Compost and biochar impact on immobilisation of pesticide residues in alkaline soils under canola (

Context The application of soil amendments to immobilise pesticide residues is a promising technology for meeting human health requirements, environmental protection and cost-effective remediation. Aims This study aims to evaluate the effect of rice straw biochar (RB), rice straw compost (RC) and their mixtures at rates of 0.5% and 1.0% in pots, on the immobilisation of pesticides (such as atrazine, glyphosate and chlorpyrifos) in contaminated soil, using spectroscopy analysis under grown canola (Brassica napus L.) plants. Methods Determination of immobilisation of pesticide residues by GC or HPLC and chemical properties of RB and RC and adding them at differentrates to the contaminated soil. Keyresults The results showed that the addition of RB or RC alone or their mixtures led to a significant increase in the exchangeable Ca2+ contents, organic matter (OM), cation exchange capacity (CEC), uptake of N, P and K and dry weight of canola plants. Pesticide concentrations decreased with increasing OM, CEC, and exchangeable Ca2+ with the soil amended by RC and RB. The data indicated that adding RB at levels of 0.5% and 1.0% resulted in reductions in chloropyrifos by 43.2% and 63.1%, glyphosate by 32.8% and 77.3%, and atrazine by 21.9% and 72.2%, respectively, as compared to the control. Addition of (RC + RB) at 0.5% gave the highest pesticide immobilisation, followed (RC+RB) at 1.0%. Conclusion These results indicate that the dominant mechanisms of pesticides immobilisation in the alkaline soils amended with RC and RB by FTIR and XRD analysis were π–π interaction, pore filling, hydrophobic effect, H-bonding, degradation as well as improvement of soil properties and dry yield of canola plants. Implications Our results suggested the possibility of adding recycled rice straw in the form of compost or biochar to the contaminated soil to improve its properties, immobilise pesticides and increase its production capacity.