Mitigation of Cadmium Stress in Lettuce (Lactuca sativa L.) Using Rice Husk Biochar and Silica Fertilizer

Abstract

Heavy metal contamination, particularly cadmium (Cd), can arise from the use of organic fertilizers derived from urban waste. Cd is highly toxic and mobile, posing serious health risks when accumulated in edible crops such as lettuce. This study aimed to evaluate the potential of rice husk biochar (RHB) and silica fertilizer to mitigate Cd stress on lettuce growth. The research employed a factorial Completely Randomized Design with two factors: biochar dose (0, 15, 30, 45 tons/ha) and silica dose (0, 3, 6 g per 3 kg soil per polybag). Soil was spiked with 15 ppm Cd. Parameters measured included plant height, leaf number, fresh weight, soil Cd, and plant Cd. Data were analyzed using ANOVA and LSD test at 5%. Results showed that biochar significantly affected plant height and leaf number (P<0.01), with 45 tons/ha producing the tallest plants (19.81 cm) and most leaves (18.56 leaves), while reducing plant Cd to 0.47 ppm. The combination of P3S1 (45 tons/ha biochar + 3 g/3 kg silica) resulted in the lowest soil Cd (1.16 ppm) and plant Cd (0.32 ppm). Regression analysis showed a weak correlation (R² = 22.74%) between soil and plant Cd. Although the interaction between biochar and silica was not statistically significant (P > 0.05), the main effect of biochar significantly reduced plant Cd concentration (P < 0.05), with the highest dose (45 tons/ha) producing the lowest plant Cd (0.47 ppm). The treatment combination P3S1 (45 tons/ha biochar + 3 g/3 kg silica) numerically produced the lowest soil Cd (1.16 ppm) and plant Cd (0.32 ppm), but did not show synergistic interaction.