Eurasian Journal of Soil Science

Volume 13, Issue 3, Jun 2024, Pages 190-201
DOI: 10.18393/ejss.1433418
Stable URL: http://ejss.fess.org/10.18393/ejss.1433418
Copyright © 2024 The authors and Federation of Eurasian Soil Science Societies



Characterization of humic acids from soil of Delhi regions and their impact on plant growth

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Singh,C., Chauhan,A., Arora,J., Ranjan,A., Rajput,V., Sushkova,S., Minkina,T., Eswaran,S., Jindal,T., 2024. Characterization of humic acids from soil of Delhi regions and their impact on plant growth. Eurasian J Soil Sci 13(3):190-201. DOI : 10.18393/ejss.1433418
Singh,C.Chauhan,A.Arora,J.Ranjan,A.Rajput,V.Sushkova,S.Minkina,T.Eswaran,S.,& Jindal,T. (2024). Characterization of humic acids from soil of Delhi regions and their impact on plant growth Eurasian Journal of Soil Science, 13(3):190-201. DOI : 10.18393/ejss.1433418
Singh,C.Chauhan,A.Arora,J.Ranjan,A.Rajput,V.Sushkova,S.Minkina,T.Eswaran,S., and ,Jindal,T. "Characterization of humic acids from soil of Delhi regions and their impact on plant growth" Eurasian Journal of Soil Science, 13.3 (2024):190-201. DOI : 10.18393/ejss.1433418
Singh,C.Chauhan,A.Arora,J.Ranjan,A.Rajput,V.Sushkova,S.Minkina,T.Eswaran,S., and ,Jindal,T. "Characterization of humic acids from soil of Delhi regions and their impact on plant growth" Eurasian Journal of Soil Science,13(Jun 2024):190-201 DOI : 10.18393/ejss.1433418
C,Singh.A,Chauhan.J,Arora.A,Ranjan.V,Rajput.S,Sushkova.T,Minkina.S,Eswaran.T,Jindal "Characterization of humic acids from soil of Delhi regions and their impact on plant growth" Eurasian J. Soil Sci, vol.13, no.3, pp.190-201 (Jun 2024), DOI : 10.18393/ejss.1433418
Singh,Charu ;Chauhan,Abhishek ;Arora,Jayati ;Ranjan,Anuj ;Rajput,Vishnu D. ;Sushkova,Svetlana ;Minkina,Tatiana ;Eswaran,Sambasivan Venkat ;Jindal,Tanu Characterization of humic acids from soil of Delhi regions and their impact on plant growth. Eurasian Journal of Soil Science, (2024),13.3:190-201. DOI : 10.18393/ejss.1433418

How to cite

Singh, C., Chauhan, A., Arora, J., Ranjan, A., Rajput, V., Sushkova, S., Minkina, T., Eswaran, S., Jindal, T., 2024. Characterization of humic acids from soil of Delhi regions and their impact on plant growth. Eurasian J. Soil Sci. 13(3): 190-201. DOI : 10.18393/ejss.1433418

Author information

Charu Singh , Amity Institute of Environmental Sciences, Amity University, Noida, Uttar Pradesh, India
Abhishek Chauhan , Amity Institute of Environmental Toxicology, Safety, and Management, Amity University, Noida, Uttar Pradesh, India
Jayati Arora , Amity Institute of Environmental Sciences, Amity University, Noida, Uttar Pradesh, India
Anuj Ranjan , Amity Institute of Environmental Toxicology, Safety, and Management, Amity University, Noida, Uttar Pradesh, India
Vishnu D. Rajput , Academy of Biology and Biotechnology, Southern Federal University, Rostov-On-Don, Russia
Svetlana Sushkova , Academy of Biology and Biotechnology, Southern Federal University, Rostov-On-Don, Russia
Tatiana Minkina , Academy of Biology and Biotechnology, Southern Federal University, Rostov-On-Don, Russia
Sambasivan Venkat Eswaran , St Stephen's College, Delhi, 110007; Amity University, Noida, Uttar Pradesh-201313, India
Tanu Jindal , Amity Institute of Environmental Toxicology, Safety, and Management, Amity University, Noida, Uttar Pradesh, India

