Soil Amendment-Mediated Herbivory Resistance, Crop Improvement, and Phytoremediation in Canola: Physiological Defense Mechanism and Health Risk Assessment

A two-year field study was conducted using canola to check the efficacy of different soil amendment treatments (SAT), i.e., with elemental sulfur (ES), bio-sulfur (BS), and compost (Cp) mixtures against insecticide-treated (Carbosulfan) and untreated controls regarding aphid populations. The results of the experiment revealed that ES treatments significantly reduced aphid abundance, followed by Cp and ES+Cp. However, BS improved aphid herbivory. The number of siliques, seeds, thousand-seed weight, and yield were improved with a trend of ES+Cp > Cp > BS+Cp. Similarly, physiological mechanisms revealed the regulation of nutrient and phenolic contents in canola with ES improving sulfur, BS nitrogen, Cp, and ES+Cp calcium, and BS+Cp enhancing phosphorus, potassium, iron, and zinc. Furthermore, RP-HPCL indicated that ferulic acid was highest in insecticide-treated plot. Similarly, Cp improved quercetin and gallic acid; ES+Cp caffeic, chlorogenic, m-coumaric, and sinapic acid; and BS+Cp enhances syringic, vanillic, ferulic, p-coumaric, and cinnamic acid. The analysis regarding health risk assessment revealed among different SAT, ES+Cp significantly reduced the Hazardous Quotient (HQ) of Cu and Zn. However, further research is still needed to explore SAT's potential to remediate other heavy metal stresses with possible implications for pest management in different field crops.