PERTANIKA JOURNAL OF SCIENCE AND TECHNOLOGY

The humic substance consists of humic acid, fulvic acid, and humin. Humic acid is a useful metal complexing agent, a good dispersant, and a redox agent. Humic acid showed an auxin-like activity and thus promoted root growth and development. It positively affected soil’s physical, chemical, and biological properties. Hence, humic acid indirectly improved plant growth by chelating nutrients to the plant. However, humic acid converted carcinogen compounds in chlorinated water. Still, humic acid is a good compound for agricultural purposes. Humic acid can be produced in thermophilic composting, vermicomposting, and Bokashi. The humification process can occur with decomposers such as black soldier fly. Those methods can be made in farmland and even in the housing area. Extraction of humic acid is required from those production methods. However, it is not easy to extract by farmers on a small scale. Full compost and Bokashi or its tea also showed much humic acid alone. Humic acid extraction may be optional but good as crop tonic. Nonetheless, further study should be carried out. Bokashi tea and leachate with decomposer should be further studied to obtain more evidence of their benefits. With the benefit of composting and fermentation, further study on treating is required for food security.

• Abbas, G., Rehman, S., Siddiqui, M. H., Ali, H. M., Farooq, M. A., & Chen, Y. (2022). Potassium and humic acid synergistically increase salt tolerance and nutrient uptake in contrasting wheat genotypes through ionic homeostasis and activation of antioxidant enzymes. Plants, 11(3), 263. https://doi.org/10.3390/plants11030263

• Achard, F. K. (1786). Chemische untersuchung des torfs [Chemical examination of peat]. Crell’s Chemische Annalen, 2, 391–403.

• Álvarez-Solís, J. D., Mendoza-Núñez, J. A., León-Martínez, N. S., Castellanos-Albores, J., & Gutiérrez-Miceli, F. A. (2016). Effect of Bokashi and vermicompost leachate on yield and quality of pepper (Capsicum annuum) and onion (Allium cepa) under monoculture and intercropping cultures. Ciencia e Investigacion Agraria, 43(2), 243–252. https://doi.org/10.4067/S0718-16202016000200007

• Antoun, L., Zakaria, S., & Rafla, H. (2010). Influence of compost, N-mineral and humic acid on yield and chmical composition of wheat plants. Journal of Soil Sciences and Agricultural Engineering, 1(11), 1131–1143. https://doi.org/10.21608/jssae.2010.75819

• Arancon, N. Q., Edwards, C. A., Lee, S., & Byrne, R. (2006). Effects of humic acids from vermicomposts on plant growth. European Journal of Soil Biology, 42(Suppl. 1), s65-s69. https://doi.org/10.1016/j.ejsobi.2006.06.004

• Arthur, G. D., Aremu, A. O., Kulkarni, M. G., & Van Staden, J. (2012). Vermicompost leachate alleviates deficiency of phosphorus and potassium in tomato seedlings. HortScience, 47(9), 1304–1307. https://doi.org/10.21273/hortsci.47.9.1304

• Baldotto, M. A., & Baldotto, L. E. B. (2016). Initial performance of corn in response to treatment of seeds with humic acids isolated from Bokashi. Revista Ceres, 63(1–62), 62–67. https://doi.org/10.1590/0034-737X201663010009

• Bleam, W. (2017). Natural organic matter. In Soil and environmental chemistry (pp. 333–384). Elsevier. https://doi.org/10.1016/b978-0-12-804178-9.00007-0

• Bócoli, F. A., Marcon, J. A., Izidoro, M., de Toledo Bortolon, P., de Oliveira, S. E. R., Spalevic, V., & de Souza, P. S. (2020). Bokashi use in the passionfruit (Passiflora edulis L.) germination and initial growth. Agriculture and Forestry, 66(4), 101–111. https://doi.org/10.17707/AgricultForest.66.4.08

