Enhancing chlorpyrifos degradation and plant growth through biochar-assisted microbial remediation

The extensive use of chlorpyrifos (CPF) in agriculture has led to persistent soil contamination, posing serious risks to environmental and human health. Developing sustainable, in situ remediation strategies is therefore a priority. This study evaluated an integrated plant-microbe-biochar system for the remediation of CPF-contaminated soils. Indigenous CPF-degrading bacteria were isolated from agricultural soils and screened for degradation efficiency in mineral salts medium (MSM) and soil microcosms. The most efficient isolate, designated C78, was identified by 16S rRNA gene sequencing as Klebsiella pneumoniae. In MSM supplemented with 200 mg/L CPF, K. pneumoniae C78 degraded > 80% of the pesticide within 72 h. The strain also exhibited multiple plant growth-promoting traits, including indole-3-acetic acid production, phosphate solubilization, and ammonia production, and retained these functions in the presence of CPF. Soil microcosm and pot experiments were conducted using Ricinus communis L. grown in soils spiked with CPF (100 and 200 mg/kg), with and without biochar amendment and bacterial inoculation. Inoculation with K. pneumoniae C78 significantly accelerated CPF dissipation compared with non-inoculated controls, and the combined treatment with biochar further enhanced degradation, leading to near-complete CPF removal within 21 days. GC-MS/MS analysis showed no accumulation of common toxic intermediates such as 3,5,6-trichloro-2-pyridinol (TCP) or DETP/TMP. Biochar amendment improved soil conditions and supported higher microbial activity, while plant-microbe interactions in the rhizosphere promoted seed germination, seedling vigor, biomass production, chlorophyll content, and protein levels under CPF stress. Overall, the results demonstrate that integrating CPF-degrading K. pneumoniae C78 with R. communis L. and biochar amendment constitutes a promising, eco-compatible strategy for enhancing CPF degradation and restoring the productivity of contaminated agricultural soils.