Evaluation of biostimulants and mycorrhizae to improve phytomanagement potential of lignocellulosic crops

Phytomanagement of metal(loid)-contaminated sites involves cultivating high-yielding lignocellulosic crops to achieve two main goals: biomass production for bioenergy and progressive land decontamination. This approach is a sustainable and cost-effective alternative to conventional physico-chemical remediation techniques, which can negatively impact soil structure and fertility and are impractical for large-scale application. Contaminated sites commonly suffer from additional degradation factors which limit conventional crop cultivation. Biostimulants and microorganisms offer a promising strategy to enhance crop productivity while maintaining the cost-effectiveness and simplicity of phytomanagement systems. However, most studies on plant-biostimulant interactions focus on high-profit food crops, with limited research on lignocellulosic species. Moreover, existing studies are mostly conducted in controlled environments, often using metal-spiked soils without field validation. This thesis investigates the potential of biostimulants to enhance the phytomanagement efficiency of three promising lignocellulosic crops: Sorghum bicolor, Cannabis sativa, and Miscanthus × giganteus. Three biostimulants were tested: mycorrhizae (M), protein hydrolysates (B1), and humic substances (B2), applied alone or in combination. The study involved an upscaling from pot to field conditions, providing a progressive selection of crop and biostimulant combinations. Miscanthus × MB2 combination emerged as the most effective strategy and was further investigated in controlled environment, showing reduced Cu bioavailability (-21% in soil pore water) and increased root dry weight density (almost tripled). This enhanced root proliferation led to a 23% increase in shoot biomass from the second year in the field. Furthermore, the Arungro crop model was recalibrated to incorporate MB2 effects on Miscanthus productivity, confirming aboveground biomass as the key factor for phytoextraction potential. In conclusion, miscanthus cultivation paired with mycorrhizae and humic substances is a viable phytomanagement strategy to couple processable biomass production with progressive contaminant stripping and metal phytostabilization. It can be further implemented through the use of crop models that can simulate miscanthus productivity and metal-uptkae dynamics.