• Bottomley, W. B. (1917). Some effects of organic growth-promoting substances (auximones) on the growth of Lemna minor in mineral culture solutions. Proceedings of the Royal Society of London. Series B, Containing Papers of A Biological Character, 89(621), 481–507. https://doi.org/10.1098/rspb.1917.0007

• Bradley, S. W., & Sheppard, D. C. (1984). House fly oviposition inhibition by larvae of Hermetia illucens, the black soldier fly. Journal of Chemical Ecology, 10(6), 853–859. https://doi.org/10.1007/BF00987968

• Burges, N. A., Hurst, H. M., & Walkden, B. (1964). The phenolic constituents of humic acid and their relation to the lignin of the plant cover. Geochimica et Cosmochimica Acta, 28(10–11), 1547–1554. https://doi.org/10.1016/0016-7037(64)90005-5

• Canellas, L. P., Olivares, F. L., Okorokova-Façanha, A. L., & Façanha, A. R. (2002). Humic acids isolated from earthworm compost enhance root elongation, lateral root emergence, and plasma membrane H+-ATPase activity in maize roots. Plant Physiology, 130(4), 1951–1957. https://doi.org/10.1104/pp.007088

• Canellas, L. P., Piccolo, A., Dobbss, L. B., Spaccini, R., Olivares, F. L., Zandonadi, D. B., & Façanha, A. R. (2010). Chemical composition and bioactivity properties of size-fractions separated from a vermicompost humic acid. Chemosphere, 78(4), 457–466. https://doi.org/10.1016/j.chemosphere.2009.10.018

• Cheshire, M. V., Cranwell, P. A., Falshaw, C. P., Floyd, A. J., & Haworth, R. D. (1967). Humic acid - II: Structure of humic acids. Tetrahedron, 23(4), 1669–1682. https://doi.org/10.1016/S0040-4020(01)82565-5

• Christel, D. M. (2017). The use of Bokashi as a soil fertility amendment in organic spinach cultivation [Master’s thesis, The University of Vermont]. ScholarWorks. https://scholarworks.uvm.edu/graddis/678

• Day, M., Krzymien, M., Shaw, K., Zaremba, L., Wilson, W. R., Botden, C., & Thomas, B. (1998). An investigation of the chemical and physical changes occurring during commercial composting. Compost Science and Utilization, 6(2), 44–66. https://doi.org/10.1080/1065657X.1998.10701920

• de Brito, A. M., Gagne, S., & Antoun, H. (1995). Effect of compost on rhizosphere microflora of the tomato and on the incidence of plant growth-promoting rhizobacteria. Applied and Environmental Microbiology, 61(1), 194–199. https://doi.org/10.1128/aem.61.1.194-199.1995

• de Melo, B. A. G., Motta, F. L., & Santana, M. H. A. (2016). Humic acids: Structural properties and multiple functionalities for novel technological developments. Materials Science and Engineering: C, 62, 967–974. https://doi.org/10.1016/j.msec.2015.12.001

• El Sheikha, A. F., Allam, A. Y., Taha, M., & Varzakas, T. (2022). How does the addition of biostimulants affect the growth, yield, and quality parameters of the snap bean (Phaseolus vulgaris L.)? How is this reflected in its nutritional value?. Applied Sciences, 12(2), 776. https://doi.org/10.3390/app12020776

• Epelde, L., Jauregi, L., Urra, J., Ibarretxe, L., Romo, J., Goikoetxea, I., & Garbisu, C. (2018). Characterization of composted organic amendments for agricultural use. Frontiers in Sustainable Food Systems, 2, 44. https://doi.org/10.3389/fsufs.2018.00044

• Erickson, M. C., Islam, M., Sheppard, C., Liao, J., & Doyle, M. P. (2004). Reduction of Escherichia coli O157:H7 and Salmonella enterica serovar Enteritidis in chicken manure by larvae of the black soldier fly. Journal of Food Protection, 67(4), 685–690. https://doi.org/10.4315/0362-028X-67.4.685

