Lead-induced nutrient imbalance and biochar-mediated nutrient responses in purslane ( Portulaca oleracea L.)

Lead (Pb) stress disrupts growth and nutrient balance, while biochar (BC) effects vary with dose and stress level. The effects of chicken-manure-derived BC on shoot growth, shoot Pb concentration, and macro- and micronutrient concentrations and uptake in purslane across Pb levels were determined. A semi-controlled factorial pot experiment with three replications included added Pb levels of 0, 50, and 100 mg kg−1 and BC doses of 0, 5, and 10 g kg−1. Data were evaluated using two-way ANOVA and Pearson correlation analysis. The Pb × BC interaction was significant for shoot dry weight, shoot height, and Ca concentration. Pb100–BC10 produced the lowest mean shoot dry weight and height. Shoot Pb concentration increased with Pb dose, whereas BC5 produced a lower value than BC0. The interaction was significant for the uptake of all measured nutrients except Mg. The lowest numerical mean uptake values of N, P, K, Ca, Fe, Cu, Zn, Mn, and B occurred under Pb100–BC10. Shoot Pb concentration was negatively correlated with all measured nutrient concentrations. Pb dominated plant responses, while BC effects were nonlinear across doses and Pb levels, emphasizing the need to evaluate nutrient concentrations and uptake and to consider the limitations of high BC doses.