Publication information

Article first published online : 07 Feb 2024
Manuscript Accepted : 31 Jan 2024
Manuscript Received: 02 Nov 2023
DOI: 10.18393/ejss.1433418
Stable URL: http://ejss.fesss.org/10.18393/ejss.1433418

Abstract

Humus materials are considered complex organic substances generated through a chain of chemical reactions and responsible for many processes in soil that ultimately govern soil health. The structural and functional characteristics of humus depend upon the location, quality, and microbial abundance of the soils. However, the differential characteristics of soil organic matter, seasonal changes, parent rock, plant cover, microbial abundance, and anthropogenic activities majorly affect it. The present study has aimed toward the extraction of humus from five different locations in the Delhi region of India and their characteristics were investigated through elemental analysis, Fourier Transform infrared (FT-IR) spectroscopy, and UV spectroscopy. The results showed that there was a higher degree of unsaturation detected in the Forest soil sample. The results of FT-IR showed the presence of characteristic peaks of humus in the samples however the intensity of bands was weak in sample disposable site soil sample and clayey soil sample due to the variation in soil physicochemical properties. The study also aimed to assess the growth of Oryza sativa (rice) plants observed in the hydroponics system. The significant finding was observed with the forest soil sample in 1000 mgL-1 and treatment in which the growth was minimum in clayey soil of 1500 mgL-1. Our investigation infers the diverse nature of humus in different soils and its implications for plant growth, highlighting the importance of understanding soil organic matter for sustainable agriculture and soil health management.

Keywords

Humus, humic acid, fulvic acid, organic matter, soil health.

Corresponding author

References

Adani, F., Genevini, P., Zaccheo, P., Zocchi, G., 1998. The effect of commercial humic acid on tomato plant growth and mineral nutrition. Journal of Plant Nutrition 21(3): 561–575.

Almendros, G., Guadalix, M.E., González-Vila, F.J., Martin, F., 1996. Preservation of aliphatic macromolecules in soil humins. Organic Geochemistry 24(6–7): 651–659.

Amir, S., Hafidi, M., Merlina, G., Hamdi, H., Revel, J.-C., 2004. Elemental analysis, FTIR and 13C-NMR of humic acids from sewage sludge composting. Agronomie 24(1): 13–18.

Arnon, D.I., 1949. Copper enzymes in isolated chloroplasts. Polyphenoloxidase in beta vulgaris. Plant Physiology 24(1): 1–15.

Castro, T.A.V.T., García, A.C., Tavares, O.C.H., Pereira, E.G., Souza, C.C.B., Torchia, D.F.O., Pinho, C.F., Castro, R.N., 2022. Humic acids affect photosynthetic quantum efficiency in rice under water deficit. Theoretical and Experimental Plant Physiology 34(4): 463–483.

Chang, R.R., Mylotte, R., Hayes, M.H.B., Mclnerney, R., Tzou, Y.M., 2014. A comparison of the compositional differences between humic fractions isolated by the IHSS and exhaustive extraction procedures. Naturwissenschaften 101(3): 197–209.

Chen, J., Gu, B., LeBoeuf, E. J., Pan, H., Dai, S., 2002. Spectroscopic characterization of the structural and functional properties of natural organic matter fractions. Chemosphere 48(1): 59–68.

Chen, X., Wu, J., Opoku-Kwanowaa, Y., 2020. Effects of returning granular corn straw on soil humus composition and humic acid structure characteristics in saline-alkali soil. Sustainability 12(3): 1005.

Chen, Y., Senesi, N., Schnitzer, M., 1977. Information provided on humic substances by e4/e6 ratios. Soil Science Society of America Journal 41(2): 352–358.

Cocozza, C., D’Orazio, V., Miano, T. M., Shotyk, W., 2003. Characterization of solid and aqueous phases of a peat bog profile using molecular fluorescence spectroscopy, ESR and FT-IR, and comparison with physical properties. Organic Geochemistry 34(1): 49–60.

