Aminocyclopyrachlor Sorption in Biochar and Activated Charcoal Amended Soils.

Aminocyclopyrachlor is a new herbicide active ingredient, classified as a member of the new chemical class “pyrimidine carboxylic acids”. It is used for control of broadleaf weeds and brush on non-cropland. Due to its potential mobility in some soils, there is interest in whether aminocyclopyrachlor mobility could be reduced by soil amendments. This study is aimed at characterizing the adsorption of aminocyclopyrachlor in soils amended with woodchip biochar, activated woodchip biochar, and activated charcoal. Three surface soils and three subsurface soils in Minnesota with varying soil properties (pH 5.8-7.6, 1-3% organic carbon, 3-23% clay) were used in the study. Adsorption-desorption studies were performed using the batch equilibration method. Sorption values in nonamended soils ranged from K_d 0.17-0.63 mL/g. Biochar did not significantly increase adsorption. The range of K_d values for activated biochar amended soils was approximately 4X higher. The greatest K_d values were observed in the activated charcoal amended soils, which ranged from 1,259 to 8,992 mL/g. The surface soils generally had higher K_d values as compared to the subsurface soils. More research is needed to further characterize aminocyclopyrachlor adsorption-desorption in soils amended with biochars from various feed stocks.