• Frías, I., Caldeira, M. T., Pérez-Castiñeira, J. R., Navarro-Aviñó, J. P., Culiañez-Maciá, F. A., Kuppinger, O., Stransky, H., Pagés, M., Hager, A., & Serrano, R. (1996). A major isoform of the maize plasma membrane H(+)-ATPase: Characterization and induction by auxin in coleoptiles. The Plant Cell, 8(9), 1533-1544. https://doi.org/10.1105%2Ftpc.8.9.1533

• Frimmel, F. H., & Christman, R. F. (Eds.) (1988). Humic substances and their role in the environment. Wiley.

• Gautam, R. K., Navaratna, D., Muthukumaran, S., Singh, A., Islamuddin, & More, N. (2021). Humic substances: Its toxicology, chemistry and biology associated with soil, plants and environment. In A. Makan (Ed.), Humic substance. IntechOpen. https://doi.org/10.5772/intechopen.98518

• Ghani, M. J., Akhtar, K., Khaliq, S., Akhtar, N., & Ghauri, M. A. (2021). Characterization of humic acids produced from fungal liquefaction of low-grade Thar coal. Process Biochemistry, 107, 1–12. https://doi.org/10.1016/j.procbio.2021.05.003

• Gholami, H., Saharkhiz, M. J., Raouf Fard, F., Ghani, A., & Nadaf, F. (2018). Humic acid and vermicompost increased bioactive components, antioxidant activity and herb yield of Chicory (Cichorium intybus L.). Biocatalysis and Agricultural Biotechnology, 14, 286–292. https://doi.org/10.1016/J.BCAB.2018.03.021

• Guo, X., Liu, H. T., & Wu, S. B. (2019). Humic substances developed during organic waste composting: Formation mechanisms, structural properties, and agronomic functions. Science of The Total Environment, 662, 501–510. https://doi.org/10.1016/j.scitotenv.2019.01.137

• Gutiérrez-Miceli, F. A., García-Gómez, R. C., Rincón Rosales, R., Abud-Archila, M., María Angela, O. L., Cruz, M. J. G., & Dendooven, L. (2008). Formulation of a liquid fertilizer for sorghum (Sorghum bicolor (L.) Moench) using vermicompost leachate. Bioresource Technology, 99(14), 6174–6180. https://doi.org/10.1016/j.biortech.2007.12.043

• Hager, A., Debus, G., Edel, H. G., Stransky, H., & Serrano, R. (1991). Auxin induces exocytosis and the rapid synthesis of a high-turnover pool of plasma-membrane H+-ATPase. Planta, 185(4), 527–537. https://doi.org/10.1007/BF00202963

• Hayes, M. H. B., MacCarthy, P. E., Malcolm, R. L., & Swift, R. S. (1989). Humic substances II. Wiley.

• Hervas, L., Mazuelos, C., Senesi, N., & Saiz-Jimenez, C. (1989). Chemical and physico-chemical characterization of vermicomposts and their humic acid fractions. Science of The Total Environment, 81–82, 543–550. https://doi.org/10.1016/0048-9697(89)90162-9

• Jaramillo-López, P. F., Ramírez, M. I., & Pérez-Salicrup, D. R. (2015). Impacts of Bokashi on survival and growth rates of Pinus pseudostrobus in community reforestation projects. Journal of Environmental Management, 150, 48–56. https://doi.org/10.1016/j.jenvman.2014.11.003

• Jiang, Z., Li, X., Li, M., Zhu, Q., Li, G., Ma, C., Li, Q., Meng, J., Liu, Y., & Li, Q. (2021). Impacts of red mud on lignin depolymerization and humic substance formation mediated by laccase-producing bacterial community during composting. Journal of Hazardous Materials, 410, 124557. https://doi.org/10.1016/j.jhazmat.2020.124557