Dębska, B., Szombathova, N., Banach-Szott, M., 2009. Properties of humic acids of soil under different management regimes. Polish Journal of Soil Science 42(2): 131-138.

Enev, V., Pospíšilová, Ľ., Klučáková, M., Liptaj, T., Doskočil, L. 2014. Spectral characterization of selected humic substances. Soil and Water Research 9(1): 9–17.

Ertani, A., Francioso, O., Tugnoli, V., Righi, V., Nardi, S., 2011. Effect of commercial lignosulfonate-humate on zea mays l. Metabolism. Journal of Agricultural and Food Chemistry 59(22): 11940–11948.

García, A.C., Santos, L.A., Izquierdo, F.G., Rumjanek, V.M., Castro, R.N., Dos Santos, F.S., De Souza, L.G.A., Berbara, R.L.L., 2014. Potentialities of vermicompost humic acids to alleviate water stress in rice plants (Oryza sativa L.). Journal of Geochemical Exploration 136: 48–54.

González Pérez, M., Martin-Neto, L., Saab, S.C., Novotny, E.H., Milori, D.M.B.P., Bagnato, V.S., Colnago, L.A., Melo, W.J.,  Knicker, H., 2004. Characterization of humic acids from a Brazilian Oxisol under different tillage systems by EPR, 13C NMR, FTIR and fluorescence spectroscopy. Geoderma 118(3–4): 181–190.

Guggenberger, G., 2005. Humification and mineralization in soils. In: Microorganisms in Soils: Roles in Genesis and Functions. Varma, A., Buscot, F., (Eds.) Vol. 3. Springer-Verlag. pp. 85–106.

Hayes, M.H.B., Mylotte, R., Swift, R.S., 2017. Humin: Its composition and importance in soil organic matter. Advances in Agronomy 143: 47–138.

IHHS, 2024. Isolation of ihss soil fulvic and humic acids. Available at [Access date: 25.01.2024]: https://humic-substances.org/isolation-of-ihss-soil-fulvic-and-humic-acids/

Ikan, R., 1991. Natural products: a laboratory guide. Academic Press. 316p.

Jackson, W.R., 1993. Humic, fulvic and microbial balance: organic soil conditioning Evergreen: Jackson Research Center. 329p.

Javanshah, A., Saidi, A., 2016. Determination of humic acid by spectrophotometric analysis in the soils. International Journal of Advanced Biotechnology and Research 7: 19-23.

Jindo, K., Hernández, T., García, C., Sánchez-Monedero, M.A., 2011. Influence of stability and origin of organic amendments on humification in semiarid soils. Soil Science Society of America Journal 75(6): 2178–2187.

Kelleher, B.P., Simpson, A.J., 2006. Humic substances in soils: Are they really chemically distinct? Environmental Science and Technology 40(15): 4605–4611.

Kolchanova, K., Tolpeshta, I., Izosimova, Y., 2021. Adsorption of fulvic acid and water extractable soil organic matter on kaolinite and muscovite. Agronomy 11(12): 2420.

Kononova, M.M., 1961. Soil organic matter: Its nature, its role in soil formation and in soil fertility. Soil organic matter, its nature, its role in soil formation and in soil fertility. Pergamon Press. 450p.

Kononova, M.M., 1981. Materia orgánica del suelo: su naturaleza, propiedades y métodos de investigación. Oikos-Tau, Barcelona, Spain. 365p. [in Spanish]

Kögel‐Knabner, I., Zech, W., Hatcher, P.G., 1988. Chemical composition of the organic matter in forest soils: The humus layer. Zeitschrift Für Pflanzenernährung Und Bodenkunde 151(5): 331–340.

Körschens, M., 2002. Importance of soil organic matter (SOM) for biomass production and environment (A review). Archives of Agronomy and Soil Science 48(2): 89–94.

Lal, R., 2020. Soil organic matter content and crop yield. Journal of Soil and Water Conservation 75(2): 27A-32A.

Lehmann, J., Kleber, M., 2015. The contentious nature of soil organic matter. Nature 528(7580): 60–68.

