The group method of data handling (GMDH) model for lead and cadmium uptake by <i>Bromus tomentellus</i> under the effect of biochar and urban waste compost organic amendments addition

Modeling and predicting heavy metal uptake by plants using organic amendments helps reduce metal concentrations in contaminated soils. This study examined the effects of 1% and 2% (W/W) biochar and urban waste compost on the growth and cadmium (Cd) and lead (Pb) uptake by <i>Bromus tomentellus</i> in contaminated soil. The highest plant height (34.0 cm) and biomass (30.0 g) occurred with 2% biochar, compared to 16.0 cm and 9.0 g in control. For Pb, the maximum bioconcentration factor (BCF) was 2.25 with 1% compost, and the highest translocation factor (TF) was 1.4 with 2% biochar. For Cd, both max BCF (3.40) and TF (1.4) were seen at 1% biochar. Metal uptake and transfer significantly correlated with biomass and soil factors such as fertility (N, P, and K), pH, sodium adsorption ratio (SAR), and organic matter (OM) (Mantel test: <i>p</i> = 0.1, <i>r</i> = 0.4). The Group Method of Data Handling (GMDH) model, with high accuracy (<i>R</i>² = 0.998), showed compost caused an initial rise then decline in Cd uptake, while biochar had the opposite effect. Pb uptake increased with compost up to 1.052%, peaking at 763.7 ppm, then decreased. The GMDH model can optimize biochar or compost levels to enhance metal uptake by plants in polluted soils.