• Jim, C. Y. (1998). Urban soil characteristics and limitations for landscape planting in Hong Kong. Landscape and Urban Planning, 40(4), 235–249. https://doi.org/10.1016/S0169-2046(97)00117-5

• Khaled, H., & Fawy, H. (2011). Effect of different levels of humic acids on the nutrient content, plant growth, and soil properties under conditions of salinity. Soil and Water Research, 6, 21–29. https://doi.org/10.17221/4/2010-swr

• Khandan-Mirkohi, A., Pirgazi, R., Taheri, M. R., Ajdanian, L., Babaei, M., Jozay, M., & Hesari, M. (2021). Effects of salicylic acid and humic material preharvest treatments on postharvest physiological properties of statice cut flowers. Scientia Horticulturae, 283, 110009. https://doi.org/10.1016/j.scienta.2021.110009

• Kinniburgh, D. G., van Riemsdijk, W. H., Koopal, L. K., & Benedetti, M. F. (1998). Ion binding to humic substances: Measurements, models, and mechanisms. In Adsorption of metals by geomedia: Variables, mechanisms, and model applications (pp. 483–520). Academic Press. https://doi.org/10.1016/b978-012384245-9/50024-4

• Kögel-Knabner, I. (2002). The macromolecular organic composition of plant and microbial residues as inputs to soil organic matter. Soil Biology and Biochemistry, 34(2), 139–162. https://doi.org/10.1016/S0038-0717(01)00158-4

• Lal, R. (2004). Soil carbon sequestration impacts on global climate change and food security. Science, 304(5677), 1623–1627. https://doi.org/10.1126/science.1097396

• Lamar, R. T., Olk, D. C., Mayhew, L., & Bloom, P. R. (2014). A new standardized method for quantification of humic and fulvic acids in humic ores and commercial products. Journal of AOAC International, 97(3), 721-730. https://doi.org/10.5740/jaoacint.13-393

• Lazcano, C., Arnold, J., Tato, A., Zaller, J. G., & Domínguez, J. (2009). Compost and vermicompost as nursery pot components: Effects on tomato plant growth and morphology. Spanish Journal of Agricultural Research, 7(4), 944-951. https://doi.org/10.5424/sjar/2009074-1107

• Li, G., Sun, G.-X., Ren, Y., Luo, X.-S., & Zhu, Y.-G. (2018). Urban soil and human health: A review. European Journal of Soil Science, 69(1), 196–215. https://doi.org/10.1111/ejss.12518

• Li, Q., Zheng, L., Cai, H., Garza, E., Yu, Z., & Zhou, S. (2011). From organic waste to biodiesel: Black soldier fly, Hermetia illucens, makes it feasible. Fuel, 90(4), 1545–1548. https://doi.org/10.1016/J.FUEL.2010.11.016

• Liao, W., Christman, R. F., Johnson, J. D., Millington, D. S., & Hass, J. R. (1982). Structural characterization of aquatic humic material. Environmental Science and Technology, 16(7), 403–410. https://doi.org/10.1021/es00101a007

• Liu, M., Wang, C., Wang, F., & Xie, Y. (2019). Maize (Zea mays) growth and nutrient uptake following integrated improvement of vermicompost and humic acid fertilizer on coastal saline soil. Applied Soil Ecology, 142, 147–154. https://doi.org/10.1016/j.apsoil.2019.04.024

• Liu, Q., Tomberlin, J. K., Brady, J. A., Sanford, M. R., & Yu, Z. (2008). Black soldier fly (Diptera: Stratiomyidae) larvae reduce Escherichia coli in dairy manure. Environmental Entomology, 37(6), 1525–1530. https://doi.org/10.1603/0046-225X-37.6.1525

