The Potential Role of Humic Substances in the Amelioration of Saline Soils and Its Affecting Factors

Daniel Moro, Elisa Pellegrini, Marco Contin (), Daniele Zuccaccia, Ali Khakbaz and Maria De Nobili
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Daniel Moro: Department of Life Sciences, University of Trieste, 34100 Trieste, Italy
Elisa Pellegrini: Department of Agrifood, Environmental and Animal Sciences, University of Udine, 33100 Udine, Italy
Marco Contin: Department of Agrifood, Environmental and Animal Sciences, University of Udine, 33100 Udine, Italy
Daniele Zuccaccia: Department of Agrifood, Environmental and Animal Sciences, University of Udine, 33100 Udine, Italy
Ali Khakbaz: Department of Agrifood, Environmental and Animal Sciences, University of Udine, 33100 Udine, Italy
Maria De Nobili: Department of Agrifood, Environmental and Animal Sciences, University of Udine, 33100 Udine, Italy

Sustainability, 2025, vol. 17, issue 19, 1-17

Abstract: The application of organic amendments and humic acids (HA) often ameliorates saline soils, but the mechanisms responsible for their positive action have never been fully clarified. HA from four different origins (Elliott soil—EHA, peat—PHA, leonardite—LHA and compost—CHA) and polyacrylic acid (PAA) were characterized by acid–base titrations and 1 H-NMR spectroscopy and tested in laboratory experiments by measuring changes in electric conductivity (EC) and pH following micro-additions of Na 2 CO 3 or NaCl. The effective salinity amelioration potential (SAP eff ) of HA, which expresses the amount of Na 2 CO 3 neutralized per unit weight of HA at a given pH, was calculated. PAA had the highest capacity of mitigation, corresponding to 49.9 mg Na 2 CO 3 g −1 , followed by LHA, EHA and PHA, whose SAP eff values were similar and only slightly lower, and with CHA having the lowest value (25.1 mg Na 2 CO 3 g −1 HA). All substances failed to display any effect at constant pH when NaCl was the only salt present. The dissociation of acid groups, when HA become exposed to a more alkaline pH, produces an excess of negative charges that attracts more cations within the diffuse double layer. Because of the slower diffusion of HA and their tendency to aggregate at high ionic strengths, this action reduces the osmolarity of the soil solution and therefore mitigates salinity stress.

Keywords: humic acids; soil salinity; soil electrical conductivity; alkalinity; salinity mitigation (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2025
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