Dual-Action Physical Weed Control by Pulse-Charged Expanded Metal: Dissecting Lethal Discharge and Stage-Dependent Growth Suppression in Monocots and Dicots

Integrated weed management requires environmentally friendly alternatives to conventional herbicides. We previously developed a pulse-charged expanded metal (PCEM) system that provides dual-action weed control depending on installation height: direct killing of young seedlings at lower heights and growth suppression at higher heights. This study elucidated the underlying biophysical mechanisms using electrostatic modeling, pulse-current measurements, and multi-species experiments under greenhouse and field conditions. Needle-to-plane simulations demonstrated that emerging shoot apices strongly enhance local electric fields through a lightning-rod effect. Current measurements revealed distinct electrical responses between dicotyledonous and monocotyledonous seedlings. Dicotyledonous seedlings progressively developed high electrical impedance during structural maturation (45–95 mm height), limiting discharge currents (attenuated to 28.9–46.6 μA) and achieving 100% height-dependent growth suppression without foliar injury. Conversely, 100% of monocotyledonous seedlings were lethally electrocuted across all stages, driven by pointed apex field concentration and conductive guttation droplets (inducing peak currents up to 491.5 ± 17.8 μA). Three-year field trials across 60 multi-habitat installations demonstrated 100% prevention of weed canopy penetration and stable species-selective weed suppression under natural environmental fluctuations.