Li, J.-J., Ji, H.-B., Wang, W.-J., Dong, F., Yin, C., Zhang, L., Li, R., Gao, J., 2022. Study on the profile distribution and morphology of soil humic substances in Karst area of Zunyi city, China. Sustainability 14(10): 6145.

Nardi, S., Schiavon, M., Francioso, O., 2021. Chemical structure and biological activity of humic substances define their role as plant growth promoters. Molecules 26(8): 2256.

Ndzelu, B. S., Dou, S., Zhang, X., 2020. Changes in soil humus composition and humic acid structural characteristics under different corn straw returning modes. Soil Research 58(5): 452-460.

Pedra, F., Plaza, C., Fernández, J. M., García-Gil, J. C., Polo, A., 2008. Effects of municipal solid waste compost and sewage sludge on chemical and spectroscopic properties of humic acids from a sandy Haplic Podzol and a clay loam Calcic Vertisol in Portugal. Waste Management 28(11): 2183–2191.

Peña-Méndez, E. M., Gajdošová, D., Novotná, K., Prošek, P., Havel, J., 2005. Mass spectrometry of humic substances of different origin including those from Antarctica. Talanta 67(5): 880–890.

Polyakov, V.I., Chegodaeva, N.A., Abakumov, E.V., 2019. Molecular and elemental composition of humic acids isolated from selected soils of the Russian Arctic. Bulletin of Tomsk State University, Biology 47: 6-21.

Pospíšilová, Ľ., Fasurová, N., 2009. Spectroscopic characteristics of humic acids originated in soils and lignite. Soil and Water Research 4(4): 168–175.

Qiang, T., Xiao-quan, S., Zhe-ming, N., 1993. Comparative characteristic studies on soil and commercial humic acids. Fresenius Journal of Analytical Chemistry 347: 330-336.

Ribeiro, J.S., Ok, S.S., Garrigues, S., De La Guardia, M., 2001. FTIR tentative characterization of humic acids extracted from organic materials. Spectroscopy Letters 34(2): 179–190.

Rodríguez-Lucena, P., Lucena, J.J., Hernández-Apaolaza, L., 2009. Relationship between the structure of Fe-Lignosulfonate complexes determined by FTIR spectroscopy and their reduction by the leaf Fe reductase. UC Davis: Department of Plant Sciences. Available at [Access date: 02.11.2023]: https://escholarship.org/uc/item/9k69q71d

Senesi, N., Loffredo, E., 1999. The chemistry of soil organic matter. In: Soil Physical Chemistry.  Spark, D.L. (Ed.). CRC Press, pp. 239-370.

Senesi, N., Miano, T.M., 1994. Humic substances in the global environment and implications on human health. Proceedings of the 6th International Meeting of the International Humic Substances Society, 20-25 September 1992, Monopoli (Bari), Italy, Elsevier. 1368p.

Stevenson, F.J., 1982. Humus chemistry: Genesis, composition, reactions. John Wiley & Sons. Inc. 496p.

Stuijfzand, S.C., Jonker, M.J., Van Ammelrooy, E., Admiraal, W., 1999. Species-specific responses to metals in organically enriched river water, with emphasis on effects of humic acids. Environmental Pollution 106(1): 115–121.

Tadini, A.M., Bernardi, A.C.C., Milori, D.M.B.P., Oliveira, P.P.A., Pezzopane, J.R.M., Martin-Neto, L. 2022. Spectroscopic characteristics of humic acids extracted from soils under different integrated agricultural production systems in tropical regions. Geoderma Regional 28: e00476.

Tadini, A.M., Nicolodelli, G., Mounier, S., Montes, C.R., Milori, D.M.B.P., 2015. The importance of humin in soil characterisation: A study on Amazonian soils using different fluorescence techniques. Science of The Total Environment 537: 152–158.

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Timofeevna Shirshova, L., Ghabbour, E.A., Davies, G., 2006. Spectroscopic characterization of humic acid fractions isolated from soil using different extraction procedures. Geoderma 133(3–4): 204–216.

