Barren to green in a single application: Revitalizing brownfield soil with simulated root exudates

Abstract

Barren, metal-contaminated soils lack plants and root exudate inputs, exhibit low microbial abundance and functioning, and often require soil revitalization to revegetate. While the effects of simulated root exudates (SRE) have been investigated in uncontaminated, vegetated soils, their potential for remediating post-industrial barren, contaminated soils has not been examined or leveraged. We asked whether priming brownfield soils with a laboratory-prepared SRE solution stimulates native soil microbial metabolism and functioning and how long the effects last. Moreover, we compared a cost-effective single SRE addition to repeated SRE additions. We collected soils from a metal-contaminated, abandoned industrial rail yard (barren and vegetated sites) and a vegetated agricultural reference site, established microcosms, and treated the soils with either a single or repeated SRE addition/s. By day 30, SRE-enriched barren, brownfield soils showed significantly higher soil respiration rates than the untreated control soils. Phosphatase activities were significantly higher even 210 days after a single SRE addition. Plants were introduced 282 days after the single SRE addition. The average shoot height (16 ± 0.3 cm) and total plant biomass (0.5 ± 0.02 g) of plants grown in single addition SRE enriched barren soil were significantly higher than the controls (9 ± 0.9 cm and 0.3 ± 0.02 g, respectively). The increased soil microbial functioning and productivity indicate that a single SRE application holds promise as a field-ready technology to revitalize barren, poorly functioning brownfield soils. SRE application may also be a pragmatic and innovative approach to enable successful phytoremediation and re-greening of industrial barrens.