This study examines the agronomic viability and environmental remediation potential of industrial hemp (Cannabis sativa L.) in anthropogenically altered edaphic conditions, specifically in post-mining terrains. We explored the feasibility of utilising residual rock phosphate dust (containing 30% w/w P2O5), an inadvertent byproduct of phosphate extraction, as a supplemental phosphorus (P) source for hemp cultivation. This dust has a cadmium (Cd) concentration of ~40 ppm, thereby presenting a unique opportunity to study the dual dynamics of P supplementation and Cd phytotoxicity in Cannabis sativa L.
Our study employed an experimental design under controlled conditions within a phytotron, simulating the diurnal and thermal parameters of Christmas Island's climate. A low-phosphorus, comprehensive macronutrient substrate served as the basal medium across all treatments and different amounts of Christmas Island phosphate dust (containing 30% w/w P2O5 and 40 ppm Cd) were applied. Following a 12-week cultivation period, phenotypic and physiological differences were markedly evident between the control and those subjected to phosphate dust enrichment. Notably, the application of 54 g L-1 phosphate dust caused a 38% increase in the above-ground biomass and the addition of 162 g L-1 increased this parameter by 85%. Concurrently, Δ9-tetrahydrocannabinol concentrations positively correlated with elevated phosphate levels.
Interestingly, despite its elevated presence in the phosphate dust, the bioaccumulation of Cd did not display a proportional increase across varying application rates. This observation underscores the potential of Cannabis sativa L. as a phytostabiliser in environments with heavy metal residues. These findings illustrate the dual use of industrial hemp as a high-value crop in post-mining ecosystems and its role in phytoremediation, particularly in hemp industrial hemp ability of growing in contaminated substrate by heavy metals like Cd, thereby contributing to the ecological restoration of mining-impacted landscapes.