Pesticide effects on crop physiology, production and soil biological functions

Over-dose pesticide application disrupts plant physiological processes and soil biological functions; however, the toxicity mechanisms of pesticides and the effectiveness of mitigation measures are still unclear. Our review shows that over-dose of pesticide can cause plant phytotoxicity by enhancing reactive oxygen species and cellular membrane electrolyte leakage, which subsequently decrease chlorophyll biosynthesis, vegetative growth and yield. However, the optimum use of pesticides (insecticides at 0.21 kg a.i. ha−1; herbicides at 1.44 kg a.i. ha−1 and fungicides at ≤0.4 kg a.i. ha−1) may not interfere with plant physiological functions, while indirectly improving plant nutrients absorption, translocation and yield. In the soil system, pesticide application decreases microbial population by disrupting the microbial metabolism and cellular protein denaturation. Moreover, pesticide application can restrict (by adsorption, etc.) glucose release from organic matter by decreasing the hydrolysis of extracellular enzymes, thereby reducing the labile C source for microbes and resulting in lower soil organic carbon cycling. The pesticide residue can decrease biological nitrogen fixation and nitrogen mineralization by decreasing diazotrophs and saprophytic bacterial population due to cellular hyperkinesis and misfunctions, respectively. Organo-phosphate pesticides can induce oxidative stress to microbes which can affect phosphorus (P) mineralization, but may also enhance P-solubilizing bacterial activities and P availability. The use of biosurfactants, exogenously induced microbes, and soil amendments (e.g., biochar) can effectively remediate pesticide toxicity through solubilization, microbial catabolism and sorption of pesticides by 70%, 78% and 69%, respectively. However, field application of biosurfactants and optimization of biochar characteristics remain challenging for effective pesticide sorption and remediation.