• Liu, T., Awasthi, M. K., Awasthi, S. K., Zhang, Y., & Zhang, Z. (2020a). Impact of the addition of black soldier fly larvae on humification and speciation of trace elements during manure composting. Industrial Crops and Products, 154, 112657. https://doi.org/10.1016/J.INDCROP.2020.112657

• Liu, Y., Hu, H., Wang, Y., Wang, L., & Feng, Y. (2020b). Effects of heavy metals released from sediment accelerated by artificial sweeteners and humic acid on a green algae Scenedesmus obliquus. Science of the Total Environment, 729, 138960. https://doi.org/10.1016/j.scitotenv.2020.138960

• López-Bucio, J., Millán-Godínez, M., Méndez-Bravo, A., Morquecho-Contreras, A., Ramírez-Chávez, E., Molina-Torres, J., Pérez-Torres, A., Higuchi, M., Kakimoto, T., & Herrera-Estrella, L. (2007). Cytokinin receptors are involved in alkamide regulation of root and shoot development in Arabidopsis. Plant Physiology, 145(4), 1703–1713. https://doi.org/10.1104/pp.107.107953

• Lu, M., Shi, X., Feng, Q., Li, X., Lian, S., Zhang, M., & Guo, R. (2021). Effects of humic acid modified oyster shell addition on lignocellulose degradation and nitrogen transformation during digestate composting. Bioresource Technology, 329, 124834. https://doi.org/10.1016/j.biortech.2021.124834

• Maji, D., Misra, P., Singh, S., & Kalra, A. (2017). Humic acid rich vermicompost promotes plant growth by improving microbial community structure of soil as well as root nodulation and mycorrhizal colonization in the roots of Pisum sativum. Applied Soil Ecology, 110, 97–108. https://doi.org/10.1016/j.apsoil.2016.10.008

• Malik, K. A., & Azam, F. (1985). Effect of humic acid on wheat (Triticum aestivum L.) seedling growth. Environmental and Experimental Botany, 25(3), 245–252. https://doi.org/10.1016/0098-8472(85)90008-5

• Merfield, C. N. (2012). Treating food preparation “waste” by Bokashi fermentation vs. composting for crop land application: A feasibility and scoping review. https://bhu.org.nz/future-farming-centre/ffc/information/soil-management/treating-food-preparation-waste-by-bokashi-fermentation-vs-composting-for-crop-land-application-a-feasibility-and-scoping-review-2012-ffc-merfield.pdf

• Milinković, M., Lalević, B., Jovičić-Petrović, J., Golubović-Ćurguz, V., Kljujev, I., & Raičević, V. (2019). Biopotential of compost and compost products derived from horticultural waste—Effect on plant growth and plant pathogens’ suppression. Process Safety and Environmental Protection, 121, 299–306. https://doi.org/10.1016/J.PSEP.2018.09.024

• Miller, F. C. (1996). Composting of municipal solid waste and its components. In Microbiology of solid waste (1st ed., pp. 115–154). CRC Press. https://doi.org/10.1201/9780138747268-4

• Morquecho-Contreras, A., Méndez-Bravo, A., Pelagio-Flores, R., Raya-González, J., Ortíz-Castro, R., & López-Bucio, J. (2010). Characterization of drr1, an alkamide-resistant mutant of Arabidopsis, reveals an important role for small lipid amides in lateral root development and plant senescence. Plant Physiology, 152(3), 1659–1673. https://doi.org/10.1104/pp.109.149989

• Mosa, A., Taha, A. A., & Elsaeid, M. (2021). In-situ and ex-situ remediation of potentially toxic elements by humic acid extracted from different feedstocks: Experimental observations on a contaminated soil subjected to long-term irrigation with sewage effluents. Environmental Technology and Innovation, 23, 101599. https://doi.org/10.1016/j.eti.2021.101599

• Naidu, Y., Meon, S., & Siddiqui, Y. (2013). Foliar application of microbial-enriched compost tea enhances growth, yield and quality of muskmelon (Cucumis melo L.) cultivated under fertigation system. Scientia Horticulturae, 159, 33–40. https://doi.org/10.1016/j.scienta.2013.04.024