Tzou, Y.-M., Wang, S.-L., Liu, J.-C., Huang, Y.-Y., Chen, J.-H., 2008. Removal of 2,4,6-trichlorophenol from a solution by humic acids repeatedly extracted from a peat soil. Journal of Hazardous Materials 152(2): 812–819.

Vaccaro, S., Ertani, A., Nebbioso, A., Muscolo, A., Quaggiotti, S., Piccolo, A., Nardi, S., 2015. Humic substances stimulate maize nitrogen assimilation and amino acid metabolism at physiological and molecular level. Chemical and Biological Technologies in Agriculture 2(1): 5.

Volkov, D., Rogova, O., Proskurnin, M., 2021. Temperature dependences of IR spectra of humic substances of brown coal. Agronomy 11(9): 1822.

Wei, S., Li, Z., Sun, Y., Zhang, J., Ge, Y., Li, Z., 2022. A comprehensive review on biomass humification: Recent advances in pathways, challenges, new applications, and perspectives. Renewable and Sustainable Energy Reviews 170: 112984.

Woelki, G., Friedrich, S., Hanschmann, G., Salzer, R., 1997. HPLC fractionation and structural dynamics of humic acids. Fresenius' Journal of Analytical Chemistry 357(5): 548–552.

Wolf, B., Snyder, G., 2003. Sustainable soils: The place of organic matter in sustaining soils and their productivity. CRC Press. 376p.

Xiao, L., Zhang, W., Hu, P., Xiao, D., Yang, R., Ye, Y., Wang, K., 2021. The formation of large macroaggregates induces soil organic carbon sequestration in short-term cropland restoration in a typical karst area. Science of The Total Environment 801: 149588.

Abstract

Humus materials are considered complex organic substances generated through a chain of chemical reactions and responsible for many processes in soil that ultimately govern soil health. The structural and functional characteristics of humus depend upon the location, quality, and microbial abundance of the soils. However, the differential characteristics of soil organic matter, seasonal changes, parent rock, plant cover, microbial abundance, and anthropogenic activities majorly affect it. The present study has aimed toward the extraction of humus from five different locations in the Delhi region of India and their characteristics were investigated through elemental analysis, Fourier Transform infrared (FT-IR) spectroscopy, and UV spectroscopy. The results showed that there was a higher degree of unsaturation detected in the Forest soil sample. The results of FT-IR showed the presence of characteristic peaks of humus in the samples however the intensity of bands was weak in sample disposable site soil sample and clayey soil sample due to the variation in soil physicochemical properties. The study also aimed to assess the growth of Oryza sativa (rice) plants observed in the hydroponics system. The significant finding was observed with the forest soil sample in 1000 mgL-1 and treatment in which the growth was minimum in clayey soil of 1500 mgL-1. Our investigation infers the diverse nature of humus in different soils and its implications for plant growth, highlighting the importance of understanding soil organic matter for sustainable agriculture and soil health management.

Keywords: Humus, humic acid, fulvic acid, organic matter, soil health.

References

Adani, F., Genevini, P., Zaccheo, P., Zocchi, G., 1998. The effect of commercial humic acid on tomato plant growth and mineral nutrition. Journal of Plant Nutrition 21(3): 561–575.

Almendros, G., Guadalix, M.E., González-Vila, F.J., Martin, F., 1996. Preservation of aliphatic macromolecules in soil humins. Organic Geochemistry 24(6–7): 651–659.

Amir, S., Hafidi, M., Merlina, G., Hamdi, H., Revel, J.-C., 2004. Elemental analysis, FTIR and 13C-NMR of humic acids from sewage sludge composting. Agronomie 24(1): 13–18.

Arnon, D.I., 1949. Copper enzymes in isolated chloroplasts. Polyphenoloxidase in beta vulgaris. Plant Physiology 24(1): 1–15.

Castro, T.A.V.T., García, A.C., Tavares, O.C.H., Pereira, E.G., Souza, C.C.B., Torchia, D.F.O., Pinho, C.F., Castro, R.N., 2022. Humic acids affect photosynthetic quantum efficiency in rice under water deficit. Theoretical and Experimental Plant Physiology 34(4): 463–483.

