Impact of Lignosulfonate on Solution Chemistry and Phospholipid Fatty Acid Composition in Soils

An incubation experiment (Exp. 1) with three soils, two from Australia and one from Norway, was carried out to investigate the fate of dissolved BorreGro (a lignosulfonate, produced by Borregaard LignoTech Company, Norway) at different concentrations (0, 10 and 100 mg C L−1) in soil solutions. A rhizobox experiment (Exp. 2) was also done in a Norwegian clay soil, mixed with four levels of BorreGro-carbon (BG-C) added (0, 2, 20 and 200 mg BG-C kg−1) to test the impact of BorreGro on root growth, rhizosphere chemistry (pH, metals and dissolved organic carbon (DOC)) and the composition of phospholipid fatty acids (PLFAs). The BorreGro addition increased the concentration of Mn due to the high concentrations in BorreGro. The BorreGro addition to soil had an indirect but significant impact on the rhizosphere chemistry and PLFAs. The lowest amounts of added BorreGro facilitated the DOC excretion at plant roots, and thereby increased the bacterial and fungal biomass, likely as an effect of increased Mn solubility from BorreGro in the root zone.