• Ndzelu, B. S., Dou, S., Zhang, X., Zhang, Y., Ma, R., & Liu, X. (2021). Tillage effects on humus composition and humic acid structural characteristics in soil aggregate-size fractions. Soil and Tillage Research, 213, 105090. https://doi.org/10.1016/j.still.2021.105090

• Nelson, D. W., & Sommers, L. E. (1982). Total carbon, organic carbon, and organic matter. In A. L. Page (Ed.), Methods of soil analysis: Part 2 Chemical and microbiological properties (2nd, ed., pp. 539–579). https://doi.org/10.2134/agronmonogr9.2.2ed.c29

• Olle, M. (2020). Short communication: The improvement of the growth of tomato transplants by Bokashi tea. Agraarteadus, 31(1), 70–73. https://doi.org/10.15159/jas.20.10

• Olle, M. (2021). Review: Bokashi technology as a promising technology for crop production in Europe. The Journal of Horticultural Science and Biotechnology, 96(2), 145–152. https://doi.org/10.1080/14620316.2020.1810140

• Pakkish, Z., Asghari, H., & Mohammadrezakhani, S. (2022). Application of humic acid on improving the vegetative and reproductive growth of pistachio cultivar Akbari. Applied Biology, 34(4). https://doi.org/10.22051/JAB.2021.33511.1385

• Pang, L., Song, F., Song, X., Guo, X., Lu, Y., Chen, S., Zhu, F., Zhang, N., Zou, J., & Zhang, P. (2021). Effects of different types of humic acid isolated from coal on soil NH3 volatilization and CO2 emissions. Environmental Research, 194, 110711. https://doi.org/10.1016/j.envres.2021.110711

• Pant, A. P., Radovich, T. J. K., Hue, N. V., & Miyasaka, S. C. (2012a). Pak Choi (Brassica rapa, Chinensis group) yield, phytonutrient content, and soil biological properties as affected by vermicompost-to-water ratio used for extraction. HortScience, 47(3), 395–402. https://doi.org/10.21273/hortsci.47.3.395

• Pant, A. P., Radovich, T. J. K., Hue, N. V., & Paull, R. E. (2012b). Biochemical properties of compost tea associated with compost quality and effects on pak choi growth. Scientia Horticulturae, 148, 138–146. https://doi.org/10.1016/j.scienta.2012.09.019

• Phooi, C. L., Azman, E. A., & Ismail, R. (in press). Bokashi leachate as a biopriming on Basella rubra L. seed germination and root development. Research Square. https://doi.org/10.21203/RS.3.RS-855828/V1

• Prisa, D. (2020). EM-Bokashi addition to the growing media for the quality improvement of Kalanchoe blossfeldiana. International Journal of Multidisciplinary Sciences and Advanced Technology, 1(1), 52–59.

• Qi, H., Zhang, A., Du, Z., Wu, J., Chen, X., Zhang, X., Zhao, Y., Wei, Z., Xie, X., Li, Y., & Ye, M. (2021). δ-MnO2 changed the structure of humic-like acid during co-composting of chicken manure and rice straw. Waste Management, 128, 16–24. https://doi.org/10.1016/j.wasman.2021.04.039

• Rashwan, M., Naser Alkoaik, F., Morsy, M., Blanqueza Fulleros, R., & Nagy Ibrahim, M. (2021). Influence of tomato waste compost ratios on plant growth and fruit quality of cucumber and summer squash. Journal of the Air and Waste Management Association, 71(9), 1067-1075. https://doi.org/10.1080/10962247.2021.1890278

• Richard, J. B. (1982). Health effects of drinking water disinfectants and disinfectant by-products. Environmental Science and Technology, 16(10), 554-559. https://doi.org/10.1021/es00104a719

• Riggle, D. (1996). Compost teas in agriculture. Biocycle, 37(12), 65–67.