Chang, R.R., Mylotte, R., Hayes, M.H.B., Mclnerney, R., Tzou, Y.M., 2014. A comparison of the compositional differences between humic fractions isolated by the IHSS and exhaustive extraction procedures. Naturwissenschaften 101(3): 197–209.

Chen, J., Gu, B., LeBoeuf, E. J., Pan, H., Dai, S., 2002. Spectroscopic characterization of the structural and functional properties of natural organic matter fractions. Chemosphere 48(1): 59–68.

Chen, X., Wu, J., Opoku-Kwanowaa, Y., 2020. Effects of returning granular corn straw on soil humus composition and humic acid structure characteristics in saline-alkali soil. Sustainability 12(3): 1005.

Chen, Y., Senesi, N., Schnitzer, M., 1977. Information provided on humic substances by e4/e6 ratios. Soil Science Society of America Journal 41(2): 352–358.

Cocozza, C., D’Orazio, V., Miano, T. M., Shotyk, W., 2003. Characterization of solid and aqueous phases of a peat bog profile using molecular fluorescence spectroscopy, ESR and FT-IR, and comparison with physical properties. Organic Geochemistry 34(1): 49–60.

Dębska, B., Szombathova, N., Banach-Szott, M., 2009. Properties of humic acids of soil under different management regimes. Polish Journal of Soil Science 42(2): 131-138.

Enev, V., Pospíšilová, Ľ., Klučáková, M., Liptaj, T., Doskočil, L. 2014. Spectral characterization of selected humic substances. Soil and Water Research 9(1): 9–17.

Ertani, A., Francioso, O., Tugnoli, V., Righi, V., Nardi, S., 2011. Effect of commercial lignosulfonate-humate on zea mays l. Metabolism. Journal of Agricultural and Food Chemistry 59(22): 11940–11948.

García, A.C., Santos, L.A., Izquierdo, F.G., Rumjanek, V.M., Castro, R.N., Dos Santos, F.S., De Souza, L.G.A., Berbara, R.L.L., 2014. Potentialities of vermicompost humic acids to alleviate water stress in rice plants (Oryza sativa L.). Journal of Geochemical Exploration 136: 48–54.

González Pérez, M., Martin-Neto, L., Saab, S.C., Novotny, E.H., Milori, D.M.B.P., Bagnato, V.S., Colnago, L.A., Melo, W.J.,  Knicker, H., 2004. Characterization of humic acids from a Brazilian Oxisol under different tillage systems by EPR, 13C NMR, FTIR and fluorescence spectroscopy. Geoderma 118(3–4): 181–190.

Guggenberger, G., 2005. Humification and mineralization in soils. In: Microorganisms in Soils: Roles in Genesis and Functions. Varma, A., Buscot, F., (Eds.) Vol. 3. Springer-Verlag. pp. 85–106.

Hayes, M.H.B., Mylotte, R., Swift, R.S., 2017. Humin: Its composition and importance in soil organic matter. Advances in Agronomy 143: 47–138.

IHHS, 2024. Isolation of ihss soil fulvic and humic acids. Available at [Access date: 25.01.2024]: https://humic-substances.org/isolation-of-ihss-soil-fulvic-and-humic-acids/

Ikan, R., 1991. Natural products: a laboratory guide. Academic Press. 316p.

Jackson, W.R., 1993. Humic, fulvic and microbial balance: organic soil conditioning Evergreen: Jackson Research Center. 329p.

Javanshah, A., Saidi, A., 2016. Determination of humic acid by spectrophotometric analysis in the soils. International Journal of Advanced Biotechnology and Research 7: 19-23.

Jindo, K., Hernández, T., García, C., Sánchez-Monedero, M.A., 2011. Influence of stability and origin of organic amendments on humification in semiarid soils. Soil Science Society of America Journal 75(6): 2178–2187.

Kelleher, B.P., Simpson, A.J., 2006. Humic substances in soils: Are they really chemically distinct? Environmental Science and Technology 40(15): 4605–4611.

Kolchanova, K., Tolpeshta, I., Izosimova, Y., 2021. Adsorption of fulvic acid and water extractable soil organic matter on kaolinite and muscovite. Agronomy 11(12): 2420.

