Bioash amendments from biomass energy systems reshape rhizosphere bacterial communities and reduce metal bioavailability in contaminated soils

Kostešić, Ema (author), Horvatinec Isaković, Jelena (author), Školjarev, Danijela (author), Atlija, Benjamin (author), Zupan, Marko (author), Manterola-Barroso, Carlos (author), Ondrasek, Gabrijel (author)

Biomass-derived ashes (bioash) from energy production are increasingly promoted within circular bioeconomy frameworks as soil amendments that recycle nutrients and mitigate soil acidity. However, their impacts on rhizosphere bacterial communities in metal-contaminated soils (MCS) remain poorly understood. Here, we investigated how four bioash types applied at three rates influence rhizosphere biogeochemistry and bacterial community dynamics of lettuce (Lactuca sativa L.) grown in MCS. Bioash amendment consistently increased soil pH and electrical conductivity, while significantly decreasing bioavailable Zn and Cd fractions. High-throughput 16S rRNA gene amplicon sequencing revealed limited effects on bacterial alpha diversity, with only slight increases at the highest bioash doses. In contrast, beta diversity analyses demonstrated pronounced, dose- and type-dependent shifts in community composition (PERMANOVA, R² = 0.46, p = 0.009). Multivariate analyses identified rhizosphere pH, salinity, DTPA-extractable K and Cd, and mineral N as the main physicochemical variables associated with bacterial community composition. At the phylum level, bioash application increased the relative abundance of Pseudomonadota, while the relative abundances of Bacillota, Bacteroidota, and Gemmatimonadota declined under high application rates. Differential abundance analysis highlighted a distinct subset of bioash-responsive taxa, with enrichment of genera such as Galbitalea, Dongia, and Caulobacter, alongside depletion of several putatively metal-sensitive groups. Overall, bioashes reduced metal bioavailability and restructured rhizosphere microbiomes, supporting their role in sustainable remediation, while emphasizing the need to optimize application rates to balance soil recovery and microbial ecological integrity.

• Language: English
• Keywords: biomass-derived ashes, soil metal contamination, 16S rRNA gene amplicon sequencing, rhizosphere bacterial community
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: BF - Biotechnical Faculty
• Publication status: Published
• Publication version: Version of Record
• Year: 2026
• Number of pages: 14 str.
• Numbering: Vol. 24, art. 100872
• PID: 20.500.12556/RUL-190428
• UDC: 631.4
• ISSN on article: 2772-4271
• DOI: 10.1016/j.nexus.2026.100872
• COBISS.SI-ID: 302937859
• Publication date in RUL: 28.10.2026

Record is a part of a journal

• Title: Energy nexus
• Publisher: Elsevier Ltd.
• ISSN: 2772-4271
• COBISS.SI-ID: 103569155

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: pepel iz biomase, onesnaženje tal s kovinami, sekvenciranje, bakterijske združbe, rizosfera

Projects

• Funder: HRZZ - Croatian Science Foundation
• Project number: P-2022-10-7906
• Name: Amelioration of metal-contaminated soil by bioash
• Acronym: BioAsh4Metals