• Rook, J. J. (1976). Haloforms in drinking water. Journal - American Water Works Association, 68(3), 168–172. https://doi.org/10.1002/j.1551-8833.1976.tb02376.x

• Rook, J. J. (1977). Chlorination reactions of fulvic acids in natural waters. Environment Science Technology, 11(5), 478–482. https://doi.org/10.1021/es60128a014

• Santos, C. C., do Carmo Vieira, M., Zárate, N. A. H., de Oliveira Carnevali, T., & Gonçalves, W. V. (2020). Organic residues and Bokashi influence in the growth of Alibertia edulis. Floresta e Ambiente, 27(1). https://doi.org/10.1590/2179-8087.103417

• Satheesh Ananda, S., & Mehendale, H. M. (2005). Chlorination by-products. In Encyclopedia of toxicology (2nd ed., pp. 546–553). Academic Press. https://doi.org/10.1016/B0-12-369400-0/00214-3

• Saxena, J., Choudhary, S., Pareek, S., Choudhary, A. K., & Iquebal, M. A. (2015). Recycling of organic waste through four different composts for disease suppression and growth enhancement in mung beans. Clean - Soil, Air, Water, 43(7), 1066–1071. https://doi.org/10.1002/clen.201300748

• Schnitzer, M. (1991). Soil organic matter — The next 75 years. Soil Science, 151(1), 41–58. https://doi.org/10.1097/00010694-199101000-00008

• Schnitzer, M. (2015). Organic matter characterization. In Methods of soil analysis: Part 2 Chemical and microbiological properties (2nd ed., pp. 581–594). https://doi.org/10.2134/agronmonogr9.2.2ed.c30

• Shi, Y., Ma, W., Han, F., Geng, Y., Yu, X., Wang, H., Kimura, S. Y., Wei, X., Kauffman, A., Xiao, S., Zheng, W., & Jia, X. (2020). Precise exposure assessment revealed the cancer risk and disease burden caused by trihalomethanes and haloacetic acids in Shanghai indoor swimming pool water. Journal of Hazardous Materials, 388, 121810. https://doi.org/10.1016/j.jhazmat.2019.121810

• Singh, R. (2015). Water and membrane treatment. In Membrane technology and engineering for water purification: Application, system design and operation (2nd ed., pp. 81–178). Elsevier. https://doi.org/10.1016/b978-0-444-63362-0.00002-1

• Steelink, C. (1964). Free radical studies of lignin, lignin degradation products and soil humic acids. Geochimica et Cosmochimica Acta, 28(10–11), 1615–1622. https://doi.org/10.1016/0016-7037(64)90010-9

• Stevenson, F. (1994). Humus chemistry: Genesis, composition, reactions (2nd ed.). Wiley.

• Susic, M. (2016). Replenishing humic acids in agricultural soils. Agronomy, 6(4), 45. https://doi.org/10.3390/agronomy6040045

• Swift, R., & Hayes, M. (1989). Humic Substances II. Wiley.

• Tiller, K. G. (1992). Urban soil contamination in australia. Australian Journal of Soil Research, 30(6), 937–957. https://doi.org/10.1071/SR9920937

• Tognetti, C., Laos, F., Mazzarino, M. J., & Hernández, M. T. (2005). Composting vs. vermicomposting: A comparison of end product quality. Compost Science and Utilization, 13(1), 6–13. https://doi.org/10.1080/1065657X.2005.10702212

• Walters, D. (Ed.) (2009). Disease control in crops: Biological and environmentally friendly approaches. Wiley-Blackwell. https://doi.org/10.1002/9781444312157

• Wang, Q., Ren, X., Sun, Y., Zhao, J., Awasthi, M. K., Liu, T., Li, R., & Zhang, Z. (2021a). Improvement of the composition and humification of different animal manures by black soldier fly bioconversion. Journal of Cleaner Production, 278, 123397. https://doi.org/10.1016/j.jclepro.2020.123397

