Controlled Release of Soil Active Herbicides: Use of Activated Charcoal for Extended Weed Control

Soil activated herbicides such as hexazinone have chemical properties that increase their potential for leaching out of the root zone in regions with sandy soil and high rainfall patterns. Activated charcoal may form reversible physical bonds with such herbicides, depending on their chemical properties. The powdered form of charcoal can be preabsorbed with a suitable herbicide and then applied for weed control uses as directed by the herbicide label. Physical absorption onto the charcoal protects the active ingredients from biotic and abiotic degradation until rainfall releases the herbicide from the charcoal surfaces. Each rainfall event releases a percentage of the active ingredients so that effective weed control can be maintained over a longer time period. The critical factors for making this an effective weed control formulation are the charcoal and herbicide properties, the mixing ratio, soil properties and the rainfall patterns.