Incorporation Effect of Lignin and Wheat Straw Biochar on Promoting Maize Growth and Reducing Cd Uptake Under Different Irrigation Regimes

Cadmium (Cd) contamination of soils is a major agricultural and environmental concern. Biochar (BC) is well known for enhancing crop production, while incorporating lignin (LN) with BC for decreasing Cd uptake and availability has not been studied. Herein, we investigated the effects of LN+BC under different irrigation regimes on Cd uptake, soil properties, and maize growth in Cd-contaminated soil. We used three irrigation regimens as main treatments: 60%, 80%, and 100% of evapotranspiration (ET₀). Sub-treatments were soil amendments consisting of 5% BC, 5% LN+BC, and control (CK). Results showed that 60% and 80% irrigation regimens increased Cd concentrations in plant parts while LN+BC application decreased Cd uptake. However, LN+BC and BC significantly decreased Cd uptake across all irrigation regimes. The combination of LN+BC was found to be more efficient in reducing Cd uptake. The order of Cd concentration in plant tissues was as follows: CK > BC > LN+BC. LN+BC significantly increased relative leaf water content (LRWC), membrane stability index (MSI), all growth indicators, and yield attributes compared to CK. Among organic amendments, LN+BC improved grain quality by increasing starch grains, decreasing protein matrix, enhancing side scattered (SSC), and forward scattered (FSC) light signals, followed by BC and CK. The incorporation of LN+BC boosted soil pH, cation exchange capacity (CEC), and organic matter (OM). Combining BC and LN can minimize Cd phytoavailability, enhance soil quality, and boost crop growth in contaminated agricultural soils. This study suggests that a combination of LN and BC can be added as an organic amendment in Cd-contaminated soil.