• Wang, X., Lyu, T., Dong, R., Liu, H., & Wu, S. (2021b). Dynamic evolution of humic acids during anaerobic digestion: Exploring an effective auxiliary agent for heavy metal remediation. Bioresource Technology, 320(Part A), 124331. https://doi.org/10.1016/j.biortech.2020.124331

• Wei, Z., Xi, B., Zhao, Y., Wang, S., Liu, H., & Jiang, Y. (2007). Effect of inoculating microbes in municipal solid waste composting on characteristics of humic acid. Chemosphere, 68(2), 368–374. https://doi.org/10.1016/j.chemosphere.2006.12.067

• Weltzien, H. C. (1990). The use of composted materials for leaf disease suppression in field crops. British Crop Protection Council: Organic and Low Input Agriculture, 45, 115–120.

• Xu, D. B., Wang, Q. J., Wu, Y. C., Yu, G. H., Shen, Q. R., & Huang, Q. W. (2012). Humic-like substances from different compost extracts could significantly promote cucumber growth. Pedosphere, 22(6), 815–824. https://doi.org/10.1016/S1002-0160(12)60067-8

• Xue, S., Xiao, Y., Wang, G., Fan, J., Wan, K., He, Q., Gao, M., & Miao, Z. (2021). Adsorption of heavy metals in water by modifying Fe3O4 nanoparticles with oxidized humic acid. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 616, 126333. https://doi.org/10.1016/j.colsurfa.2021.126333

• Yang, C. M., Chang, I. F., Lin, S. J., & Chou, C. H. (2004a). Effects of three allelopathic phenolics on chlorophyll accumulation of rice (Oryza sativa) seedlings: II. Stimulation of consumption-orientation. Botanical Bulletin of Academia Sinica, 45(2), 119–125. https://doi.org/10.7016/BBAS.200404.0119

• Yang, C. M., Lee, C. N., & Chou, C. H. (2002). Effects of three allelopathic phenolics on chlorophyll accumulation of rice (Oryza sativa) seedlings: I. Inhibition of supply-orientation. Botanical Bulletin of Academia Sinica, 43(4), 299–304.

• Yang, C. M., Wang, M. C., Lu, Y. F., Chang, I. F., & Chou, C. H. (2004b). Humic substances affect the activity of chlorophyllase. Journal of Chemical Ecology, 30(5), 1057–1065. https://doi.org/10.1023/B:JOEC.0000028467.82191.f9

• Yildirim, E. (2007). Foliar and soil fertilization of humic acid affect productivity and quality of tomato. Acta Agriculturae Scandinavica Section B: Soil and Plant Science, 57(2), 182–186. https://doi.org/10.1080/09064710600813107

• Zandonadi, D. B., Roberto, C., Matos, R., Castro, R. N., Spaccini, R., Olivares, F. L., & Canellas, L. P. (2019). Alkamides: A new class of plant growth regulators linked to humic acid bioactivity. Chemical and Biological Technologies in Agriculture, 6, 23. https://doi.org/10.1186/s40538-019-0161-4

• Zhang, X., Dou, S., Ndzelu, B. S., Guan, X. W., Zhang, B. Y., & Bai, Y. (2020). Effects of different corn straw amendments on humus composition and structural characteristics of humic acid in black soil. Communications in Soil Science and Plant Analysis, 51(1), 107–117. https://doi.org/10.1080/00103624.2019.1695827

• Zhu, J., Gao, W., Ge, L., Zhao, W., Zhang, G., & Niu, Y. (2021). Immobilization properties and adsorption mechanism of nickel(II) in soil by biochar combined with humic acid-wood vinegar. Ecotoxicology and Environmental Safety, 215, 112159. https://doi.org/10.1016/j.ecoenv.2021.112159