The Utility of Activated Charcoal for the Remediation of Herbicide Contaminated Soils.

Injury caused by herbicide carry over is a significant cause of crop damage for vegetable producers and gardeners. Carry over may occur when traces of residual herbicides used in rangelands and pastures persist through the composted manure of the animals fed with the grasses, causing significant damage to sensitive plants. Herbicide residue issues can also occur due to inadvertent applications of a wrong herbicide product or in situations where planting occurs prior to the plant-back interval. Activated charcoal is known to have herbicide absorption properties, but little scientific information is available on the utility of this material for remediating herbicide contaminated sites. Experiments were conducted in the greenhouse to investigate the activity of three pasture herbicides (aminopyralid at 124 g ai/ha; aminocyclopyrachlor at 64 g ai/ha; and picloram at 300 g ai/ha) on three vegetable crops (tomato, okra, and melon) when combined with different levels of activated charcoal (0.5, 1, and 2X rates with 1X=300 lb of product/A). Adequate controls were maintained for comparison. Field soil was treated with the recommended rate of the test herbicides and mixed with a given rate of activated charcoal as per the treatment structure. The soil was then placed in cone-tainers and the crop species were seeded individually in each cone. The plots were arranged in a factorial completely randomized design with six replications. Crop injury assessments were conducted at 14 and 28 days after emergence (DAE) and biomass was measured at 28 DAE. Application of activated charcoal significantly reduced crop injury compared to non-treated control and the reduction in injury levels were greater with higher application rates. Additional experiments are currently being conducted, but preliminary results strongly suggest the utility of activated charcoal for remediating herbicide contaminated soils.