spiller M, Vlaeminck SE (2020) Purple non-sulphur bacteria and plant production: benefits for fertilization, stress resistance and the environment. Microb Biotechnol 13(5):1336–1365. https://doi.org/10.1111/1751-7915.13474
Sakpirom J, Kantachote D, Nunkaew T, Khan E (2017) Characterizations of purple non-sulfur bacteria isolated from paddy fields, and identification of strains with potential for plant growth-promotion, greenhouse gas mitigation and heavy metal bioremediation. Res Microbiol 168(3):266–275. https://doi.org/10.1016/j.resmic.2016.12.001
Samy PMA, Singh RK, Gregorio GB, Gautam RK, Krishnamurthy SL, Thirumeni S (2024) Genetic improvement of rice for salt tolerance. In: Singh RK, Prakash M, Gautam RK, Krishnamurthy SL, Thirumeni S (eds) Genetic improvement of rice for salt tolerance. Springer, Singapore, pp 1–8. https://doi.org/10.1007/978-981-99-3830-8_1
Simarmata T, Setiawati MR, Fitriatin BN, Herdiyantoro D, Khumairah FH (2023) Enhancing the ability of rice to adapt and grow under saline stress using selected halotolerant rhizobacterial nitrogen fixer. Open Agric 8(1):20220195
Sparks DL, Page AL, Helmke PA, Loeppert RH (eds) (2020M) Methods of Soil Analysis, Part 3: Chemical Methods. John Wiley Sons, Hoboken
Sundar LS, Yen KS, Chang YT, Chao YY (2024) Utilization of Rhodopseudomonas palustris in crop rotation practice boosts rice productivity and soil nutrient dynamics. Agriculture 14(5):758. https://doi.org/10.3390/agriculture14050758
Sundar LS, Wu JY, Tu YK, Chen HW, Chao YY (2025) Mitigation of salinity stress in salt-sensitive rice seedlings via phytohormone synthesis, antioxidant defence enhancement, and ion balance regulation induced by 5-aminolevulinic acid-producing purple non-sulfur bacteria. Plant Biol 27(3):388–400. https://doi.org/10.1111/plb.13773
Tan LV, Thanh T (2021) The effects of salinity on changes in characteristics of soils collected in a saline region of the Mekong Delta, Vietnam. Open Chem 19(1):471–480. https://doi.org/10.1515/chem-2021-0037
Thongnok S, Siripornadulsil W, Siripornadulsil S (2022) Responses to arsenic stress of rice varieties coinoculated with the heavy metal-resistant and rice growth-promoting bacteria Pseudomonas stutzeri and Cupriavidus taiwanensis. Plant Physiol Biochem 191:42–54. https://doi.org/10.1016/j.plaphy.2022.09.014
Touloupakis E, Chatziathanasiou A, Ghanotakis DF, Carlozzi P, Pecorini I (2023) Poly (3-hydroxybutyrate) production by Rhodopseudomonas sp. S16-VOGS3 cells grown in digested sludge. Environ Technol Innov 30:103058. https://doi.org/10.1016/j.eti.2023.103058
Truong QC, Nguyen TH, Pham VT, Nguyen TH (2024) Land-use optimization and allocation for saltwater intrusion regions: a case study in Soc Trang Province, Vietnam. Climate 12(2):16. https://doi.org/10.3390/cli12020016
Wang N, Fu F, Wang H, Wang P, He S, Shao H, Ni Z, Zhang X (2021a) Effects of irrigation and nitrogen on chlorophyll content, dry matter and nitrogen accumulation in sugar beet (Beta vulgaris L.). Sci Rep 11(1):16651. https://doi.org/10.1038/s41598-021-95792-z
Wang Y, Peng S, Hua Q, Qiu C, Wu P, Liu X, Lin X (2021b) The long-term effects of using phosphate-solubilizing bacteria and photosynthetic bacteria as biofertilizers on peanut yield and soil bacteria community. Front Microbiol 12:693535. https://doi.org/10.3389/fmicb.2021.693535
Wu JY, Chen HW, Sundar LS, Tu YK, Chao YY (2025) Exploring the potential of purple non-sulfur bacteria strains A3–5 and F3–3 in sustainable agriculture: a study on nutrient solubilization, plant growth promotion, and acidic stress tolerance. J Soil Sci Plant Nutr 25(2):2294–2313. https://doi.org/10.1007/s42729-025-02268-4
Xuan LNT, Thu LTM, Quang LT, Long TKT, Khuong NQ (2024) Increase of in-dyke alluvial soil fertility, growth and yield of maize (Zea mays L.) by potent Rhodopseudomonas palustris strains. Soil Sci Ann 75(1):186457. https://doi.org/10.37501/soilsa/186457
Yen KS, Sundar LS, Chao YY (2022) Foliar application of Rhodopseudomonas palustris enhances the rice crop growth and yield under field conditions. Plants 11(19):2452. https://doi.org/10.3390/plants11192452
Zhou H, Ren ZH, Zu X, Yu XY, Zhu HJ, Li XJ, Zhong J, Liu EM (2021) Efficacy of plant growth-promoting bacteria Bacillus cereus YN917 for biocontrol of rice blast. Front Microbiol 12:684888. https://doi.org/10.3389/fmicb.2021.684888
Faculty of Crop Science, College of Agriculture, Can Tho University, Can Tho, Vietnam