Kononova, M.M., 1961. Soil organic matter: Its nature, its role in soil formation and in soil fertility. Soil organic matter, its nature, its role in soil formation and in soil fertility. Pergamon Press. 450p.

Kononova, M.M., 1981. Materia orgánica del suelo: su naturaleza, propiedades y métodos de investigación. Oikos-Tau, Barcelona, Spain. 365p. [in Spanish]

Kögel‐Knabner, I., Zech, W., Hatcher, P.G., 1988. Chemical composition of the organic matter in forest soils: The humus layer. Zeitschrift Für Pflanzenernährung Und Bodenkunde 151(5): 331–340.

Körschens, M., 2002. Importance of soil organic matter (SOM) for biomass production and environment (A review). Archives of Agronomy and Soil Science 48(2): 89–94.

Lal, R., 2020. Soil organic matter content and crop yield. Journal of Soil and Water Conservation 75(2): 27A-32A.

Lehmann, J., Kleber, M., 2015. The contentious nature of soil organic matter. Nature 528(7580): 60–68.

Li, J.-J., Ji, H.-B., Wang, W.-J., Dong, F., Yin, C., Zhang, L., Li, R., Gao, J., 2022. Study on the profile distribution and morphology of soil humic substances in Karst area of Zunyi city, China. Sustainability 14(10): 6145.

Nardi, S., Schiavon, M., Francioso, O., 2021. Chemical structure and biological activity of humic substances define their role as plant growth promoters. Molecules 26(8): 2256.

Ndzelu, B. S., Dou, S., Zhang, X., 2020. Changes in soil humus composition and humic acid structural characteristics under different corn straw returning modes. Soil Research 58(5): 452-460.

Pedra, F., Plaza, C., Fernández, J. M., García-Gil, J. C., Polo, A., 2008. Effects of municipal solid waste compost and sewage sludge on chemical and spectroscopic properties of humic acids from a sandy Haplic Podzol and a clay loam Calcic Vertisol in Portugal. Waste Management 28(11): 2183–2191.

Peña-Méndez, E. M., Gajdošová, D., Novotná, K., Prošek, P., Havel, J., 2005. Mass spectrometry of humic substances of different origin including those from Antarctica. Talanta 67(5): 880–890.

Polyakov, V.I., Chegodaeva, N.A., Abakumov, E.V., 2019. Molecular and elemental composition of humic acids isolated from selected soils of the Russian Arctic. Bulletin of Tomsk State University, Biology 47: 6-21.

Pospíšilová, Ľ., Fasurová, N., 2009. Spectroscopic characteristics of humic acids originated in soils and lignite. Soil and Water Research 4(4): 168–175.

Qiang, T., Xiao-quan, S., Zhe-ming, N., 1993. Comparative characteristic studies on soil and commercial humic acids. Fresenius Journal of Analytical Chemistry 347: 330-336.

Ribeiro, J.S., Ok, S.S., Garrigues, S., De La Guardia, M., 2001. FTIR tentative characterization of humic acids extracted from organic materials. Spectroscopy Letters 34(2): 179–190.

Rodríguez-Lucena, P., Lucena, J.J., Hernández-Apaolaza, L., 2009. Relationship between the structure of Fe-Lignosulfonate complexes determined by FTIR spectroscopy and their reduction by the leaf Fe reductase. UC Davis: Department of Plant Sciences. Available at [Access date: 02.11.2023]: https://escholarship.org/uc/item/9k69q71d

Senesi, N., Loffredo, E., 1999. The chemistry of soil organic matter. In: Soil Physical Chemistry.  Spark, D.L. (Ed.). CRC Press, pp. 239-370.

Senesi, N., Miano, T.M., 1994. Humic substances in the global environment and implications on human health. Proceedings of the 6th International Meeting of the International Humic Substances Society, 20-25 September 1992, Monopoli (Bari), Italy, Elsevier. 1368p.

Stevenson, F.J., 1982. Humus chemistry: Genesis, composition, reactions. John Wiley & Sons. Inc. 496p.

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