Urease Inhibitor Strengthening Nano Zerovalent Iron Performance in Plant Growth Regulator-Paclobutrazol Degradation and Mitigating Its Negative Impact on Agricultural Soil Microbial Community Stability: Based on Incubation and Plant Growth Experiments

Plant growth regulators such as paclobutrazol are widely used in agriculture, but repeated applications can accumulate in soil and crops, negatively impacting the environment and microbial communities. This study conducted incubation and plant-growth experiments to evaluate the combined effects of nano zerovalent iron (nZVI) and urease inhibitor (NBPT) on paclobutrazol degradation, crop yields, and microbial communities. Sole nZVI reduced paclobutrazol residues and increased endophytic microbial diversity and functionality but destabilized soil microbial communities. The combination of nZVI and NBPT significantly reduced paclobutrazol residues in lettuce by 34.4% and in soil by 15.4% while improving the crop yield. NBPT mitigated the negative impact of nZVI on soil microbial stability and enhanced its effects on paclobutrazol degradation and yield stimulation. The combined treatment also improved the ecological functions of endophytic microbes and maintained the stable functional potentials of soil microbial communities, providing a basis for managing paclobutrazol residue risks and enhancing crop safety.