Metal-mobilizing bacteria enhance phytoremediation efficiency, growth, and nutrient uptake in Salix alba under controlled conditions

Beneficial microorganisms that colonize plants are useful biotools for improving phytoremediation. In a two-year pot experiment conducted at Punjab Agricultural University in Ludhiana, India, Salix alba was evaluated in a nursery conditions in response to soil treated with sewage sludge and native metal-mobilizing Bacillus species, specifically B. thuringiensis (I1), B. cereus (I2), B. pumilus (I3), and their consortium (I4), along with three levels of inorganic fertilizer (F1-100% Recommended dose of fertilizer (RDF), F2-75% RDF, and F3-50% RDF). A comparison was made between each inoculation treatment and its corresponding uninoculated control (I0). In comparison to I0, the application of I4 with F1 resulted in a considerable increase in shoot length and biomass of 13.8% and 32.9%, respectively. While phytoremediation efficiency reached up to 28.0% and 27.2% compared to I0, nitrogen uptake in shoots and roots increased by 29.5% and 22.0%, respectively. With the exception of zinc and cadmium, the majority of the accumulation of elements was found in roots. F1×I4 and F2×I4 were statistically comparable for the majority of the parameters. I4 increased soil chemical and biological characteristics by up to 22.5% and phytoremedial efficacy by 35.9% (shoot) and 33.9% (root), respectively, regardless of fertilizer dosage, as opposed to 7.1% and 8.8% in I0. These findings demonstrate application of native microbial inoculants can lower soil heavy metal levels and allow for improved, sustainable phytoremediation with a 25% lower fertilizer input.