Charged-Spray Deposition Characteristics Within Cereal Crops

Fluorescent tracer studies experimentally quantified the spatial distribution of droplet mass transfer and charge transfer characterizing three modes of electrostatic pesticide spraying onto barley-weed-soil target arrays. Droplet charging in the 1.5-4.5 mC/kg range provided significant deposition increases on all plant surfaces while beneficially reducing residues on underlying soil. With the intense space-charge spray clouds utilized (e.g., 10 µC/m3), externally applied driving fields as great as 37 kV/m provided no significant deposition increases but instead exacerbated gaseous charge exchange between the spray cloud and the target via undesirable leaf-tip coronas. Nonuniformity characterized deposition of both uncharged and charged sprays throughout the target array, with no improvement provided by spray-entrainment air velocities as great as 2 m/s. Results will guide prototype design by establishing the relative importance of the space charge, the applied field, and the aerodynamic force components for selectively targeting specific sites within living-plant arrays.