Silica-embedded nutrient-doped biochar improves nutrient availability and safflower (Carthamus tinctorius L.) growth in cadmium- and lead-contaminated soil

Purpose Heavy metal(loid) contamination has degraded over 20 million ha of global land with soil concentrations far above geo-baseline, consequently posing economic impacts of > 10 billion USD per year. The present study was aimed at mitigating heavy metal-mediated pollution in contaminated soil by using olive mill waste-derived biochar (BC), nutrient-doped BC, silica-embedded BC, and silica-embedded nutrient-doped BC. Methods The BC was produced from olive mill waste at 500℃. A greenhouse experiment was conducted using agriculture soil artificially spiked by Pb and Cd, using safflower ( Carthamus tinctorius L) as a test crop, and soil was amended with synthesized pristine and fabricated BCs at the rate of 1% and 2% (w/w). Results The results showed that silica-embedded nutrient-doped BC (SNBC) increased plant shoot and root length by 65% and 70%, while fresh and dry biomass were enhanced by 66% and 57%, respectively. Additionally, the uptake of P and K by plant was significantly increased by the addition of BCs, while on contrarily, heavy metal concentration and uptake were reduced in plants grown in NBC- and SNBC-amended soil (2%). Overall plant growth was increased by two-fold by the addition of pristine and fabricated BCs as compared to control. Significant increment in bioconcentration factor suggested the potential of using fabricated amendments for phytoremediation process. Conclusion In a nutshell, silica-embedded nutrient-doped BC showed excellent potential in mitigating heavy metals (Pb and Cd) toxicity, enhancing nutrient availability, and improving safflower plant growth.