Abstract: A contact bar of permeable, absorbant, exudative material such as a paint roller is attached by a spring bar to a mounting bracket. The contact bar is moistened with a treatment liquid such as a herbicide. Each time the contact bar rubs against a plant, additional herbicide is applied to the contact bar, e.g., a spring arm, carrying the contact bar, can be pushed back by the plant against a microswitch, which will open a solenoid valve. The opening of the solenoid valve may apply liquid to the contact bar by spraying the liquid from a nozzle onto the bar or by feeding liquid through a perforated tube under the surface of the material on the contact bar.

Abstract: A tractor is equipped with a tool bar to which are attached a plurality of cultivators. Sensors are fixed by means of clamps and shanks located over the drill of the planted crop in such a manner that weeds growing above the height of the crop are detected. Once the weed is detected, a spray nozzle is activated and the weed is treated with herbicide. Weeds which are not taller than the growing crop are sprayed as the driver of the tractor manually activates spray nozzles to spray low lying weeds which he visually detects.